SANDEC, the Department for Water and Sanitation in Developing Countries (formerly IRCWD) at EAWAG, has been involved in the development and promotion of roughing filters for over a decade. Horizontal-flow roughing filtration was originally studied in the laboratory, then field tested by our cooperation partners in developing countries and finally implemented in demonstration projects. A manual containing a description of this treatment process was published in 1986 as IRCWD Report No. 06/86.
However, the roughing filter technology continued to be developed in the following years, and different types of prefilters and roughing filters were studied and tested. Some of the field staff, not aware of this development, continued to apply exclusively horizontal-flow roughing filters also in places where other filter types would have been more appropriate.
This new manual has been compiled to bridge this information gap. It is based on a complete revision of the old manual, on a draft presented at the International Conference on Roughing Filtration held in Zurich, Switzerland, in June 1992 and on SANDEC's field experience in the implementation of roughing filters. This manual received valuable information from our cooperation partners in developing countries.
SANDEC is grateful for the collaboration and support provided by all the institutions and persons involved in this project. I should like to express my gratitude to the Swiss Development Cooperation, particularly to Messrs Armon Hartmann and Paul Peter who have strongly supported EAWAG's roughing filter project. Last but not least, I extend my thanks to the reviewers of this manual for their valuable comments.
Duebendorf, October 1996