williamsburg treatment plant: nutrient removal upgrades ......nutrient removal upgrades may 9, 2019...
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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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3
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
5
Liquid Process Flow - May 2011 to January 2017
6
Aeration
tanks
converted to
MLE process
Liquid Process Flow – May 11 to January 2017 – MLE Configuration
Historical Data Review and Modeling
7
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
8
Phased Upgrades
9
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
12
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
13
• Material costs = $4,000 (each) • Fiberglass
• 1/8” PVC roofing panels
• Stainless steel accessories
• Fabrication & Installation by HRSD maintenance staff
Baffle Wall Addition
14
Construction Details – Swing Zone Mixing created by HRSD staff using low pressure air
15
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
17
Minion
Phase I and II Upgrades Spent to Date – Operating Budget
18
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
22
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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