HWTS and Geogenic Contamination

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1 HWTS and Geogenic Contamination Rick Johnston, Addis Ababa, February 8, 2013 Eawag: Swiss Federal Institute of Aquatic Science and Technology

2 HWTS principally target pathogens Viruses, bacteria, protozoa Type of HWTS Example Effect on As, F Thermal Boiling None Ultraviolet SODIS None (SORAS) Filtration Slow sand filters Ceramic filters Synthetic membranes Disinfection Liquid chlorine None Variable usually low Can be source! Combined e.g. flocculation + disinfection P&G Purifier of Water Can be significant - As more easily removed

3 Geogenics can also be removed at household level Arsenic, Fluoride (Iron) Removal Mechanism Coagulation Adsorption Example Nalgonda method Ferric chloride, alum Bone char Activated alumina Membrane filtration Granular Ferric Hydroxide Iron Oxide Coated Sand Reverse Osmosis Nanofiltration

4 Household arsenic removal filters (Bangladesh) Provisionally verified in 2003, formally in 2009 SIDKO READ-F MAGC/ALCAN SONO Granular ferric hydroxide Activated Alumina Cerium Oxide Zero Valent Iron UNIC EF $4,300 $50 $80 $40

5 Household arsenic removal filters (Bangladesh) Verified in 2009 NELIMA SHAWDESH Proprietary Media Oxidation, Coagulation, Filtration

6 Household fluoride removal filters (bone char) 04/04/

7 Microbiological effects of F-removal filters Field Studies in Kenya, MSc., Rahel Künzle, urban filters monitored for 2.5 months Source: piped water, good quality E, coli Total Coliforms Source Candle Tap Glass Source Candle Tap Glass

8 Microbiological effects of F-removal filters Field Studies in Ethiopia. MSc., Nina Küng, 2011 Sand filter instead of candle E. coli measured in 40 rural filters, 4 villages Source quality effect Surface water improved Groundwater deteriorated Significant contamination between source and filter (~2 log units) Within filter: Increased after sand filter Decreased after bone char filter Net: slight decrease (0.75 log units). Again increased at glass level

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10 N. Küng, 2011 Conclusions: Much contamination occurs during transport & storage Bone char filter improves microbial quality (a bit) Sand filter pretreatment doesn t (makes it worse)

11 Challenges of geogenic HWTS High cost Compared to centralized treatment, WTP Replacement Monitoring or predicting breakthrough Supply and service chains Compliance Data suggest << 2 lpcd treated Efficiency Dependent on water quality and hydraulics

12 Comparison to microbial HWTS High cost of geogenic No very low-cost options Replacement Comparable to some HWTS products Lifetime harder to predict Compliance Low compliance is less a problem Household contamination Critical for microbial, not an issue for chemical

13 Implications for geogenic HWTS As and F removal may be better at semi-central scale Easier monitoring and replacement Easier access by poor Economies of scale - Risk of faecal contamination during collection, transport and storage (N. Küng) Main applications Short-term measure Areas of low population density

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15 Microbial HWTS in As/F endemic areas Emphasis on avoiding rather than removing arsenic Many alternatives are microbially compromised Risk substitution Lokuge (2004) estimates arsenic avoidance in Bangladesh could increase diarrheal disease burden by 20% Possible linkage: alternative water source + HWTS Two behaviour changes

16 Risk substitution in Bangladesh Deep Tubewell Arsenic DALYs Rainwater Shallow Tubewell Reference risk is 10-6, or up to 10-5 (On this scale, to 0.01) Dug Well Pond Sand Filter DALY/1000 person-years Howard, 2005, RAAMO

17 Risk substitution in Bangladesh Deep Tubewell Arsenic DALYs Rainwater Shallow Tubewell Dug Well Pond Sand Filter DALY/1000 person-years Howard, 2005, RAAMO

18 Risk substitution in Bangladesh Deep Tubewell Rainwater Shallow Tubewell Microbial DALYs Arsenic DALYs Reference risk is 10-6, or up to 10-5 (On this scale, to 0.01) Dug Well Pond Sand Filter DALY/1000 person-years Howard, 2005, RAAMO

19 Risk substitution in Bangladesh Deep Tubewell Rainwater Microbial DALYs Arsenic DALYs Shallow Tubewell Dug Well Pond Sand Filter DALY/1000 person-years Howard, 2005, RAAMO

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21 Microbial quality of sources in Ethiopia (Küng, 2011)