Extractive Nutrient Recovery as a Green Option for Managing Phosphorus in Sidestreams and Biosolids Wendell Khunjar, Ph.D. Ron Latimer, P.E. Katya Bilyk, P.E. Joe Rohrbacher, P.E. Paul Pitt, Ph.D., P.E.
Agenda Sidestream treatment overview Phosphorus Removal/Recovery Options Case Study 1 - Nansemond Treatment Plant Case Study 2 FWHWRC Case Studies 3 and 4 Miami Dade Treatment Plants Summary
Biological treatment is a cost effective, robust option for carbon and nutrient removal Biological nutrient removal uses microorganisms To solids handling To solids handling Solids generated must be processed before disposal Anaerobic digestion is a common solids treatment option
Water resource reclamation facilities accumulate nutrients within the solids process Adapted from Cornel et al., 2009 Urine 67% Feces 33% Primary Sludge 10-15% Secondary Sludge 25-40% EBPR or Chem - P Removal 35-50% Effluent 10% Up to 90% of the influent P can be present in the solids stream Sludge Up to 90% Adapted from Phillips et al., 2011 Urine 80% Gaseous emission 67% Feces 20% Sludge 20% Effluent 13% Up to 20% of the influent N can be present in the solids stream
Solids stabilization generates nutrient rich liquid stream 1 0 Treatment 2 0 Treatment Fe or Alum Fe or Alum Disinfection Screenings Sidestreams are typically returned to the head of the plant for treatment Examples of sidestream BFP filtrate GBT filtrate Filter backwash Centrate Digester supernatant Grit 1 0 Sludge Biosolids Handling 2 0 Sludge Effluent Residual
High nutrient recycle loads can upset the mainstream process TP Load (lb/day) 900 800 700 600 500 400 300 200 100 0 Description 7/11/06 Recycle Stream Percent Sampling of Phosphorus Total Influent Nitrogen Load Up to 50% of the total influent P load can be present in the Nansemond, Suffolk, VA Centrate sidestream Bowery Bay, NYC Centrate Henrico County, VA Centrate High Point Eastside, NC Fermenter Percent of Total Influent Phosphorus Load 13% 29% 17% * 15% * * 50% Wards Island, NYC Centrate 30-40% * Centrate Ash Lagoon Decant Primary Effluent North Durham, Sampling NC Location 19% 30% Centrate Total P South Durham, NC Centrate 21% 25%
Struvite can be a significant maintenance concern with anaerobic digestion Struvite = Mg + NH 4 + PO 4 NH 4 & PO 4 released in digestion Typically Mg limited Mg addition (i.e. Mg(OH) 2 ) can promote struvite formation NYC Newtown Creek WPCP Miami Dade SDWRF
Sidestream treatment is the manipulation of the return liquid stream for a treatment purpose Typically focused on nutrient removal or recovery Usually economical when sidestreams contribute: 15% of the influent TN 20% P load Can often reuse existing infrastructure to reduce costs Biological mainstream process Sidestream treatment Dewatering Anaerobic Digestion Thickening Biosolids
What options are available for sidestream nutrient treatment? Nutrient rich sidestream Treatment process Nutrient free effluent Removed/recovered nutrient N Removal and recovery Nitrification/Denitrification Nitritation/Denitritation Deammonification Gas stripping and/or ion exchange P removal and recovery Coagulant aided precipitation Struvite crystallization
P removal from sidestreams relies on chemical precipitation Coagulant aided precipitation o o o o Uses Alum or Ferric Non-proprietary Traditionally used for controlling sidestream P at this plant High O&M requirement Struvite recovery o o Forms struvite which can be used as a slow release fertilizer Proprietary Ostara MFH Procorp/DHV Paques Veolia
Struvite recovery exploits ph dependent chemical precipitation phenomena Struvite precipitation N:P ratio in struvite = 0.45 lbs N required per lb P removed N:P ratio in filtrate ~ 2.4-2.6, ammonia in excess Mg(NH 4 )PO 4 (s) = struvite External NaOH External Mg +2 Mg +2 NH 4+ -N PO 4-3 - P Struvite Recovery Reactor Mg(NH 4 )PO 4 (s)
Intentional struvite recovery exploits ph dependent chemical precipitation phenomena Fluidized bed reactor or CSTR used for struvite recovery FBR Effluent N:P ratio in struvite = 0.45 lbs N required per lb P removed Dewatering Dryer Struvite Magnesium Caustic Sand (Procorp) Centrate/Filtrate N:P ratio in filtrate ~ 2.4-2.6, ammonia in excess
There are several commercial options for struvite recovery Name of Technology Ostara Pearl Multiform Harvest struvite technology Phospaq Crystalactor NuReSys Name of product recovered Crystal Green struvite fertilizer struvite fertilizer Struvite, Calcium phosphate, Magnesium phosphate BioStru % efficiency of recovery from sidestream 80-90% P 10-40% NH 3 -N 80-90% P 10-40% NH 3 -N 80% P 10-40% NH 3 -N 85-95% P 10-40% NH 3 -N >80% P 5-20% N Product marketing/resale # of full-scale installations in design/operation Ostara Multiform Harvest N/A Third party facilitated by Procorp 8 2 2 4 7 N/A
Nansemond Treatment Plant is a 30 MGD facility that employs a 5-stage BNR for N and P removal Nansemond HRSD, Virginia TN = 8 mg/l 30 MGD BNR 5 Stage 8 mg TN/L 1 mg TP/L TP = 1 mg/l
Nansemond Treatment Plant is a 30 MGD facility that employs a 5-stage BNR for N and P removal TP (mg/l) 16.00 14.00 12.00 Sidestream load represents up to 30% of the plant influent P load Diurnal Sampling TN = 8 mg/l TP = 1 mg/l 10.00 8.00 6.00 4.00 2.00 Day 1 Influent TP Day 2 Influent TP Day 1 PE TP Day 2 PE TP 0.00 12:00 AM 2:00 am 4:00 am 6:00 am 8:00 AM 9:00 AM 12:00 PM 2:00 PM 4:00 pm 6:00 pm 8:00 pm 10:00 pm Time
Two options were considered for sidestream P Treatment at NTP Ferric addition o o o o Forms ferric phosphate and ferric hydroxide Non-proprietary Traditionally used for controlling sidestream P at this plant High O&M requirement Struvite recovery o o o Ostara Pearl Treatment fee option o OSTARA provides facility and HRSD pays fee for use Capital purchase option o NTP purchases equipment and receives annual payments from OSTARA
Net present worth analyses indicated that the capital purchase option was the most cost-effective solution Item Treatment Fee Capital Purchase Option Option Ferric Chloride Chemical Cost $ (290,000) $ (290,000) Sludge Savings $ (155,000) $ (155,000) Methanol Savings $ (29,000) $ (29,000) Oxygen Savings $ (19,000) $ (19,000) Ostara Paybacks $ (87,850) $ (135,850) Total Annual Savings $ (580,850) $ (628,850) Caustic Cost Allowance $ 25,000 $ 25,000 Ostara Annual Fee $ 444,000 $ - Total Annual Operating Cost $ 469,000 $ 25,000 Nutrient recovery option was more cost effective than Total Capital Cost $ 1,080,000 $ 4,143,000 Ferric addition option Present Worth Operating Costs $ (1,505,750) $ (8,129,160) Net Present Worth 5 $ (425,750) $ (3,986,050) Present worth cost of line 10 over 20 years at 5% cost of financing
NTP constructed and has operated the nutrient recovery facility for ~ 2 years
Full scale struvite recovery facility at NTP System has produced ~ 1100 lb struvite/day
The struvite recovery facility has reduced ortho-p concentrations by approximately 85% Concentration mg/l Percent Removal 1000 Inf.& Eff. Ortho-P and % Removal for Ostara Influent ortho-p to Ostara Average Eff. ortho-p % ortho-p Removal 7 per. Mov. Avg. (Influent ortho-p to Ostara) 7 per. Mov. Avg. (Average Eff. ortho-p) 7 per. Mov. Avg. (% ortho-p Removal) 100% 900 90% 800 80% 700 70% 600 60% 500 50% 400 40% 300 30% 200 20% 100 10% 0 0% May-10 Aug-10 Nov-10 Mar-11 Jun-11 Sep-11 Dec-11 Apr-12 Jul-12 Oct-12 Jan-13 May-13
Concentration mg/l Percent Removal Ammonia removal has averaged 25% 1000 Inf and Eff Ammonia and % Removal for Ostara Influent Ammonia to Ostara Average Eff. Ammonia from Ostara % Ammonia Removal 7 per. Mov. Avg. (Influent Ammonia to Ostara) 7 per. Mov. Avg. (Average Eff. Ammonia from Ostara) 7 per. Mov. Avg. (% Ammonia Removal) 100% 900 90% 800 80% 700 70% 600 60% 500 50% 400 40% 300 30% 200 20% 100 10% 0 0% Jan-11 Mar-11 Jun-11 Aug-11 Nov-11 Feb-12 Apr-12 Jul-12 Oct-12 Dec-12 Mar-13 May-13
F. Wayne Hill Water Reclamation Center Gwinnett County, GA 60 MGD advanced WWTP 0.08 mg/l TP effluent limit Bio-P and chemical trim for P-removal
In 2009, F. Wayne Hill Changed from Bioxide to Mg(OH) 2 in Collection System for Odor Control Pros: Eliminated need for ALK addition at plant Cons: Struvite formation in centrate lines, centrifuges, digester complex Sludge from 22 mgd Yellow River Bio-P plant coming, which would substantially increase P load in sidestreams and SFP Struvite taken from centrifuge
Limiting effluent P and struvite formation are key drivers for this plant Phosphorus outlets: o Effluent (Limit TP = 0.08 mg/l) o Sludge cake (precipitated complex, biomass, struvite) o Struvite solids from nuisance formation Study goal: determine best solution for struvite issue (Mg continues) or P recycle issue (Mg stops) o Nutrient Recovery o Metal salts
Five options were considered for sidestream P removal from F. Wayne Hill AWRF Do Nothing Ferric addition with and without Mg(OH) 2 addition Struvite recovery with and without WASStrip TM
WASSTRIP concept minimizes nuisance struvite production Release P from sludge using VFA rich stream Send P rich sidestream to recovery process Low P content of sludge minimizes nuisance struvite formation from digester onwards
Bench scale testing of the WASSTRIP process was performed Determine levels and rates of PO 4 release from WAS Optimize parameters to maximize PO 4 release in pilot studies o Anaerobic retention time and WAS:PS blend ratio
Using the pilot data, Biowin process modeling was used to simulate each alternative 1. Use calibrated whole plant model to simulate alternatives at each flow scenario 2. Do Nothing scenario is modeled for comparison of struvite formation 3. The modeling results were used to assess effectiveness of the nutrient control strategy and also to estimate costs for the BCE. Raw INF Grit tank YR Sludge Grit BRB 5-10- A1 BRB 5-10- C3+C4 BRB 5-10- A2 BRB 5-10- B1 BRB 5-10- B2 BRB 5-10- C5+C6BRB 5-10- C7 BRB 5-10- C8 BRB 5-10- C1+C2 Tertiary Clarifier Metal Salt Tertiary Caustic Influent (SV)7 P release Sec Scum Influent (SV)17 Combined Filter Effluent - Pre Anaerobic Digesters Bioreactor21 Dewatered Sludge Influent (SV)51 Bioreactor33 OSTARA struvite
P recovery provides equivalent struvite reduction compared with the ferric addition option PPD of Struvite in Sludge Cake 14,000 12,000 30 mgd 40 mgd 50 mgd 10,000 8,000 6,000 4,000 2,000 0 Do Nothing Ostara + WASSTRIP + Mag Ostara + WASSTRIP + No Mag Ostara Centrate No Mag Ferric Digesters Mag Ferric Centrate No Mag Scenario
Struvite recovery + WASSTRIP has lowest net present cost and 8-Year Payback NPC, $ Millions $25.0 $20.0 $15.0 Ostara + WASSTRIP, Mag Ostara + WASSTRIP, No Mag Ostara Centrate, No Mag Ferric Digesters, Mag Ferric Centrate, No Mag $10.0 $5.0 $0.0 2033 2032 2031 2030 2029 2028 2027 2026 2025 2024 2023 2022 2021 2020 2019 2018 2017 2016 2015 2014 2013 Year FWHWRC is pursuing nutrient recovery option
Miami-Dade resource recovery Pure oxygen facilities Meets secondary treatment standards Disposal through deep injection wells CDWWTP 143 mgd AADF Significant nuisance struvite formation issue SDWWTP 112.5 mgd AADF
Miami Dade resource recovery - evaluations In-situ Coupon Testing to Determine Degree of Struvite Formation and Confirm Theoretical Ferric Dose Bench Scale Testing to Determine Optimal Ferric Dose Modeled Struvite Potential and Reduction for Each Alternative & Performed Cost Evaluation Ostara Pilot Test
Nutrient Recovery was the most cost effective option at both plants Notes: * 6% interest and escalation ** Could be significantly higher Long term recommendation is to implement nutrient recovery at both facilities
Summary To mainstream 1. Reduce energy and chemical consumption in the mainstream process 2. Provide factor of safety for mainstream nutrient removal process clarificatio n 3. Minimize nuisance struvite formation and reduce O&M costs Sidestream treatment Dewatering Anaerobic Digestion Thickening Biosolids 1. Manipulate the nutrient content of the biosolids 2. Provide plant with alternative revenue stream
Summary Compare struvite crystallization with precipitation with coagulant (i.e., alum or ferric) Payback site-specific and dependent on the P load Tool for Evaluating Resource RecoverY (TERRY) developed through WERF grant to help facilities perform high level evaluation for implementing P recovery
Contact Information Wendell O. Khunjar, PhD 4035 Ridge Top Road, Suite 400, Fairfax VA 22030 703 267-2759 (direct) wkhunjar@hazenandsawyer.com Katya Bilyk 4011 Westchase Blvd., Suite 500, Raleigh, NC 27607 Phone: 919-755-8593 kbilyk@hazenandsawyer.com Ron J. Latimer, PE 5775 Peachtree Dunwoody Rd. Suite D-520, Atlanta, GA 30342 404-459-6363 (main) rlatimer@hazenandsawyer.com