Chemical Measurements in Drinking Water: Their Use in Monitoring Disinfection and its Consequences

1. Chemical Measurements in Drinking Water: Their Use in Monitoring Disinfection and its Consequences Kusum Perera, Ph.D.

2. Objectives • Overview of water disinfection • Importance of disinfectant (chlorine) dose measurements • Disinfectant By-Product (DBPs) formation • DBP measurement and mitigation • Alternative disinfectants and other DBPs

3. Water Disinfection by Chlorination • Water chlorination was a major advancement in public health protection • By the 1920s water systems in most major cities in the USA were chlorinating their DW supply • 1940s and 1950s saw major advancements in chromatographic techniques to separate, identify and quantify chemicals • First chemicals resulting from disinfectant treatment were isolated in the 1970s, called Disinfection By Products - DBPs

4. Analysis of DBPs • Samples collected in a 40 mL vial and kept cold – analysis within 14 days • An inert gas is purged through the sample and the volatilizing gases are trapped on to an adsorbent medium – XAD resin • The resin is heated and the emanating gases are injected into the separating column • The separated gases are detected, identified and quantified

7. DBP Formation Chloroform Dichlorobromomethane NOM + Chlorine Trihaloacetic Acids X = Br, Cl Dibromochloromethane Bromoform

9. EPA Method 524.2 Chromatogram USGS recently published a study on the occurrence of the 15 most prevalent volatiles in US groundwater using this method

11. Biostatistics and Epidemiology THMs • Occurrence - Base on NORS (National Organics Reconnaissance Survey, 1975), ~75% TTHMs is from chloroform. In some case, chloroform was found at 300 ppb. • Risk Assessment - Base on National Academy of Sciences’ report (1977), cancer risk = 3.4x10-6 / ppb (chloroform) at upper 95% confidence limits, assuming 70 year daily consumption of water at 2 L/day. • Risk Reduction - Chloroform reduction from 300 ppb to 100 ppb, about 2500 cancer cases would been avoided in a population of 250 million people annually. Source: NAS, 1977, “Drinking Water and Health”, Washington, D.C.

12. Regulating Chemicals • Maximum Contaminant Level Goals - MCLGs Considers only health effects (NOT the limits of detection and treatment technology) - Non-Carcinogen: NOAEL (no-observed-adverse-effect level) - Carcinogen & Public Health Risk Microbes: Zero • Maximum Contaminant Level - MCLs MCL set as close to MCLGs as feasible, consider best available analytical technology, treatment techniques, cost and benefit. USEPA

13. Trihalomethanes (THM) Rule - 1979 Public health risk exists from exposure to TTHMs in drinking water, the potential for the risk need to be reduced as much as is technologically and economically feasible without increasing the risk of micro-biological contaminations. Basis of the THM Rule: - TTHMs first regulated at 100ug/L - based on cancer deaths prevented - Methods to reduce formation; NOM reduction in source water and alternative disinfectants - Availability of removal technology - Cost considerations

14. Summary of C.t values (mg/L.min) for 99% inactivation at 5°C a Values for 99.9% inactivation at pH 6-9, b 99% inactivation at pH7 and 25°C, c 90% inactivation at pH7 and 25°C WHO Report, (Clark et al, 1993) What is an effective disinfectant dose for pathogen inactivation in water? Depends on …. The type of pathogen, pathogen load, turbidity, pH and temperature

16. Control of THMs • Reduce NOM prior to treatment • Enhanced coagulation, pH control • Control chlorination dose or use alternative disinfectants • Minimize effective dose • Chlorine dioxide, UV, etc. • Removal THMs • GAC, Synthetic resins

17. Advancements in Analytical Technology • THMs have high vapor pressure and less soluble in water - P&T GC • Semivolatiles have lower vapor pressure but easily extracted from water - GC/MS • Polar, non-volatiles difficult to pull out of water - LC/MS • Mass spectrometry gives selectivity • Last count – over 700s DBPs!

18. Some Chlorine DBPs • Trihalomethanes (THMs) • Chlorinated Acetic Acids • Halogenated Acetonitriles • Chloral hydrate (trichloroacetaldehyde) • Chlorophenols • MX (3-chloro-dichlomethyl-5-hydroxy-2(5H)-furanone)

19. D/DBP Rule Implementation USEPA • Transition from THM rule to D/DBP rule: • 1979 to 1994 • Advances in analytical techniques, new tox and epi data, risk management • Discovery of other DBPs – Haloacetic Acids • D/DBP rule stage 1 – 1999 and stage 2 - 2006

20. Disinfection’s Public Health Effect Source: US EPA

24. EIC of LC/MS for Haloacetic acids by Electrospray Ionization Applied Biosystems API 4000

25. Disinfectant & Disinfection Byproducts Chlorine Trihalomethanes, Halo Acetic Acids, Halogenated Acetonitriles, Chloral hydrate, Chlorophenols, MX Chloramines Same as above but at lower level, Cyanogen Chloride, Nitrosamines (e.g. NDMA) Chlorine Dioxide Chlorite, Chlorate, Chloride Ozone Formaldehyde, Aldehydes, Hydrogen Peroxide, Bromomethanes, Bromate

28. Conclusions • Drinking water disinfection is an essential component in the protection of public health. However, the type of DBPs formed is dependent on the water quality and disinfectant used. • Disinfection generates DBPs that can be measured reliably. Studies on Health effects and risks associated with DBPs follow. Strategies for risk mitigation are sought out. Proposed legislation addresses the problem and provides an opportunity for public comment. • In the US, THM rule and the accompanying regulations is the first legislation to address the issue of risks associated with DBPs. Under the rule, water systems are required to monitor for DBPs to ensure control public exposure DBPs. • Alternative disinfectants leads to other DBPs and the ongoing public health challenge is to address the emerging concerns