Phosphorous Removal using Tertiary UF How Low Can You Go? and Other Design Considerations

Transcription

1 Phosphorous Removal using Tertiary UF How Low Can You Go? and Other Design Considerations BCWWA Conference 2016 Whistler, BC Samantha Kendrick, P. Eng

2 Presentation Outline Ultrafiltration for Phosphorus Removal Full Scale Examples Pilot Scale Data Design Considerations

3 Ultrafiltration Membranes Ultrafiltration is a size exclusion membrane process that rejects particles, colloids, and pathogens

4 Principles of Phosphorous Removal Physical Chemical Remove particulate P that is already within the influent suspended solids by primary settling or enhanced settling Convert soluble P to insoluble precipitants of metal phosphates, which is then removed using the solids separation process. Biological Convert soluble P to biocell mass and polyphosphate, which is then removed using the solids separation process.

5 P Removal + Membrane Filtration = Ideal Combination Step #1: Form Solids P always removed in a solids form Step #2: Reject Solids Membrane is a barrier to solids Chemical precipitates Biological bio-cells P-containing particulates Small pore size Physical barrier Consistent effluent quality

6 How does Tertiary UF compare to MBR? * With appropriate coagulant dosing ** After disinfection Typical MBR Effluent Quality Typical Tertiary UF Effluent Quality BOD 5 < 2 mg/l Not impacted TSS Non Detect < Non Detect NH 3 -N < 0.05 mg/l Not impacted TN < 3 mg/l Not impacted TP < 0.05 mg/l * < 0.05 mg/l * Turbidity < 0.1 NTU < 0.1 NTU Fecal Coliform 0 cfu/100 ml ** 0 cfu/100 ml ** SDI < 3 < 3

7 Top 3 Tertiary UF System Drivers 1. Effluent quality 2. Performance reliability 3. Compact footprint 4.8 MGD 17.2 MGD

8 Full Scale Facilities

9 Ashland WWTP, OR 4 MGD Commissioned May 2002 Treat secondary effluent Dual point precipitation Effluent TP target < 0.07 mg/l Direct discharge to sensitive receiving stream during 7 months per year

10 Ashland WWTP, OR Re-aeration Ultra Filtration

11 Effluent Total Phosphorous Average Effluent TP (mg/l) Effluent Total Phosphorus Concentration (mg/l) Ultrafiltration TP<0.07 mg/l Ultrafiltration TP<0.07 mg/l 0 Jan-03 Mar-03 May-03 Jul-03 Sep-03 Nov-03 Jan-04 Mar-04 May-04 Jul-04 Sep-04 Nov-04 Chemical addition and membrane filtration reliably achieved effluent TP < 0.05 mg/ L

12 Tertiary Plants with P Removal F. Wayne Hill, GA: 50 mgd, < 0.05 mg P/L Qinghe, China: 21 mgd, < 0.3 mg P/L Goldbar, AB: 4.4 mgd, < 1.0 mg P/L Ashland, OR: 4.0 mgd, < 0.07 mg P/L Keswick, ON: 4.8 mgd < 0.03 mg P/L

13 Pilot Studies for Ultra-Low Phosphorous

14 Pilot Process Flow Diagram Alum Screen Flash Mixer Flocculation Tank Ultrafiltration Membrane

15 ON Pilot: Influent & Effluent TP 1 Influent Total Phosphorous, mg P/L Effluent Phase I Alum dose: ~100 mg/l Phase II Alum: 80 mg/l Phase III Alum 135 mg/l Apr 23-Apr 28-Apr 3-May 8-May 13-May 18-May 23-May 28-May 2-Jun

16 ON Pilot: Effluent TP Concentrations Immediate Target = mg/l Total Phosphorous, mg P/L UtimateTarget = 0.01 mg/l Reportable Detection Limit = mg/l Apr 23-Apr 28-Apr 3-May 8-May 13-May 18-May 23-May 28-May 2-Jun Effluent Blank with distilled water

17 AB Pilot: Influent & Effluent TP

18 AB Pilot: Effect of Coagulant Dosing

19 Design Considerations

20 Which membrane should I use? Pressurized Immersed Immersed wit h Supported Fiber

21 TP Removal What Coagulant Dose is Required? Coagulant Dose (mg/l) Metal Precipitant (mg/l) Soluble P (mg/l) Actual Coagulant Dose mg/l Total Metal precip mg/l

22 Immersed or Pressurized Capex Price Adjustments Immersed Pressurized Concrete Tanks N/ A Bridge Crane N/ A Opex 20 Year Present Worth Cost Evaluation Membrane Replacement Immersed Variable Pressurized Power Lower higher Foot print Lower higher Chemicals Variable

23 Fouling Mechanisms in Tertiary Treatment Visible Foulants TSS Turbidity BOD Invisible Foulants Biopolymers Polysaccharides Macromolecular Proteins Proteins Polysaccharides Humics Cake Layer Blocking

24 Strategies for Reliable Operation Conservative flux selection Minimum Temperature Provision for multi-point coagulant addition Provision for flux reduction (spare space) Robust cleaning regime

25 Strategies for Optimizing Costs Consider blending options Quantify soluble fractions Understand seasonal variability Minimum temperature Maximum flow Maximum load

26 Conclusions Ultrafiltration is an ideal solution for low effluent TP applications P levels below 0.05 mg/l are consistently achieved, with coagulant dosing depending on soluble fraction present Optimum Tertiary UF design solutions take into account seasonal variability and include provisions for dealing with changes in water quality

27 Thank You!