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Assessment of Technology Advancements for Future Energy Reduction

Water Environment Research Foundation635 Slaters Lane, Suite G-110 n Alexandria, VA 22314-1177

Phone: 571-384-2100 n Fax: 703-299-0742 n Email: [email protected]

WERF Stock No. ENER7C13b

December 2015

Assessment of Technology Advancementsfor Future Energy Reduction

Energy

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IWA PublishingAlliance House, 12 Caxton StreetLondon SW1H 0QSUnited KingdomPhone: +44 (0)20 7654 5500Fax: +44 (0)20 7654 5555Email: [email protected]: www.iwapublishing.comIWAP ISBN: 978-1-78040-803-3

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ENER7C13b

ASSESSMENT OF

TECHNOLOGY ADVANCEMENTS

FOR FUTURE ENERGY REDUCTION

by:

Nancy Andrews, P.E. John Willis, P.E., BCEE

Chris Muller, P.E. Brown and Caldwell

2015

ii

The Water Environment Research Foundation, a not-for-profit organization, funds and manages water quality

research for its subscribers through a diverse public-private partnership between municipal utilities, corporations,

academia, industry, and the federal government. WERF subscribers include municipal and regional water and water

resource recovery facilities, industrial corporations, environmental engineering firms, and others that share a

commitment to cost-effective water quality solutions. WERF is dedicated to advancing science and technology

addressing water quality issues as they impact water resources, the atmosphere, the lands, and quality of life.

For more information, contact:

Water Environment Research Foundation

635 Slaters Lane, Suite G-110

Alexandria, VA 22314-1177

Tel: (571) 384-2100

Fax: (703) 299-0742

www.werf.org

[email protected]

This report was co-published by the following organization.

IWA Publishing

Alliance House, 12 Caxton Street

London SW1H 0QS, United Kingdom

Tel: +44 (0) 20 7654 5500

Fax: +44 (0) 20 7654 5555

www.iwapublishing.com

[email protected]

© Copyright 2015 by the Water Environment Research Foundation. All rights reserved. Permission to copy must be

obtained from the Water Environment Research Foundation.

Library of Congress Catalog Card Number: 2015948333

IWAP ISBN: 978-1-78040-803-3

This report was prepared by the organization(s) named below as an account of work sponsored by the Water

Environment Research Foundation (WERF). Neither WERF, members of WERF, the organization(s) named below,

nor any person acting on their behalf: (a) makes any warranty, express or implied, with respect to the use of any

information, apparatus, method, or process disclosed in this report or that such use may not infringe on privately

owned rights; or (b) assumes any liabilities with respect to the use of, or for damages resulting from the use of, any

information, apparatus, method, or process disclosed in this report.

Brown and Caldwell

This document was reviewed by a panel of independent experts selected by WERF. Mention of trade names or

commercial products or services does not constitute endorsement or recommendations for use. Similarly, omission

of products or trade names indicates nothing concerning WERFs or EPA's positions regarding product effectiveness

or applicability.

Assessment of Technology Advancements for Future Energy Reduction iii

About WERF

The Water Environment Research Foundation, formed in 1989, is America’s leading

independent scientific research organization dedicated to wastewater and stormwater issues.

Throughout the last 25 years, we have developed a portfolio of more than $134 million in water

quality research.

WERF is a nonprofit organization that operates with funding from subscribers and the federal

government. Our subscribers include wastewater treatment facilities, stormwater utilities, and

regulatory agencies. Equipment companies, engineers, and environmental consultants also lend

their support and expertise as subscribers. WERF takes a progressive approach to research,

stressing collaboration among teams of subscribers, environmental professionals, scientists, and

staff. All research is peer-reviewed by leading experts.

For the most current updates on WERF research, sign up to receive Laterals, our biweekly

electronic newsletter.

Learn more about the benefits of becoming a WERF subscriber by visiting www.werf.org.

http://www.werf.org/i/News/Laterals/a/d/Laterals/Laterals.aspx?hkey=b359886e-7b29-4e98-beae-f6198e578674

http://www.werf.org/i/Get_Involved/Benefits/a/w/Join_WERF.aspx?hkey=a259cc40-297e-4a78-82ae-1faa4a264010

iv

The authors wish to acknowledge the funding support provided by the New York State

Energy Research and Development Authority (NYSERDA) and the Water Environment

Research Foundation (WERF), and the helpful guidance of Kathleen O’Connor, P.E. and Lauren

Fillmore, Project Officers for NYSERDA and WERF, respectively. They would also like to

acknowledge Mark Philbrick with the United States Department of Energy (DOE), who assisted

in planning for the Technology Maturity Expert Panel.

The project team gratefully acknowledges the utility personnel who voluntarily

participated in this project, including the focus group participants listed below. The success of

the project is directly attributed to the dedication and enthusiasm of these utilities to share their

experiences regarding creating energy efficiency.

The authors also wish to express their appreciation to the project advisory committee for

its guidance in the design and conduct of the project.

Report Preparation Principal Investigator:

John Willis, P.E., BCEE

Brown and Caldwell

Project Team:

Nancy Andrews, P.E.

Chris Muller, P.E.

Brown and Caldwell

Rob Greenwood

Ross Strategic

Survey and Workshop Participants Damien Batstone, Ph.D.

Zhiguo Yuan, Ph.D.

The University of Queensland

Abhijeet P. Borole, Ph.D.

Oak Ridge National Laboratory

Charles Bott, Ph.D., P.E., BCEE

Hampton Roads Sanitation District

Jeanette Brown, P.E., DEE

Manhattan College

Jeff Brown, P.E., BCEE

Orange County Sanitation District

Bob Bucher

King County Department of Natural Resources and

Parks Wastewater Treatment Division

ACKNOWLEDGMENTS

Assessment of Technology Advancements for Future Energy Reduction v

Kartik Chandran, Ph.D.

Columbia University

Linda Figueroa, Ph.D. , P.E.

Colorado School of Mines

William Cooper, Ph.D.

National Science Foundation

Anthony J. Fiore

New York City Department of Environmental Protection

Jeremy Guest, Ph.D.

University of Illinois at Urbana-Champaign

Nirmal Khandan, Ph.D.

New Mexico State University

Tom Kunetz, P.E.

Metropolitan Water Reclamation District of Greater Chicago

Barry Liner, Ph.D., P.E.

Lisa McFadden

Matt Ries, M.S.

Water Environment Federation

Bruce Logan, Ph.D.

Pennsylvania State University

Nancy Love, Ph.D., P.E., BCEE

University of Michigan

James McQuarrie

Denver MWRD

Jeff Moeller, P.E.

Water Environment Research Foundation

Sudhir Murthy , Ph.D., P.E., BCEE

DC Water

John Novak, Ph.D.

Virginia Tech

Paige Novak, Ph.D., P.E.

University of Minnesota

Chul Park, Ph.D.

University of Massachusetts Amherst

Wayne Parker, Ph.D.

University of Waterloo

Mark Philbrick, Ph.D.

Department of Energy

vi

Grace Richardson, P.E.

Alexandria ReNew

Diego Rosso, Ph.D.

University of California, Irvine

Peter Schauer, P.E.

Clean Water Services

Yaniv Scherson, Ph.D.

Stanford University

Andrew Schuler, Ph.D.

University of New Mexico

Lori Stone, P.E.

LA STONE LLC

Chi-Chung Tang, Ph.D. P.E.

Sanitation Districts of Los Angeles County

Ana Pena-Tijerina, Ph.D.

City of Fort Worth

Jason Turgeon

U.S. Environmental Protection Agency, Region 1

John Willis, P.E.

Brown and Caldwell

Daniel Zitomer, Ph.D., P.E. BCEE

Marquette University

Joe Zuback, Ph.D.

Global Water Advisors, Inc.

WERF Project Steering Committee Stephen Fok, P.E.

Pacific Gas and Electric Company (PG&E)

James Horne

U.S. EPA: Sustainable Management Branch

Scott Hutchins*

U.S. Department of Energy

Maryanne E. McGowan, CPA, CEM

Duke Energy

Kathleen O’Connor, P.E.*

New York State Energy Research and Development Authority

Sudeshna Pabi, Ph.D.

Electrical Power Research Institute (EPRI)

Assessment of Technology Advancements for Future Energy Reduction vii

Claudio Ternieden

Water Environment Federation

Phil Zahreddine, MSEnvEng*

U.S. Environmental Protection Agency

*Also participated in workshop

Water Environment Research Foundation Staff Director of Research: Amit Pramanik, Ph.D., BCEEM

Senior Program Director: Lauren Fillmore, M.S.

viii

Abstract:

The wastewater industry is continuously seeking new technologies that will reduce the

need for purchased energy and improve its ability to beneficially recover resources. In addition,

within energy-positive technologies such as co-digestion that have begun to see wide levels of

deployment, there are continuing efforts to improve performance. This research reviews 18

specific technology areas to assess their current level of maturity, projected impact on sector-

wide energy use, and potential opportunities for adoption.

Based on input from researchers active in emerging technologies, mainstream shortcut

nitrogen and pyrolysis/gasification appear to be the technology areas most likely to be adopted in

the near term. These technologies are the most mature and their deployment timeline is estimated

to be relatively short. Mainstream shortcut N removal and mainstream anaerobic treatment are

expected to have the greatest impact on energy use in the wastewater sector in the near term.

Increased fundamental understanding of anaerobic communities was cited as a crucial

component of future advancement for both new technologies, and for optimization of existing

technologies such as anaerobic digestion. Refining new methods to accomplish real-time

monitoring of anaerobic community system functions was seen as a crucial part of this research.

Benefits:

Aggregates viewpoints from active academic researchers and wastewater industry

representatives.

Gauges which technologies are likely to have the greatest impact on wastewater sector

energy use.

Estimates deployment timelines for emerging technologies.

Summarizes the key areas of innovation expected to improve the energy performance and

economic viability of existing technologies and processes.

Keywords: Research, innovative treatment technologies, energy-efficient treatment, energy

generation.

ABSTRACT AND BENEFITS

Assessment of Technology Advancements for Future Energy Reduction ix

Acknowledgments.......................................................................................................................... iv Abstract and Benefits ................................................................................................................... viii List of Tables ................................................................................................................................. xi List of Figures ............................................................................................................................... xii List of Acronyms and Abbreviations ........................................................................................... xiii

Executive Summary .................................................................................................................. ES-1

1.0 Introduction .................................................................................................................... 1-1 1.1 Research Context ................................................................................................. 1-1

1.1.1 EPA Manual of Emerging Technologies for Wastewater Treatment

and In-Plant Wet Weather Flow ................................................................ 1-1 1.1.2 WERF Technology Roadmap for Sustainable Wastewater Treatment

Plants in a Carbon-Constrained World ...................................................... 1-1 1.1.3 Parallel DOE Initiative .............................................................................. 1-3

1.2 Project Overview ................................................................................................. 1-4 1.2.1 Research Objective .................................................................................... 1-4

1.2.2 Research Scope and Approach .................................................................. 1-4 1.3 Report Organization ............................................................................................. 1-4

2.0 Technology Summaries ................................................................................................. 2-1

2.1 Characterizing Technology Maturity Levels ....................................................... 2-2 2.2 Improving Energy Efficiency in Existing Treatment Facilities/Processes .......... 2-3

2.2.1 Deammonification (Mainstream Shortcut Nitrogen Removal) ................. 2-3 2.2.2 Fundamental Understanding of Anaerobic Communities ......................... 2-6

2.2.3 Improved Biogas Conditioning ................................................................. 2-8 2.2.4 Pretreatment Processes for Anaerobic Digestion .................................... 2-10 2.2.5 Aerobic Granular Sludge Systems .......................................................... 2-12

2.3 Enhanced Chemical Energy Recovery ............................................................... 2-15 2.3.1 N2O Production to Supercharge Biogas Engines (e.g., CANDO) ........... 2-15

2.3.2 Higher Hydrocarbons from Biosolids, Including HTL Methods ............ 2-17 2.3.3 Higher Hydrocarbons from Biogas or Bioliquids ................................... 2-20

2.3.4 Enhanced Methane Production from Anaerobic Digestion ..................... 2-23 2.3.5 Optimizing Co-Digestion of Food Wastes .............................................. 2-25 2.3.6 Membrane Production and Capture of Hydrogen from Wastewater ....... 2-29 2.3.7 Pyrolysis/Gasification of Biosolids ......................................................... 2-31

2.4 Technologies that Combine Efficient Treatment with Energy Recovery .......... 2-34 2.4.1 Mainstream Anaerobic Treatment ........................................................... 2-34 2.4.2 Microbial Fuel Cells ................................................................................ 2-38

2.4.3 Microbial Electrolysis Cells .................................................................... 2-41 2.4.4 Supercritical/Subcritical Water Oxidation for Sludge

Treatment and Energy ............................................................................. 2-43 2.4.5 Integration of Algal Treatment for BNR with Algal Energy Production .. 2-45

TABLE OF CONTENTS

x

2.4.6 Thermally Regenerative Ammonia-Based Batteries ............................... 2-48 2.5 Other Technologies ............................................................................................ 2-49

3.0 Technology Comparisons and Prioritization............................................................... 3-1 3.1 Technology Readiness Level ............................................................................... 3-1 3.2 Impact vs. Technology Readiness Level ............................................................. 3-3

3.3 Economic and Energy Benefits ............................................................................ 3-4

4.0 Deployment of Research Funding ................................................................................ 4-1 4.1 Discussion Framework......................................................................................... 4-1 4.2 Visualizing Research Objectives ......................................................................... 4-2

4.3 Current Research Initiative Examples ................................................................. 4-2 4.3.1 WEF and WERF ........................................................................................ 4-2 4.3.2 Department of Energy ............................................................................... 4-2

4.3.3 National Science Foundation ..................................................................... 4-3 4.3.4 U.S. Environment Protection Agency ....................................................... 4-3 4.3.5 International Example ............................................................................... 4-4

4.3.6 Wastewater Utilities .................................................................................. 4-4 4.4 Ideas to Maximize Effectiveness of Research Funding Deployment .................. 4-4

4.4.1 Collaborations ........................................................................................... 4-4 4.4.2 Increasing Partnerships between Research Institutions and Utilities ........ 4-5 4.4.3 Stimulating Research Activity ................................................................... 4-5

4.4.4 Grant Size .................................................................................................. 4-5 4.4.5 Grant Types ............................................................................................... 4-5

4.4.6 Team Organization .................................................................................... 4-6 4.5 Sample Framework to Maximize the Impact of Increased Research .................. 4-6

4.5.1 WERF “Restocking” – $5 Million ............................................................ 4-6

4.5.2 Centers of Excellence – $24 Million ......................................................... 4-6

4.5.3 Seed and Subsequent – $21 Million .......................................................... 4-6

References ................................................................................................................................... R-1

Assessment of Technology Advancements for Future Energy Reduction xi

ES-1 Approximate Technology Readiness Levels ................................................................ ES-2

ES-2 Approximate Level of Economic Benefit ..................................................................... ES-5

ES-3 Key Innovation Approaches in Existing Technology or Scientific Areas .................... ES-6

2-1 Technology Readiness Levels .......................................................................................... 2-2

2-2 Mainstream Shortcut Nitrogen Removal ......................................................................... 2-4

2-3 Anaerobic Communities .................................................................................................. 2-7

2-4 Improved Biogas Conditioning Approaches .................................................................... 2-9

2-5 Anaerobic Digestion Pretreatment ................................................................................. 2-11

2-6 Aerobic Granular Sludge ............................................................................................... 2-13

2-7 CANDO ......................................................................................................................... 2-16

2-8 Higher Hydrocarbon Production from Biosolids ........................................................... 2-18

2-9 Higher Hydrocarbon Production from Biogas or Bioliquids ......................................... 2-21

2-10 Enhanced Methane Production from Anaerobic Digestion ........................................... 2-24

2-11 Food Waste Co-Digestion .............................................................................................. 2-26

2-12 Hydrogen Production from Wastewater ........................................................................ 2-29

2-13 Gasification and Pyrolysis ............................................................................................. 2-31

2-14 Anaerobic Mainstream Treatment ................................................................................. 2-35

2-15 Microbial Fuel Cells ...................................................................................................... 2-38

2-16 Microbial Electrolysis Cells ........................................................................................... 2-41

2-17 Supercritical/Subcritical Water Oxidation for Sludge Treatment .................................. 2-43

2-18 Integration of Algal Treatment and Harvesting ............................................................. 2-45

2-19 Thermally Regenerative Ammonia-Based Batteries (TRAB) ....................................... 2-48

3-1 Approximate Technology Readiness Levels ................................................................... 3-1

3-2 Approximate Level of Economic Benefit ........................................................................ 3-4

3-3 Approximate Level of Energy Benefit ............................................................................. 3-5

LIST OF TABLES

xii

ES-1 Technology Prioritization Based on TRL and Deployment Timeline .......................... ES-3

ES-2 Approximate Sector Energy “Impact” vs. Technology Readiness Level ..................... ES-4

1-1 Technology Prioritization ................................................................................................ 1-2

1-2 Equipment Prioritization .................................................................................................. 1-2

1-3 Management Prioritization............................................................................................... 1-3

3-1 Technology Prioritization Based on TRL and Deployment Timeline ............................. 3-2

3-2 Technology Prioritization Based on Technology Readiness Level vs.

Approximate Sector Energy “Impact” ............................................................................. 3-3

LIST OF FIGURES

Assessment of Technology Advancements for Future Energy Reduction xiii

A Amps

AFMBR Anaerobic fluidized bed membrane bioreactor

AMBR Anaerobic membrane blanket reactor

AnMBR Anaerobic membrane bioreactor

AOB Ammonia-oxidizing bacteria

ARPA-E Advanced Research Projects Agency-Energy

ASP Activated sludge process

BES Bioelectrochemical system

BETO Bioenergy Technologies Office

BNR Biological nutrient removal

BOD Biochemical oxygen demand

°C Degree(s) Celsius

C Carbon

CAPEX Capital expenditures

CH4 Methane

CHP Combined heat and power

CO Carbon monoxide

CO2 Carbon dioxide

COD Chemical oxygen demand

DAF Dissolved air flotation

DAMO Denitrifying anaerobic methane oxidation

DNA Deoxyribonucleic acid

DO Dissolved oxygen

DOE U.S. Department of Energy

DWU Dallas Water Utilities

EBPR Enhanced biological phosphorus removal

EERE Office of Energy Efficiency and Renewable Energy

EPRI Electrical Power Research Institute

EPWRR Energy-Positive Water Resource Recovery

ERC Engineering Research Center

FOG Fats, oils, and grease

LIST OF ACRONYMS AND ABBREVIATIONS

xiv

GHG Greenhouse gas

gpd Gallon(s) per day

gpm Gallon(s) per minute

H2 Hydrogen gas

H2S Hydrogen sulfide

HRT Hydraulic retention time

HTL Hydrothermal liquefaction

INFEWS Innovations at the Nexus of Food, Energy, and Water Systems

kg Kilogram(s)

kW Kilowatt(s)

kWh Kilowatt-hour(s)

L Liter(s)

LA Los Angeles

LED Light-emitting diode

LIFT Leaders Innovation Forum for Technology

m2 Square meter(s)

m3 Cubic meter(s)

MBfR Membrane biofilm reactor

MEC Microbial electrolysis cell

MFC Microbial fuel cell

mg Milligram(s)

MG Million gallons

mgd Million gallons per day

MPa Megapascal

MxC Microbial fuel cell-based technology

N Nitrogen

N2O Nitrous oxide

NOB Nitrite-oxidizing bacteria

NPDES National Pollutant Discharge Elimination System

NSF National Science Foundation

NYC DEP New York City Department of Environmental Protection

NYSERDA New York State Energy Research and Development Authority

Assessment of Technology Advancements for Future Energy Reduction xv

OCSD Orange County Sanitation District

OFMSW Organic fraction of municipal solid waste

OPEX Operating expenditures

P Phosphorus

PAH Polycyclic aromatic hydrocarbon

PG&E Pacific Gas and Electric Company

PHA Polyhydroxyalkanoate

RAS Return activated sludge

R&D Research and development

RD&D Research, development, and demonstration

RDD&D Research, development, demonstration, and deployment

RNA Ribonucleic acid

SBR Sequencing batch reactor

SBIR Small Business Innovation Research

SRT Solids retention time

TAG Technology Approval Group

TPAD Temperature-phased anaerobic digestion

TRAB Thermally regenerated ammonia battery

TRL Technology Readiness Level

TSS Total suspended solids

TWAS Thickened waste activated sludge

UASB Upflow anaerobic sludge blanket reactor

UC University of California

U.S. EPA U.S. Environmental Protection Agency

VFA Volatile fatty acid

VS Volatile solids

WAS Waste activated sludge

WASAC Waste activated sludge anaerobic contact

WEF Water Environment Federation

WERF Water Environment Research Foundation

WPCP Water pollution control plant

WRRF Water resource recovery facility

Assessment of Technology Advancements for Future Energy Reduction ES-1

EXECUTIVE SUMMARY

ES.1 Purpose



within energy-positive technologies such as co-digestion that have begun to see wide levels of

deployment, there are continuing efforts to improve performance. This research reviews several

specific technology areas in an effort to assess their current level of maturity and potential

opportunities for adoption. The review also considers which wastewater treatment, solids

stabilization, and energy generation technologies are of greater interest relative to established

technologies, considering factors such as:

Magnitude of incremental energy efficiency improvement over existing technologies.

Reduced life-cycle cost.

Manageable safety and operational risks.

Environmental co-benefits such as improvements in effluent quality, or reduced greenhouse

gas (GHG) emissions, conventional air emissions, or chemical use.

ES.2 Methods

Eighteen technology areas were selected for the technology maturity assessment.

Researchers representing academic institutions, wastewater utilities, government agencies, and

wastewater industry organizations provided their views of these technologies based on their

knowledge of the status of current research and development (R&D) efforts. Input was gathered

via survey and workshop participation.

Because accelerated advancement in these technologies is contingent upon increasing

ongoing research progress, the workshop participants also discussed approaches to improving the

effective deployment of research grants. In the context of potential increased future funding,

participants weighed in on optimizing factors such as grant size, type, number, targeted team

organization, and selection/award criteria.

ES.3 Findings: Technology Maturity

The estimated Technology Readiness Level (TRL) statuses of the reviewed technology

areas are summarized in Table ES-1. Low TRL levels correspond to early phases of research. As

noted at the bottom of Table ES-1, some technology areas covered by this research were new

approaches to established technologies or scientific areas, so these technology areas were not

assessed for TRL.

ES-2

Table ES-1. Approximate Technology Readiness Levels.

Technology Readiness

Level TRL

Description Technology Areas

1-3

Basic or applied research

Critical function

Thermally regenerated ammonia batteries (TRABs).

Membrane production of hydrogen from wastewater

Microbial fuel cells (MFCs).

4-6 Lab testing

Prototype

Microbial electrolysis cells (MECs).

Higher hydrocarbon production: biosolids.

Higher hydrocarbon production: biogas/bioliquids.

Mainstream shortcut nitrogen (N).

Nitrous oxide (N2O) production to supercharge engines.

Mainstream anaerobic treatment.

Pyrolysis and gasification.

7-9 Pilot system

Commercial design

Deployment

Supercritical water oxidation for sludge treatment.

Aerobic granular sludge systems.

Existing

technologies

or scientific

areas: new

approaches

Modifications to deployed

technologies

Fundamental understanding of anaerobic communities

Biogas cleanup.

Pretreatment processes for anaerobic digestion.

Enhanced methane (CH4) from anaerobic digestion (other than co-digestion

and pretreatment).

Food waste co-digestion.


Figure ES-1 compares the research needs for new technologies (based on TRL) to the

deployment timelines projected by the survey respondents. The estimated deployment timelines

ranged from approximately five years to 20 years. Technologies in the blue lower left quadrant

(mainstream shortcut nitrogen [N] and pyrolysis/gasification) appear most likely to be adopted in

the near term because these technologies are the most mature and the deployment timeline is

estimated to be relatively short.

Figure ES-1. Technology Prioritization Based on TRL and Deployment Timeline.

ES-4

The TRL was also compared to a composite gauge of impact on wastewater industry

energy use based on estimated levels of energy savings, applicability, and size niche

considerations. Figure ES-2 depicts the relative positions of the technologies based on these

criteria. This analysis implies that the two technologies in the upper right corner (mainstream

shortcut N removal and mainstream anaerobic treatment) will have the greatest impact on energy

use in the wastewater sector in the near term.

Figure ES-2. Approximate Sector Energy “Impact” vs. Technology Readiness Level.


Survey respondents were also asked to gauge the economic viability of the technologies

based on energy savings relative to the cost of retrofits. Table ES-2 summarizes these results.

Most technologies were expected to be used in new projects or “end of useful life” retrofits. This

economic benefit level implies a longer deployment timeline because wastewater assets are fairly

long-lived and new projects are infrequently initiated.

Table ES-2. Approximate Level of Economic Benefit.

Economic Benefit Level Technology Area

Retrofits of existing equipment are likely to be cost-effective. Mainstream shortcut nitrogen.

Most likely to be used in new projects and retrofits triggered by

“end of useful life.”




Membrane production of hydrogen from wastewater.

Microbial electrolysis cells.


Microbial fuel cells.

N2O production to supercharge engines.

Thermally regenerated ammonia batteries.

Somewhat challenging to make this technology economically

beneficial.



ES-6

As noted previously, some of the technologies considered by this research are

enhancements or advancements in existing areas. Table ES-3 provides examples of the key

innovation approaches identified by participants for these technologies.

Table ES-3. Key Innovation Approaches in Existing Technology or Scientific Areas.

Technology or Scientific Area Key Areas Example Approaches

Fundamental understanding

of anaerobic communities

• Molecular measurements to better

understand system functions.

• RNA, not just DNA.

• Other real-time assessments, viable in a

plant operations setting.

• Protein analysis.

• Process stability indexing and the tools

to monitor it.

• Process performance under very cold

temperatures (e.g., below 12C).

• Online volatile acid monitoring,

Vmax, or biomarkers.

• To be developed.

Biogas cleanup

• Methods to detect low levels of biogas

constituents such as siloxanes.

• To be developed.

Pretreatment processes for

anaerobic digestion

• Identifying highest-value carbon (C)

product.

• Producing products other than

methane.

Enhanced/accelerated

methane production from

anaerobic digestion (other

than co-digestion and

pretreatment)

• Defining systems and operations

practices that maximize the benefits of

biogas generation.

• Determining optimal feeding

strategies.

• Definition of the microbial

communities involved in digestion.

• Direct interspecies electron transfer

(DIET) to accelerate and stabilize

anaerobic digestion.

• Maximizing C feed to digestion.

• Streamline and strengthen

electron exchange between

syntrophs and methanogens.

• Waste activated sludge (WAS)

anaerobic contact.

Food waste co-digestion • Rapid waste characterization and

process model input.

• Improved materials

characterization techniques.

• Better define the synergistic effects of

food waste co-digestion.

• Improved C fractionation.


ES.4 Findings: Enhanced Deployment of Research Funding

Workshop participants discussed several ideas to maximize the effectiveness of a

hypothetical infusion of $50 million per year of additional future research funding, including:

Collaborations. Proposed collaborative approaches included test bed facilities, research

centers to tackle individual multi-year projects, and third-party validation services.

Wastewater utility partnerships. Programs that connect new technology collaborations

with wastewater utilities were noted to be most effective if they can be timed to address a

specific utility need. In other words, utilities will be most interested in demonstrating or

piloting new technologies when they are evaluating alternatives to meet a pending process

objective such as replacing aging equipment, increasing nutrient removal, or expanding plant

capacity. Collaborations with utilities were also seen as most effective when they were long-

term, almost permanent.

Approaches to stimulate new research activity. Participants proposed creating challenge

prizes or grants to stimulate grassroots ideas and enthusiasm. Another suggestion proposed

deploying an annual group of postdoctoral researchers who would be trained as a cohort,

networked to share ideas, and then deployed to various utilities to work on site-specific

research projects as a means to keep good researchers active in the industry.

Grant types. Some participants proposed devoting half of the hypothetical $50 million to

two centers organized geographically around certain needs, with a five-year funding period.

Beyond five years, the centers would be funded through subscription payments from private

entities. Others proposed add-on grants to provide a pool of money for third-party oversight

of demonstration projects. Proponents felt that this auxiliary funding would make research

results more powerful.

Assessment of Technology Advancements for Future Energy Reduction 1-1

CHAPTER 1.0

INTRODUCTION



within technologies that have begun to see wide levels of deployment, such as co-digestion,

efforts to improve performance continue. This research reviews several specific technology areas

in an effort to assess their current level of maturity and potential opportunities for adoption.

1.1 Research Context

Several previous studies have documented new and emerging technologies, often with an

eye toward methods that significantly reduce energy use. These studies provide useful technical

background and previous assessments of the technologies reviewed in this publication.

1.1.1 EPA Manual of Emerging Technologies for Wastewater Treatment and

In-Plant Wet Weather Flow

Chapter 3 of the U.S. Environmental Protection Agency (U.S. EPA) Manual of Emerging

Technologies for Wastewater Treatment and In-Plant Wet Weather Flow (U.S. EPA, 2013)

discusses several of the technologies addressed in this report, including deammonification,

aerobic granular sludge, anaerobic mainstream systems such as anaerobic membrane blanket

reactors (AMBR) or anaerobic membrane bioreactors (AnMBR), and microbial fuel cells

(MFCs). Chapter 6 provides assessments of energy conservation measures. Most of the methods

featured in this manual are focused on optimizing aeration energy via methods such as enhanced

controls or improved diffuser efficiency.

1.1.2 WERF Technology Roadmap for Sustainable Wastewater Treatment Plants

in a Carbon-Constrained World

The 2010 Water Environment Research Foundation (WERF) report, Technology

Roadmap for Sustainable Wastewater Treatment Plants in a Carbon-Constrained World

(Technology Roadmap, Project No. OWSO4R07d), presented a roadmap for the next generation

of wastewater treatment processes, with a focus on resource recovery, including energy/carbon

(C) recovery.

The Technology Roadmap visualized the research status and projected timeline

for several approaches, grouped under 1) technologies, 2) equipment innovations, and

3) management strategies. A quadrant framework was used to prioritize future approaches

proposed by work group participants, with the most developed, shortest timeline in the lower left

corner. Technologies are depicted in this manner in Figure 1-1, equipment in Figure 1-2, and

management strategies in Figure 1-3.

It is interesting to note that in the five years since the Technology Roadmap report was

published, several of the listed technologies have progressed and in some cases become

established, while others are still emerging. The technologies that have gained traction in the

wastewater industry are highlighted in Figures 1-1 through 1-3.

1-2

Figure 1-1. Technology Prioritization*.

Figure 1-2. Equipment Prioritization. *Source: Technology Roadmap for a Sustainable Wastewater Treatment Plants in a Carbon-Constrained World

(WERF, 2010), with modifications.

Technologies that have gained

traction since 2010


traction since 2010


Figure 1-3. Management Prioritization. Source: Technology Roadmap for a Sustainable Wastewater Treatment Plants in a Carbon-Constrained World

(WERF, 2010), with modifications.

1.1.3 Parallel DOE Initiative

This research included collaboration with a federal effort to gain insights and identify

specific technical and non-technical barriers that are hindering development and deployment of

the water resource recovery facilities of the future. This initiative was organized around three

workshops:

Bioenergy Technologies Office (BETO) in the U.S. Department of Energy’s (DOE)

Office of Energy Efficiency and Renewable Energy (EERE) Workshop focused on

commercial production of drop-in hydrocarbon fuels from wet waste biomass. The

participants identified 17 advancement activities as high in priority in the areas of pre-

processing, process research, process engineering, and analysis. Some of these activities

apply broadly to wet waste conversion (including wastewater sludge), while others apply to

specific technologies.

BETO-Sponsored Workshop on Hydrogen, Hydrocarbons, and Bioproduct Precursors

from Wastewaters. It gathered experts to share information and identify the current status

and research, development, and demonstration (RD&D) possibilities for production of

hydrogen and higher hydrocarbons (containing four or more C atoms) from wastewaters

using biological, biochemical, and other techniques. In particular, the workshop focused on

microbial fuel cell-based technologies (MxCs) and AnMBRs.


traction since 2010

1-4

The National Science Foundation (NSF), EPA, and DOE Jointly Hosted Workshop on

Energy-Positive Water Resource Recovery (EPWRR) to envision what a state-of-the art

facility would look like in 20 or more years, assessing gaps and hurdles, and considering

where additional research, development, demonstration, and deployment (RDD&D) could

have the greatest impact.

1.2 Project Overview

This section presents the research objectives, scope, and approach of this project.

1.2.1 Research Objective

The intent of this research was to consider which wastewater treatment, solids

stabilization, and energy generation technologies are of greater interest relative to established

technologies, considering factors such as:

Magnitude of incremental energy efficiency improvement over existing technologies.

Reduced life-cycle cost.

Manageable safety and operational risks.

Environmental co-benefits such as improvements in effluent quality, or reduced GHG

emissions, conventional air emissions, or chemical use.

1.2.2 Research Scope and Approach

Eighteen technologies were selected for the technology maturity assessment. The

following criteria were used to narrow the list of technologies:

Degree of energy benefit.

Degree of maturity or experience in North America.

Research and development (R&D) status ranging from theory to pilot scale.

Potential for scalability to have significant impact at facilities of various sizes.

Widespread applicability to existing water resource recovery facilities (WRRFs).

Participants were asked to complete a survey to gather information regarding research

needs, expected maturity timeline, and expected magnitude of the energy benefit (survey

questions included in Appendix A). Survey findings were reviewed and refined in a workshop

setting on June 11, 2015.

Because progress with these technologies is contingent upon ongoing research progress,

the workshop participants also discussed factors affecting deployment of research grants,

including grant size, type, number, targeted team organization, and selection/award criteria.

1.3 Report Organization

This report is divided into the following chapters that document the methodology used to

collect data and the findings in various focus areas:

Chapter 1.0: Introduction

Chapter 2.0: Technology Summaries

Chapter 3.0: Technology Comparisons and Prioritization

Chapter 4.0: Deployment of Research Funding


CHAPTER 2.0

TECHNOLOGY SUMMARIES

Technologies considered in this assessment were grouped into the following major categories:

Improving energy efficiency in existing treatment facilities/processes: Energy-saving

alternatives to conventional biological nutrient removal (BNR), improvements to biogas

scrubbing, and digestion pretreatment.

Enhancing chemical energy recovery: Digestion and co-digestion technology

enhancements and other fuel production approaches, pyrolysis, and gasification.

Combining efficient treatment with energy recovery: Transformative technologies that

replace conventional aerobic treatment systems and/or provide new methods of recovering

energy from wastewater.

This chapter summarizes the technology maturity survey and workshop findings related

to each of the eighteen technologies within these groups. Survey respondents answered questions

for which they indicated either 1) very high level of expertise, 2) high level of expertise, or

3) very high level of interest. The summaries found in this chapter sometimes draw a distinction

between the answers given by respondents with high expertise (often from academic settings)

and those with high interest (often from wastewater utility settings). In some cases, the number

of respondents with high expertise or interest was relatively few, so the number of respondents is

shown for each technology as a gauge for sample size.

It should be noted that this report is focused on technology maturity status and hurdles.

Refer to the References section for related publications that include more detailed technology

descriptions and background.

2-2

2.1 Characterizing Technology Maturity Levels

Panel members assessed maturity levels using the DOE “Technology Readiness Level”

(TRL) scale (DOE, 2011). This is a fairly granular scale, using nine levels to describe the

progression from basic research to commercial deployment, as summarized in Table 2-1.

Table 2-1. Technology Readiness Levels.

Technology Readiness Level Description

1

Basic research: basic principles observed.

2 Applied research: initial practical applications identified.

3

Critical function: studies and initial laboratory measurements to validate analytical

predictions of separate elements of the technology.

4

Laboratory testing/validation of alpha prototype component/process: design,

development, and lab testing of technological components.

5

Laboratory testing of integrated/semi-integrated system: component and/or process

validation in relevant environment.

6

Prototype system verified: system/process prototype demonstration in an

operational environment.

7

Integrated pilot system demonstrated: demonstration of an actual system prototype

in a relevant environment.

8 System incorporated in commercial design: pre-commercial demonstration.

9 System proven and ready for full commercial deployment: actual system proven.


2.2 Improving Energy Efficiency in Existing Treatment Facilities/Processes

The following technologies include incremental changes to existing processes, including

energy-saving alternatives to conventional BNR, improvements to biogas scrubbing, and

digestion pretreatment.

2.2.1 Deammonification (Mainstream Shortcut Nitrogen Removal)

Low-energy (shortcut) deammonification systems using anammox bacteria in lieu of

conventional nitrifying bacteria have been implemented at full-scale for treating warm, high-

strength sidestreams from dewatering digested solids. This short-cut nitrogen removal

technology is currently being researched and adapted for use in mainstream treatment.

Deammonification involves anammox bacteria working synergistically with ammonia-oxidizing

bacteria (AOB) to oxidize ammonium without organic C to produce nitrogen (N) gas. The

overall deammonification process requires less oxygen to remove nitrogen, thereby reducing the

energy demand on the aeration process. In addition, the solids retention time (SRT) pressure used

to suppress nitrite-oxidizing bacteria (NOB) results in a capacity benefit.

This technology is the subject of significant research efforts and pilot testing, but

currently lacks any full-scale facilities in the U.S. and associated performance and stability data.

There is also a need for advanced control systems to continuously monitor in-process and

upstream variables that affect operational parameters and allow timely operational adjustments.

Some of the most significant hurdles to widespread implementation of this technology are

regulatory. For example, an effluent N concentration of 2-3 milligrams per liter (mg/L) is

required to maintain high growth rates in mainstream deammonification processes, but this

concentration is too high for plants that must meet very strict N effluent permit limits, in which

case a polishing step must be added. Daily and weekly permit limits are also problematic, with

longer averaging periods or 95th

percentile approaches significantly reducing permit risks.

Workshop participants discussed the prospective energy savings from mainstream

shortcut N removal. The primary energy benefit was tied to concurrent C diversion from

upstream processes. In other words, because the shortcut N removal process requires little or no

carbon, upstream processes can be optimized to maximize C feed to anaerobic digestion and

minimize secondary aeration. Upstream processes could include 1) mainstream anaerobic

treatment, 2) A-stage reactors, with or without chemical enhancement, and 3) enhanced primary

treatment. Each of these three scenarios would have varying impacts on energy savings because

of their relative impact on particulate, colloidal, and soluble C fractions.

A secondary energy benefit could be derived from lower dissolved oxygen (DO) set

points, because shortcut N removal processes can operate at lower DO concentrations than

conventional nitrification processes.

Table 2-2 summarizes survey and workshop discussion findings regarding mainstream

shortcut N removal.

2-4

Table 2-2. Mainstream Shortcut Nitrogen Removal.

Respondents: 19

• Very high level of expertise: 5

• High level of expertise: 5

• High level of interest: 9 Majority Consensus Response Contrary Response(s)

How would you characterize the current technology status?

High level of

expertise

Two thirds of respondents classified the technology as prototype

or pilot scale.

One third of respondents classified

the technology as applied research

with an identified application.

High level of

interest

Prototype or pilot scale.

Applied research with an identified application

(40% each).

One respondent classified the

technology as ready for full-scale

implementation.

What are the most pressing research needs for advancing this technology?

High level of

expertise • Gaining better control of the system and population

selection.

• Understanding overall system operation variability from

location to location.

• Improve prediction and control of long-term energy costs

and operating costs.

• Techniques such as fixed-film anammox for residual

polishing to meet low N concentration permit

requirements.

• Development of sensor-mediated control strategies that

enhance efficiency and stability.

What are the most significant non-technical hurdles to commercialization or widespread adoption?

High level of

expertise

Lack of information, risk aversion, and experience with real-

time control.

High level of

interest

Perceived process risk (long recovery times), lack of design

standards, and perception of complexity verses benefits.


High level of

expertise

Most likely to be used in new projects and retrofits triggered by

"end of useful life" situations (making adoption slower)” (55%).

Retrofits of existing "adequate"

equipment could be cost-effective

(45%).

High level of

interest

Retrofits of existing “adequate” equipment could be cost-

effective (60%).

Comments:

• The nitrite shunt mode should be economically beneficially

if modifications are related only to process control. The

nitritation + anammox is a challenge at mainstream

concentrations.

• They could be cost-effective if use of existing tankage is

sufficient from a size/SRT perspective.

Most likely to be used in new

projects and retrofits triggered by

"end of useful life" situations

(making adoption slower)(40%).

How would you characterize the applicability of this technology (economics aside, just looking at plant characteristics)?

High level of

expertise

Industry best practice (66%).

Potential for universal application

(11%).

A niche application (22%).

High level of

interest

Industry best practice (57%). Only 14% responded that it has the

potential for universal application

while 28% responded that it is a

niche application.


Respondents: 19




Does this technology have scale considerations or niches?

High level of

expertise

No scale or niche limitation (66%).

10 mgd minimum size (33%).

High level of

interest

4 of 5 respondents indicated that there are no scale or niche

limitations, while one believed there to be a 100 mgd limit.

The scale is one part with larger

plants being more likely to adopt.

Also, more likely in an existing facility

that is set up for BNR with the ability

to have multiple zones of varying DO.

If you had to guess, how many years will it take to overcome technical challenges? Comments

High level of

expertise

1-3 years and 3-5 years (33% each).

5-10 years (22%).

Greater than 10 years (12%).

High level of

interest

1-3 years and 3-5 years (40% each). 5-10 years (20%).

Following technical maturity and proof of concept, how long will commercialization or adoption take (e.g., at least two North

American installations)?

High level of

expertise

3-5 years (66%).

1-3 years (33%).

High level of

interest

1-3 years (60%). 3-5 years (40%).

What performance metrics are required to make this technology economically viable?

High level of

expertise • Cost, energy, and C emissions reductions based on real-

world data with demonstration of effective N removal.

• Achieving sufficient retention time for biomass.

• Hitting discharge limits for N without a polishing step.

High level of

interest • A process that demonstrates ammonia removal with

defined chemical, energy, oxygen, and reasonable process

metrics (retention time).

• Strong financial benefit to the implementing utility.

What is your best estimate of the potential impact of this technology on overall plant energy use?

High level of

expertise

Greater than 50% (40%) and 10-25% savings (37% each).

Greater than 50% savings contingent on upstream C removal

as noted above.

25-50% savings, <10% savings

(12.5% each).

High level of

interest

10-25% savings (75%). 25-50% savings (25%).

2-6

2.2.2 Fundamental Understanding of Anaerobic Communities

Future strategies for energy-efficient or energy-positive wastewater treatment will rely

heavily on anaerobic systems. A fundamental understanding of heterotrophic anaerobic

communities' activities and interactions is necessary to advance anaerobic approaches to

secondary/mainstream treatment, and digestion advancement. Examples of this type of research

include:

Microbial ecology studies, improving control and optimization of microbial communities.

Investigating biological intermediates.

Understanding interspecies electron transfer, biofilms, and granules.

Fundamentally understanding changes in community structure with change loadings and

materials composition.

Identifying metabolic pathways to improve the cost benefit of digestion.

Investigating short-term anaerobic contact flocculation mechanisms.

Recovering carbon in forms that can be used in N removal.

Making hydrogen in lieu of using methanogens to produce methane (CH4).

Discovering improved systems modeling for design development.

Studying yields and kinetics for phase-separated systems.

Improving monitoring and controls for systems managers.

Refining process performance under very cold temperatures (e.g., below 12C)

Workshop attendees discussed approaches to leverage anaerobic communities to improve

current utilities operations and to advance the state of the art. This research is needed to drive the

further development and refinement of mainstream anaerobic processes and further advance the

anaerobic digestion process. Molecular tools present a promising avenue to enhance our

understanding of anaerobic communities. The application of reverse transcript ribonucleic acid

(RNA) techniques can provide a better understanding of system function, beyond the

presence/absence type of information that current deoxyribonucleic acid (DNA)-based analysis

provides. Additional research into protein activity in anaerobic systems would also further the

industry’s understanding of system function. However, to be effective, these tools need to be

integrated to provide near real-time assessments and demonstrated to be viable in a plant

operations setting.

Along with molecular techniques to monitor and define community form and function,

additional process metrics and monitoring techniques for daily operations are needed. An area of

need identified by the group is process stability indexing and the tools to monitor it, such as

online volatile acid monitoring, Vmax, or biomarkers for varying substrates of interest.

Through a better understanding of the function of anaerobic communities, the

fundamental question of do we engineer the community or process? may be better answered by

examining what better anaerobic digester process control and design models could be developed.


Table 2-3 summarizes survey and workshop findings regarding energy-related

applications of research into the function of anaerobic communities.

Table 2-3. Anaerobic Communities.

Respondents: 17



• High level of interest: 2 Response

What future applications do you foresee resulting from research related to fundamental understanding of heterotrophic

anaerobic communities?

High level of expertise Mainstream anaerobic treatment to increase biogas production was the most

prevalent area of potential growth.

Other areas identified include:

• Enhanced digestion (high temp., high ammonia).

• Improved fermentation.

• Anaerobic membrane reactors.

• Denitrifying anaerobic methane oxidation (DAMO).

• Sulfide oxidation.

• Biological hydrogen, electricity, and biofuel production; conversion of influent

organic carbon to products of commercial value (to chemical industry, textile

manufacturing, etc.).

• Impact of process parameters such as organic loading and cell density on

conversion.

• Hybrid anaerobic/aerobic mainstream treatment.

• Anaerobic contact reactors to sorb colloidal material and particulate carbon,

enhancing digestion.

High level of interest • Mainstream anaerobic treatment.

• Approaches to intensify the anaerobic digestion process (reduced SRT,

increased organic loading and digester sizing).

How will these applications impact WRRF energy use?

High level of expertise All respondents indicated that processes/approaches centered around anaerobic

conversion of carbon, in place of traditional aeration, have the potential to reduce

the energy requirements of municipal WRRFs, although there was a range of

expectations regarding the extent of the benefit achieved. It was further noted that

these technologies need to be coordinated with end uses to maximize benefits (e.g.,

VFA generation for conversion to biodiesel).

High level of interest Those with a high level of interest in this particular topic indicated that savings

through mainstream anaerobic treatment would save on energy costs but also noted

that enhancement/intensification of anaerobic digestion can save energy. These

individuals further noted that these efforts must be coordinated with other resource

recovery efforts to maximize the benefit.

2-8

2.2.3 Improved Biogas Conditioning

Biogas conditioning systems have become industry standard for use in removing

contaminants that increase engine maintenance, including moisture, hydrogen sulfide (H2S), and

siloxane compounds. Biogas conditioning systems used for vehicle fuel (BioCNG) or natural gas

pipeline injection (biomethane) also separate the carbon dioxide (CO2) gas fraction.

These systems impact plant energy consumption, because of both their impact as parasitic

electrical loads and their expense in enabling reliable power generation. Improvements in these

systems enhance biogas utilization by reducing life-cycle costs. Examples of these considerations

include:

Loss of biogas in purge streams for some regenerative and CO2 separation systems.

Frequent and labor-intensive media replacement for H2S removal systems.

Reduced engine maintenance intervals.

The expert reviewers indicated that these technologies are mature and their further

development was going to be heavily driven by market conditions. However, it was noted that

some fundamental research into low detection levels for biogas constituents such as siloxanes

would be beneficial as gas quality standards have been tightened in some areas to close to the

limits of detection of current methods. Another area where research may benefit the industry is in

smaller-scale systems that are economical.

Table 2-4 highlights the improved biogas conditioning approaches being tracked by

survey respondents.


Table 2-4. Improved Biogas Conditioning Approaches.

Respondents: 16



• High level of interest: 2

Technology Contaminant (s) How is Technology Superior

to Existing Systems Current Challenges Pilot or New Installations

Membranes Siloxanes, CO2 The cost and energy usage of

these systems has come down

in the past 5 years. BioCNG is

valuable as a vehicle fuel, but

CO2 typically needs to be

removed. Membranes are now

less expensive.

Still need to

reduce energy of

CO2 removal and

BioCNG

compression.

Janesville, WI

Regenerable

adsorption

(pressure or

temperature

swing,

molecular gate)

Siloxanes Some enable higher-efficiency

energy generation.

Application and

translation from

existing

technologies in

some cases and

demonstration in

other cases.

Methane loss

during

regeneration.

Biological

treatment

example

technology:

BioGasclean

H2S More sustainable, less

chemical-intensive.

Stability, costs,

upsets,

size/space

requirements.

LA County is testing a

slightly aerated

biotrickling filter.

Solvent

separation

CO2 Better constituent removal

performance with new gas

quality requirements being

instituted.

Process

complexity and

limited

performance

data on systems

operated with

WRRF biogas.

Only aware of recent

installations on landfill

gas.

InnoSepra

CO2 A flue gas CO2 adsorbent,

which potentially requires

lower heat of absorption than

competing processes.

Bench-scale tests,

seeking funding for

pilots.

http://www.netl.doe.go

v/research/coal/carbo

n-capture/post-

combustion/sorbent-

innosepra

Water scrubbing H2S, CO2 No chemicals are needed; can

be used on low pressure gas;

only consumable is plant

water.

Size/space

requirements.

Demonstrated

only at small

scale.

OCSD is evaluating water

scrubbing after conducting

some very small-scale testing,

it may expand into a larger

demonstration project.

2-10

2.2.4 Pretreatment Processes for Anaerobic Digestion

In recent years, various processes have been developed to pretreat solids prior to

digestion, especially to break down refractory cell structures and particulate matter. The

objective of these pretreatment systems is primarily to increase 1) the rate of digestion,

2) volatile solids destruction, and 3) digester gas production. Some systems also improve

pathogen destruction and dewaterability and reduce digester reactor size requirements. Various

approaches have been developed. The thermal hydrolysis approach has attained commercial

viability and widespread interest, and was mentioned by almost all survey respondents. Other

systems are still in development.

Table 2-5 summarizes the various technologies being tracked by respondents. A few

other technologies were mentioned but not described by respondents (biological pretreatment,

ozonation, electron beam technology). Some challenges apply to several technologies:

Ability to predict increased methane yield and solids reduction performance at specific

plants.

Obstacles related to retrofits of existing equipment, footprint requirements.

Reducing energy inputs and achieving life-cycle sustainability.

Regaining utility trust, especially after several early pretreatment approaches did not really

work.

Prediction of process impacts on return streams, sludge viscosity, and rheology.

Expansion of treatment beyond waste activated sludge (WAS).

Highest-value carbon management strategies (methane or other carbon forms).


Table 2-5. Anaerobic Digestion Pretreatment.

Respondents: 16




Technology How is Technology Superior

to Existing Systems Current Challenges Pilot or New Installations Thermal

hydrolysis

Reducing viscosity to allow

significant increase in loading

rates, Class A product,

compatible with co-digestion,

improved dewaterability.

Education, broad

acceptance.

DC Water

operational, Trinity

River planned

installation.

Chemical

treatment

“Lodomat”

Pretreatment of WAS in mixing

tank at ambient temperature

and pressure. Low chemical

consumption (nitrite and acid).

Increased biogas production.

Modified version can achieve N

removal via the nitrite pathway:

RAS NOB are killed while AOB

remain viable.

Full-scale trials needed

to verify the results.

Being developed by

University of Queensland.

Being implemented in

Australia at 7.9 mgd plant.

Caustic and

medium

temperature

treatment

“Lystek”

Caustic and medium-

temperature treatment with

high shear mixing. Synergies

with BNR, volume reduction,

biogas increase, liquid Class A

product.

Unknown. Several full-scale

installations in

Canada.

Microwave Break down particulate matter Lack of fundamental

understanding of the

mechanism of energy

transfer to particulates

and specificity in

wastewater treatment.

Research stage (Oak

Ridge National Lab).

Cavitation Low energy input required Demonstration of

increased methane yield

and solids reduction for

mixed TWAS and primary

sludge.

WERF and TAG are

organizing a

collaborative,

Upcoming Arisdyne

tests at several

utilities, including

Columbus, GA.

Combined

anaerobic/aerobic

treatment

Better dewaterability, less odor Minimal. Spokane, WA.

Electric-energy

processing

Improve digestion of secondary

solids

Small-scale results have

not been replicated at

full-scale.

OpenCEL Racine, WI,

Test at OCSD

(recently canceled).

Ultrasound,

sonication

No specific advantages listed High energy input and

insignificant digestion

improvement.

Anergia has tested

ultrasonic

conditioning .

2-12

2.2.5 Aerobic Granular Sludge Systems

Aerobic granular sludge uses granules in place of light biological floc structures for

secondary treatment and BNR. The granular structure in this process is stratified so that both

aerobic and anaerobic/anoxic layers are present and the biological processes for N, phosphorus

(P), and C removal occur simultaneously. Granular sludge reactors can be operated at higher

biomass concentrations, allowing higher loading rates while maintaining the longer SRT

necessary for stable nitrification. Reactors are most often configured as sequencing batch

reactors (SBRs). Some granular activated sludge systems could be operated at a low DO set point

for energy efficiency, while achieving total N removal. Granular sludge systems are the subject

of current WERF research project U1R14, Balancing Flocs and Granules for Activated Sludge

Process Intensification in Plug Flow Configurations.

Table 2-6 summarizes the survey and workshop findings regarding aerobic granular

sludge systems.


Table 2-6. Aerobic Granular Sludge Systems.

Respondents: 9





High level of expertise Half of the respondents indicated that the technology was proven and ready for full

commercial deployment. The other half of the respondents indicated that the technology is

not developed to the commercial level yet, with responses ranging from the technology is at

the pre-commercial demonstration stage (33%) to the demonstration of a prototype (17%)

level of development.

Comments:

Need to expand on existing system configuration being operated in Europe: demonstrate

ability to integrate into existing WRRF.

Examples:

• Existing plants in operation in Europe and South Africa, and ~40 plants in the pipeline to

be designed by DHV (a Netherlands company commercializing this process).

• Lab studies done by the universities in U.S. (e.g., Belinda Sturm at Kansas).

• University of Michigan lab-scale system to achieve N removal and dissolved methane

removal from mainstream AnMBR effluent.

High level of interest Aerobic granular sludge was viewed by highly interested parties as not nearly as developed

as the Expert survey respondents. The technology is viewed as being strong but at the

laboratory level of evaluation with validation in a relevant environment.


High level of expertise • Greater understanding of the engineering of the granule architecture, process biology,

chemistry, and physics.

• Better understanding on integrating the process into existing facilities, including plug flow

tankage. Consideration of external selectors (e.g., cyclone, screen, or settling column) to

manage granular cell mass and impart selection pressure to favor granule formation.

• Development operating parameters to make operations reliable and robust.

• Controls for operation under variable loading conditions.

• Integration with modeling elements (e.g., BioP).

• Development of metrics without being linked to a specific patent (e.g., DHV).

• Pilot-scale demonstration.

High level of interest • Improved understanding of mass transfer within the system.

• Environmental conditions required to maintain the appropriate ratios of different bacterial

populations within the system.


High level of expertise • Challenges in retrofitting the technology into existing systems and a one-size-fits-all

approach.

• Education about the process and the need for greater education of the industry because

of the relative newness of the technology to the U.S. market.

• Potential impact of patents was raised as a potential barrier as well.

High level of interest The perception within the U.S. wastewater industry that the activated sludge process (ASP) is

the only solution.

2-14

Respondents: 9




How economically beneficial do you expect this technology to be?

High level of expertise Retrofits of existing “adequate” equipment could be cost-effective (60%).

Comments:

• Retrofitting existing systems: according to DHV, can be done, but it is not clear if it is

economical.

• More realistic as a downstream process for anaerobic mainstream treatment.

High level of interest Retrofits of existing “adequate” equipment could be cost-effective (50%).

Most likely to be used in new projects and retrofits triggered by “end of useful life” situations

(making adoption slower) (50%).


High level of expertise or interest A majority of respondents indicated that this technology has a broad level of applicability to

the industry, with 33% indicating near universal acceptance or as a transition to best

practice by a majority of plants vs. 25% indicating it is a niche market.


High level of expertise None.

Comment: DHV is designing plants of pretty good size.

High level of interest None.

If you had to guess, how many years will it take to overcome technical challenges?

High level of expertise 3-5 years (80%).

5-10 years (20%).

High level of interest The responses were evenly split between the 3-5-year range and the 5-10-year range.

Following technical maturity and proof of concept, how long will commercialization or adoption take (e.g., at least two North American

installations)?

High level of expertise and

interest

3-5 years (40%).

5-10 years (40%).

1-3 years (20%).



interest • Proof of performance for the system.

• Similar or better performance to activated sludge or biofilm systems.

• Reduced energy costs.

• Comparable surface overflow rates for setting.

• Demonstrated ability to manage seasonal temperature changes and wet weather events.



interest

Wide range of opinions on potential energy savings:

Less than 10% (3 responses).

25-50% reduction (2 responses).

Greater than 50% (1 response).

Comment: According to studies from the Netherlands, energy savings will depend on the

effluent water quality standard. Savings higher if integrated with C, N, and P cycling.

Workshop discussion: Workshop participants attributed energy savings to lower DO set

points and reduced internal mixed liquor pumping. Based on these two factors, the

anticipated energy reduction was less than 10%.


2.3 Enhanced Chemical Energy Recovery

The following technologies improve chemical energy recovery, either via new types of

energy streams (nitrous oxide [N2O], hydrogen, higher hydrocarbons, syngas, pyrolysis oil), or

enhancements to methane production from existing anaerobic digestion and food waste co-

digestion techniques.

2.3.1 N2O Production to Supercharge Biogas Engines (e.g., CANDO)

The CANDO process operates in conjunction with the SHARON shortcut N process to

improve energy production. The CANDO process captures the high energy value of the N2O off-

gas from the sidestream treatment process. The effect of the CANDO N2O combustion process is

similar to jet propulsion or nitrous injection in race cars. SHARON is a well-established

sidestream treatment process, reducing sidestream oxygen demands by up to 25%, whereas the

CANDO process is an emerging process, recently tested at the Delta Diablo Sanitation District.

Table 2-7 summarizes the survey findings regarding the CANDO process.

2-16

Table 2-7. CANDO Process.

Respondents: 4





High level of

expertise

Demonstrated at the laboratory scale (66%) or pilot scale (33%) in a relevant

environment.

Skepticism regarding

whether this technology will

be feasible or cost-

effective.


High level of

expertise

The process requires a stronger business case to make it successful including:

• Improved N2O utilization.

• Reduction in system complexity.

• Improved N2O recovery.

• Implementation beyond the sidestream to mainstream.

Comment: Sidestream treatment barrier may be reduced if co-digestion requires

strategies to manage increased N load.


High level of

expertise • Process risk.

• Long-term reliability.

• Cost-effectiveness.

• Lack of regulatory and renewable energy drivers to adopt new technologies.


High level of

expertise

There was a unanimous consensus that this technology is a niche technology.


High level of

expertise

10 mgd (1 response).



High level of

expertise

The responses were divergent on the scale of facility this technology is suitable

for, with a low of 10 mgd to a high of 100 mgd. It was noted that in larger plants

with high N loads in sidestreams, there is a clearer energy benefit.


High level of

expertise

A majority of responses indicated that the CANDO process will take more than

10 years of additional development to overcome its technical challenges.

1-3 years (1 response).


installations)?

High level of

expertise

Greater than 10 years (2 responses). 3-5 years (1 response).


High level of

expertise

10% reduction or less (1 response).



High level of

expertise

• >80% N conversion to N2O.

• >80% N removal.

• >1 kg-N/m3/d loading.


2.3.2 Higher Hydrocarbons from Biosolids, Including HTL Methods

The focus of this research area is on developing higher-value fuel products from biosolids

feedstocks, including drop-in fuels to be compatible with existing transportation infrastructure

(e.g., petroleum-derived gasoline and diesel fuel). In this context, DOE has defined higher

hydrocarbons as molecules with four or more C atoms, produced from biosolids and other wet

organic wastes. This approach can be advantageous relative to digestion and biogas combined

heat and power (CHP) in cases where air permits are especially restrictive or electrical rates are

low.

This topic area encompasses many process approaches in various phases of development,

including hydrothermal liquefaction (HTL) and other techniques. As one survey respondent

noted, this topic requires a shift in thinking toward chemical synthesis because we have hardly

scratched the surface in terms of products, platforms, and pathways.

Workshop participants listed the following broad range of potential solids, liquids, and

gas hydrocarbon products that could be produced by various processes:

Breakdown product (pyrolysis oil).

Produced gas from pyrolysis: CO, H2, CH4, CO2.

Syngas from gasifier: CO, H2 ethane, and other gases.

Methanol (intermediate).

Naphtha: feed for plastics.

N-butanol.

Biodiesel production from volatile fatty acids (VFAs) (non-algae based systems).

Products for blending with conventional fuels.

Shrimp food (highest value animal food product).

As one possible technical approach, Fischer-Tropsch reactors could be used to convert

gaseous products (syngas or biogas) to liquid fuels. However, workshop participants noted that

Fischer-Tropsch reactors are difficult to scale down to match the output of a WRRF (generally

less than 100 barrels per day).

Participants also suggested that scale issues might be addressed via a depot system. In

this approach, an intermediate product (e.g., pyrolysis oil) would be produced at the WRRF, then

transported for additional processing at a centralized facility that would accept similar

intermediates from several plants.

As an example of the fuel production scale of these systems, workshop participants cited

projects that produced 1/2 barrel (42-gallon barrel) of syncrude (paraffin and diesel) per wet ton

of dewatered biosolids. Another participant noted that they had found a similar production rate of

60 gallons of syncrude per dry ton of biosolids.

Table 2-8 presents the survey and workshop findings regarding hydrocarbon production

from biosolids. Findings regarding hydrocarbon production from wastewater liquids and biogas

are presented in Section 2.3.3.

2-18

Table 2-8. Higher Hydrocarbon Production from Biosolids.

Respondents: 11





High level of

expertise

Answers widely spread, with respondents indicating technology status as:

• Applied research (2 responses).

• Laboratory testing/validation of alpha prototype (2 responses).

• Lab testing of integrated system (1 response).

• Integrated pilot system demonstrated (2 responses).

Prototype system verified

(1 response).

System incorporated into

commercial design

(1 response).

High level of

interest

Three responses:

• Applied research.

• Critical function studies.

• Prototype system verified.


High level of

expertise and

interest

• A clear path for conversion of biosolids to hydrocarbons has to be laid

out. For example: biosolids-preconditioning/treatment-pyrolysis-bio-oil

upgrading-hydrogen production from aqueous phase of bio-oil:

hydrotreatment of bio-oil to produce gasoline and diesel.

• What to do with any residual tar, polycyclic aromatic hydrocarbon

(PAH), or other hazardous constituents that become wastes/by-

products.

• Pyrolysis oil conditioning cost and energy to remove moisture, acids,

and other unwanted constituents in the pyrolysis oil (raw bio-oil).

• Improving product quality and downstream processing.

• More test data from a variety of biosolids sources.

• Scale-up beyond bench/lab scale.

• Economics (but not in competition with chemical process industry

production costs).

• Demonstrating high conversion of biosolids energy content to

fuel/evaluating “real-world” net energy balance (energy input vs.

output).

• For HTL: fundamental understanding of how variability in biomass

composition and characteristics influence system performance (cost,

oil yield, quality).



High level of

expertise • Integration of know-how from other fields; knowledge base needs

to be built up.

• High CAPEX.

• Water management/separation, extraction of soluble organics in

water phase to fuel/hydrogen.

• Economy of scale issues. Need operating experience and data

showing reliability for full-scale/commercial-scale operations. Co-

location of privately held demonstration plant equipment onsite at

WRRFs.

• Potential to combine biosolids with other biomass to make fuels.

• Reliability.

• Lack of incentive to increase energy production or reduce biosolids

disposal.

• Life-cycle cost analysis to show that the process is more

sustainable than others.

• Management of aqueous phase from HTL (can contain high levels

of toxicity).

Can HTL address

economic/energy issues

with wet sludge?

High level of

interest

Funding.


High level of

expertise

Most likely to be used in new projects and retrofits triggered by “end of

useful life” situations (making adoption slower) (43%).

Comment: Economically favorable, but depends on benchmark. Should

not be compared against the chemical process industry. Look at other

factors, localized availability.

Retrofits of existing

“adequate” equipment could

be cost-effective (28%).

Challenging to be cost-

effective (28%).

High level of

interest

Challenging to be cost-effective (66%). Most likely to be used in new

projects and retrofits

triggered by end of life

(33%).


High level of

expertise

Niche market (62%).

Comment: Not a niche market, if we stop talking about it in terms of

wastewater treatment (re-phrased to chemical synthesis).

Transition to industry best

practice (25%).

Potential for almost

universal acceptance (13%).

High level of

interest

Niche market (2 responses).

Transition to best practice

(1 response).

Does this technology have scale considerations or niches? Comments

High level of

expertise

10 mgd (42%)

Comments:

• Opportunity for regional biosolids facility (single biorefinery) to

achieve economies of scale.

• Technology is modular and easily scaled.

100 mgd or greater (29%).

No scale or niche limitations

(29%).

High level of

interest

100 mgd limit (2 responses). 10 mgd (1 response).


High level of

expertise

1-3 years (38%).

3-5 years (38%).

5-10 years (25%).

High level of

interest

Answers split between: 1-3 years, 3-5 years, and more than 10 years .

2-20



High level of

expertise

3-5 years (57%).

1-3 years (29%).

More than 10 years (14%).

High level of

interest

Answers split between 1 year, 3-5 years, 5-10 years .


High level of

expertise

10% reduction or less (37%).

10-25% reduction (25%).

25-50% reduction (14%).

More than 50% reduction

(25%).

High level of

interest


10% reduction or less (1 response).


High level of

expertise • Reduced capital cost.

• Alternative to offsite disposal costs (less than $50/dry ton).

• Percent conversion of biosolids to energy, fuel, or energy

efficiency of the process.

• Production yield (e.g., gallons of hydrocarbon/ton of dry biosolids).

• Recovery of nutrients as well as energy.

• Production kinetics.

• Availability of (appropriate) feedstock.

• Aqueous phase characteristics (including toxicity).

• Positive net present value and low cost per pound of renewable C

utilized (or barrels of petroleum displaced).

High level of

interest • Cost of disposal vs. energy usage/production.

2.3.3 Higher Hydrocarbons from Biogas or Bioliquids

Similar to the previous topic, this technology area includes a wide range of processes in

various stages of development. In the case of biogas, the objective is to produce an upgraded fuel

or chemical product with higher value than the biogas itself.

Technologies to convert biogas to liquid hydrocarbons are similar to technologies being

investigated for stranded gas outputs in oil fields, and include dry reforming using CO2.

Workshop participants also noted that biological processes could be used to convert biogas

methane to methanol or butanol, with a significant positive impact on GHGs from replacing

methanol feeds in BNR processes.

In lieu of hydrocarbons, a potential product stream is bioplastics. For example, DOE has

provided Small Business Innovation Research (SBIR) funding for Mango Materials, a bioplastics

startup from Stanford University. Its process feeds biogas to methanotropes, cycling the process

to promote polyhydroxyalkanoate (PHA) accumulation (up to 50% of cell mass).

Table 2-9 summarizes survey findings regarding higher hydrocarbon production from

biogas or bioliquids.


Table 2-9. Higher Hydrocarbon Production from Biogas or Bioliquids.

Respondents: 5





High level of

expertise

Integrated pilot system (2 responses).

Comment: proven, but not in wastewater context.

System incorporated into

commercial design

(1 response).

System proven and ready for

full commercial deployment

(1 response).

High level of

interest

System incorporated in commercial design/pre-commercial

demonstration.


High level of

expertise • None, reformation technology well understood.

• Energy analysis, energy integration of all unit operations (drying,

gasification, conversion to liquids).

• By-product yields.

• Cost-effective small-scale sulfur removal.

• Feedstock quality, quantity, and availability.


High level of

expertise • Extremely expensive and large scale.

• Operational complexity.

• Integration of know-how from other fields; knowledge base needs

to be built up.

• Demonstration at commercial scale, co-location of privately held

plant equipment onsite at WRRFs.

High level of

interest • Benefit-cost analysis.


High level of

expertise

Most likely to be used in new projects and retrofits triggered by “end of

useful life” situations (making adoption slower) (2 responses).

Comment: Economically favorable, but depends upon benchmark.

Should not be compared with chemical process industry production

costs. Look at other factors, including benefits of localized feedstock

and product availability.



be cost-effective (1 response).

Challenging to be cost-

effective (1 response).

High level of

interest

Challenging to be cost-effective (1 response).


High level of

expertise

Niche market (3 responses). Transition to industry best

practice (1 response).

Not a niche market, if we stop

talking about it in terms of

wastewater treatment (re-

phrased to chemical

synthesis).

High level of

interest

Niche market (1 response).

2-22

Respondents: 5





High level of

expertise

10 mgd (2 responses).

No scale or niche limitations (2 responses).

Comment: aggregation required for economies of scale

Order of magnitude above

WWRF size.

High level of

interest



High level of

expertise

1-3 years (2 responses).


High level of

interest

More than 10 years.



High level of

expertise

1-3 years (3 responses). 3-5 years (1 response).

High level of

interest



High level of

expertise


Comments: enables production of value-added fuels.

10% reduction or less

(1 response).

More than 50% reduction

(1 response).

High level of

interest

10% or less reduction.


High level of

expertise

Low temperature/low cost catalyst.

Conversion of carbon in organics to commercially viable liquid

transportation fuel, e.g., diesel that meets low sulfur highway specs.

End use needs to be identified before going down this pathway.


2.3.4 Enhanced Methane Production from Anaerobic Digestion

This topic area is intended to focus on potential methods other than sludge pretreatment

(Section 2.2.5) and co-digestion (Section 2.3.5) for increasing methane production from

anaerobic digestion. Table 2-10 summarizes the approaches mentioned by survey respondents.

Note: Responses below are grouped by estimated impact on energy production, with technical

challenges noted. Some approaches are repeated if respondents had differing estimates of the

increased energy production potential.

In addition to the specific digestion approaches listed below, one respondent viewed the

question in the context of a plant as a whole. Energy production from digestion is sometimes

limited by the need to reduce primary clarification capture in order to support a BNR process:

“We need to reduce the carbon demand for N removal to enable the use of

primary settling tanks (no longer existing in many plants to supply more COD to support

N removal). In addition to the mainstream anammox process, N removal via nitrite

(nitritation+denitritation) should be implemented.”

Workshop attendees also noted several other factors that are impacting the enhancement

of methane recovery from wastewater systems. These include:

Regulatory and incentive barriers (i.e., lack of mandates).

A general lack of cooperation between utilities to promote additional energy generation.

Beyond the regulatory barriers identified, additional work is needed to better define

systems and operations practices that maximize the benefits of biogas generation. These

knowledge gaps included:

Better definition of the acid/gas process.

Improved understanding of how feeding strategies impact biogas generation.

Identification of best-in-class operations standards and practices to serve as industry models.

Further definition of the microbial communities involved in digestion.

While significant improvements in methane generation from WRRFs have been made,

further development is needed to maximize the potential of the systems.

2-24

Table 2-10. Enhanced Methane Production from Anaerobic Digestion.

Respondents: 12



• High level of interest: 3 Majority Consensus Response

What techniques are you pursuing or tracking regarding enhanced methane production from anaerobic digestion (other than

pretreatment and co-digestion)?

What is the expected increase in energy production?

What technical challenges apply to these techniques?

~10% increase In energy production • Waste activated sludge anaerobic contact (WASAC): Receives WAS and a

fraction of carbon directed away from activated sludge,

<30-minute contact time, then anaerobic digestion. 10-30% enhanced biogas

production at pilot scale.

• Acid-gas digestion: effective only on primary sludge.

• TPAD: high cost of implementation.

10-25% increase in energy

production

• Phased digestion: odor suppression.

• AnMBRs: membrane fouling and sophistication of operation.

• Improving hydrolysis: understanding the science of what limits hydrolysis.

• Post-digestion thermal hydrolysis: numerous technical challenges.

• Bioaugmentation: additional basic research required.

• Microbial resource management: additional research required.

• Trace nutrient addition for methane maximization: applied and basic research

and demonstration required.

• Acid-gas digestion: applied and basic research and demonstration required.

• Pilot anaerobic digestion at varying loading rates: time required and

complexity in optimizing the system.

• Recuperative thickening: energy consumption, additional process units,

complex operations.

25-50% increase • Methane potential testing for VS and COD fractions of FOG and food waste:

sample collection, process conditions (mixing): correlation between lab and

full-scale without side-by-side systems.

• Catalytic augmentation, microbial gene manipulation to intensify metabolic

pathways.


2.3.5 Optimizing Co-Digestion of Food Wastes

Although use of food wastes for co-digestion has increased dramatically in recent years,

the industry’s understanding of the process is still evolving. Table 2-11 considers new methods

for optimizing co-digestion of various waste streams, including commercial, industrial, and

ideally residential sources.

While the practice of co-digestion is maturing within the wastewater industry, there are

still several challenges to its implementation and realization of ultimate benefit. Some of these

challenges are technical while others are programmatic and logistical:

Improved materials characterization techniques for rapid characterization and process model

input.

Improved C fractionation to better define the synergistic effects of food waste co-digestion.

Identification of non-energy uses for food waste constituents (proteins, lipids,

carbohydrates).

Adoption of separation practices by communities will increase program viability.

Reductions in the variability in the regulatory barriers for interconnection between the

wastewater plant and power utilities.

Improved strategies for N diversion to agriculture for fertilizer use.

Development of more comprehensive and accurate business models demonstrating the value

of a program.

2-26

Table 2-11. Food Waste Co-Digestion.

Respondents: 14




What types of new methods for optimizing co-digestion of food waste are you tracking?

High level of expertise • Digester capacity optimization and control.

• Risk management.

• Materials characterization.

• Impact and fate of materials during digestion.

• Process control.

• Stoichiometry.

• Integration of digestion with microbial electrolysis.

• Pretreatment (thermal hydrolysis).

• Food waste pre-processing .

• Recuperative thickening, high solids digestion.

• Optimization of materials blends.

• Microbial communities.

High level of interest Interested parties were tracking:

• Leather tanning waste.

• Materials composition and feed rates.

How are these new methods superior to existing systems?

High level of expertise The improvements associated with the research being

tracked included:

• A reduction in risk and optimization of the economic

outcomes.

• Improved characterization will allow for more stable

operation and increased loadings, and reduce the risk

of upsets.

• Coupling digestion with microbial electrolysis cells

(MECs) could produce hydrogen (a more valuable fuel),

provide reductions in effluent BOD, and high recovery

rates of energy from wastewater solids.

• Improvements in pre-processing technologies can

provide cleaner/less difficult to manage substrate for

digestion, reducing contamination. Potential for

improving the digestibility of the sludge and making it

compatible with municipal anaerobic digesters.

• Recuperative thickening can improve the loading rate of

the digester, allowing for more food waste to be

processed in the same tankage.

• Optimized blending may improve overall energy yield

per unit volume of digester.

High level of interest • Leather tanning waste, could shift a problem waste

material to a commodity opportunity.


Respondents: 14




What are the current technical challenges with these new methods?

High level of expertise A majority of respondents indicated some level of technical

challenge associated with food waste co-digestion, including:

• Standardization of methodologies.

• Integration of materials characterization with

operations.

• Optimization of the digestion with the MEC process to

achieve higher energy recovery.

• Slow adoption and drivers are limiting a demonstrated

concept.

• Identification of waste sources.

• Pilot studies, good metrics to allow for comparison.

• Lack of capital resources.

• A general gap in knowledge surrounding the microbial

structure, feedstock digested, and methane yield from

the process.

A counter opinion on

the subject matter

indicated that no

current technical

challenges are

associated with food

waste co-digestion.

High level of interest The technical challenges identified included:

• Process inhibition from the digestion of tannery waste.

• Supply chain, reliability and control of materials, and

source separation.

Are you aware of any pilot or new installations of these new methods?


interest

The ongoing research on specific topics was identified as

follows:

• Process control and stoichiometry: DC Water, Bucknell

University, Spain.

• Digestion with MEC: no ongoing research.

• Materials pre-processing: 11 full-scale demonstration

projects in Europe.

• Recuperative thickening: Victorville, CA.

• High solids digestion: Europe and new facilities to be

installed in the U.S..

• Co-digestion operations listed in survey: Deer Island

WWTP, DWU has a facility under construction. LA

County is doing a co-digestion study at one plant.

• Pre-processing operations: ClearCove, Ithaca, NY;

Grind2Energy, multiple facilities; Salsnes and others,

multiple facilities.

• High solids digestion: Oshkosh, WI.

• OFMSW digestion: San Jose, CA and Toronto, Canada.

• Pre-processed food waste: LA County Joint WPCP and

Waste Management (20,000 gpd).

• Tannery waste co-digestion: Florence, Italy.

2-28

Respondents: 14




Additional Comments

High level of expertise Additional comments from survey participants included:

• This is the largest energy opportunity for most WRRFs

because food waste in municipal solid waste is

generally the largest source of organic feedstock; it can

provide 5-10% of California’s energy demand, for

example.

• Optimizing feedstock blends. University of Michigan has

simulated functional operating space of co-digestion

systems, considering which design factors are most

predictive of performance and which factors the system

is most sensitive to.

• Food waste is a moving target, because as we focus on

it people tend to stop wasting so much food in the first

place. Movement seen toward eating less and wasting

less, saving C footprint of food production and

transportation chain.


2.3.6 Membrane Production and Capture of Hydrogen from Wastewater

Hydrogen is extracted by contacting wastewater with a membrane laden with hydrogen-

generating bacteria. As the bacteria metabolize organic matter, hydrogen is passed into hollow fibers

for removal and can be utilized by fuel cells for energy production. The bacterial process removes

organic contaminants, reducing aeration demands. The system is modular and can be altered to fit

many liquid waste streams including industrial, agricultural, and sanitary waste. Table 2-12 presents

the survey findings regarding membrane production and capture of hydrogen from wastewater.

Table 2-12. Membrane Production of Hydrogen from Wastewater.

Respondents: 3


• High level of expertise: 2 Majority Consensus Response How would you characterize the current technology status?

High level of expertise Basic research (1 response).

Applied research (1 response).

Critical function (1 response).


High level of expertise • Fundamental research in bioelectrochemical systems (BESs).

• Using microbial electrolysis for hydrogen production.

• This technology has been laboratory-tested using some real wastewaters. The next

step is to optimize materials with scale-up in mind.

Comment: Oak Ridge has used biorefinery wastewater to generate hydrogen at higher

than 50% efficiency from the organic content in wastewater.


High level of expertise • Cost of membranes.

• Life of materials.

• Maintaining high performance of system over long term (months or more).

• Funding for optimization and scale-up phase. This type of funding is challenging to

get from many funding agencies (NSF, etc.), but is critical if the technology is going

to be demonstrated as viable, enabling adoption. In addition, an early adopter is

critical to push and champion this technology.


High level of expertise It will be challenging to make this technology economically beneficial (1 response).

Most likely to be used in new projects and retrofits triggered by “end of useful life”

situations (making adoption slower) (1 responses).

Retrofits of existing “adequate” equipment could be cost-effective.


High level of expertise Niche market (2 responses).

Potential for almost universal acceptance (1 response).


High level of expertise No scale or limitations (3 responses), but high-strength wastewater such as industrial or

food streams preferred.


High level of expertise 1-3 years (2 responses).



installations)?


More than 10 years (1 response).

2-30

Respondents: 3


• High level of expertise: 2 Majority Consensus Response What is your best estimate of the potential impact of this technology on overall plant energy use?

High level of expertise More than 50% reduction (3 responses).


High level of expertise Hydrogen productivity > 15 L H2/L reactor-day.

Current density > 20 A/m2.

Energy efficiency > 50%.

Material costs (membrane costs) and/or longevity.


2.3.7 Pyrolysis/Gasification of Biosolids

This topic area included potential future enhancements in thermal treatment of biosolids

(pyrolysis and gasification), with an emphasis on how to improve energy generation from these

processes. Pyrolysis and gasification can be used to process either raw or digested solids.

Gasification and pyrolysis are closely related technologies, with the key differentiator

being the presence or absence of oxygen and the nature of the products produced. Pyrolysis

operates at a temperature of over 300°C, in the absence of oxygen and with limited water.

Pyrolysis produces oil, which can be refined or digested as an energy source. Under certain

operating conditions, syngas can also be produced. The solids residual is biochar, which has been

proposed for use as an agricultural amendment because of its water-retention capacity and

phosphate content.

Gasification operates under sub-stoichiometric conditions, with small amounts of oxygen

and steam added to control gas production. The solid residual produced via gasification is ash.

Biogas (syngas) is produced, but in recent projects the biogas is used primarily to dry the feed

sludge, leaving no surplus gas available to generate additional energy. Workshop participants

suggested that increased thermal heat recovery could be used to improve the energy balance.

Workshop participants believed that both technologies held promise for future

development. The advantage of one approach over the other would depend on which fuel and

residual products are best suited for a given project application. Participants stated that there

would be value to a separate workshop focused on overcoming barriers to wider deployment of

this technology.

Survey and workshop findings regarding gasification and pyrolysis of biosolids are

summarized in Table 2-13.

Table 2-13. Gasification and Pyrolysis.

Respondents: 10





High level of expertise Answers widely spread; majority response: system

incorporated into commercial design (37%).

Comments: pilot pyrolyzer at Marquette and full-

scale demonstration at Encina, CA.

Applied research (12%).

Lab testing of alpha prototype (12%).

Prototype verified (12%).

Integrated pilot system demonstrated

(12%).

System proven and ready for

commercial deployment (12%).

High level of interest Lab testing of integrated system (1 response) .

Prototype system verified (1 response).

2-32

Respondents: 10





High level of expertise • Downstream processing/What to do with bio-

oil/tar.

• Consistency of feed.

• Robustness/reliability.

• Full-scale demonstration.

• Improving cost structure/cost-effective

improvement in energy balance (wet sludge).

• Sulfur in biogas, other sulfur management

issues.

High level of interest • Residuals characterization and beneficial use

pathway.


High level of expertise • High CAPEX.

• Robustness relative to incineration.

• Water content.

• Lack of incentive to reduce biosolids disposal

cost or to reuse solids in soils .

• Lack of regulatory driver for increasing energy

recovery, reducing GHG.

• Risk aversion.

• Issues with subsequent processes can be

more problematic that thermal reactor itself.

HTL to address economic/energy issues

with wet sludge?

High level of interest • High CAPEX.

• Siting.


High level of expertise Most likely to be used in new projects and retrofits

triggered by “end of useful life” situations (making

adoption slower) (50%).

Retrofits of existing “adequate”

equipment could be cost-effective

(35%).

High level of interest Challenging to be cost-effective: best used for

destruction of sludge to reduce digestion and

dewatering costs.


High level of expertise Niche market (55%). Transition to industry best practice

(33%).

High level of interest Niche market (one response).


High level of expertise No scale or niche limitations (50%).

100 mgd or greater (25%).

10 mgd (25%).

High level of interest No scale or niche limitations (1 response).

100 mgd limit (1 response).


Respondents: 10






3-5 years (37%).

1 year (12%).

5-10 years (12%).

High level of interest 3-5 years (1 response).





3-5 years (37%).

More than 10 years (12%).

High level of interest 5-10 years (2 responses).


High level of expertise 10-25% reduction (50%).

25-50% reduction (37%).

10% reduction or less (12%).

High level of interest 10-25% reduction (2 responses).


High level of expertise • Reduced capital cost.

• Solid mass degradation >50%.

• Reduced disposal costs relative to existing

methods.

• Net energy production and GHG reductions.

• Ability to recover phosphorus, metals from

ash, clinker, or production of higher-value

products.

• Reduction of criteria air pollutants, air permits

for engines’ burning point: gas.

High level of interest • Net energy production.

2-34

2.4 Technologies that Combine Efficient Treatment with Energy Recovery

The transformative technologies presented in this section represent a break with current

liquid and solids treatment approaches. On the liquid treatment side, technologies considered

include anaerobic treatment in lieu of aerobic activated sludge technology, using MFCs to

remove organic contaminants, using batteries to remove nitrogen, or algal nutrient removal with

energy harvesting. On the solids side, supercritical wet oxidation for energy production is

reviewed.

2.4.1 Mainstream Anaerobic Treatment

Several approaches have been researched to treat wastewater anaerobically, including but

not limited to AnMBRs, anaerobic fluidized bed membrane bioreactors (AFMBRs), and upflow

anaerobic sludge blanket reactors (UASBs). Some treatment configurations use combinations of

these anaerobic approaches, or combinations that include downstream aerobic systems, in order

to achieve plant performance that meets effluent standards.

Some types of anaerobic systems have been successfully applied to high-strength

industrial wastewater for many years, but researchers are working to configure systems to treat

dilute and colder domestic wastewater, with the goal of generating biogas and dramatically

reducing energy inputs for organic removal. Additional work is needed to further develop the

technology. Primary areas of additional development include:

Management and recovery of dissolved methane.

Treatment/management strategies for ammonia and sulfides.

Integration with other mainstream N removal technologies.

Nutrient recovery from dilute streams (e.g., struvite).

Synergies with microbial electrolysis cells (MECs).

Generation of alternative products (methanol, VFAs).

Economic pretreatment of particulates to improve conversion.

Management of peak and other transient conditions.

Along with additional research, it was noted that increased efforts to disseminate the

advances surrounding this particular unit operation are still needed. Partnerships with utilities to

demonstrate full-scale process efficacy would support the further development and ultimate

commercialization of the process. However, it was noted that gaining regulatory support for the

process would improve the viability of the system. The development of a fully monetized triple-

bottom-line analysis was recommended to demonstrate the full value of the technology.

Table 2-14 summarizes survey and workshop findings regarding anaerobic mainstream

treatment technologies.


Table 2-14. Anaerobic Mainstream Treatment.

Respondents: 15





High level of expertise More than half of the respondents believed that

mainstream anaerobic treatment was at the pilot level with

demonstration in relevant environments (53%). The next

largest group believed it was in the applied research stage,

alpha prototype (15%). It was noted that this technology is

currently used primarily in warmer climates or on

processes with higher-strength wastewater, such as

industrial pretreatment systems.

A small percentage

(15%) indicated the

process is ready for full

commercial design or

deployment.


High level of expertise The following research needs were identified by the survey

group:

• Integration of N and P removal: anammox may not be

the primary N-removing process because of the

presence of residual VFAs, dissolved methane, and

sulfide.

• Improvements in methane recovery and utilization,

efficiency and cost, soluble methane management

(avoiding GHG release).

• Operation at lower wastewater temperatures and at

lower wastewater strengths.

• Improved effluent through membranes, address

membrane fouling issues, and efficient polishing of

permeate.

• For microbial electrolysis: demonstration of 20 A/m2

in domestic wastewater.

• Demonstration of process in large-scale domestic

wastewater pilot (e.g., Stanford University project) to

verify efficacy of all process elements with highly

instrumented systems, modeling, and integrated

(economic, environmental, energy) analysis.

• Verification of process performance against stringent

permit limits.

• Expansion beyond methane end use with treated

carbon.

2-36

Respondents: 15





High level of expertise The significant non-technical challenges identified by the survey group included:

• Broad commercial providers.

• Operator training.

• Allowing for deployment in low-temperature and low-wastewater strength systems.

• Regulatory acceptance.

• Impact on biosolids characteristics.

• Lack of pilot studies.

• Long-term performance and scalability.

• Sunk capital investments (e.g., primary clarifiers).

• Cost associated with retrofit from current activated sludge systems.

• Depth and breadth of operating systems and conditions relative to permit limit

demands.

• Improved energy efficiency, especially regarding energy consumption for fouling

mitigation.

• Sustainable way to remove/recover ammonia and nitrogen from AnMBR effluent.


High level of expertise The majority (57%) believed this technology would be

adopted for new systems or “end of useful life” scenarios,

resulting in slower adoption.


“adequate” equipment

could be cost-effective

(43%).


High level of expertise A majority of responses had a view of broad applicability of

this technology: universal acceptance (21%) or a transition

to best practices for a majority of plants (42%).

A good number of

respondents indicated

that this is only a niche

technology (36%),

contrary to the majority

opinion.


High level of expertise The majority believed mainstream anaerobic treatment did

not have any specific scale considerations (71%).

10 mgd (21%).

100 mgd (7%).


High level of expertise The majority responses indicated that 3-10 years of work

will be required to overcome the technical challenges. • 3-5 years (57%).

• 5-10 years: (35%).

1-3 years (7%).


Respondents: 15






High level of expertise 5-10 years (43%). 1-3 years (28%).

3-5 years: (28%).


High level of expertise • Metrics surrounding enabling technologies.

• Sludge and energy balances.

• 1-year membrane cleaning cycle (demonstrated).

• Operating costs ($/MG-treated) and energy demand (kW/MG-

treated).

• Methane recovery rates and GHG inventory impacts (soluble

methane loss).

• Effluent values in line with NPDES permits (BOD, TSS, N, and P

removal rates).

• Sludge production metrics.

• Chemical use data (savings/costs).

• Demonstration of reliable operation.


High level of expertise A large majority of respondents indicated a large savings

on plant energy use with mainstream anaerobic treatment:

>50% savings (72%)

Comments:

• Process could become energy and chemical positive if

wastewater is more concentrated and if coupled with

low energy demanding downstream processes.

• Depends on whether post-process aerobic treatment

is necessary for polishing.

10-25% and

20-50% reduction

(14% each).

2-38

2.4.2 Microbial Fuel Cells

Bioelectrochemical systems (BESs) are electrochemical cells that use electrochemically

active microorganisms as catalysts on one or both electrodes. BESs can be divided into

electricity-producing MFCs and electricity-consuming MECs. Table 2-15 presents survey and

workshop findings regarding MFCs. Findings regarding MECs are presented in Section 2.4.3.

An MFC is a device that generates electricity from bacterial metabolism of organic

matter (which is measured as chemical oxygen demand [COD] in wastewater). During the final

stage of bacterial metabolism, electrons are passed along the cell membrane and deposited onto a

terminal electron acceptor, usually oxygen under aerobic conditions. In an MFC, bacteria

transfer their electrons externally to an anode. Electrons flow from the anode to a positively

charged cathode through an external circuit; this flow of electrons represents an electrical

current. The cathode is exposed to oxygen and protons (H+) that chemically react with the

incoming electrons to form water (U.S. EPA, 2013).

While some have raised low wastewater condition as a barrier to this technology,

researchers attending the workshop noted that they have found good current production at COD

concentrations above 150-200 mg/L. At high organic concentrations (3,000 mg/L), the reactor

goes anaerobic. Therefore, the viable organic concentration range would be well-matched for

COD concentrations found in typical municipal wastewater.

The most likely use for MFCs envisioned by workshop participants was to reduce COD

concentrations prior to secondary treatment, either to reduce aeration or as pretreatment for

anaerobic reactors. In addition to reduced secondary treatment energy, this potential approach

has the advantage of not using a methane pathway, reducing concerns about fugitive methane

emissions and ideally simplifying the electrical generation process.

Table 2-15. Microbial Fuel Cells.

Respondents: 10 • Very high level of expertise: 2 • High level of expertise: 5 • High level of interest: 3 Majority Consensus Response Contrary Response(s)


High level of expertise Applied research (57%).

Laboratory testing/validation of alpha prototype

(2 responses) (29%).

Lab testing of

integrated/semi-integrated

system (1 response).

High level of interest Laboratory testing/validation of alpha prototype

components (2 responses).

Critical function: validate analytical predictions of

separate elements (1 response).

What are the most pressing research needs for advancing this technology? High level of expertise • Current efficiency (mainly electrodes).

• Manufacturing of cathodes (specialized

design; manufacturers unwilling to make

custom designs).

• Application to real wastewater.

• Scale up, especially anode design (goal of

1 gpm unit for next demonstration).

• Improving long-term operation.

• Finding low-voltage uses.

• Solids management; biomass yield is midway

between conventional aerobic and anaerobic

yield rates.

MFC has proved to be

unsuitable for energy

recovery from wastewater,

but may have some niche

applications.

MFC technology has been

stuck on the bench for years.

Microbial electrolysis rather

than microbial fuel cells will

provide the economic benefits.

High level of interest Understanding microbial populations and metabolic

pathways; electrochemical pathways.




High level of expertise • Cost of equipment.

• Understanding the effect of process.

parameters over long term.

• Demonstration at pilot scale.

• Downstream nutrient removal required.

High level of interest • Cost: electrode pricing.

• Treat in the same footprint as current aerobic

systems.


High level of expertise Challenging to be cost-effective (57%).

Comment: MFC technology can perform well, but

can the energy savings offset the cost within a

reasonable time frame? This will be a challenge

because technology is currently costly and energy is

cheap.



be cost-effective (29%).

Most likely used in new

projects or triggered by

retrofits (1 response).

High level of interest Most likely used in new projects or triggered by

retrofits (2 responses).



High level of expertise Niche market (71%). Transition to industry best

practice at majority of plants

(29%).

High level of interest Niche market (2 responses) .

Transition to industry best practice at majority of

plants (1 response).


High level of expertise No scale or niche limitations (71%).

Comment: influent strength more likely to be a

consideration than plant size.

10 mgd (29%).

High level of interest





More than 10 years

(1 response).

High level of interest 5-10 years (2 responses). More than 10 years

(1 response).

2-40







More than 10 years

(1 response).

High level of interest 3-5 years (2 responses), more than 10 years

(1 response).


High level of expertise More than 50% reduction (4 responses). 10% reduction or less

(1 response).

10-25% reduction

(1 response).

High level of interest 25-50% reduction (2 responses), 10-25% reduction

(1 response).


High level of expertise • Current >25 A/m2

• CAPEX <$500/m2

• Electrodes that cost less than $100-$150/m2 and that are easy to

manufacture.

Comment: A current density of > 20 A/m2 has been demonstrated at

laboratory scale. This is close to being sufficient for commercial consideration.

Further understanding of performance stability over long term is necessary.

Following that, pilot-scale studies will be needed to demonstrate performance at

larger scale.

High level of interest • Ability to meet NPDES permit limits including N and P. If not, what follow-on

treatment is required?

• Cost of treatment per MG treated (including pretreatment and polishing steps).

• Solids generation compared to current practices.

• Energy generated/consumed per 1 MG treated.


2.4.3 Microbial Electrolysis Cells

Many possible wastewater related applications for BESs have been developed recently.

Microorganisms can be used to catalyze cathodic reactions (at biocathodes), such as oxygen

reduction to water, proton reduction to hydrogen, nitrate reduction to nitrogen gas, and

bicarbonate reduction to methane (Sleutels et al., 2012). Other applications include hydrogen

peroxide production, desalination (Logan, 2010), and recovery of ammonia. Many of the new

applications for cathode reactions need additional energy input, which is determined by

thermodynamics of the overall reaction. Table 2-16 summarizes survey findings regarding

MECs.

Table 2-16. Microbial Electrolysis Cells.

Respondents: 5





High level of expertise Laboratory testing/validation of alpha prototype

(2 responses).

Applied research

(1 response).

Lab testing of

integrated/semi-integrated

system (1 response).

High level of interest Applied research (1 response).


High level of expertise • Current efficiency (mainly electrodes).

• Continuous flow tests with domestic wastewater

(performance metrics have been demonstrated

with biorefinery wastewater).

Need to find niche

applications; H2 production

only will not get this

technology anywhere.

High level of interest Understanding microbial populations; catalysts.


High level of expertise • Acceptance of new technology.

• Maintaining high performance over long term.

• Identifying need for products.

High level of interest • Cost.


High level of expertise Most likely used in new projects or triggered by

retrofits (2 responses).


“adequate” equipment

could be cost-effective

(1 response).

High level of interest Challenging to be cost-effective (1 response).


High level of expertise Niche market (2 responses). Transition to industry best

practice at majority of

plants (1 response).

High level of interest Niche market (1 responses)


High level of expertise and interest No scale or niche limitations (all responses).

2-42

Respondents: 5





High level of expertise 1-3 years (1 response).



High level of interest More than 10 years (1 response). More than 10 years

(1 response).








High level of expertise More than 50% reduction (2 responses). 10% reduction or less

(1 response).

High level of interest 10-25% reduction (1 response).


High level of expertise • > 15 L H2/L anode-day .

• > 20 A/m2 > 50% energy efficiency.

• > 70% cathode potential efficiency.

• > 80% anode coulombic efficiency.


2.4.4 Supercritical/Subcritical Water Oxidation for Sludge Treatment and Energy

As temperature and pressure increase, water approaches what is known as the “critical

point” (≥374.2°C and 22.1 megapascals [MPa]), above which water becomes “supercritical.”

Supercritical water can be used as a solvation media for rapid gasification and destruction of raw

or digested sludge, without pre-thickening or dewatering. Pure oxygen is fed to the reactor for

oxidation and COD is converted to CO2 within one minute. The effluent is a slurry of inorganic

ash in a water phase. Heat energy can be recovered directly by heat exchange in the reactor, or

from effluent leaving the reactor (Kalogo, 2008).

Table 2-17 summarizes the survey findings regarding supercritical/subcritical water

oxidation for sludge treatment and energy.

Table 2-17. Supercritical/Subcritical Water Oxidation for Sludge Treatment.

Respondents: 3





High level of expertise System incorporated in commercial design: pre-commercial demonstration

(1 response).

System proven and ready for full commercial deployment (1 response).

High level of interest Laboratory testing/validation of alpha prototype (1 responses).


High level of expertise Full-scale demonstration and validation of performance and costs.

High level of interest Pilot-scale demonstration.


High level of interest • Reluctance to adopt an unfamiliar technology.

• Fear of change.

• Initial capital cost.


High level of expertise Retrofits of existing “adequate” equipment could be cost-effective (1 response).



High level of expertise and interest

Niche market (2 responses).

Potential for almost universal acceptance (1 response).


High level of expertise and interest 10 mgd (1 response).

No scale or niche limitations (1 response).


High level of expertise and interest 1 year (2 responses).




High level of expertise 1 year (1 response).



2-44

Respondents: 3





High level of expertise and interest 10% reduction or less (1 response).

More than 50% reduction (2 responses).


High level of expertise • Demonstrated reliable operation at full-scale.

• Efficiency reasonably consistent with predictions.

Comment: “If this works, it might be the most transformative technology for

solids processing our industry has.”


2.4.5 Integration of Algal Treatment for BNR with Algal Energy Production

As an alternative or adjunct to current BNR strategies, the nutrients contained within

wastewater may be removed via the growth of aquatic plants such as algae, microalgae, and

duckweed. Because various algae have evolved to uptake nutrients from water bodies with low

nutrient concentrations, they have the potential to polish effluent nutrient concentrations to very

low levels.

As one survey respondent noted, algae is the only approach to nutrient management that

has the potential to achieve energy-positive nutrient recovery. Algae also have the potential to

meet more stringent effluent nutrient limits than chemotrophic bacterial systems (e.g., enhanced

biological phosphorus removal [EBPR], nitrification/denitrification) can.

Mixed algae and bacterial cultures can be used to reduce reliance on sunlight, because a

portion of the culture can use COD for energy.

A key aspect of the viability of this technology is realizing value from the algae.

Workshop participants noted various views of how value could be obtained from future algae

processes:

High-value products. Algae can be used as a feedstock for production of high-value products

such as fish food or nutricuticals (nutrients, dietary supplements), improving the financial

viability algae processes relative to fuel production via algae lipids.

Increased carbon for energy production. Compared to conventional aerobic processes, algae

processes do not “lose” carbon to biological respiration (CO2). Furthermore, algae processes

harvest solar energy used in photosynthesis, growing additional algal mass. The net result is a

significant increase in the amount of organic material available for downstream energy

production (e.g., biofuel production, methane generation through anaerobic digestion).

Carbon credits. Because algae treatment has the potential to significantly reduce aeration

energy inputs and increase energy production, it could have potential future value for its

carbon-reducing attributes.

Table 2-18 summarizes survey and workshop findings regarding current areas of algae

research.

Table 2-18. Integration of Algal Treatment and Harvesting.

Respondents: 7




Responses

What types of new methods for optimizing algal treatment are you tracking?

High level of expertise • Artificial light, natural light, light collectors (e.g., top of digesters).

• Research on oxygenic biogranules that are a mixture of microalgae

and bacteria growing in granules.

• Lab systems for nutrient removal.

• Mixotrophic algal cultivation.

• Clearas Water Recovery (packaged/modular system to recover

nutrients).

• Removing N and P from secondary effluent and sidestreams.

• Treating primary influent.

High level of interest • Biofilm high-rate photobioreactors.

2-46

Respondents: 7



• High level of interest: 1 Responses

How are these new methods superior to existing systems?

High level of expertise • Allows for aeration-free wastewater treatment and nutrient

removal.

• Conserves 100% of chemical energy in wastewater in the form of

biofeedstock (harvested algae or biogranules). Produces large

amounts of biomass, but has potential for biofuel production via

downstream energy production processes (methane production via

anaerobic digestion, oil production via HTL, bioethanol production,

biodiesel production, etc.). Alternatively, algae are a very good and

widely used soil amendment.

• For biogranule approach: the biomass separates well from water

(10-minute settling), allowing high flow-through wastewater

treatment, such as hydraulic retention time (HRT) < 0.5 day.

• For mixotrophic cultivation: In contrast to photoautotrophic strains,

mixotrophic strains offer BOD, N, and P removal in one step.

• For Clearas: Vendor claims that algae oxygenates water,

potentially reducing need for aeration if recycled to secondaries or

re-aeration before discharge to water body.

High level of interest • For biofilm high-rate photobioreactors: Smaller footprint. Not as

weather-dependent.

What are the current technical challenges with these new methods?

High level of expertise • Land area, especially for large facilities: may be best suited for

rural sites. Biomass growth rates, long detention time.

• Efficient recovery (harvesting) of algae. Need cost-effective DAF or

membrane separation of algae, or gravity settling process

improvements such as bioflocculation or granules.

• Control of biomass types (speciation) and quantity in reactors.

• Finding uses of algae after separation (e.g., digestion of algae).

• Making life-cycle costs competitive with conventional alternatives.

This analysis could also look at the cost per pound of carbon

harvested relative to other C reduction approaches.

• For oxygenic biogranules: finding and controlling optimum size of

granules, which will allow maintenance of effective treatment and

energy: solids separation, production of high-quality effluent,

production of biofuels.

• Growing algae 24x7.

• Growing algae in cold climates, or variety of wastewaters.

Potential development of phototrophic bacteria as a competing

process.

Comment: We simply do not have enough of an understanding to

design such systems today and know that they will work.

High level of interest The technical challenges identified included:

• Nutrients occur in too small of concentrations to make process

economical at large scale.


Respondents: 7



• High level of interest: 1 Responses

Are you aware of any pilot or new installations of these new methods?

High level of expertise or interest Ongoing research and pilot projects were identified in the survey and

workshop as follows:

• Europe, Australia (Melbourne).

• Pending at Chicago (MWRDGC).

• First oxygenic biogranules pilot at Amherst WRRF, summer 2015.

The pilot will run through winter in Massachusetts; increasing the

SRT of the granule process is expected to help overcome

challenges associated with reduced sunlight and low water

temperature during winter. Granules are half bacteria and half

algae.

• Upper Blackstone Water Pollution Abatement District (Worcester,

MA) large-scale pilot (Clearas). This system uses specialized LEDs

for nighttime illumination, at reduced costs because of off-peak

power rates.

• There are “Algaewheel” systems (an attached growth systems) at

various small installations (e.g., Hamilton, VA), and the Iowa State

attached growth system may be tested at Metropolitan Water

Reclamation District of Greater Chicago.

• NYC DEP pilot-tested an algal turf racetrack system for centrate

treatment, but found that it was not suitable for bulk N removal.

• New Mexico State University is testing a closed algae reactor using

algae culture gathered from hot spring environments treating

primary effluent. The specialized algae culture withstands warm

environments in a closed reactor and the closed reactor improves

process stability by maintaining consistent cultures.

• Cal Poly is conducting research at the San Luis Obispo Water

Reclamation Facility, including biofuel production. This project is

operating a 7-acre algal raceway facility with drying beds, with a

focus on increasing algae production.

2-48

2.4.6 Thermally Regenerative Ammonia-Based Batteries

Low-grade waste heat is an artifact of many energy-generating methods, including CHP

heat recovery, which sometimes generates more heat than the wastewater plant and digestion

system can use. Thermally regenerated ammonia-based batteries (TRABs) are being developed

as a means to utilize low-grade waste heat for power production.

TRABs consist of copper electrodes with ammonia added only to the anolyte – the

electrolyte surrounding the anode. This type of battery would be useless as a constant source of

electricity if the reaction were not regenerative. Using low-grade waste heat from an outside

source, the researchers distill ammonia from the effluent left in the battery anolyte and then

recharge it into the original cathode chamber of the battery.

In preliminary research, a power density of about 60 watts per square meter was

produced over multiple cycles, which is six to 10 times higher than the power density produced

by other liquid-based thermal-electric energy conversion systems (Logan, Messer, 2014).

Table 2-19 summarizes the TRAB survey responses from the one survey respondent with

expertise in this area.

Table 2-19. Thermally Regenerative Ammonia-Based Batteries.

Respondents: 1

Very high level of expertise: 1 Response


High level of expertise Basic research: basic principles are observed (1 response).


High level of expertise Understanding how to optimize the chemistry.


High level of expertise None listed.


High level of expertise Most likely to be used in new projects and retrofits triggered by “end of useful life”

situations (making adoption slower) (1 response).


High level of expertise Transition to best practice at majority of plants (1 response).


High level of expertise No scale or niche limitations (1 response).



Following technical maturity and proof of concept, how long will commercialization or adoption take

(e.g., at least two North American installations)?



2.5 Other Technologies

Several workshop participants strongly recommended that membrane biofilm reactors

(MBfRs) or membrane aerated biofilm reactors (MABR) be included as an important technology

with significant potential to reduce energy use. MBfRs use pressurized membranes to supply a

gaseous substrate to a biofilm formed on the membrane’s exterior. MBfRs are suited for various

treatment applications, including the removal of C and N when oxygen is supplied. Alternatively,

other gases can be diffused to serve as electron donors and acceptors in anaerobic and other

treatment configurations. Membrane diffusion greatly increases gas transfer efficiency, reducing

the energy needed for aeration or other gas transfer requirements.

In addition, survey respondents were asked to name other approaches that should be

considered to reduce energy use in the wastewater industry. Survey responses are noted below

for consideration in subsequent efforts.

Sewer heat recovery, non-chemical energy-heat recovery.

Pressure-retarded osmosis (osmotic power).

Anaerobic nutrient removal.

Advanced sensors for aeration control.

Non-chemical energy: micro-hydro.

Enhanced primary treatment.

“Recyllose”: fiber removal technology to reduce total suspended solids (TSS) in the aeration

basin reducing aeration need.

Bioaugmentation.


CHAPTER 3.0

TECHNOLOGY COMPARISONS AND PRIORITIZATION

This chapter presents an organized comparison of the technologies presented in Chapter

2.0 based on technology maturity, expected deployment timeline, magnitude of energy impact,

and expected applicability to existing North American wastewater treatment infrastructure.

3.1 Technology Readiness Level

The estimated TRL statuses of the reviewed technologies are summarized in Table 3-1.

As noted at the bottom of Table 3-1, some survey questions were related to new approaches to

existing technologies, but these technologies were not assessed for TRL.

Table 3-1. Approximate Technology Readiness Levels.

Technology Readiness

Level TRL

Description Description

1-3

Basic or applied research

Critical function

Thermally regenerated ammonia batteries (TRABs).



4-6 Lab testing

Prototype





Mainstream shortcut nitrogen.

7-9 Pilot system

Commercial design

Deployment





Existing

technologies

or scientific

areas: new

approaches

Modifications to deployed

technologies

Fundamental understanding of anaerobic communities.

Biogas cleanup.

Pretreatment processes for anaerobic digestion.

Enhanced methane from anaerobic digestion (other than co-digestion and

pretreatment).

Food waste co-digestion.

3-2

As noted in Chapter 1.0, previous WERF technology assessments have used a quadrant

graphic to group technologies. A similar graphical approach to prioritizing various technologies

based on input from the technical panel is shown in Figure 3-1. This figure compares the

research needs (based on TRL) to the deployment timelines projected by the survey respondents.

The deployment timeline is the sum of the estimated time required to overcome technical

challenges and the time required for commercialization. This composite timeline ranged from

approximately five years to 20 years. Technologies in the lower left quadrant appear most likely

to be adopted in the near term because these technologies are close to maturing and the

deployment timeline is estimated to be relatively short.

Figure 3-1. Technology Prioritization Based on TRL and Deployment Timeline.


3.2 Impact vs. Technology Readiness Level

The TRL was also compared to a composite gauge of industry “impact.” The impact was

approximated as the product of the applicability, scale niche, and energy reduction ratings. This

metric is not a precise effort to estimate total savings (sector-wide kilowatt-hours [kWh] per

year), but reflects an approximate method for suggesting the overall potential for electrical

reductions.

Figure 3-2 depicts the relative positions of the technologies based on these criteria. This

analysis implies that the two technologies in the upper right corner will have the greatest impact

on energy use in the wastewater sector in the near term.

Figure 3-2. Technology Prioritization Based on Technology Readiness Level vs. Approximate Sector Energy “Impact”.

3-4

3.3 Economic and Energy Benefits

Survey respondents were asked to gauge the economic viability of the technologies based

on the energy savings relative to the cost of retrofits. Table 3-2 summarizes these results. While

these findings are based on divergent opinions and high-level estimates of future capital

expenditures (CAPEX) and operating expenditures (OPEX) scenarios, it provides some insight

regarding the likely relative magnitude of economic hurdles. Technologies that are used in new

projects or “end of useful life” retrofits would be expected to have a longer deployment timeline

because wastewater assets are fairly long-lived and new projects are infrequently initiated.

Table 3-2. Approximate Level of Economic Benefit.

Economic Benefit Description

Retrofits of existing equipment are likely to

be cost-effective.

Mainstream shortcut nitrogen.

Most likely to be used in new projects and

retrofits triggered by “end of useful life.”









Thermally regenerated ammonia batteries.

Somewhat challenging to make this

technology economically beneficial.




Similar to the economic benefit level, survey respondents were asked to estimate the

energy savings benefit relative to total plant energy consumption (not relative to current common

comparable processes). The results in Table 3-3 provide approximate relative rankings of these

technologies based on their perceived prospective energy savings. However, workshop

discussions clearly indicated that energy savings for individual technical approaches cannot be

accurately estimated without considering nutrient removal requirements and impacts on other

WRRF operations (e.g., upstream C diversion with mainstream deammonification).

Table 3-3. Approximate Level of Energy Benefit.

Economic Benefit Description

10% reduction or less. N2O production to supercharge engines.

10-25% reduction. Thermally regenerated ammonia batteries.






Enhanced methane production from anaerobic digestion.

25-50% reduction. Mainstream shortcut nitrogen.



More than 50% reduction. Membrane production of hydrogen from wastewater.



CHAPTER 4.0

DEPLOYMENT OF RESEARCH FUNDING

More and more often, elected leadership and utility managers have adopted aggressive

energy- or GHG-reduction goals. While some improvements can be made by upgrades to

existing equipment, processes, and control, achieving net-zero status for many WRRFs will

require more than efficiency improvements and digester-gas-fueled CHP. For many,

transformative advances will be needed to create the necessarily dramatic reductions in power

consumption.

In juxtaposition to these goals is an apparently small investment in ongoing research to

assist in achieving these goals. WEF has recently conducted a study of research funding in the

wastewater industry. This investigation included a survey of some of the largest, most proactive

research utilities. The survey estimated how many full-time research staff (0.2-1.9%) these

utilities employ and how much of the operating budgets (0.3-2.2%) are spent on research; these

relatively low percentages are for the most proactive research utilities and suggest industry-wide

investments that are on the order of 1/10 or 1/20 of these rates. More research funding would

provide improved understanding that would identify and accelerate adoption/implementation of

new tools that might actually enable energy-reduction goals to be achieved on time, if not on an

even earlier timeline.

4.1 Discussion Framework

During this technology maturity investigation, the research team posed a question

focused on how to employ the funds. This question was not intended to rank technological

options for this investment.

“If our industry had an extra $50 million for research on energy efficiency and/or

process improvements to achieve net-zero energy, how do you think it could best be

deployed?” Specifically, the discussion addressed the following topic areas:

Size, type, number, and leveraging of grants.

What is the appropriate size for grants under this research?

Targeted team organization.

What kinds of teams would be best suited to implement this research?

Selection/award criteria.

What should the selection criteria be for award?

4-2

4.2 Visualizing Research Objectives

In order to frame the discussion of research deployment, discussion participants offered

comments related to appropriate goals for a scaled-up future research program. These goals

included:

Initiatives that target reduction in capital costs for new technology alternatives.

Award processes that appropriately define and quantify the value of projects, including

factors of potential supply and demand for technologies under consideration.

Funding targeted largely to transformative approaches.

Support for all TRL levels, from basic research all the way to commercialization, structured

to avoid the “valley of death” in which technologies are proved technically but fail in their

commercial launch.

Projects that include at minimum academic researchers and utilities; utility involvement

ground-truths the academic work and academic team members are involved early and

throughout the project duration.

Developing relationships that make it “easier to play.”

4.3 Current Research Initiative Examples

Current research programs were also cited as benchmarks for future funding structures.

Potential increased future funding would not necessarily be limited to the programs listed below,

but they do illustrate potential programs that could be expanded, leveraged via collaborations, or

modified to accelerate research progress.

4.3.1 WEF and WERF

WEF and WERF are cosponsoring the Leaders Innovation Forum for Technology (LIFT)

program. The main components of LIFT are:

Technology evaluations: Stakeholders share the cost of conducting demonstrations to

accelerate adoption of new technologies.

People and policy: Benchmarking how individual utilities accomplish R&D and

identification of resources and policies needed to implement effective R&D (WEF Lead).

Communication: Training, education, and outreach.

Informal forum for R&D: Managers and individuals responsible for technology identification

and deployment share experiences, activities, and interests .

Workshop participants believed there was potential to expand the LIFT model to drive

large research projects, including taking technology from development to implementation.

4.3.2 Department of Energy

DOE is supporting wastewater research through the following programs:

DOE’s funding structure provides initial SBIR grants in the range of $100,000 to $150,000

for small businesses to develop new technology concepts.


DOE’s Advanced Research Projects Agency-Energy (ARPA-E) program provides grants on

the order of $3 million to $5 million for high-potential energy technologies that are too early

for private-sector investments.

4.3.3 National Science Foundation

NSF is supporting wastewater research through several current and upcoming programs:

The ReNUWIt Engineering Research Center (ERC) was launched in 2011. It is a 10-year

program with a total program budget of $40 million, focused on “Urban Water Reinvention”

and is a collaboration between academic organizations (New Mexico State University,

Colorado School of Mines, Stanford University, and UC Berkeley) and partner companies

and utilities. A goal of the program is to ensure support for a stream of basic research all the

way through to implementation. Future ERCs are contemplated in the food/energy/water

nexus sector.

Sustainable Research Centers are funded at $12 million over five years and support

research at 10 to 15 universities. The goal is that after five years, the research must transition

to being self-funded.

The Research Coordination Network is funded at $500,000 to $700,000 for three years.

The network’s goal is to allow principal investigators (mostly academic) to talk with one

another.

The Water Sustainability and Climate Program is funded at $25 million. This program

does not fund basic research, but rather focuses on data mining, behavioral research, and

integrating models.

An upcoming partnership between NSF and WERF will use WERF’s model of utility

collaboration to deploy NSF funding, potentially in conjunction with the LIFT program. A

similar partnership to advance energy efficiency in wastewater treatment is planned with the

Electrical Power Research Institute (EPRI).

Technical Area Workshops. NSF can provide up to $50,000 to fund workshops for a

specific topic area. For example, a workshop was proposed on identifying research needs and

gaps related to increased use of pyrolysis and gasification.

The Innovations at the Nexus of Food, Energy, and Water Systems (INFEWS) program

recently authorized $75 million for 2016 funding to support integrated experimental research,

advance knowledge/technologies, and build the future sector workforce.

4.3.4 U.S. Environment Protection Agency

The U.S. EPA is supporting research through its National Nutrients Center initiative as follows:

EPA's Office of Research and Development's Science to Achieve Results (STAR) grant

program is funding grants for several national research centers including multi-million dollar

grants for water research on National Priorities Related to a Systems View of Nutrient

Management. This includes a current multi-year STAR grant to WERF (one of four centers)

that covers projects in several areas including mainstream deammonification, low input

ammonia stripping, and urine separation.

4-4

4.3.5 International Example

Singapore was noted as an example of a leader in water research that integrated industry

and research partners and made huge advances through government investment in research and

demonstration.

4.3.6 Wastewater Utilities

To facilitate the necessary research, relationships among research institutions, industry

practitioners, and utilities need to be fostered. Examples identified included:

The City of New York fosters research through partnering with universities within the city to

answer technical challenges presented by any city agency. By matching city needs with

specific research institutions, strong working relationships have developed and long-term

research objectives are being met.

King County, Washington, developed a fellowship program with the University of

Washington to conduct needed research. The program has been in existence for 15 years.

4.4 Ideas to Maximize Effectiveness of Research Funding Deployment

Ideas for maximizing the effectiveness of research funding reflected the diverse

perspectives of the workshop participants, including academic researchers, wastewater-utility

based researchers, WERF, WEF, EPA, DOE, and NSF. The following sections summarize the

major points raised in the discussion.

4.4.1 Collaborations

Various structures and approaches were proposed to foster collaboration between

research entities and other relevant partners.

Test bed facilities were proposed to reduce the barriers for pilot testing by providing a

shared, cost-effective venue to try out new technologies and approaches. The test-bed would

be configured to minimize the risk of process disruption by discharging to a plant influent

for further treatment. The test bed facility could serve as a nucleus for a more

comprehensive research center.

Research centers were envisioned to tackle individual multi-year projects.

Research centers could also provide third-party validation services. For example, vendors

might pay a subscription for ongoing access to the research center facilities and services, but

may also pay additional fees for specific testing.

Programs that connect new technology collaborations with wastewater utilities will be most

effective if they can be timed to address a specific utility need. In other words, utilities will

be most interested in demonstrating or piloting new technologies when they are evaluating

alternatives to meet a pending process objective such as replacing aging equipment,

increasing nutrient removal, or expanding plant capacity.

Collaborations with utilities were seen as most effective when they were long term, almost

permanent. The benefits of this long-term collaboration included more robust results and

continued refinement of understanding.


Participants noted that while collaborations that include in-kind support have a role in

research funding, leveraging may be less applicable to technologies that are lower on the

TRL scale.

4.4.2 Increasing Partnerships Between Research Institutions and Utilities

Participants advocated for increased partnering between research institutions with

utilities, with benefits including facilities, scale and availability, construction services, and

access to tradespeople (e.g., electrical, mechanical, etc.). However, current graduate student

program requirements can prevent research from being conducted at a utility. Many research

tools are available at universities to support utilities, but better access and funding mechanisms

need to be in place to foster their use.

4.4.3 Stimulating Research Activity

Workshop participants proposed various strategies to stimulate new research concepts

and motivate individuals who might not be well-connected to current funding sources:

Creating challenge prizes or grants to stimulate grass roots ideas and enthusiasm.

Forming an “army of new researchers.” For example, 20 postdoctoral researchers per year

could be trained as a cohort, networked to share ideas, and then deployed to various utilities

to work on site-specific research projects.

Increasing the use of “Dear colleague” letters to solicit the best ideas.

4.4.4 Grant Size

The size of grants was discussed and related to the level of technology development.

Participants noted that grants grow as the level of development increases and the stakes get

higher. For example, initial technology research could be supported by grants of $100,000 to

$200,000. As projects progress to demonstration level, grants on the order of $1 million to $5

million may be appropriate for high-potential energy technologies that are too early for private-

sector investments.

Other participants noted that the grant size factors into whether utilities are willing to

collaborate. For example, $200,000 might not be sufficient to get buy-in from the utility; the

grant size must be adequate to make it worth its while.

4.4.5 Grant Types

Various types of grants were proposed, either to expand existing approaches or to address

research needs that are not currently well funded.

Some participants proposed devoting half of the hypothetical $50 million to two centers

organized geographically around certain needs, with a five-year funding period. Beyond five

years, the centers would be funded through subscription payments from private entities.

Add-on grants were proposed to provide a pool of money for third-party oversight of

demonstration projects. Proponents stated that this auxiliary funding would make research

results more powerful and more widely accepted.

4-6

4.4.6 Team Organization

With regard to research team organization, one utility mentioned that the entity that

manages the money is an important factor of which projects they are able to participate in. For

example, they are allowed to collaborate in projects that are financially administered by a

university, but not other entities, in part because university overhead rates are relatively low.

4.5 Sample Framework to Maximize the Impact of Increased Research

Using the general concepts developed by the workshop participants and summarized

above, the authors of this report created a sample program structure based on a hypothetical $50

million increase in funding for technologies that support “Utilities of the Future” goals to recover

more resources and minimize negative environmental impacts. The dollar values indicated are

not exact targets, but rather conceptual illustrations of how additional funding could be allocated

via three primary channels.

4.5.1 WERF “Restocking” – $5 Million

In recent years, WERF has seen progressive erosion in funding levels. This funding

channel would support five to 10 more, $100,000-$200,000 WERF projects per year. In contrast

to other funding channels, this research would allow more diverse research to proceed on small-

scale, investigative projects. Currently, WERF receives between 100 and 140 proposals per year

under its unsolicited program and funds five or six projects. This very high rejection rate and the

associated level of interest suggests that additional funding could be used effectively to bolster

investment (and associated returns) using the conventional, smaller-scale, and largely “one-off”

research projects.

4.5.2 Centers of Excellence – $24 Million

The Centers of Excellence would likely be targeted at utility-led teams supported by

academics, consultants, and vendors. University-led teams could also propose and would likely

need similarly diverse teams. The proposed funding level would allow competition for six

~$4 million grants. This funding would be leveraged by a minimum 100% in-kind

cash/labor/materials contribution.

At this approximate level of funding, in combination with in-kind support, the Centers of

Excellence could either bring two or three study areas from concept to pilot-scale, or bring one

study area through pilot scale and then through full-scale demonstration. Alternatively, a portion

of the Centers of Excellence investment could be made in new or adapted test-bed facilities that

would serve multiple projects.

If a research grant-funded study area proves non-viable, the Center could petition for

adjusting or completely reassigning the grant to another study area, pending evaluation of

continued investment by a monitoring panel.

After these initial investments, these exploratory efforts should be financially self

sufficient through private capital.

4.5.3 Seed and Subsequent – $21 Million

Seed funding allows for a broader and more diverse set of proponents during the initial

phase, including smaller entities that have fewer resources to provide in-kind support. If outcome


of the seed-funded research is positive, utility or private-financing backing would be required to

advance through the second stage. Only the most promising technologies would advance.

The seed funding program could start with 12 $250,000 grants with little or no leveraging

required.

Two subsequent competitions for second-stage funding would be held:

1. The first competition would be held 1.5 years after the initial solicitation and would award

two grants of approximately $3 million (with a minimum of $1 million of

cash/labor/materials in-kind leveraging).

2. The second competitions would be held three years after outset and would award four more

$3 million grants with a similar $1 million leveraging requirement. Those who were not

granted awards in the first competition would still be eligible to compete in the second.

Assessment of Technology Advancements for Future Energy Reduction R-1

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Messer, A., Logan, B, Zhang, F., http://news.psu.edu/story/336898/2014/12/03/research/low-

grade-waste-heat-regenerates-ammonia-battery, December 2014.

Ries, Matthew P., Murthy, Sudhir, Water Utility R&D: Establishing Metrics to Justify the

Investment, The Utility Management Conference, Savannah, Georgia, February 25-28, 2014.

U.S. EPA, Emerging Technologies for Wastewater Treatment and In-Plant Wet Weather

Management, EPA 832-R-12-011, March 2013.

WERF, State of Science Report: Energy and Resource Recovery from Sludge, Water

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Constrained World, Water Environment Research Foundation, 2010.

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http://news.psu.edu/story/336898/2014/12/03/research/low-grade-waste-heat-regenerates-ammonia-battery

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