20 Years of Nutrient Removal City of Beloit

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1 20 Years of Nutrient Removal City of Beloit Leon Downing, PhD, PE, & Bill Marten, PE, BCEE Donohue Harry Mathos & Nate Tillis City of Beloit IWEA Nutrient Removal and Recovery Workshop September 12, 2013

2 Agenda History of P Removal at Beloit Factors Affecting Performance Influent COD:P Nitrate Sidestreams The Future of P Removal at Beloit WQBEL limits/tertiary filter demonstration testing

3 Beloit, WI Nitrifying Activated Sludge Plant 11.2 mgd Design Flow, 4-5 mgd Average Daily Flow Started Up in 1992 Anoxic Selectors for Filament Control (MLE Configuration) Anaerobic Digestion Gravity Belt Thickening of WAS & Digested Sludge

4 BNR Configuration Influent Selector Aerobic To Disinfection Primary Sludge to Thickening RAS IMLR WAS to Thickening No RAS denitrification prior to PE addition

5 Beloit Achieves Bio-P Influent TP Final Effluent TP TP Removal 120% 100% Concentration (mg/l) % 60% 40% Percent Removal 5 20% %

6 ...Due to Its Strong Wastewater % % Concentration/Ratio Influent BOD:TP Ratio 80% 60% 40% Percent Removal 10 Final Effluent TP TP Removal 20% %

7 Strong Wastewater: Good BNR Plenty of carbon to go around BOD:P > 35:1 Influent Selector Aerobic To Disinfection Primary Sludge to Thickening RAS IMLR WAS to Thickening No RAS denitrification prior to PE addition Take Home Message 1: Wastewater characterization is critical!

8 Moving Towards Improved Bio-P Influent Selector Aerobic To Disinfection Primary Sludge to Thickening RAS IMLR Eliminate IMLR Decrease nitrate recycle to selector zone WAS to Thickening

9 Beloit: 10 Years After Startup Effluent TP Limit: 2 mg/l Monthly Average Daily Effluent TP (mg/l)

10 Until Daily Effluent TP (mg/l)

11 Once Again BOD:TP is the Issue Eff TP Inf BOD:TP Daily Effluent TP (mg/l) Inf BOD:TP Ratio

12 Addressing Influent BOD:TP Industrial inputs and variability Industry Had Changed Process, Leading to Increased P Loads Industry Modified Process to Control P Plant Back in Compliance Within 2-3 Days Sidestreams Contribute ~ 25-35% of P Load Jar Testing Shows Iron Salt Addition Effective at Controlling Sidestream Loads Installed Ferric Chloride Addition to GBT Filtrate

13 Sidestream P Control at Beloit Polymer Anaerobic Digester Gravity Belt Thickener GBT Thickened Sludge Ferric Chloride Addition Filtrate

14 A few years later Daily Effluent TP (mg/l) year average effluent TP: 0.6 mg/l Liquid stream: Bio-P Chemical sidestream management Next Step: 0.2 mg/l effluent TP /01/09 07/20/09 02/05/10 08/24/10 03/12/11 09/28/11 04/15/12 11/01/12

15 Nitrogen and Phosphorus SIDE NOTE July Spikes: chemical toilets?? Effluent Phosphorus Change in Ammonia Daily Effluent TP (mg/l) Daily Nitrate Produced (mg/l) /01/09 07/20/09 02/05/10 08/24/10 03/12/11 09/28/11 04/15/12 11/01/12 0

16 Existing: A/O Process Influent Selector Aerobic To Disinfection RAS Primary Sludge to Thickening WAS to Thickening No RAS denitrification prior to PE addition

17 Future: A 2 O Process Influent Selector Selector Aerobic To Disinfection Primary Sludge to Thickening RAS IMLR WAS to Thickening Reduced nitrate in RAS RAS denitrification

18 Nitrogen and Phosphorus Chemical requirements to meet 0.2 mg/l Activated sludge modifications $100,000 in annual savings A/O A2O Simulated Biological Sol. P Effluent 0.38 mg/l 0.09 mg/l Average annual chemical addition 50,000 gallons 9,000 gallons Annual chemical cost $125,000 $22,500 Take Home Message 2: Nitrogen is important for phosphorus

19 Low Level Phosphorus Testing Demonstration testing for low-level P Upcoming limit: 0.2 mg/l

20 Low Level Phosphorus Testing % % Effluent TP (mg/l) Effluent TP Percent Removal 60% 40% TP Removal (%) % 0 0% TP feed to filters: <1 mg/l TP feed to filters: 3 to 10 mg/l!

21 Phosphorus Removal: Online Control Take Home Message 3: Online control is an important consideration

22 20 Years of BNR at Beloit Optimization to 1 mg/l TP Limit (Bio-P) Wastewater characteristics Understand strength of wastewater Monitor BOD:P for changes Anaerobic digestion: sidestream P management Nitrification effects at Increased TN Loads and Lower Ammonia Limits Manage nitrate in RAS to improve Bio-P Optimization to Lower TP Limits (0.2 mg/l TP) Chemical Polishing Online control considerations Possible Filters

23 Questions? Leon Downing, Ph.D., PE Donohue & Associates (920)