Re Thinking Enhanced Biological Phosphorus Removal

Transcription

1 Looking for a different photo? Click view slide show and click this link to access the Black & Veatch Digital Gallery. If you need to create an account, use code bvphotos09. Re Thinking Enhanced Biological Phosphorus Removal 13 July 28 James Barnard Patrick Dunlap

2 Bardenpho Pilot Plant m 3 /d The purpose of the dead zone was to allow relative adjustments to the other zones

3 Some early observations Pilot Plant Fermenter resulted from basin configuration and not deemed important Excellent phosphorus removal resulted Phosphorus profile shown in ellipses Performance could not be replicated in laboratory Barnard suggested organisms (PAO) should pass through anaerobic phase with low ORP which triggered EBPR Suggested Phoredox process by adding an anaerobic zone up front Barnard 100 m 3 /d pilot 1972

4 Concept of passing all PE through AN Zone Become standard with early designs These were followed by others such as UCT, JHB & Westbank

5 VFA from Fermenters First Acinetobacter and then Accumulibacter identified as PAO

6 Westbank Process Incorporated a Fermenter (While also allowing for Primary Effluent bypass around the Anaerobic Zone) (Knight & Piesold, 1984) X TN < 6 mg/l BOD < 5 mg/l TSS < 2 mg/l TP < 0.15 mg/l Mixing energy 0.15 hp/kcf

7 Westside Regional WWTP Primary Anaerob Anoxic 1 Anoxic 2 Anoxic 3 Aerobic 1 Aerobic 2 Aerobic Phosphorus mg/l Tetrasphaera like PAO can denitrify and uptake P under anoxic conditions Bioreactor Profile Phosphorus by Zone Primary Anaerob Anoxic 1 Anoxic 2 Anoxic 3 Aerobic 1 Aerobic 2 Aerobic 3 Note P uptake in Anoxic Zone

8 South Cary, NC 4Q Influent AX AER AX AER Effluent Bardenpho plant Ferment AN AX WAS RAS Fermentation Based on Lamb Patent (1994) to ferment some RAS to provide VFA for PAO Stroud, R and Martin, C. (20) South Carey Water Reclamation Facility s Nutrient Removal Modifications and Reduction Success, Town of Carey, NC, Proceedings of WEFTEC20

9 Charlotte NC (CNC) Process Primary Effluent VFA Fermenter Anoxic Aeration WAS Experiment at McDowell Creek Worked in summer but not well in winter Probable cause over mixing at 20 W/m3 (0.75 hp/kcf) 9

10 RAS Fermentation In mid 90s the RAS Fermentation process was developed Fraction of RAS, long fermenter HRT, no supplemental carbon Now >60 of these processes worldwide, mostly in Denmark Recent patent by Kruger comes out of this tradition Stokholm Bjerregaard (25)

11 1/ / / / / / / / Phosphorus (mg/l) Carousel Plant Henderson NV 60 ML/d Upgraded to BNR Switching off a mixer in the anaerobic zone resulted in In plant Fermentation Ortho-P for May ANA Eft SPS SCC Final Eft

12 Experiment at Metro Denver Item Total plant flow Total RAS flow RAS to Fermenter Total Ferm. volume HRT Anaerobic SRT GR. Th. Overflow ORP end of Fermenter RbCOD in GTO Mixing energy 100 mgd 104 mgd 24 mgd 1.36 mgd 1.25 h 1 day 5.4 mgd 230mV 320 mg/l 0.08 hp/kcf Cavanaugh, L., Carson, K., Lynch, C., Phillips, H., Barnard, J. and McQuarrie, J. (22) A Small Footprint Approach for Enhanced Biological Phosphorus Removal: Results from a 106 mgd Full Scale Demonstration. Proceedings of the 85 th Annual Water Environment Federation Technical Exhibition and Conference, New Orleans, LA, October 22.

13 Phosphorus Removal by RAS Fermentation Metro Denver NSEC Effluent TP NSEC Effluent TSS NSEC Effluent PO4 P /41 10/61 10/81 10/101 10/121 10/141 10/161 10/ /301 11/11 11/ /71 11/91 11/111 11/131 11/121 11/171 11/ /11 12/ mg P/L mg TSS/L Cavanaugh, L., Carson, K., Lynch, C., Phillips, H., Barnard, J. and McQuarrie, J. (22) A Small Footprint Approach for Enhanced Biological Phosphorus Removal: Results from a 106 mgd Full Scale Demonstration. Proceedings of the 85 th Annual Water Environment Federation Technical Exhibition and Conference, New Orleans, LA, October 22.

14 Why Conventional EBPR selected for Accumulibacter Accumulibacter species don t ferment need supply acetic & propionic acid? short anaerobic residence time relatively weak anaerobic conditions (ORP > 150 mv) due to nitrates in RAS and DO concentrations in primary effluent Many AN zones are over mixed: surface agitation and DO entrainment prevents deeper anaerobic conditions Standard mixing energy 20 W/m 3 (0.75 hp/kcf) When 2 W/m 3 (0.08 hp/kcf) is adequate (huge saving in energy) and does not entrain air Too much primary effluent low in VFA and high in DO going to AN zone, thus reducing AN SRT and raise ORP 14

15 Deeper Anaerobic Zones Select for Fermenting PAO s Advantages of PAOs like Tetrasphaera that can ferment : ferment glucose and amino acids and other higher carbon forms and store phosphorus produce VFA that allow a population of Accumulibacter to grow alongside them, and can denitrify and uptake P under anoxic conditions Completely independent of wastewater characteristics It would appear an ORP of less than < 250 mv is needed to select for Fermenting PAOs Longer AN SRT (1.5 to 2.0 days) for fermenting RAS or mixed liquor Can be achieved when passing primary effluent to anoxic zone Use PS fermentate when available to reduce required SRT Reduce dilution by limiting RAS to fermenter to between 10 and 20% Reduce mixing energy to less than 2 W/m3 (0.08 hp/kcf) for top entry mixers 15

16 Examples of S2EBPR Processes (As classified by WERF S2EBPR Project) 16

17 POSSIBLE EXPLANATION OF RAS FERMENTATION Hydrolysis RAS (10%) Gravity thickener overflow OHO Other heterotrophs FAC Facultative bacteria TSA Tetrasphaera ACC Accumulibacter OHO Hydrolysis RbCOD TSA FAC VFA ACC P 1.5 d to 2 d SRT for RAS only 8 to 12 h when feeding fermentate 17

18 And the latest Wakarusa KS On line April, 28 2 mgd no primaries Side stream mixed liquor fermentation Eventually Bardenpho EBPR kicked in May 20, 28 18

19 Conversion of McAlpine, Charlotte to S2EBPR Feed Gravity thickener overflow Splitter Box AN Keep one Pass as Anaerobic or Construct New Unit Reverse flow of one or two basins Possible Future Aeration Existing anaerobic zones RAS Existing aeration basins Pilot Demo Gravity Thickeners Convert to S2EBPR 10 to 20% of RAS Add GTE to Fermenter Increase RAS to anoxic zones FC Nitrate reduction may not be required 19

20 Take home Message Undisputable benefit of S2EBPR Independent of wastewater characteristics Easily retro fitted to existing plants PAOs need anaerobic conditions (< 250 mv ORP) Reduce mixing energy to avoid air entrainment Reliable removal to lower than 0.1 mg/l P Modeling catching up

21 QUESTIONS? 21