1. Phosphorus Removal at Sand Creek Water Reuse Facility by Duane “Bear” Steib and Kathy Bill/City of Aurora Steve Polson/CH2M HILL by Duane “Bear” Steib and Kathy Bill/City of Aurora Steve Polson/CH2M HILL presented at the 2006 Water Reuse Workshop Co-sponsored by RMSAWWA, RMWEA, and the Water Reuse Association Thursday, August 10th, 2006 Colorado School of Mines – Golden, Colorado presented at the 2006 Water Reuse Workshop Co-sponsored by RMSAWWA, RMWEA, and the Water Reuse Association Thursday, August 10th, 2006 Colorado School of Mines – Golden, Colorado

2. Purpose of Study Determine the advanced phosphorus removal capabilities of the Sand Creek Water Reuse Facility Determine the advanced phosphorus removal capabilities of the Sand Creek Water Reuse Facility

3. Treatment Facility Primary clarification Primary clarification Activated sludge Activated sludge Nutrient (N and P) removalNutrient (N and P) removal Filtration Filtration UV disinfection UV disinfection Ferric chloride addition (available) Ferric chloride addition (available) Polymer addition (available) Polymer addition (available) Primary clarification Primary clarification Activated sludge Activated sludge Nutrient (N and P) removalNutrient (N and P) removal Filtration Filtration UV disinfection UV disinfection Ferric chloride addition (available) Ferric chloride addition (available) Polymer addition (available) Polymer addition (available)

5. Primary Clarifiers

6. Anoxic Cell Anerobic Cell Anoxic Cell 3 Aerobic Cells Biological Nutrient Removal Basin 3650 diffusion heads3650 diffusion heads 3864 diffusers

7. Secondary Clarifiers

8. Secondary Effluent

9. Chemical Pumps & Storage

10. DynaSand Filters Backwash Waste Filtered Effluent Filtered Influent Upflow, Continuous Backwash Filter Filter Media (sand)

11. Trojan 3000 Ultraviolet System 864 Low Pressure Low Intensity Bulbs

12. Reuse Distribution Pumps

13. Design Criteria Plant capacity: 5.0 mgd Plant capacity: 5.0 mgd Secondary effluent TP: 0.5 - 1.0 mg/L Secondary effluent TP: 0.5 - 1.0 mg/L Tertiary effluent TP: 0.2 mg/L limit (anticipated) Tertiary effluent TP: 0.2 mg/L limit (anticipated) Discharge to Sand Creek: Discharge to Sand Creek: BOD 5 /TSS30 mg/L each (monthly)BOD 5 /TSS30 mg/L each (monthly) Fecal coliform2,000 mpn/100 mL (monthly)Fecal coliform2,000 mpn/100 mL (monthly) AmmoniaDriven by WET requirementsAmmoniaDriven by WET requirements Plant capacity: 5.0 mgd Plant capacity: 5.0 mgd Secondary effluent TP: 0.5 - 1.0 mg/L Secondary effluent TP: 0.5 - 1.0 mg/L Tertiary effluent TP: 0.2 mg/L limit (anticipated) Tertiary effluent TP: 0.2 mg/L limit (anticipated) Discharge to Sand Creek: Discharge to Sand Creek: BOD 5 /TSS30 mg/L each (monthly)BOD 5 /TSS30 mg/L each (monthly) Fecal coliform2,000 mpn/100 mL (monthly)Fecal coliform2,000 mpn/100 mL (monthly) AmmoniaDriven by WET requirementsAmmoniaDriven by WET requirements

14. Design Criteria (cont) Reuse quality: Reuse quality: BOD/TSS5 mg/L each (monthly)BOD/TSS5 mg/L each (monthly) Total coliform2.2 org/100 mL (7-day)Total coliform2.2 org/100 mL (7-day) Turbidity2 NTU (daily)Turbidity2 NTU (daily) Requirements are different now:Requirements are different now: E. coli 126 org/100 mL E. coli 126 org/100 mL Turbidity3.0 NTU Turbidity3.0 NTU Phosphorus not currently regulated Phosphorus not currently regulated Reuse quality: Reuse quality: BOD/TSS5 mg/L each (monthly)BOD/TSS5 mg/L each (monthly) Total coliform2.2 org/100 mL (7-day)Total coliform2.2 org/100 mL (7-day) Turbidity2 NTU (daily)Turbidity2 NTU (daily) Requirements are different now:Requirements are different now: E. coli 126 org/100 mL E. coli 126 org/100 mL Turbidity3.0 NTU Turbidity3.0 NTU Phosphorus not currently regulated Phosphorus not currently regulated

15. Why Mess With Near Perfection? Leading up to the study, the Sand Creek WRF consistently produced an effluent with a total phosphorus (TP) concentration of 0.10 – 0.20 mg/L. These low levels were achieved utilizing a very efficient biological nutrient removal process. Analysis in mg/L: Leading up to the study, the Sand Creek WRF consistently produced an effluent with a total phosphorus (TP) concentration of 0.10 – 0.20 mg/L. These low levels were achieved utilizing a very efficient biological nutrient removal process. Analysis in mg/L: 1.50 0.13 5.26 5.98 2004 1.71 0.24 4.93 5.76 2003 2.62 0.27 4.68 5.17 2002 Plant Effluent TSS Plant Effluent TSS Plant Effluent TP Plant Effluent TP Primary Effluent TP Plant Influent TP Year

16. Goal of Study -- Determine the Limits of Tertiary P-Removal at the Sand Creek WRF Design target: 0.10-0.12 mg/L (0.2 mg/L limit) Design target: 0.10-0.12 mg/L (0.2 mg/L limit) “Metal salt addition followed by effluent filtration has been used successfully to meet monthly average effluent discharge standards of approximately 0.20 mg P/L.” (Phosphorus and Nitrogen Removal from Municipal Wastewater -- Principles and Practice, Richard Sedlak, Editor, 1991) “Metal salt addition followed by effluent filtration has been used successfully to meet monthly average effluent discharge standards of approximately 0.20 mg P/L.” (Phosphorus and Nitrogen Removal from Municipal Wastewater -- Principles and Practice, Richard Sedlak, Editor, 1991) Study goal: 0.05 mg/L Study goal: 0.05 mg/L

17. BNR System Treats Nitrogen and Phosphorus RASRAS MLRMLR SESE DenitrificationDenitrification Carbon Oxidation NitrificationNitrification AnaerobicAnaerobicAerobicAerobicAnoxicAnoxic Phosphorus Uptake P-ReleaseP-Release WASWAS PEPE BNR Reactor Secondary Clarifier AnoxicAnoxic RASRAS DenitrificationDenitrification Johannesburg Process

18. Chemical-P Removal Alternatives Capability to add metal salts at several locations Capability to add metal salts at several locations Primary clarifier influentPrimary clarifier influent Secondary clarifier influentSecondary clarifier influent Secondary clarifier effluentSecondary clarifier effluent Multiple-point chemical addition – add at several locationsMultiple-point chemical addition – add at several locations Alum or ferric chloride can be usedAlum or ferric chloride can be used Ferric used to comply with Metro Denver request Ferric used to comply with Metro Denver request Capability to add metal salts at several locations Capability to add metal salts at several locations Primary clarifier influentPrimary clarifier influent Secondary clarifier influentSecondary clarifier influent Secondary clarifier effluentSecondary clarifier effluent Multiple-point chemical addition – add at several locationsMultiple-point chemical addition – add at several locations Alum or ferric chloride can be usedAlum or ferric chloride can be used Ferric used to comply with Metro Denver request Ferric used to comply with Metro Denver request

19. First Steps in the AWT Process are Chemical Addition and Flocculation Chemicals added at the rapid mix chamber Chemicals added at the rapid mix chamber Flocculation occurs in the filter influent flow distribution structure Flocculation occurs in the filter influent flow distribution structure Chemicals added at the rapid mix chamber Chemicals added at the rapid mix chamber Flocculation occurs in the filter influent flow distribution structure Flocculation occurs in the filter influent flow distribution structure

20. Filtration and Disinfection Follow... Next, the flocculated water flows through four DynaSand filters to remove the precipitate formed Next, the flocculated water flows through four DynaSand filters to remove the precipitate formed The filters are mono-media, deep bed, upflow, continuous backwash typeThe filters are mono-media, deep bed, upflow, continuous backwash type The sand size is 1 mm and the sand depth is 80”The sand size is 1 mm and the sand depth is 80” The filtration rate is 3.5 gal/min/ft 2The filtration rate is 3.5 gal/min/ft 2 The filtered water then flows through two UV disinfection channels The filtered water then flows through two UV disinfection channels Next, the flocculated water flows through four DynaSand filters to remove the precipitate formed Next, the flocculated water flows through four DynaSand filters to remove the precipitate formed The filters are mono-media, deep bed, upflow, continuous backwash typeThe filters are mono-media, deep bed, upflow, continuous backwash type The sand size is 1 mm and the sand depth is 80”The sand size is 1 mm and the sand depth is 80” The filtration rate is 3.5 gal/min/ft 2The filtration rate is 3.5 gal/min/ft 2 The filtered water then flows through two UV disinfection channels The filtered water then flows through two UV disinfection channels

21. The Pilot Project Plan Determine the types of phosphorus in the secondary effluent Determine the types of phosphorus in the secondary effluent Bench studies – jar tests Bench studies – jar tests Full scale pilot test Full scale pilot test Determine the types of phosphorus in the secondary effluent Determine the types of phosphorus in the secondary effluent Bench studies – jar tests Bench studies – jar tests Full scale pilot test Full scale pilot test

22. Analytical Method Used to Determine Types of Phosphorus in the Secondary Effluent Analysis determined soluble and insoluble forms for total, polyphosphate and ortho phosphate using Hach equipment and methods Analysis determined soluble and insoluble forms for total, polyphosphate and ortho phosphate using Hach equipment and methods Procedures used to ensure the validity of results including dedicated acid washed glassware, reagent blanks, standards and splits with QC laboratory Procedures used to ensure the validity of results including dedicated acid washed glassware, reagent blanks, standards and splits with QC laboratory Analysis determined soluble and insoluble forms for total, polyphosphate and ortho phosphate using Hach equipment and methods Analysis determined soluble and insoluble forms for total, polyphosphate and ortho phosphate using Hach equipment and methods Procedures used to ensure the validity of results including dedicated acid washed glassware, reagent blanks, standards and splits with QC laboratory Procedures used to ensure the validity of results including dedicated acid washed glassware, reagent blanks, standards and splits with QC laboratory

23. Bench Studies Method – Jar Tests Set up to simulate operations from the rapid mix to the filter effluent Set up to simulate operations from the rapid mix to the filter effluent Chemicals used were ferric chloride and anionic polymers Chemicals used were ferric chloride and anionic polymers Analysis on secondary effluent and simulated filter effluent included phosphorus, alkalinity, pH, turbidity and iron residual Analysis on secondary effluent and simulated filter effluent included phosphorus, alkalinity, pH, turbidity and iron residual Set up to simulate operations from the rapid mix to the filter effluent Set up to simulate operations from the rapid mix to the filter effluent Chemicals used were ferric chloride and anionic polymers Chemicals used were ferric chloride and anionic polymers Analysis on secondary effluent and simulated filter effluent included phosphorus, alkalinity, pH, turbidity and iron residual Analysis on secondary effluent and simulated filter effluent included phosphorus, alkalinity, pH, turbidity and iron residual

24. Bench Studies Results 20 – 40 % reduction in total phosphorus noted 20 – 40 % reduction in total phosphorus noted Little or no effect on pH and alkalinity Little or no effect on pH and alkalinity Turbidity increased and iron residual present Turbidity increased and iron residual present 20 – 40 % reduction in total phosphorus noted 20 – 40 % reduction in total phosphorus noted Little or no effect on pH and alkalinity Little or no effect on pH and alkalinity Turbidity increased and iron residual present Turbidity increased and iron residual present

25. Full-Scale Pilot Test Method (Objectives) Feed chemicals at the AWT to reduce the total phosphorus in the plant effluent to 0.05 mg/L Feed chemicals at the AWT to reduce the total phosphorus in the plant effluent to 0.05 mg/L Determine the effect of chemical treatment on the plant effluent Determine the effect of chemical treatment on the plant effluent Feed chemical doses at reasonable doses that will not the negatively impact AWT equipment and filter media Feed chemical doses at reasonable doses that will not the negatively impact AWT equipment and filter media Feed chemicals at the AWT to reduce the total phosphorus in the plant effluent to 0.05 mg/L Feed chemicals at the AWT to reduce the total phosphorus in the plant effluent to 0.05 mg/L Determine the effect of chemical treatment on the plant effluent Determine the effect of chemical treatment on the plant effluent Feed chemical doses at reasonable doses that will not the negatively impact AWT equipment and filter media Feed chemical doses at reasonable doses that will not the negatively impact AWT equipment and filter media

26. Full-Scale Pilot Test Results

27. ConclusionsConclusions Bench and full- scale pilot testing did reduce the total phosphorus, however in this study the target level of 0.05 mg/L was not reached. Bench and full- scale pilot testing did reduce the total phosphorus, however in this study the target level of 0.05 mg/L was not reached.

28. Conclusions (cont) Experience at Sand Creek was similar to that at other advanced P-removal facilities: Experience at Sand Creek was similar to that at other advanced P-removal facilities: Achieving a reliable effluent TP less than 0.1 mg/L was not feasible using ferric chloride and direct filtrationAchieving a reliable effluent TP less than 0.1 mg/L was not feasible using ferric chloride and direct filtration Lower concentrations would require major process modificationsLower concentrations would require major process modifications Increased chemical feed Increased chemical feed Flocculation/sedimentation + filtration Flocculation/sedimentation + filtration Membranes Membranes Experience at Sand Creek was similar to that at other advanced P-removal facilities: Experience at Sand Creek was similar to that at other advanced P-removal facilities: Achieving a reliable effluent TP less than 0.1 mg/L was not feasible using ferric chloride and direct filtrationAchieving a reliable effluent TP less than 0.1 mg/L was not feasible using ferric chloride and direct filtration Lower concentrations would require major process modificationsLower concentrations would require major process modifications Increased chemical feed Increased chemical feed Flocculation/sedimentation + filtration Flocculation/sedimentation + filtration Membranes Membranes