Discussion on WHO Guidelines on Evaluation of Household Water Treatment Options

1. Discussion on WHO Guidelines on Evaluation of Household Water Treatment Options Regu P. Regunathan PhD ReguNathan & Associates, Inc. Technical Consultant to WQA 10 Aug 2011

2. Guidelines released • Released in June 2011 after considerable reviews and discussions • Intended Audiences are: • National Certifiers • Regulatory Authorities • Researchers • Manufacturers & Implementers • Arranged in 3 short Sections and 4 detailed Appendices

3. Tiered Approach • One of the most contentious subject by reviewers • Modified from original proposal but still retained the essence of the concept . Interim Target approach has been altered significantly. • Based on WHO’s regularly and extensively used target levels of DALY (Disability Adjusted Life Years) • Quantitative Microbial Risk Assessment (QMRA) was employed to estimate Health based Performance Targets

4. DALY • Measure to estimate burdens of disease and injuries • Health effects weighed - 0 (good health) to 1 (death) • Years of life lost due to mortality = YLL • Years of life lived with disability = YLD • DALY = YLL + YLD • 10⁻⁶ DALY/person/year = loss of 365 healthy days/one million/year = 1 excess case of cancer/100000 people drinking water over 70 years

5. Target Pathogens Selected • Bacteria - Campylobacter jejuni • Virus – Rotavirus • Protozoa - Cryptosporidium

6. Tiers presented • Highly Protective ----- 10⁻⁶ DALY /person/year • Protective -------------- 10⁻⁴ DALY/person/year • Interim ----------------- Achieves “protective” targets for two classes of pathogens & results in health gains in applications.

7. Health Based HWT Performance Targets

8. Derivation of Targets using QMRA • Based on known sets of data and several assumptions • Pathogens selected had been cited in GDWQ of WHO along with being involved in several outbreaks • Pathogen levels in raw water calculated on the basis of adding wastewater to a concentration of 0.01% • Daily water consumption, probability of infection by each pathogen, risk of diarrheal illness, and susceptible population were all assumed for the calculations of the DALY and thus these target levels

9. Technologies described in Appendices • Chemical Disinfection (chlorine, bromine, iodine, chlorine dioxide, ozone, etc. • Filters of all types (Membrane, ceramic, Granular, etc) • Solar Disinfection • UV • Thermal Technologies • Coagulation, precipitation and settling • Combination of relevant technologies

10. Protocol Details • Two types of test waters similar to EPA protocol • Differentiation of protocols based on technology • Alternate indicator microbes suggested (E. coli, MS2, C. perfringens spores, inert particles, etc.) • But not very detailed directions for carrying out the actual tests with the selected pathogens or suggested alternates • Mostly guidelines for development of national regulations and protocols along with certification approaches

11. Few thoughts

12. Potentially Simpler Approach • Present approach for interim targets appears well thought out and appropriate compared to earlier 1/1/1 log reductions proposed. • Had to make several assumptions to reach these two tiers and targets. Any different assumptions would have lead to very different results • Could have decided on ONE suggested goal to be reached by different countries. • 10⁻⁵ DALY/person/year could have been selected as the only one approach • This approach would have lead to targets of 3/4/3 for bacteria/virus/ protozoa. If one gets 4 logs of virus reduction along with 3 logs of protozoan reduction that technology would have easily also achieved 6 logs or more of bacteria reduction. Same as EPA protocol of 6/4/3!!!