Using PAA as an Alternative WWTP Disinfection Method

Transcription

1 Using PAA as an Alternative WWTP Disinfection Method Angie Mettlen WK Dickson Jeremy Brashears, PE WK Dickson John Thorne - WDJ Environmental March 26, 2018

2 What is Peracetic Acid?

3 Comparative Oxidation Potential Hydroxyl Radical 2.85 Ozone 2.08 Peracetic Acid 1.81 Hydrogen Peroxide 1.78 Permanganate 1.68 Hypochlorite Ion 1.64 Hypochlorous Acid 1.48 Monochloramine 1.40 Sodium Hypochlorite 1.36 Dichloramine 1.34 Hypobromous Acid 1.33 Oxygen 1.23 Chlorine Dioxide 0.95 Lide (1995); AWWA (1990); Stumm and Morgan (1996)

4 Peracetic Acid: Environmentally Friendly? Benefits Less increase in total dissolved solids (conductivity) Not persistent in environment (removal of residual not needed) No RMP, SARA or CERCLA constraints Doesn t form chlorinated disinfection byproducts Limitations Slight increase in total organic carbon in treated water Reduced half life above ph of 8.5 Cannot be stored in mild steel containers

5 Peracetic Acid: Disinfection Pros Small footprint for chemical feed Can be fed in neat form Low freezing point Long shelf life (12-18 months) No extensive capital improvements necessary Minimal ph and temperature dependency for efficacy No chlorinated disinfection byproducts Much safer than chlorine gas Approved as a wastewater disinfectant by USEPA

6 Peracetic Acid: Disinfection Cons Requires state by state approval (if not already approved) Cost is site specific Limited suppliers 3 major manufacturers

7 Peracetic Acid for Case Study Solvay Proxitane 15:23 15% peracetic acid; 17% acetic acid; 23% hydrogen peroxide No harmful byproducts Breaks down to acetic acid, CO2 and H2O

8 Design Flow 6.0 MGD Current Permitted Flow 4.5 MGD Current Average Flow 1.0 MGD Receiving Stream Middle Tyger River (Spartanburg Co.) NPDES Permit reissued in 2016 with disinfection byproduct limits Chlorodibromomethane (0.013 mg/l daily mg/l monthly) Dichlorobromomethane (0.019 mg/l daily mg/l monthly)

9 Initial Steps Sampling for DBPs throughout the plant, including at influent Evaluation of disinfection alternatives to chlorine Laboratory bench testing of peracetic acid (Proxitane 15:23)

10 Laboratory Bench Test Results Summary Date PAA Dosage (ppm) ph (predosage) ph (postdosage) Temperature (C) Sample Volume (ml) Detention Time PAA residual E. coli results (MPN/100ml) 11/5/16 BLANK /5/ hour /5/ hour /5/ hour /5/ hour /5/ hour /6/16 BLANK /6/ min /6/ hour /6/ hours /6/ hours

11 Based on bench testing, developed pilot study plan for approval by SCDHEC First phase included recirculating flow (no discharge) Primary PAA feed rate 5ppm Sampling of E. coli at four points (clarifier and 3 points in chamber) every four hours Hourly sampling of PAA residual at two points in chamber Full permit parameter sampling including toxicity testing (dual species) First phase began at 8:45am on August 23, 2017 and was concluded at 12:00pm on August 26, 2017

12 E. coli sampling point #2 PAA Residual sampling point #1 E. coli sampling point #3 E. Coli sampling point #4 PAA residual sampling point #2

13

14

15 Parameter Sample Date Permit Limit 4.5 MGD) Biological Oxygen Demand 8/24/ mg/l (monthly) 33 mg/l (weekly) Total Suspended Solids 8/24/ mg/l (monthly) 45 mg/l (weekly) Result 14.1 mg/l 18 mg/l Limit of Quantitation NH3-N (Mar-Oct) 8/24/2017 8/25/ mg/l (monthly) 3.0 mg/l (weekly) 0.10 mg/l NH3-N (Nov-Feb) 4.29 mg/l (monthly) 6.44 mg/l (weekly) Dissolved Oxygen 8/24/ mg/l (minimum) 8.4 mg/l ph 8/24/ S.U S.U. Total Phosphorus 8/24/2017 8/25/2017 MR 5.4 mg/l 4.7 mg/l 0.25 mg/l Total Nitrogen 8/24/2017 8/25/2017 MR 40 mg/l 37 mg/l 0.40 mg/l Total Cadmium 8/24/2017 8/25/ mg/l (monthly) mg/l (daily) mg/l Total Copper 8/24/2017 8/25/ mg/l (monthly) 0.28 mg/l (daily) mg/l mg/l mg/l Color 8/24/2017 8/25/2017 MR C.U. 74 C.U. 78 C.U. 25 C.U. Antimony 8/24/2017 8/25/ mg/l (monthly) mg/l (daily) mg/l mg/l mg/l Chlorodibromomethane 8/24/2017 8/25/ mg/l (monthly) 0.20 mg/l (daily) mg/l Dichlorobromomethane 8/24/2017 8/25/ mg/l (monthly) mg/l (daily) mg/l Toxicity - Ceriodaphnia 8/24-25/2017 Pass Pass Toxicity - Fathead Minnow 8/24-25/2017 Pass Pass E. coli (average at 5ppm PAA) 8/23-25/ MPN/100ml (monthly) 349 MPN/100ml (daily) 20.8 MPN/100ml

16 Key points from first phase of pilot study No toxicity seen with PAA residual 42% average reduction in E. coli levels from clarifier to first sampling point in chamber after approximately 10 minutes 96% average reduction in E. coli levels from clarifier to second sampling point in chamber after approximately 20 minutes 99% average reduction in E. coli levels from clarifier to end of chamber after approximately 30 minutes Non-detect for disinfection byproduct parameters Normal results for other permit parameters

17 The results from the first phase of the pilot study were submitted to SCDHEC and approval was received to initiate the second phase Normal discharge to Middle Tyger River Sampling of PAA residual at same locations at least twice per day Daily E. coli effluent sampling Full permit parameter sampling including toxicity testing (single species) Second phase began on November 3, 2017 and was concluded on November 10, 2017

18 Parameter Sample Date Permit Limit 4.5 MGD) Result Limit of Quantitation Biological Oxygen Demand 11/8/ /8/ /9/ mg/l (monthly) 33 mg/l (weekly) 3.41 mg/l 4.44 mg/l 3.41 mg/l Total Suspended Solids 11/7/ /8/ /9/ mg/l (monthly) 45 mg/l (weekly) 4.5 mg/l 8.0 mg/l 6.7 mg/l NH3-N (Mar-Oct) 2.0 mg/l (monthly) 3.0 mg/l (weekly) NH3-N (Nov-Feb) 11/7/ /9/ mg/l (monthly) 6.44 mg/l (weekly) 0.10 mg/l Dissolved Oxygen 11/8/ /8/ /9/2017 ph 11/7/ /8/ /9/ mg/l (minimum) 8.32 mg/l 8.31 mg/l 8.42 mg/l S.U. 7.2 S.U. 6.9 S.U. 7.1 S.U. Total Phosphorus 11/7/2017 MR 4.6 mg/l 0.25 mg/l Total Nitrogen 11/7/2017 MR 38 mg/l 0.40 mg/l Total Cadmium 11/7/ mg/l (monthly) mg/l (daily) mg/l Total Copper 11/7/ mg/l (monthly) 0.28 mg/l (daily).038 mg/l mg/l Color 11/7/2017 MR C.U. 54 C.U. 25 C.U. Antimony 11/7/ mg/l (monthly) mg/l (daily).0028 mg/l mg/l Chlorodibromomethane 11/7/ mg/l (monthly) 0.20 mg/l (daily) mg/l Dichlorobromomethane 11/7/ mg/l (monthly) mg/l (daily) mg/l Toxicity - Ceriodaphnia 11/6-10/2017 Pass Pass E. coli (average at 5ppm PAA) 11/4-9/ MPN/100ml (monthly) 349 MPN/100ml (daily) 6.63 MPN/100ml

19 Key points from the second phase of pilot study Better results with normal discharge operations Still no toxicity with PAA residual Average E. coli result of 6.63 MPN/100ml Non-detect for disinfection byproduct parameters Normal results for other permit parameters

20 Cost Comparison: Chlorine gas /SO2 v. Proxitane 15:23 Current Average Flow (MGD) Permitted Flow (MGD) Design Flow (MGD) Chemical Doseage PPM Price per pound Chlorine Gas 10 $0.30 $ 10,959 $ 41,095 $ 54,794 Sulfur Dioxide Gas 5.7 $0.45 $ 9,370 $ 35,137 $ 46,849 Total Cost $ 20,328 $ 76,232 $ 101,642 Peroxitane 15:23 5 $1.20 $ 21,918 $ 82,191 $ 109,588 Total Cost $ 21,918 $ 82,191 $ 109,588 * Does not factor in potable water cost savings when injectors are used for chlorine and Peroxitane 15:23 is fed neat.

21 Next steps Requested conditional SCDHEC approval for Proxitane 15:23 Complete a full 30-day implementation with normal discharge Will increase flows slowly to 4.5 MGD (current permitted flow) to determine optimal disinfection contact time Will increase PAA feed rate to determine effects on disinfection contact time (no more than 10ppm) Sampling protocol similar to first phase

22 Special Thanks to the Town of Lyman and Scott Miller, Public Works Director

23 Want More Information? WDJ Environmental WK Dickson & Co., Inc. 156 Reserve Drive 128 Millport Circle, Suite 200 Piedmont, SC Greenville, SC John Thorne Jeremy Brashears, PE Angie Mettlen