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© 2014 HDR, Inc., all rights reserved.
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David Hux, City of Shelby; Will Shull, Mary Knosby, and Christopher Crotwell, HDR
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CONSTRUCTION OF AMMONIA REMOVAL UPGRADES FOR FIRST BROAD RIVER WWTP
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2015 NC AWWA WEA Annual ConferenceNovember 17, 2015, Raleigh
04 Construction Sequencing
05 Summary and Conclusions
01 Overview of Existing Plant
02 Revised Ammonia Permit Limits
03 Ammonia Removal Upgrades Project
Topics for Today’s Presentation
01
Overview of Existing Plant
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Permitted for 6 mgdo Current avg flows
• 2.75 mgd prior to new industry (2009-2012)• Approx. 3.5 mgd with new industry
Originally constructed in 1960’so Trickling Filter Plant
Upgraded in 1993o Added polishing activated sludge aeration
basins• Two 0.75 MG aeration basins• Jet pod aeration system
» Not sized for nitrification
First Broad River WWTP
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First Broad River WWTPProcess Flow Diagram
Polishing Aeration Basin
02
Revised Ammonia Permit Limits
2010 Permit Renewal included revised ammonia permit limitso Summer Monthly average NH3-N
• From 18.5 mg/L to 4.7 mg/Lo Summer Weekly average NH3-N
• From 35 mg/L to 14.1 mg/L Based on DWR’s current ammonia policy
o 1 mg/L summer in-stream NH3-N Permit notes “EPA’s recent proposal have
the potential to lower ammonia criteria further”
6-year compliance schedule provided
Revised Ammonia Permit Limit
YAD1391A
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WWTP upgrades required to meet revised ammonia limit
Current Effluent NH3-N Performance Picture or Color Block
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Parameter Monthly Average
Weekly Average
Daily Max
Flow (mgd) 6.0 - -
BOD5 (mg/L) 25 37.5 -
TSS (mg/L) 30 45 -
Ammonia-N (Summer)
(mg/L)
4.7 14.1 -
Ammonia-N (Winter)(mg/L)
18.5 35 -
Fecal Coliform
200/100 mL 400/100 mL -
TRC (mg/L) - - 28 µg/L
pH >6.0 pH < 9.0 standard units
Total Nickel 261 µg/L
NPDES Permit LimitSummary
03
Ammonia Removal Upgrades Project
Upgrade biological treatment process o Enhance nitrification to meet more stringent ammonia limits
Repair and replace several deficient treatment components Improve treatment reliability Accommodate flows up to the permitted capacity of 6.0 mgd. Meet project schedule requirements for Clean Water State Revolving Fund (CWSRF) program
Project Goals
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Convert existing process to conventional activated sludge system
Decommission trickling filters Add third 0.75 MG aeration basin Replace jet pods with fine bubble diffusers
o Provide additional blower capacity Add baffles / mixers for pre-anoxic zone
For denitrification and alkalinity recovery
Biological Treatment Process Upgrades
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August 2014
October 2014
March 2015
September 2015
Construction of Aeration Basin 3
Replace Existing DIP Air Header with Stainless Steel
Construction of Aeration Basin 3
Route Stainless Steel Air Header under Walkway
Zone 1, Cell A Zone 2 Zone 3 Zones 4 & 5
New MLE Process
FLOW
Anoxic / Internal Recycle Discharge / Mixers
Aerobic (Fine Bubble)
Aerobic(Fine Bubble)
Aerobic (Fine Bubble)Internal Recycle Suction
IR
04
Construction Sequencing
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Maintenance of Plant Operationo Identity threats to operationo Durationo Coordinationo Contingency Plan
Communication is vital to success
Construction Sequencing
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How to install while continuing plant operation?
AB Splitter Box Phasing
PC2
PC1
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How to install while continuing plant operation?o Put trickling filters back into serviceo How is the plant going to react
AB Splitter Box Phasing
PC2
PC1
TF2
TF1
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How to install while continuing plant operation?o Put trickling filters back into serviceo How is the plant going to react
AB Splitter Box Phasing
PC2
PC1
ABSB
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Conversiono Self-priming centrifugal to non-clog submersibleo Selective demolition of structureo Valve vault installation
WAS Pump Station Conversion
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Phasing Challengeso How can we waste?o Temporary bypass?o Conflicts with trickling filter
Solutiono Pump to existing thickener with new pumpso Similar heads and flow rates to existing system
WAS Pump Station Conversion
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Positive displacement to Turblex variable diffusero More control o More efficient
Replace ductile iron with stainless steel piping
Blower Upgrades
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Phasing challengeso Existing room full of blowerso Keep plant operational
Phasing Solutionso Route new piping overheado Short coordinated shutdown
Blower Upgrades
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Startup challengeso Lower flows (less I&I)o One AB in operation during retrofito Trouble meeting low air demand
Proposed Solutionso Waste to atm. via header blow-off valve
• Incomplete blower functiono Waste to atm. via AB2 header
• Noise pollutiono Waste to AB3 via AB2 header
• Introduce coarse Bubble but little effect on DO
Blower Upgrades
Replace Influent Screen Recondition Clarifiers No. 1 and 2 and replace
drive units, weirs, bridges and scrapers
Replace and upgrade RAS pumps
Rehab Primary Clarifiers
Repair and Replacement Upgrades
Install new 40-ft Gravity Thickener
Install new Thickened WAS Pump Station
Rehab 26-ft Gravity Thickeners and convert
to Belt Filter Press Filtrate EQ
Rehab Sludge Holding Tank
Repair and Replacement Upgrades, Cont’d
05
Summary and Conclusions
Ammonia upgrades provide future flexibilityo Accounts for future industrial changeso Positioned for potentially more stringent effluent NH3-N limit
Other upgrades will improve overall process reliabilityo Better process control (ie, RAS / WAS pumping)o Equalize side stream flows (filtrate EQ)
Communication is vital to a projects success
Summary and Conclusions
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© 2014 HDR, Inc., all rights reserved.
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Questions?
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