Williamsburg Treatment Plant:

Nutrient Removal Upgrades

May 9, 2019

• Williamsburg Plant Background

• Recent Process Upgrades (2017 – present)

– Improve TN removal

– Decrease ferric sulfate required for TP removal

• Further Enhancements for SWIFT

Agenda

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Williamsburg Treatment Objectives

Annual Average Limit Concentration

(mg/L)

TN 14

TP 2

Concentration Based Limits

James River Bubble – WB Objectives

• TN < 4-8 mg/L

• TP < 0.7 mg/L

• As low as reasonably possible without

spending a lot of $$

Parameter Value

Daily Influent Flow 9 mgd (1 mgd

from brewery)

Influent COD Conc 815 mg/L

Influent TKN Conc 49 mg/L

Primary Effluent COD Conc 644 mg/L

Intermediate Clarifier

Effluent sCOD Conc 74 mg/L

Liquid Process Flow Pre-2011

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Liquid Process Flow - May 2011 to January 2017

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Aeration

tanks

converted to

MLE process

Liquid Process Flow – May 11 to January 2017 – MLE Configuration

Historical Data Review and Modeling

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Aeration

Effluent

Intermediate Clarifier

Effluent RAS

PE Flow

Diversion

Tank #1

Tank #4

Tank #3

Tank #2

Splitter

Box

Aerobic Anoxic Anoxic

Upgrade Evaluation Using Process Modeling

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Phased Upgrades

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Original MLE

Phase I: 5-Stage

Phase II: 5-Stage

• Installation of 3 baffle walls (yellow dashed lines)

• Adjusted NRCY discharge piping

• Addition of step feed of MLSS

• Moved mixer to 2nd anoxic zone

• Aeration grid modifications

Phase I: 5-Stage Upgrade

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January 2017 – August 2017

Phase I: 5-Stage Upgrade

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• Additional baffle wall for swing zone

• Addition of large bubble mixing in swing zone

• Aeration grid modifications

• NRCY intake modifications

• Actuators for DCS control

Phase II: 5-Stage Upgrade

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August 2017 - current

• Controlled by nitrate, phosphate, and ammonia sensors in aeration effluent

• Low DO • DO = 0.2 mg/L

• Anoxic • Not aerated

• Mixing by large bubble

• ABAC (Ammonia Based Aeration Control)

• DO = 0.2 to 2 mg/L

Swing Zone Aeration Control

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• Material costs = $4,000 (each) • Fiberglass

• 1/8” PVC roofing panels

• Stainless steel accessories

• Fabrication & Installation by HRSD maintenance staff

Baffle Wall Addition

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Construction Details – Swing Zone Mixing created by HRSD staff using low pressure air

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Sizes tested ranged from 0.25 cf to 7.0 cf

Construction Details – Development of Big Bubble Mixing System

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Plastic Cup Small Trashcan Bucket

Aluminum Box Larger Trashcan

Large Trashcan

PVC Fittings

Big Bubble Mixers in Action

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Minion

Phase I and II Upgrades Spent to Date – Operating Budget

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Phase Modifications per Treatment Train Total Cost

I

• Installation of 3 baffle walls

• Adjusted NRCY discharge piping

• Addition of step feed of MLSS

• Moved mixer to 2nd anoxic zone

• Aeration grid modifications

$78,000

II

• Additional baffle wall for swing zone

• Addition of large bubble mixing in swing zone

• Aeration grid modifications

• NRCY intake modifications

• Actuators for DCS control

$100,000

Total $178,000

Post-Upgrade Performance – Historical Effluent TN (Monthly Avg.)

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Post-Upgrade Performance – Effluent TN by Phase

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SWIFT Effluent Goals

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Anticipated Future Effluent Goals Concentration

(mg/L)

TIN < 5 (instantaneous)

TN < 4 (monthly avg)

TP < 1 (monthly avg)

2018 Williamsburg Averages

TN = 3.2 mg/L

TP = 0.6 mg/L

Post-Upgrade Performance – Effluent TIN for SWIFT Treatment Goals

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SWIFT

requires

< 5 mg/L TIN

• SWIFT upgrades can build on recent Phase I

and II process modifications

• Further upgrades in support of SWIFT to

enhance TN removal reliability and biological

P removal stability

– $450,000 - HRSD staff designed and constructed

SWIFT Upgrades – Phase 3

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• NRCY flow control based on nitrate sensors

• ABAC in cell 3 and cell 5 (reaeration in effluent channel)

• Better DO control and handling excess air

• BioP improvements in anaerobic zone

Phase 3

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• Capture a portion of influent solids and let settle in the first stage of the anaerobic zone

• Mix this zone every couple days

• Initial results look promising • ORP less than -200 mV

• TSS greater than 30,000 mg/L

Biological Phosphorus Removal Improvements

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• BNR upgrades greatly improved N removal • Phase I: Baffle walls, step feed, NRCY mods

• Phase II: Swing Zone, NRCY mods

• Bio P operation more stable • Anaerobic Zone, NRCY mods

• Design and construction effort completed in-house for only $178,000

• 2018 TN avg = 3.2 mg/L

Summary

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