© 2014 HDR, Inc., all rights reserved. David Hux, City of Shelby; Will Shull, Mary Knosby, and...

© 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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