Evaluation of bleach pretreatment in the performance of personal water filters

Families in rural areas of the Dominican Republic have limited access to potable water. Personal water filtration systems, consisting of two 5-gallon buckets, a ceramic filter element and a spigot, have been made available to remove the bacterial contamination found in normal sources of drinking water. Pretreatment with bleach is possible as the ceramic filter element contains activated carbon that will remove excess chlorine. This will eliminate bacteria, but reduce the life of the filter element and increase the cost of ownership. Bleach use is limited by cultural, economic, and physical limitations. Our studies indicate that bleach pretreatment may be unnecessary. Severely contaminated water was purified to determine the limitations of purification without bleach. Six personal filters were assembled and allowed to filter multiple trials of water from a local river. The river water was analyzed for E.Coli prior to filtration and purified water was analyzed after 12 hours. Despite the extremely high levels of bacterial contamination in the source water, the ceramic filter elements were effective in eliminating over 99.9% of E.Coli bacteria. There was a correlation between the levels of bacteria of the river water and the filtered water for each trial. In most cases, source water purified without bleach pretreatment will be of little health risk. However, for rivers and shallow wells bleach pretreatment is required.