STRUVITE HARVESTING: A UTILITY S PERSPECTIVE

Transcription

1 STRUVITE HARVESTING: A UTILITY S PERSPECTIVE MWEA Annual Conference June 2016 Mike Harvey, PE

2 Agenda Why the focus on Phosphorus? Struvite What does it mean for me? Phosphorus Management and Harvesting Take Away

3 Why the focus on Phosphorus?

4 Phosphorus Production 2.5E E+08 Phosphate Rock: Non-renewable production has steadily resource increased World Phosphate Rock Production (metric tons) 1.5E+08 Phosphate production has steadily increased 1.0E E E

5 Phosphorus Resources

6 Resource Nexus: The Environmental Challenge of the 21st Century

7 Change our Mind(set) WEF believes that wastewater treatment plants are NOT waste disposal facilities, but rather water resource recovery facilities that produce clean water, recover nutrients (such as phosphorus and nitrogen), and have the potential to reduce the nation s dependence upon fossil fuel through the production and use of renewable energy.

8 Struvite What does it mean for me?

9 Struvite what is it? Struvite is a phosphate mineral with formula: NH₄MgPO₄ 6H₂O Crystallization: Higher concentrations, higher temperatures Solubility: Decreases at high ph values

10 Struvite Formation Precipitation Occurs -pqs pqs Increase ph Increase concentrations ph

11 Struvite should I be concerned? Operate a bio-p facility? Operate an anaerobic digester? Recycle filtrate from dewatering? Interested in Phosphorus recovery? Master planning for future solids handling? Future regs for land app will become more stringent?

12 Struvite Harvesting Primary Clarifiers Aeration Basins Final Clarifiers Mg 2+ P NH 4 + Digestion

13 Struvite Harvesting Primary Clarifiers Aeration Basins Final Clarifiers Mg 2+ P NH 4 + P P Mg 2+ NH 4 + Digestion

14 Struvite Harvesting Primary Clarifiers Aeration Basins Final Clarifiers Mg 2+ P NH 4 + P P Mg 2+ NH 4 + P Mg 2+ NH 4 + P Mg 2+ NH 4 + Digestion

15 Struvite Harvesting Primary Clarifiers Aeration Basins Final Clarifiers Mg 2+ P NH 4 + P P Mg 2+ NH 4 + P Mg 2+ NH 4 + Struvite production limited by: P Mg 2+ NH 4 + Mg 2+ ph Digestion

16 Struvite Harvesting Primary Clarifiers Aeration Basins Final Clarifiers Mg 2+ P NH 4 + P P Mg 2+ NH 4 + P Mg 2+ NH 4 + P Mg 2+ NH 4 + Release Tank Digestion

17 Sidestream Impacts IMPACT MITIGATION Increased effluent phosphorus Bind phosphorus Decreased Dewaterability Polyphosphate binding + cation balance? Detrimental struvite maintenance Bind phosphorus

18 Sidestream Impacts Increased Effluent Phosphorus Parameter Influent flow rate Total COD TKN Total P TSS VSS cbod5 Magnesium Value 10.8 mgd 387 mg/l 40 mg/l 4.5 mg/l 200 mg/l 120 mg/l 200 mg/l 20 mg/l Increased effluent phosphorus

19 Primary Effluent Total Phosphorus (mg/l) Sidestream Impact Phosphorus Performance Increased effluent phosphorus Sunday Monday Tuesday Wednesday Thursday Friday Saturday All Data BFP OFF BFP ON

20 Dewatering Impact with Bio-P BFP Solids (%) RBC AS - Chem P AS - Bio-P Decreased Dewaterability

21 Dewatering Impact with Bio-P Lime-Stabilization Solids Handling Facility Chem-P Initial Bio-P

22 Others Are Also Seeing This, Including: Hampton Roads Sanitary District Atlantic & Nansemond Plants Madison, WI Metropolitan Sewerage District Met Council Environmental Services Empire & Blue Lake Plants Metro Denver, CO Sheboygan, WI Ok, Is This Real or Not??? A number of European plants

23 MCES Empire Plant

24 Phosphates Phosphates: stabilizers in processed meat, bind water

25 Most Sludge Floc Surfaces Are Anionic

26 Common Cations in Wastewater Monovalent Single Plus (+) Charge: Sodium Potassium + Divalent Double Plus (++) Charge: Magnesium Calcium Iron ++

27 DVC Theory, in a Nutshell Anion Dominated Solution Keeps More Interstitial Water in Sludge Basis Unlike Charges Attract/ Like Charges Repel

28 Can t forget about detrimental struvite formation Clogged pipes Accumulation in digesters

29 Sidestream Impacts Glass-Lined Piping Increased pumping pressures Equipment / Process Downtime Labor Chemical Use Detrimental struvite maintenance

30 Phosphorus Management and Harvesting

31 Alternative 1: Chemical Precipitation Addition to digester Addition to dewatering filtrate

32 Alternative 1: Chemical Precipitation Initial estimate: alum assumed Binds phosphorus Dewaterability improvements (more so with FeCl3 or Sorb-X) 180 gpd $130k annual $5k solids

33 Alternative 2: Struvite Harvesting MgCl 2 (non-limiting) P Mg 2+ NH + 4 Struvite Harvesting System NH 4 + P NaOH (ph adjustment) Harvested Struvite Mg 2+ NH 4 +

34 Struvite Harvesting from Filtrate

35 Struvite Harvesting from Filtrate Ostara Struvite Harvesting on Filtrate or Centrate After Digested Sludge Thickening or Dewatering

36 Struvite Harvesting from Filtrate

37 Struvite Harvesting from Filtrate Hampton Roads Sanitation District Charles Bott

38 Struvite Harvesting from Biosolids Forms/Removes Struvite Before Thickening or Dewatering

39 Struvite Harvesting from Biosolids

40 Struvite Harvesting from Biosolids

41 Economics Struvite Production Alt 1 Chemical Precipitation Alt 2a From Filtrate (Ostara) Alt 2b From Biosolids (Airprex) P Removed 95% 80% P Removed (ppd) Struvite produced (ppd) Percent Capture 100% 100% Product produced (ppd) Product value ($/ton) $400 $100 Product income ($/year) $33,485 $4,935 Magnesium (gpd) Magnesium cost ($/year) $23,269 $23,269 Sodium Hydroxide (mg/l feed) 75 0 Sodium Hydroxide (DST/year) 11 0 Sodium Hydroxide ($) $5,995 $0 Power (kwh/d) Power ($) $10,921 $4,380 STRUVITE HARVESTING COST $0 $7,203 -$22,714

42 Economics Chemical Precipitation Alt 1 Chemical Precipitation P Removed (ppd) 51 Al Required (ppd) 89 Alum Required (gpd) 180 Solids Produced (ppd) 434 Yearly acreage increase 38 Annual chemical (gal/yr) 65,849 Annual chemical cost $131,000 Annual Solids Cost $4,000 Alt 2a From Filtrate Alt 2b From Biosolids Total Annual Cost -$135,000 $0 $0

43 Economics Nitrification Alt 1 Chemical Precipitation Alt 2a From Filtrate Alt 2b From Biosolids NH3 Load (ppd) AOR (ppd) 1, ,570 scfm/aor (based on existing aeration) Airflow (scfm) Energy (scfm\hp) (based on existing blowers) Energy (hp) Energy (kwh/yr) 278, , ,413 Power cost ($) -$22,306 -$10,849 -$18,913

44 Economics Biosolids Reuse Alt 1 Chemical Precipitation Alt 2b From Biosolids Alt 2a From Filtrate P Removed from solids (ppd) P Removed from solids (t/yr) Acres Required per year 1, ,018 Biosolids Reuse Cost Assuming P limitation for application -$654,000 -$483,000 -$551,000 Biosolids Reuse Cost Based on cake solids concentration -$654,000 -$575,000 -$575,000

45 Economic Comparison Relative Savings & Revenue Filtrate Struvite Harvesting Net Product Income Product value has the smallest economic impact Relative Savings & Revenue Biosolids Struvite Harvesting Net Product Income Biosolids Reuse - Improved Cake Concentration Chemical Precipitation Biosolids Reuse - Improved Cake Concentration Chemical Precipitation Nitrification Power Cost Nitrification Power Cost

46 Economic Comparison Cost in Millions (2014$) 20-Year TPW in Millions (2014$) Chemical Precipitation Ostara Struvite Harvesting Capital Annual Airprex Struvite Harvesting Airprex: lowest 20-year cost 0.0 Chemical Precipitation Ostara Struvite Harvesting Airprex Struvite Harvesting

47 Economic Comparison 20,000,000 18,000,000 16,000,000 14,000,000 Chemical Precipitation Ostara Struvite Harvesting Airprex Struvite Harvesting Cumulative Cost ($M) 12,000,000 10,000,000 8,000,000 6,000,000 4,000,000 2,000,000 Airprex: 7 year payback Years after Installation

48 Take Away Not for everyone (at least not right now) Need (Bio-P, Digestion, maybe Dewatering) When considering: Identify your drivers/costs/risk Don t assume all the claims will hold true Revenue will not offset capital investment, payback likely to be based on cost savings rather revenue generation Technology: Options have different nuances Pilot study and evaluate on a case by case basis Technology market is rapidly developing Future nutrient demands will drive the need for change

49 Any questions Mike Harvey, PE Donohue & Associates Thank you!