Household Water Treatment Techniques for Chemical Removal

1. Household Water Treatment Techniques for Chemical Removal Susan Murcott, Senior Lecturer, MIT, murcott@mit.edu Tommy Ka Kit Ngai, Research Associate, CAWST, tngai@cawst.org Although “the most common and widespread health risk associated with drinking water is microbial contamination” (WHO, 2004), in parts of the world, certain chemicals, including arsenic, fluoride and nitrate, is causing serious health effects from excessive exposure through drinking water. For example, arsenic contamination worldwide affects an estimated 160 million people (WHO, 2008). In Bangladesh, approximately 30 – 40 million people are exposed to arsenic contamination, with an expected 2.5 million people developing some form of arsenicosis symptom in their lifetime and over 320,000 people dying from arsenic induced cancer over the next 50 years (World Bank, 2005). Here we will describe some of the simple and low cost techniques to remove arsenic at the household level. Solar Oxidation and Removal of Arsenic (SORAS) Passive Oxidation Asia Arsenic Network Filter • Leave water overnight in container • Arsenic co-precipitation with natural iron in water • Manual aeration and oxidation of natural iron in water • Arsenic co-precipitate with ferric hydroxide • Followed by sand filtration • Similar to SODIS, but add lemon juice • Photo-chemical oxidation of As(III) to (V), followed by co-precipitation with iron Aeration bucket • Arsenic removal dependent on iron concentration • Typically 30-50% arsenic removal • Minimal cost • If iron > 8ppm, 75-90% arsenic removal • If iron < 5ppm, <50% arsenic removal • Excellent microbial removal (99+%) • Arsenic removal dependent on iron concentration • Typically 70-80% arsenic removal Sand filter • $15-20 capital cost 2-Kolshi PuR Bucket Treatment Unit (BTU) • Oxidation and coagulation using calcium hypochlorite and ferric sulfate • Followed by sedimentation and filtration through cloth • Oxidation and coagulation using sodium hypochlorite and ferric chloride • Followed by filtration in a ceramic filter • Oxidation and coagulation using KMnO4 and alum • Followed by filtration through cloth • Moderate arsenic removal (~60%) • $10 capital cost • $15-20 chemical cost/ family/ year • Good arsenic removal (90%) • Good microbial removal (99%) • Excellent arsenic removal (95+%) • Excellent microbial removal (99+%) • $50-100 chemical cost/ family/ year • $10 capital cost • $15-20 chemical cost/ family/ year Magc-Alcan Filter Nirmal Filter Read-F Filter • Arsenic adsorption on Indian-made activated alumina; • Followed by filtration through ceramic candle • Good arsenic removal (80-90%) • $10-15 capital cost • Regenerate alumina every 6 months • New alumina after 3 regenerations • Arsenic adsorption on Japanese-made, proprietary, hydrous cerium oxide • Excellent arsenic removal (95+%) • Long media lifespan (3+ years) • $50-70 capital cost • Arsenic adsorption on American-made activated alumina • Two identical buckets of media • Good arsenic removal (80-85%) • Good fluoride removal • Media life span about 1 year • $35-50 capital cost Sono Filter Kanchan Arsenic Filter (KAF) Shapla Filter • A regular biosand filter modified with a tray of rusty iron nails for arsenic removal through surface complexation • Surface complexation of arsenic on composite iron matrix; • Followed by sand filtration • Excellent arsenic removal (90-95+%) • $40-50 capital cost • Replacement of unit after 3-5 years • Arsenic adsorption on Bangladeshi-made iron-oxide coated brick chips • Good arsenic removal (80-90%) • Short media lifespan (3-6 months) • Excellent arsenic removal (80-95%) • Good microbial removal (85-99%) • $25-30 capital cost • Replacement of iron nails after 2-3 years ($5-8) • $10 capital cost • $10-15 media replacement cost/ family/ year References:WHO. Guidelines for Drinking Water Quality. Vol. 1. 3rd Edition. Geneva, 2004. WHO. Arsenic Contamination in the World: An International Sourcebook. Forthcoming Publication. 2008. World Bank. Towards a More Effective Operational Response – Arsenic Contamination of Groundwater in South and East Asian Countries. Vol. 1. Policy Report. Washington, 2005