Pre-treatment alternatives for drinking water supply systems : selection, design, operation and maintenance

This document is on the selection, design, operation and maintenance of different pre-treatment alternatives all using coarse media filtration followed by slow sand filtration. It also includes some general concepts relating to drinking water treatment for domestic use. It aims to fill the information gap concerning pre-treatment technologies which can be combined with slow sand filters. The document is of particular relevance to staff involved in planning, design, and the supervision of the operation and maintenance of water supply schemes in developing countries and countries with increasing water pollution problems. The findings are based on field research carried out in Colombia in the period 1989-1993. There appears to be a vast potential for combining two-stage roughing filtration and slow sand filtration. This multi-barrier concept of water treatment, without the use of chemical coagulants, only required low dose disinfection to ensure safe drinking water. Even though further technical and economic refining is anticipated, the general conclusion was that two-stage roughing filtration and slow sand filtration offer a very reliable and effective means of water treatment which can be managed even by small communities.