The use of Huwa-San peroxide as a secondary disinfection agent for halting the production of trihalomethanes in polished drinking waters

Transcription

1 The use of Huwa-San peroxide as a secondary disinfection agent for halting the production of trihalomethanes in polished drinking waters Gordon Balch, Brent Wootton, David Barnes, and Colin Guthrie Centre for Alternative Wastewater Treatment, Fleming College, Lindsay, Ontario, Canada. SanEcoTec, Ottawa, Canada

2 Acknowledgments College and Community Innovation Program: Applied Research and Development Grant

3 Goal Reduction of THMs by using a silver stabilized peroxide as the secondary disinfectant To pilot in municipal drinking water plant using HSP within an AVIVE regime 3

4 Outline 1. Framing Issue of THMs 2. Overview of Killaloe DWTP 3. Study Objectives & Design 4. Summary of Results 5. Next Steps 4

5 A Canada Wide Issue THMs HAAs Source: Chowdhury et al Disinfection byproducts in Canadian provinces: Associated cancer risks and medical expenses. J. Hazardous Materials 187:

6 The Need 14 16% of bladder & colorectal cancers in Ontario associated with DBPs Approx. 700 cancer cases per year in Canada may result from exposure to THMs Estimated medical cost per year for cancers from THM exposure in Canada estimated to be $140 million Other health effects related to exposure to chlorinated DBPs (Richardson et al & 2007; Chowdhury et al. 2011) 6 Community Eye Health

7 Peroxide Halts DBP Formation Batterman et al experimentally demonstrated THMs and HAAs formed from interaction of chlorine with DOM Contact time and DOM conc. was found to be significant factors governing formation Common THMs include: Chloroform, dichlorobromomethane, etc. Common HAAs include: Monochloroacetic acid, monobromoacetic acid, etc Demonstrated that the use of a Ag + /H 2 O 2 as 2 disinfectant halted DBP formation by quenching chlorine 7

8 Killaloe, Ontario Renfrew County, eastern Ontario 8

9 Killaloe: in situ testing Killaloe was identified by OCWA as a suitable candidate site Relatively simple system Small population Historic issues with THMs 9

10 Killaloe Water System Small system only 90+ connections Owned by the Township of Killaloe, Hagarty and Richards Operated by OCWA Groundwater wells GUDI with in-situ filtration Treatment for iron and manganese removal UV discharging to clearwells Long residency time in clearwells and distribution system (3 to 5 days) THM levels near or over the 100 µg/l limit Some individual samples approaching 200 µg/l

11 Overview of Killaloe WTP Well Chlorine 1 Disinfectant Green Sand Filter UV HSP Clearwell Distribution 2 Disinfectant 4 locations monitored HSP replaced chlorine as the secondary disinfectant Equipment needs for HSP are similar to what is required for feeding and monitoring sodium hypochlorite Chemical feed pumps (off the shelf) Peroxide residual monitors (supplied by Kramer) Handheld units for sampling in distribution system HSP intended quenched residual chlorine and stopped the formation of chlorinated DBPs and provide adequate 2 disinfection DWTP services approximately 300 people 11

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13 Project Approvals Consulted with: Ontario Ministry of the Environment Regulatory Relief Sections from O. Reg. 170/03 under the Safe Drinking Water Act Amendment to the Drinking Water Works Permit Additional sampling and reporting for initial 3 months Voluntary sampling (i.e. residential hot water systems) HSP residual should be maintained between 1 to 8 ppm Township staff and council County Health Unit Provided public notification Developed a baseline monitoring program (pre & post intervention) 13

14 Preliminary Testing, Baseline Monitoring and Enhanced Sampling Preliminary Testing Monitor THM production as a function of chlorine CT Determine conc of HSP required to both quench chlorine and produce a HSP residual in distribution system Establish Baseline (pre HSP; e.g., chlorinated regime) THMs & chlorine concentrations Microbial indicators (focus on use of ATP as rapid indicator) Enhanced Sampling Key water quality parameters monitored more frequently to assure quality of polished water prepared with HSP 14

15 Study Design On-Site Sampling occurred at: Beginning of distribution line (e.g., treated water) 4 locations alone distribution system DWTP located approx. 2 km from centre of town Difficulty with consistent water consumption at these sites Assessment of HSP stability in Hot Water laboratory Inconsistent water use in town negated proper study of HSP stability testing was completed under standardized laboratory conditions 15

16 Study Objectives 1. Evaluate the ability of HSP to reduce chlorinated DBPs 2. Evaluate the efficacy of HSP as a 2 nd disinfectant 3. Compare disinfection potential of HSP to Chlorine 4. Assess the stability of HSP in hot water 16

17 Study Highlights Overview of Results 1. Did we reduce THM formation? 2. Did the use of HSP negatively impact water quality? 3. Is the disinfection potential of HSP comparable to chlorine? 4. Can a HSP residual be maintained in Hot Water Tanks? 17

18 1.Result: HSP reduced TMH generation 250 THMs (ug/l) Year Total THM were stabilized in a range at or below 26 µg/l (Dec 2012 Aug 2013) Pre-HSP treatment - treated water Pre-HSP treatment - 12 Coll St. Post-HSP - treated water Post-HSP 12 Coll St Post-HSP 177 Queen (Visitor Centre) Post-HSP 181 Queen St. (Afelskie's shoe store) Post-HSP 2 Mill St. (McCarthy fuel) Col 1 vs Col 15 Col 1 vs 2 Mill St (McCarthy fuels) THMs: 1/1/

19 2. Result: HSP did not negatively impact the quality of the polished drinking water Schedule D (conditions for relief from regulatory requirements) Enhanced monitoring program (Nov 2012 Aug 2013) Microbial indicators (E. coli; total coliform; heterotrophic plate counts) ph Trace elements (Pb, Cu, Mn) THMs Undertaken by OCWA at request of MOE Analysis conducted as lab certified for drinking water All monitored parameters met compliance guidelines 19

20 Comparing Disinfection potential of HSP to Chlorine by the following: a. Regulatory monitoring of microbial indicators (E. coli, total coliform, HPCs) b. HSP residual in distribution line c. Decreased loading of microflora in treated water determined by rapid ATP methodology 20

21 3. Result: Microbial indicators of waterborne pathogens in HSP treated water compliant with Regulations Requirement: E. coli: none in 100 ml water sample Total Coliform: none in 100 ml of treated water leaving a DWTP; < 10% of samples in distribution system with detectable total coliforms Heterotrophic Plate Counts: used as a monitoring tool; should not exceed established background levels Results for samples treated with HSP did not differ from those treated with Chlorine 21

22 3. Result: HSP Residual within range needed for disinfection H 2 O 2 (mg/l) Treated water 177 Queen St. (Tourist centre) 181 Queen St. (Afelskie's shoe store) 158 Queen St. (Restaurant) 12 Coll St. cold water Dec Jan Feb Mar Apr Month HSP residual was maintained above minimum of 1 ppm to ensure disinfection HSP residual was refined over time with final range in Aug 2013 (not shown) being between 3.6 to 6.4 ppm 22

23 ATP Testing - Luminultra Measures Adenosine Triphosphate A chemical found in living microorganisms Quantitative indication of microbial activity in a sample Results in 5 minutes Indication of the amount of biofilm on pipe walls Testing equipment loaned to this project by Luminultra Sampling and testing undertaken by staff from OCWA and Fleming College s CAWT ATP augmented testing of Microbial Indicators Provided a rapid indicator of microbial loading Does not distinguish between indicator organisms and nonpathogenic species, but gives information on wider spectrum of microflora 23

24 3. Result: HSP microbial suppression comparable to Chlorine ATP mean values of polished water expressed as Percentage of Raw Water Values Mean ATP Equvalents expressed as % of Raw Water ATP Chlorine HSP Note: mean ATP equivalence during HSP regime was 1.9 times greater than during period of chlorination n=9 n=21 n=9 n=21 n=8 Treated Water 177 Queen 181 Queen 158 Queen 12 Coll n=21 Sample Location n=1 n=7 n=9 n=13 24

25 Assessing HSP Stability in Hot Water Test Design Jar test (measured spike concentration, no head space) All samples brought from room temperature to 60 C and incubated for 15 min (total heating / cooling time approx. 2.5h) Chlorine, HSP measured 1 and 30 min. after unsealing 25

26 Hot Water Test Matrix Non-chlorinated Tap water Tap water lab water Cl amended Cl amended not heated heated for 15 C HSP = 6.9 ppm HSP = 0 ppm HSP = 6.9 ppm Cl = 0 ppm Cl = 2.1 ppm Cl = 2.1 ppm t=1&30min t=1&30min t=1&30min n=3 n=3 n=3 HSP = 6.9 ppm HSP = 0 ppm HSP = 6.9 ppm Cl = 0 ppm Cl = 2.1 ppm Cl = 2.1 ppm t=1&30min t=1&30min t = 1 & 30 min & 72h n=3 n=3 n=3 26

27 4. Results: HSP Stability in Hot Water (60 8 HSP Concentration (ppm) HSP Spike Concentration non-heated lab water heated lab water non heated NaOCl spiked CKL tap water heated NaOCl spiked CKL tap water 0 within 30 mins Time of measurement after unsealing jar 72 hours 27

28 4. Results: Chlorine Stability in Hot Water ( Free Chlorine Concentration (ppm) Chlorine Spike Concentration non-heated NaOCl spiked CKL Tap water heated NaOCl spiked CKL Tap water Heat Treatment 28

29 Outcomes HSP halted formation of THMs HSP did not negatively impact quality of finished water Disinfection potential and residual comparable to Chlorine HSP has greater stability in Hot Water than Chlorine Easy to use for operators Similar to sodium hypochlorite No chlorine taste in the drinking water Significant consumer acceptance 29 hbarrows

30 Next Steps Repeat Study in Newfoundland Two small communities Elevated THMs and HAAs Tuberculated Pipe Study Different source waters Monitoring for liberation of Iron Use of a recirculation system 30

31 Questions 31

32 Fleming Tuberculated Pipe Experiment - Flow Diagram Flow Meter- Regulated Valve S P Sand Filter P S Legend: S - Sample Point Fill P - Pressure Gauge - Filter Bypass Water Reservoir Small Hydropneumatic Compensation Tank TPS S VSCP - Variable Speed Circulation Pump TPS - Tuberculated Pipe Section -Valve - Check valve To Drain P VSCP Notes: Target flow rate = 1.5 m/s through TPS Flow meter-regulated valve pre-set at 0, 15, 95% of desired max flow of 1.5 m/s through TPS P before TPS set at 65 psi to control VSCP at 65±2 psi for different flow rate Placing one sampling point at highest point in the loop will allow draining of air from the system 32

33 Killaloe Water System

34 System Design Chlorine (1 disinfect) to achieve CT requirements Chlorine added to incoming raw well water Used residency time in contactor tanks and pipes (before UV) to achieve CT Preliminary testing confirmed THM generation increased with CT HSP added immediately after UV system Preliminary testing confirmed HSP quenched chorine and halted THM production Preliminary testing identified HSP dosing requirements needed to maintain a HSP residual in distribution system >1ppm (target was 3 ppm) Issue of backwashing contactors with peroxidated water Filter to waste until chlorine levels restored 34

35 ATP: microbial equivalents (#/ml) 35

36 ATP Values Monitoring Period for Secondary D isinfection Agent Raw Water Treated Water 177 Queen St. 181 Queen St. 158 Queen St. 12 Coll St. Sodium H ypochlorite (Oct18 - N ov 27, 2012) Mean ± S.D ± ± ± ± ± 5204 range ( ) ( ) ( ) ( ) ( ) % AT P reduction from Raw Water H uwa-san (Dec 3 - Mar 6, 2013) Mean ± S.D ± ± ± ± ± ± 4205 range ( ) ( ) ( ) ( ) ( ) ( ) % AT P reduction from Raw Water