CONSTRUCTION OF AMMONIA REMOVAL UPGRADES FOR FIRST BROAD

CONSTRUCTION OF AMMONIA REMOVAL UPGRADES FOR FIRST BROAD RIVER WWTP David Hux, City of Shelby; Will Shull, Mary Knosby, and Christopher Crotwell, HDR 2015 NC AWWA WEA Annual Conference November 17, 2015, Raleigh © 2014 HDR, Inc. , all rights reserved.

Topics for Today’s Presentation 01 Overview of Existing Plant 02 Revised Ammonia Permit Limits 03 Ammonia Removal Upgrades Project 04 Construction Sequencing 05 Summary and Conclusions

01 Overview of Existing Plant

First Broad River WWTP § Permitted for 6 mgd o Current avg flows • 2. 75 mgd prior to new industry (20092012) • Approx. 3. 5 mgd with new industry § Originally constructed in 1960’s o § Trickling Filter Plant Upgraded in 1993 o Added polishing activated sludge aeration basins • Two 0. 75 MG aeration basins • Jet pod aeration system » Not sized for nitrification

First Broad River WWTP Process Flow Diagram Polishing Aeration Basin

02 Revised Ammonia Permit Limits

Revised Ammonia Permit Limit § 2010 Permit Renewal included revised ammonia permit limits o Summer Monthly average NH 3 -N • From 18. 5 mg/L to 4. 7 mg/L o Summer Weekly average NH 3 -N • From 35 mg/L to 14. 1 mg/L § Based on DWR’s current ammonia policy o § § 1 mg/L summer in-stream NH 3 -N Permit notes “EPA’s recent proposal have the potential to lower ammonia criteria further” 6 -year compliance schedule provided YAD 1391 A

Current Effluent NH 3 -N Performance § WWTP upgrades required to meet revised ammonia limit

NPDES Permit Limit Summary Parameter Weekly Average - Daily Max Flow (mgd) Monthly Average 6. 0 BOD 5 (mg/L) 25 37. 5 - TSS (mg/L) 30 45 - Ammonia-N (Summer) (mg/L) Ammonia-N (Winter) (mg/L) Fecal Coliform TRC (mg/L) 4. 7 14. 1 - 18. 5 35 - 200/100 m. L 400/100 m. L - - - 28 µg/L p. H Total Nickel - >6. 0 p. H < 9. 0 standard units 261 µg/L

03 Ammonia Removal Upgrades Project

Project Goals § 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

Biological Treatment Process Upgrades § § 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 Provide additional blower capacity Add baffles / mixers for pre-anoxic zone o § § For denitrification and alkalinity recovery

Construction of Aeration Basin 3 September 2015 October 2014 August 2014 March 2015

Construction of Aeration Basin 3 Replace Existing DIP Air Header with Stainless Steel Route Stainless Steel Air Header under Walkway

New MLE Process Anoxic / Internal Recycle Discharge / Mixers Aerobic (Fine Bubble) Internal Recycle Suction FLO W IR Zone 1, Cell A Zone 2 Zone 3 Zones 4 & 5

04 Construction Sequencing

Construction Sequencing § Maintenance of Plant Operation o o § Identity threats to operation Duration Coordination Contingency Plan Communication is vital to success

AB Splitter Box Phasing § How to install while continuing plant operation? PC 1 PC 2

AB Splitter Box Phasing § How to install while continuing plant operation? o o Put trickling filters back into service How is the plant going to react PC 1 TF 1 PC 2 TF 2

AB Splitter Box Phasing § How to install while continuing plant operation? o o Put trickling filters back into service How is the plant going to react PC 1 PC 2 ABS B

WAS Pump Station Conversion § Conversion o o o Self-priming centrifugal to non-clog submersible Selective demolition of structure Valve vault installation

WAS Pump Station Conversion § Phasing Challenges o o o § How can we waste? Temporary bypass? Conflicts with trickling filter Solution o o Pump to existing thickener with new pumps Similar heads and flow rates to existing system

Blower Upgrades § Positive displacement to Turblex variable diffuser o o § More control More efficient Replace ductile iron with stainless steel piping

Blower Upgrades § Phasing challenges o o § Existing room full of blowers Keep plant operational Phasing Solutions o o Route new piping overhead Short coordinated shutdown

Blower Upgrades § Startup challenges o o o § Lower flows (less I&I) One AB in operation during retrofit Trouble meeting low air demand Proposed Solutions o Waste to atm. via header blow-off valve • Incomplete blower function o Waste to atm. via AB 2 header • Noise pollution o Waste to AB 3 via AB 2 header • Introduce coarse Bubble but little effect on DO

Repair and Replacement 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, Cont’d 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

05 Summary and Conclusions

Summary and Conclusions § Ammonia upgrades provide future flexibility o o § Other upgrades will improve overall process reliability o o § Accounts for future industrial changes Positioned for potentially more stringent effluent NH 3 -N limit Better process control (ie, RAS / WAS pumping) Equalize side stream flows (filtrate EQ) Communication is vital to a projects success