Defining the Benefits of Harvesting Phosphorus from Dewatering Filtrate

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1 Defining the Benefits of Harvesting Phosphorus from Dewatering Filtrate Cameron Clark, PE CDM Smith August 1, 2013

2 Agenda Des Moines WRA Background Plant Nutrient Balance Nutrient Issues P Removal Technology Comparison Life Cycle Cost Summary

3 Des Moines WRF - Existing Program ~44 MGD Primary and Secondary Treatment Biogas Storage Process Heating Sludges Building Heating Hauled Wastes Anaerobic Digestion Power Generation Industrial User 0.14 MGD > 30 loads/day Biosolids to Land Application

4 Des Moines WRF - Existing Program Hauled-In Waste ~45% of the VS Loading Highly profitable

5 Influent 72 MGD 5,200 ppd (8.6 mg/l) Plant Phosphorus Balance Liquid Treatment Process Primary Secondary Effluent 3,400 ppd (5.6 mg/l) Sidestream 3,600 ppd Percent of influent: 69% Typical: 20-30% Solids Treatment Process Blended Sludge 5,600 ppd Biosolids 2,900 ppd Based on 2040 Design Condition Aeration SRT = 37 days at 52 deg F Special Waste - modeled 1,100 ppd (1.9 mg/l eq.)

6 Struvite Issues ~$170,000/yr in Maintenance Struvite Buildup on 10-in Digested Solids Lines

7 Influent 5,200 ppd (8.6 mg/l) Expected Effluent Nutrient Limits Liquid Treatment Process Primary Secondary Effluent 1 mg/l P Solids Treatment Process Special Waste 1,100 ppd (1.9 mg/l eq.)

8 Biosolids Regulations Currently land apply biosolids based on nitrogen content 10 dry tons/ac/yr Severe reduction if P limitation is imposed 3 dry tons/ac/yr At $15/wet ton for land application, costs would be expected to increase 65% P-based rates N-based rates 0 10,000 20,000 30,000 40,000 Present Worth Cost (1,000 $) Total Present Worth (PW) PW of O&M PW of Capital and Salvage Value

9 Influent 5,200 ppd (8.6 mg/l) Proposed Solution Sidestream Nutrient Recovery Liquid Treatment Process Primary Secondary Effluent 1 mg/l P Sidestream Treatment Struvite Solids Treatment Process Biosolids 2,500 ppd P Special Waste 1,100 ppd (1.9 mg/l eq.)

Digestion Pretreatment: Critical Defining Issues the in Benefits

10 Proposed Solution Sidestream Nutrient Removal Water Environment Association of WEAT Texas Biosolids/Odor & & Corrosion Conference Digestion Pretreatment: Critical Defining Issues the in Benefits Thermal of Hydrolysis Harvesting System Phosphorus Design from Dewatering Filtrate

11 Paques PHOSPAQ

12 PHOSPAQ Struvite Product SOURCE: YouTube

13 Ostara Pearl Process

14 Crystal Green Fertilizer

15 Struvite Recovery Model - Baseline 72 MGD influent Aeration SRT = 37 days at 52 deg F 80% removal of sidestream ortho-p

16 Influent 5,200 ppd (8.6 mg/l) Struvite Recovery Model Baseline P Balance With Struvite Harvesting Only Sidestream Without: 3,600 ppd With: 700 ppd 81% reduction Liquid Treatment Process Primary Secondary Blended Sludge Without: 5,600 ppd With: 5,200 ppd Effluent Without: 3,400 ppd (5.6 mg/l) With: 800 ppd (1.4 mg/l) 76% reduction Struvite Without: 0 ppd With: 2,700 ppd Filtrate Without: 3,600 ppd With: 3,400 ppd Solids Treatment Process Special Waste 1,100 ppd (1.9 mg/l eq.) Biosolids Without: 2,900 ppd With: 2,700 ppd About the same

17 Struvite Recovery Model AO System 72 MGD influent Carbon Addition to AB1 for Bio-P removal Aeration SRT = 10 days at 52 deg F 80% removal of sidestream ortho-p

18 Influent 5,200 ppd (8.6 mg/l) Struvite Recovery Model AO System P Balance With and Without Struvite Harvesting Sidestream Without: 3,600 ppd With: 700 ppd 81% reduction Liquid Treatment Process Primary Secondary Blended Sludge Without: 5,600 ppd With: 5,400 ppd Effluent Without: 3,400 ppd (5.6 mg/l) With: 600 ppd (1.0 mg/l) 82% reduction Struvite Without: 0 ppd With: 2,800 ppd Filtrate Without: 3,600 ppd With: 3,500 ppd Solids Treatment Process Special Waste 1,100 ppd (1.9 mg/l eq.) Biosolids Without: 2,900 ppd With: 2,900 ppd About the same

19 Struvite Recovery Model A2O System 72 MGD influent Carbon Addition to AB1 and AB2 for Bio-P and Denitrification Aeration SRT = 10 days at 52 deg F 80% removal of sidestream ortho-p

20 Struvite Recovery Model A2O System P Balance With and Without Struvite Harvesting Influent 5,200 ppd (8.6 mg/l) Sidestream Without: 3,600 ppd With: 500 ppd 86% reduction Liquid Treatment Process Primary Secondary Blended Sludge Without: 5,600 ppd With: 5,300 ppd Effluent Without: 3,400 ppd (5.6 mg/l) With: 600 ppd (1.0 mg/l) 82% reduction Struvite Without: 0 ppd With: 2,800 ppd Filtrate Without: 3,600 ppd With: 3,300 ppd Solids Treatment Process Special Waste 1,100 ppd (1.9 mg/l eq.) Biosolids Without: 2,900 ppd With: 2,900 ppd About the same

21 Struvite Recovery Model A2O System Only 72 MGD influent Carbon Addition to AB1 and AB2 for Bio-P and Denitrification Aeration SRT = 10 days at 52 deg F 80% removal of sidestream ortho-p

22 Influent 5,200 ppd (8.6 mg/l) Struvite Recovery Model No Struvite Harvesting P Balance With and Without A2O System Sidestream Without: 3,600 ppd With: 6,800 ppd 189% increase Liquid Treatment Process Primary Secondary Solids Treatment Process Blended Sludge Without: 5,600 ppd With: 11,500 ppd Special Waste 1,100 ppd (1.9 mg/l eq.) Effluent Without: 3,400 ppd (5.6 mg/l) With: 1,000 ppd (1.6 mg/l) 67% reduction Biosolids Without: 2,900 ppd With: 5,300 ppd 183% increase

23 Life Cycle Cost Assessment Continue Existing Program with Future BNR Treatment Parameter First 7 years Final 13 years Capital Costs ($) BNR treatment for P removal 68,000,000 BNR treatment for N removal 68,000,000 Total ($) $ 136,000,000 O&M Costs ($/yr) Pipe cleaning 84,000 84,000 Fe costs 120, ,000 Other cleaning chemicals (Guard, Rydlyme, or other) 64,000 64,000 Aeration for nitrification 64,000 BNR for P removal 2,497,000 BNR for N removal 1,684,000 Total ($/yr) $ 352,000/yr $ 4,597,000/yr Equivalent Annual O&M for 20 year period, ($/yr) $2,542,000

24 Cost Estimates Implement Struvite Recovery with Future BNR Treatment Parameter First 7 years Final 13 years Capital Costs ($) WASSTRIP Pipe modifications 316,000 Basin improvements 203,000 Pump station 293,000 Ostara System Equipment 7,222,000 Equipment installation 1,569,000 Filtrate handling modifications 384,000 Building, sitework, and misc. structural improvements 1,504,000 Electrical and instrumentation/controls 1,910,000 BNR treatment for P removal 36,000,000 BNR treatment for N removal 56,000,000 Total ($) $14,365,000 $92,000,000 O&M Costs ($/yr) First 7 years Final 13 years Struvite product revenue (1,079,000) (1,079,000) Struvite operating costs 1,079,000 1,079,000 Pipe cleaning 42,000 42,000 Fe costs 30,000 30,000 Other cleaning chemicals (Guard, Rydlyme, or other) 16,000 16,000 Aeration for nitrification 0 BNR for P removal 1,314,000 BNR for N removal 1,380,000 Total ($/yr) $88,000/yr $2,782,000/yr Equivalent Annual O&M for 20 year period, ($/yr) $1,531,000/yr

25 Parameter Alternative 1 Continue Current Program Alternative 2- Develop Struvite Recovery Systems Initial capital costs 0 14,365,000 Present worth of future capital costs 96,891,000 65,190,000 Present worth of annual O&M, $ 31,679,000 19,081,000 Present worth of remaining value of facilities and equipment, $ (23,294,000) (15,738,000) Total Present Worth, $ 105,000,000 83,000,000

26 Summary Performed nutrient balance on Des Moines WRA Compared two struvite recovery technologies spanning perceived range from simple to more complicated Ostara chosen based primarily on operational history Evaluated BioWin models with struvite harvesting, traditional biological nutrient removal, and both Estimated costs of both nutrient treatment approaches

27 Conclusions High amounts of P introduced in hauled waste Sidestreams are important when modeling wastewater facilities Struvite recovery significantly reduces size and cost of equivalent biological nutrient removal systems May not achieve limits with traditional BNR and existing tankage Struvite recovery may have minimal impact on biosolids P concentration Additional approaches, such as WASSTRIP, may be needed to protect digester and piping Major cost savings not from sale of struvite product, but from BNR size reduction and reduced pipe cleaning

28 QUESTIONS

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