Emerging Issues in the Water/Wastewater Industry. Austin s Full-Scale Step-BNR Demonstration

Transcription

1 Summer Seminar Emerging Issues in the Water/Wastewater Industry Austin s Full-Scale Step-BNR Demonstration Rajendra P. Bhattarai, P.E., DEE Austin Water Utility, City of Austin 625 East 10 th Street, Suite 300 Austin, Texas Phone: , Fax: Raj.Bhattarai@austintexas.gov San Antonio, Texas July 24, 2015

2 Presentation Outline Background Step-Feed Biological Nutrient Removal (BNR) System Used Operating Characteristics Results Lessons Learned

3 Background Austin s wastewater treatment plants discharge to the Colorado River Waterbody of exceptional quality Nutrient removal required in future Need for demonstration of N & P removal Goal: TP < 1mg/L; TN < 10 mg/l Full-Scale Step-Feed BNR operated at South Austin Regional (SAR) WWTP for two years: January December 1997

4 Activated Sludge Influent Aerobic Effluent RAS WAS

5 Activated Sludge For 25% increase in treatment capacity 12.5 MGD MLSS = 3,750 mg/l 10 MGD MLSS = 3,000 mg/l High MLSS can overload secondary clarifier Influent Aerobic Effluent RAS WAS

6 Step-Feed Primary Effluent 40% 30% 20% 10% 4,900 MLSS 3,800 MLSS 3,300 MLSS 3,000 MLSS Final Clarifier Aerobic Average MLSS = 3,750 mg/l RAS WAS

7 Advantages of Step-Feed Operational Flexibility Higher MLSS results in higher capacity without increasing solids loading to secondary clarifiers Maximize use of existing facilities Better handling of peak flows Robust and stable operation

8 Virginia Initiative Plant (VIP) Process Anoxic Recycle, 1-2Q (ARCY) Nitrate Recycle, 1-2Q (NRCY) Q Q Anaerobic Anoxic Aerobic RAS WAS A staged reactor configuration is provided by using at least two complete-mix cells in series for each zone of the biological reactor.

9 Step-Feed Primary Effluent 40% 30% 20% 10% 4,900 MLSS 3,800 MLSS 3,300 MLSS 3,000 MLSS Final Clarifier Aerobic RAS WAS

10 BNR demonstration system at SAR used the Step-Feed BNR Process -- combination of VIP and Step-Feed PE ARCY PE ARCY ANR ANX AER ANR ANX AER AER RAS NRCY

11 SOUTH AUSTIN REGIONAL WASTEWATER TREATMENT PLANT LIFT STATIONS INFLUENT BAR SCREENS GRIT BASINS SCREENINGS AND GRIT TO LANDFILL PRIMARY CLARIFIERS PRIMARY SLUDGE FLOW EQUALIZATION DIVERSION BOX ACTIVATED SLUDGE AERATION BASINS SECONDARY CLARIFIERS RETURN ACTIVATED SLUDGE FILTER BACKWASH CHLORINATION EFFLUENT FILTERS TO GOLF COURSE IRRIGATION SUPERNATANT GRAVITY THICKENER SLUDGE BLENDING WASTE ACTIVATED SLUDGE REUSE PUMPS SLUDGE PUMPS TO HORNSBY BEND BIOSOLIDS MANAGEMENT PLANT DECHLORINATION EFFLUENT DISCHARGE TO THE COLORADO RIVER

12 Train B Train A Control BNR South Austin Regional Wastewater Treatment Plant

13 Activated Primary for VFA Generation Raw Wastewater Primary Effluent containing VFAs Return Primary Sludge (Elutriates Sludge) Waste Primary Sludge (To Thickening)

14 Original Aeration Basin Flow Path Effluent Channel RAS Channel Influent Channel (RAS and PE mix) Flow Diversion Box Primary Effluent

15 Aeration Basin Step-BNR Modified Flow Path Effluent Channel RAS (Alt) AER AER Pass 4 ANR ANR ANX ANX AER Pass 3 AER AER Pass 2 ANR ANR ANX ANX AER Pass 1 RAS Channel Indicates Internal Recycle ANX ANX ANR ANR AER ANX ANX ANR ANR AER Influent Channel Primary Effluent 48 Bypass Flow Diversion Box Normal Input of Secondary Influent

16 Baffles added to Existing Aeration Basins to form Anaerobic, Anoxic and Aerobic Zones Volume, million gallons Step- BNR Control Total Anaerobic Anoxic Aerobic

17 Baffles for Anaerobic, Anoxic and Aerobic Zones

18 Aeration Basin on the Control side Activated Sludge No persistent foam Only air bubbles

19 BNR Basins: Aerobic Zone in the foreground; Anoxic and Anaerobic Zones in the background. Comparatively more foam and scum than control

20 BNR Basins: Anaerobic Zone in the foreground; Anoxic and Aerobic Zones in the background

21 Close-up view of the Anaerobic Zone

22 Wastewater Temperature: 19 o - 30 o C o C Influent Temperature, Operating Periods: Mar 12-Apr 24-May 5-Jul 16-Aug 27-Sep 8-Nov 20-Dec 31-Jan 14-Mar 25-Apr 6-Jun 18-Jul 29-Aug 10-Oct 21-Nov 2-Jan

23 Test flows were 6 to 20 MGD 20 Primary Effluent Flow, MGD Mar CONTROL Operating Periods: BNR Apr 24-May 5-Jul 16-Aug 27-Sep 8-Nov 20-Dec 31-Jan 14-Mar 25-Apr 6-Jun 18-Jul 29-Aug 10-Oct 21-Nov 2-Jan

24 Flow and Temperature Defined Operating Periods Startup Period 1 Period 2 Period 3 Period 4 Period 5 Period 6 Period 7 Steady 8 MGD; ~22 o C Steady 8 MGD; ~27 o C MGD; ~27 o C (Construction Outage) 9-20 MGD; ~22 o C 12 MGD; ~28 o C Improved APC, Steady 6 MGD; ~22 o C Jan-96 Mar-96 Jun-96 Sep-96 Dec-96 Mar-97 Jun-97 Sep-97 Dec-97

25 Activated Primary Clarifier worked well at times Net TSCOD Produced, mg/l Mar 12-Apr 24-May 5-Jul 16-Aug 27-Sep 8-Nov 20-Dec 31-Jan 14-Mar 25-Apr 6-Jun 18-Jul 29-Aug 10-Oct 21-Nov 2-Jan

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27 MCRT lower than in Control 25 Aerobic MCRT, days CONTROL BNR Mar 12-Apr 24-May 5-Jul 16-Aug 27-Sep 8-Nov 20-Dec 31-Jan 14-Mar 25-Apr 6-Jun 18-Jul 29-Aug 10-Oct 21-Nov 2-Jan

28 SVI for BNR was higher 180 Sludge Volume Index (SVI), ml/g Mar 12-Apr BNR 24-May 5-Jul 16-Aug 27-Sep Control 8-Nov 20-Dec 31-Jan 14-Mar Excessive Foaming Apr 6-Jun 18-Jul 29-Aug 10-Oct 21-Nov 2-Jan

29 Excessive Foaming in BNR Basins due to Nocardia Growth and poor hydraulics

30 Both systems nitrified well Trend lines are seven day moving averages Effluent NH 3 -N, mg/l CONTROL BNR Mar 12-Apr 24-May 5-Jul 16-Aug 27-Sep 8-Nov 20-Dec 31-Jan 14-Mar 25-Apr 6-Jun 18-Jul 29-Aug 10-Oct 21-Nov 2-Jan

31 Nitrogen removal was good CONTROL Effluent NO 3 -N, mg/l BNR Mar 12-Apr 24-May 5-Jul 16-Aug 27-Sep 8-Nov 20-Dec 31-Jan 14-Mar 25-Apr 6-Jun 18-Jul 29-Aug 10-Oct 21-Nov 2-Jan

32 BNR Ortho-P Profile 3/13/96 to 4/8/96 12 PASS-1 PASS-2 PASS-3 PASS-4 Ortho-P, mg / L PRI1B ANR1W ANR1E ANX1E ANX1W AER1S ANR2W ANR2E ANX2E ANX2W AER2N ANR3W ANR3E ANX3E ANX3W AER3S AER4S ZONES

33 P removal was variable Effluent Ortho- P, mg/l CONTROL BNR Mar 12-Apr 24-May 5-Jul 16-Aug 27-Sep 8-Nov 20-Dec 31-Jan 14-Mar 25-Apr 6-Jun 18-Jul 29-Aug 10-Oct 21-Nov 2-Jan

34 Lessons Learned BNR systems not that different from other treatment systems But they do require some understanding and familiarity BNR systems need more operational attention than conventional activated sludge

35 Lessons Learned (continued) Volatile Fatty Acids crucial for BNR - especially for phosphorus removal VFA production depends on Activated Primary Clarifier operation BNR systems more prone to foaming than conventional activated sludge Foaming can be controlled using polymers, water sprays and chlorine

36 Lessons Learned (continued) Allow sufficient hydraulic head between different zones for easy removal of scum and foam Provide free-flow path at water surface through all zones to secondary clarifiers for scum removal Good hydraulics for flow split critical for Step-feed

37 Lessons Learned (continued) Nitrogen removal depends on F/M in anoxic zones Phosphorus removal depends on F/M in anaerobic zones (especially VFAs) Phosphorus removal is directly proportional to the amount of phosphorus released in the anaerobic zones

38 Questions, Comments?

39 Train B Train A Train C BNR Control South Austin Regional Wastewater Treatment Plant