Are slow sand filters safe?
They can be quite safe but should be used with caution and sufficient knowledge of their operation. Water must be allowed to run through them for at least 3 weeks before any is consumed. All parts of the filter must be kept clean – contamination can come from any where outside the filter. Water must be kept over the sand always, and the filter must be allowed to run again for 3 weeks after cleaning before consuming any water from them unless “wet harrowing” is used. Slow sand filters are able to provide very good safe water free from biological pathogens. This is a well established, although not well known, fact. Beaver fever (cryptosporidium) cysts, viruses, and coliform bacteria can all be removed from water by slow sand filters at rates often exceeding 99 percent13 30. It is common knowledge that because of world wide industrialization and lack of attention to the problems of pollution, both “tap” water and rainwater can contain varying amounts of harmful substances, depending on th
They can be quite safe but should be used with caution and sufficient knowledge of their operation. The effectiveness of a slow sand filter depends on the conditions in which they operate; and on the degree of pollution in the water to be filtered. Water must be allowed to run through them for at least 3 weeks before any is consumed. All parts of the filter must be kept clean – contamination can come from anywhere outside the filter. Water must be kept over the sand always, and the filter must be allowed to run again for 3 weeks after cleaning before consuming any water from them unless “wet harrowing” is used. Slow sand filters are able to provide very good safe water free from biological pathogens. This is a well established, although not well known, fact. Beaver fever (cryptosporidium) cysts, viruses, and coliform bacteria can all be removed from water by slow sand filters at rates often exceeding 99 percent13 30. It is common knowledge that because of world wide industrialization a
