Anaerobic Technology in Texas: History, Trends, and Outlook

Leonard E. Ripley, Ph.D., P.E., BCEE Senior Process Engineer

Texas Water 2011 – Gloyna Breakfast

April 8, 2011 – Fort Worth

• In Texas: Permian sea deposits

Back to the Beginning …

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 2

• Lagoons, septic tanks, Imhoff tanks

• High(er) rate anaerobic treatment:

– Covers to contain/recover biogas

– Heating to accelerate process

– Mixing

CHAPTER 1:

ANAEROBIC DIGESTION OF MUNICIPAL SLUDGE

Early Approaches to Covers

Dorr Digester: fixed cover suspended from a truss bridge, with mixing mechanism, and heating pipes mounted to wall.

Downes (“PFT”) Digester: variable sludge volume,

floating cover, heating coils mounted to wall.

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 4

A Texas Anaerobic Timeline

> > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >

1925 1930 1935 1940

Fort Worth: Riverside

WWTP - 1928

San Antonio: Rilling Road

WWTP - 1930

El Paso: Haskell

WWTP - 1935

Austin: Govalle

WWTP - 1937

Dallas: Central

WWTP - 1939

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 5

Fort Worth Riverside WWTP

• Original Imhoff plant: 1922

Dorr

PFT

• 5 Dorr digesters: 1928 & 1936

• 4 PFT digesters: 1945 & 1950

• Flow diverted to Village Creek WWTP: 1976

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 6

Riverside Dorr Digesters

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 7

Digester #3 --, overgrown, but roof still intact

< < Security detail

San Antonio Rilling Road WWTP

• Original plant: 1930

• Four Dorr digesters Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 8

Austin Govalle WWTP

• Plant constructed: 1937

• Four digesters (2+2) with concrete roofs

• Later converted to sludge holding tanks

• Decommissioned: 2006

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 9

• Very common treatment scheme across Texas:

Then, trickling filters …

• Built as recently as 1970 in Terrell; two rectangular digesters added in 1983

Primary

Anaerobic Digesters

Tr. Filter Tr. Filter Final

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 10

• Better mixing: gas lances, pumped recirculation

• External heat exchangers

Technology Developments: 1950s

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 11

Rehabilitate or convert?

Beaumont digesters: 1970 - 2001

Cleburne digester: 1960’s – 1987 converted 1994

Key factors:

• Expensive rehab cost

• 3-4₵/kW-hr power cost

• O&M simplicity

• Odor issues

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 12

Rehabilitate or convert?

San Angelo WWTP

• Digesters constructed: 1959

• Converted to aerobic: 1975

• New digesters built: 2003; old digesters converted to WAS & digested sludge tanks

• Significant odor reduction Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 13

Who’s Digesting Now?

0

50

100

150

200

250

300

Houston SanAntonio

Dallas Austin FortWorth

El Paso

PLA

NT

CA

PAC

ITIE

S (

MG

D)

TEXAS CITIES WITH POPULATION > 500,000

187

250

150 166

94

561 Red patterns: Anaer. digestion

Black patterns: other

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 14

• 39 plants: 0.378-200 MGD, no primaries

• 69th St plant handles ~half of system sludge: gravity thickeners, dewatering centrifuges, and natural gas-fired flash dryers

Houston Solids Management

Anaerobic Technologies in Texas – Leonard Ripley 4/08/11: Slide 15

Who’s Digesting Now?

0

10

20

30

40

50

60

70

80

Arlington Plano CorpusChristi

Lubbock Garland Irving

PLA

NT

CA

PAC

ITIE

S (

MG

D)

TEXAS CITIES WITH POPULATION > 200,000

NTMWD

42.7

64

TRA TRA

31.5

Red patterns: Anaer. digestion Black patterns: other

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 16

CHAPTER 2:

ANAEROBIC TREATMENT OF INDUSTRIAL WASTEWATERS

Anaerobic Technologies in Texas – Leonard Ripley 4/08/11: Slide 18

Baby Steps … Hormel Plant

• Meat packing plant in Austin, MN -- 1965

• Anaerobic contact process (suspended growth)

– Very “low” organic loading rate ≈ 1 kg COD/m3-d (62 lb/1000 ft3-day) … compare to activated sludge

– 97% BOD removal

Anaer. Reactor

Clarifier

Degas

RAnS≈2Q

• Anaerobic Filter

– McCarty & Young (Stanford)

– Random or oriented media

– First “prototype” system in 1970

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 19

Key Milestone: Retained Biomass

• Granular sludge reactors

– Lettinga, et al (Delft, Holland)

• Upflow Anaerobic Sludge Blanket

• Expanded Granular Sludge Bed

• Internal Circulation reactor

– Suitable for soluble wastes

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 20

Anaerobic Filters: A Texas First!

• Celanese Celrobics system (1970’s)

– Upflow reactor w/ plastic pall rings

– Biomass controlled by sparging N2 gas

– Patents based on pH/alkalinity control

• Vernon, TX (guar gum waste) – 1977

– COD loading = 10-12 kg/m3-day (624 lb/1000 ft3-d)

• Pampa, TX (organic acids) – 1981

– COD loading = 12-15 kg/m3-day (749 lb/1000 ft3-d)

• Bishop, TX (alcohols) – 1981

Major brewery in Fort Worth (1995) -- reduced organic load to city’s WWTP by 10%

Major brewery in Houston (1999), installed system for surcharge reduction

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 21

Granular Reactor: Paques IC

• Internal circulation reactor (upper/lower zones)

• Organic loading rate ≈ 30 kg COD/m3-day (1870 lb COD/1000 ft3-day)

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 22

Granular Reactor: Biothane EGSB

• Hereford (2006)

– Panda Ethanol

– 0.69 MGD flow

– 0.119 MG package plant

– 90% SCOD removal

• Schulenberg

– Confidential facility

Typical package plant (identical to Hereford’s)

• Huckabay Ridge – near Stephenville (2007)

• 8 thermophilic reactors, each 0.92 MG

• Feed: dairy manure + liquid wastes

• Product: pipeline quality gas

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 23

Microgy Energy: Bigger in Texas!

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 24

Beacon Energy Plant

• First choice for treatment: Microgy facility

• Designed “hybrid” reactor, with dissolved nitrogen flotation for flocculent biomass

• Started operation in 2008

• Biodiesel plant in Cleburne

• Residuals:

– Glycerin

– Organic acids

EQ

DNF

BIOREACTOR

CHAPTER 3:

ANAEROBIC PROJECT DRIVERS

• Energy reduction

– Aerobic digestion

– Solids reduction → less diesel fuel for hauling

• Improved dewaterability … polymer, fuel

• Energy production

– Electricity to offset aeration power demand

– Heat … can be used for sludge drying

• Odor reduction • Greenhouse gasses, carbon footprint, etc.

Anaerobic Drivers (in Texas)

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 26

• Capital costs … very equipment-intensive

• Management of high-strength return streams

• Effect on biological phosphorus removal

• Perception of odor issues

• Perception of process

instability/difficulty

Anaerobic Anti-Drivers

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 27

CHAPTER 4:

COMING SOON … TO A PLANT NEAR YOU?

• Egg-shaped digesters (ESD’s)

• First US installation: Terminal Island WRP (1985)

• Many plants in US, but none (yet) in Texas

Options for Improved Mixing - 1

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 29

< Terminal Island - by Long Beach, CA

Pinellas Co. – St. Petersburg, FL

Options for Improved Mixing - 2

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 30

LMM disks at Hornsby Bend

• Jet mixing – internal nozzles & external pump

• Linear Motion Mixers (LMM’s) - axial “plunger” in center of digester … low power requirement

• Internal combustion engines, gas turbines, microturbines – all need careful gas prep, but:

• Generate ≈30 kWe/MGD, waste heat →digesters

Co-Generation (Combined Heat Power)

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 31

Waco -- 3 ea: 500 kW IC engine/gen sets Dallas -- 4.2 MW IC engine/gen sets

Fort Worth -- 2 ea: 5 MW gas turbines

• Thørso, Denmark – built 1994 … thermophilic

• Treats WWTP sludge, fish wastes & pig manure

• Digested solids trucked back to farmers

Co-Digestion of Trucked Wastes

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 32

Receiving Bldg >>

<< Slurry Pit >>

Digesters

Biogas

Mech Bldg

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 33

Co-Digestion: Pinellas Co., Florida

• County adopted grease program – concentrated grease trucked to WWTP

• Biogas to pelletizer

Digester performance:

Biogas flow

∆ VSS

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 34

Co-Digestion: Waco

• Adding food processing wastes & FOG

• Increased biogas production by 25-30%

• Provides 50% of gas for sludge drying

Truck Unloading

Receiving Tank

Ron Sieger Biosolids

Award Winner

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 35

Co-Digestion: Fort Worth

• Constructing co-digestion receiving/feed system

– New linear-motion mixers in six digesters

– Additional biogas for steam generation/blowers

• Selected industries & plant scum

• Two reactors in series

– Acidification: HRT = 1-2 days

– Methanogenesis: HRT ≈ 10 days

• Increased VSS & pathogen destruction; less foaming

• DuPage County plant in 1988

Two-Phase Digestion (Acid/Gas)

• Texas plants evaluating acid/gas: – Dallas Southside

– Waco Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 36

Acidification Tank at 12 MGD Woodridge

Greene Valley plant in DuPage County, Illinois

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 37

Class A Pathogen Reduction

• Acid/Gas digestion may produce Class A pathogen quality, but only by Alt 3 (testing)

• EPA considering eliminating Alt 3

• Alternative 1, time/temp), can meet Class A but only with batch digestion … (Terminal Island) 0

5

10

15

20

25

30

130 135 140 145

Req

uir

ed C

on

tact

Tim

e (h

ou

rs)

Contact Temperature (°F)

REQUIRED TIME vs TEMP FOR ALTERNATIVE 1

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 38

Other Options, Technologies …

Thermal Hydrolysis

(Cambi)

???

Sonication

(Crown)

HAZWASTE Detox.

Anaerobic / Aerobic

Temperature Phased (TPAD)

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 40

MSW “Dry” Digestion: Electricity

• OWS plant in Brecht, BE

• “Green” waste @ 35% total solids, no dilution

• Influent blended ~1:8 w/ effluent recycle (25% TS)

• Steam injection to reach thermophilic range

• Fed with ram pump

• Generates ~400 kW, plus low-grade steam

• Fermentation of MSW biomass to organic acid salts (no methanogenesis)

• Conversion of acid salts to ketones & alcohols

• Conversion of alcohols to gasoline or jet fuel

• Bench, pilot, demo-scale

• Full-scale: 2013

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 41

MSW Fermentation to Fuel

Demonstration Plant outside Bryan

1. Anaerobic technologies evolving – many choices

2. Major drivers for anaerobic treatment in Texas:

– Avoided costs … electricity, diesel fuel, surcharges

– Energy production … electricity and heat

– Greenhouse gasses, carbon footprint

3. Obstacles:

– Capital costs

– Concentrated return streams

4. Opportunities for synergy with MSW streams

Anaerobic Technology in Texas – Leonard Ripley 4/08/11: Slide 42

Conclusions

Be ready for the unexpected!

Into the Future …

Questions, comments, additions?