Phosphorus Removal via Chemical and Filtration
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Phosphorus Removal via Chemical and Filtration
- 1. Phosphorus Removal Via Chemical Addition and Filtration Waterborne Engineering Colorado State University
- 2. Agenda • Alternatives Summary • Decision Analysis • Cost Analysis • Selected Alternative • BioWin 3.1 Modeling • Summary/Conclusion • Questions
- 3. Alternatives • 2 Stage Chemical Addition • Biological P Removal with Chemical Addition • Tertiary Chemical Addition with Filtration • Chemical Addition with Possible Phosphoric Acid Addition
- 4. Alternative 1 (2 Stage Chemical Addition) Primary Trickling Solids Alum Final NTFs Alum DENIT Disinfectio Clarifier Filters Contact Clarifier Addition n Addition Filters • Alum addition prior to final clarifier and prior to filters • Addition of chemical feed systems • Large increase in P rich sludge production • Increased backwashing and maintenance on filters
- 5. Alternative 2 (Biological P Removal with Chemical Addition) Primary Trickling Anaerobic Solids Final NTFs Alum DENIT Disinfection Clarifier Filters Tank Contact Clarifier Addition Filters • Enhanced BPR with chemical addition for polishing • Addition of anaerobic tank creates an A/O process • May need to build additional tank • Chemical costs will be lower
- 6. Alternative 3 (Chemical Addition with Tertiary Filtration) Trickling Solids Final NTFs DENIT Disinfection Primary Alum DynaSand Clarifier Filters Contact Clarifier Filters Addition Filters • Chemical addition after DENIT filters • Addition of P removal filters • Does not affect biological processes of plant • Need to add chemical feed system
- 7. Alternative 4 (Chemical Addition with Possible Phosphoric Acid Addition) Primary Trickling Solids Alum Final NTFs Phosphoric DENIT Disinfection Clarifier Filters Contact Addition Clarifier Acid Filters Addition • Chemical addition prior to final clarifier • Addition of phosphoric acid prior to DENIT • Need two chemical feed systems • Large dose of coagulant prior to final clarifier
- 9. Decision Criteria and Weights • Performance (100) • Integration into Existing System (80) • Treatment Residuals (80) • Safety (80) • Flexibility of Design (70) • Maintenance (70) • Risk of Technology (60)
- 10. Alternative Ratings 2 Stage Alum Enhanced BPR Alum Addition Alum and Addition with Filtration H3PO4 Addition Performance (100) 95 90 100 80 Integration into Ex Sys (80) 50 55 70 45 Treatment Residuals (80) 35 60 40 45 Safety (80) 70 80 75 65 Flex. Of Design (70) 65 55 60 45 Maintenance (70) 40 60 50 65 Risk of Tech (60) 60 40 55 30
- 11. Scoring Results
- 12. Sensitivity of Scores • If % to crossover is less than 5%, then need to reassess model structure, weights, and scores • Treatment Residuals: 5.5% • Integration into Existing System: 8.7% • Risk of Technology: 9.1% • Maintenance: 10.6% • Performance: 13.1% • Safety: 18.5% • Flexibility of Design: 33.5%
- 13. Life-Cycle Cost Analysis (LCCA) • Evaluation of economic effects of alternative designs and expressing them in dollar amounts • Costs to analyze for each alternative: – Initial: Purchase, Construction, Engineering – Enduring: Operation, Maintenance, Energy, Chemicals, Sludge Removal
- 14. Cost Analysis ENG/ContENG/Cont Alternative Capital Cost O & M Cost Total Costs Cost 2 Stage Alum $2.13M $1.40M $604K $4.02M Addition Enhanced BPR $8.61M $682K $2.48M $11.8M Alum Addition with $6.01M $902K $1.80M $8.71M Filtration Alum and H3PO4 $2.01M $1.53M $604K $4.14M Addition
- 15. In Depth Cost Analysis Alum Addition Alum and In Depth Costs 2 Stage Alum Addition Enhanced BPR with Filtration H3PO4 Addition Chemicals $750K $350K $650K $850K Feed and Storage $763K $381K $381K $763K Facility: Additional Feed $250K $125K $125K $250K Points: Energy: $101K $430K $300K $101K Maintenance: $552K $251K $351K $573K Additional Anaerobic N/A $7.0M N/A N/A Tank: Additional Filters: N/A N/A $4.5M N/A
- 16. Recommended Alternative • Tertiary alum addition with filtration • Adding chemicals prior to biological processes may cause upsets • Parkson DynaSand Granular Media Filter (commonly used in WWTPs for P removal)
- 17. DynaSand Filter
- 18. Alternative Location Alum Addition DynaSand Filters Alum Storage Facility
- 19. P Removal Filters Alum Addition
- 20. Design Using BioWin 3.1 Modeling • Began model after denitrification • Denitrification effluent P concentration of 2.70 mg/L • Able to optimize alum dose based on P removal goal Alum Addition Effluent DENIT Effluent Null Bioreactor DynaSand Filters Filter Sludge
- 21. Alum Dose and P Removal Mass of Effluent P Alum Dose Annual Cost Alum Used Conc. 31,185 150 mg/L 0.04 mg/L $569,000 lbs/day 22,261 109 mg/L 0.13 mg/L $414,000 lbs/day 13,514 65 mg/L 0.70 mg/L $247,000 lbs/day
- 22. Summary • Tertiary alum addition with filtration • Does not disrupt nitrification/denitrification processes • Allows for flexibility in P removal • Used by numerous WWTPs throughout the US with excellent results
- 23. Questions?
Editor's Notes
- Additional tank is dependent on volume needed for anaerobic and aerobic zones needed to optimize P removal based on plant flow allows P to be incorporated into biomass that is removed
- Not optimal
- Lists all the criteria weights in the model, from those to which the results are most sensitive to those to which the model is least sensitive Those at the top are the most critical because small changes in their value can change the outcome of the model The percentage on each line is the amount of change in the priority of that weight required to change the outcome of the model. If the percentage was 5% or less, indicating that a change of less than 5% would change the preferred alternative, need to reassess the model structure, weights, and scores During the initial iterations of the model, 3 criterion (treatment residuals, integration into existing system, and risk of technology) were below 5% - we reassessed the structure, weights, and scores which resulted in less sensitivity to those 3 criterion
- Feed and Storage facility cost comes from Arlington County, VA Master Plan tech memo on costs for upgrade of their WWTP Energy costs assumed to be 5% of capital costs Maintenance costs assumed to be 20% of sum of costs for chemicals, feed and storage facility, additional feed points, and sludge pump Additional anaerobic tank cost based Arlington County, VA master plan update with a cost of $7,000,000 for a 2.25 MG tank (similar to 2.5 MG total volume for solids contact tank) Filters cost based on a filter with a media volume of 300,000 cubic feet costing $750,000 (Oldsmar, FL DENIT filter bid proposal), 4 filters needed for redundancy
- A relative Costs/Benefits analysis was completed and Alternative 3 was selected as the best course of action. By placing the metal addition after denitrification and adding filtration the NIT/DENIT processes will not be affected. It is our belief from our research that there will be issues with adding chemicals prior to Nitrificaiton/Denitrification and that the processes could be affected or due to Denitrification requiring P to run properly that there could be issues with meeting the standard for P in the effluent without affecting denitrificaiton Additionally, chemical costs will go up because metal addition prior to Nitrification will require addition of lime due to the alkalinity being consumed. If lime is not added, nitrification will be affected. Chose a Parkson DynaSand Granular Media Filter (commonly used in WWTPs for P removal – demonstrated in EPA’s AWT for Phosphorus Removal) WWTPs cited in EPA Advanced Wastewater Treatment document (2007) using DynaSand filters include Aurora’s Sand Creek Wastewater Reuse Plant and Breckenridge Iowa Hill Wastewater Reclamation Plant in Colorado
- The DynaSand® filter is an upflow, deep bed, granular media filter with continuous backwash. The filter media is cleaned by a simple internal washing system that does not require backwash pumps or storage tanks. The absence of backwash pumps means low energy consumption. The DynaSand filter’s deep media bed allows it to handle high levels of suspended solids.
- We received guidance from EnviroSim on how to model filtration. In BioWin, the microscreen icon is utilized to model granular media filters but a volume is not inputted for microscreens. BioWin required that an icon with a volume be inputted to run a simulation and due to this a media bioreactor with a volume of 1 cubic meter was added (labeled Null Bioreactor). This media bioreactor did not have any effect on the denitrification effluent as all values remained the same coming out of the media bioreactor.
- 0.1 to 0.5 mg/L P from various WWTPs (Breckinridge, Aurora Sand Creek)
- We looked at possibly using a couple of DENIT filters for P removal as opposed to adding new filters. However, we decided against that as we thought that L/E WWTP did not want to alter their DENIT filters for this purpose. Is this a good assumption or should we look into this possibility? Are each DENIT filter rated at 4.5 MGD for a total of 36 MGD? Can you provide a cost for one of those filters? Also, should we look at planning for filters to handle 36 MGD or 43 MGD which is your ultimate flow from your design data document?