Using solar radiation to disinfect water is not a new idea, although its application has been limited. Motivated by ancient disinfection practices still being used in several places in the world, and related indications found in old books, Prof. Aftim Acra of the American University of Beirut (Lebanon) initiated during the late 1970s research on the effect of solar radiation on the quality of water used in oral rehydration solution. The initial research project was financially supported by the Gulbenkian Foundation (Lisbon, Portugal) and the United Nations Children's Fund (UNICEF). This experience was followed by a project funded by IDRC (International Development Research Centre), in which Prof. Acra and his team examined the effectiveness of a continuous-flow solar disinfection unit in eliminating pathogenic organisms from water. This system was intended for use by small communities, refugee camps, institutions, and during emergency and disaster situations.

In the early 1980s, and based on the pioneering work of Prof. Acra, the Integrated Rural Energy Systems Association (INRESA), an associated program of the United Nations University (IJNU), supported several other research projects on solar water disinfection. Their preliminary findings confirmed those of Prof. Acra's experience, that ground and surface water can be disinfected of many kinds of bacterial pathogens through solar radiation.

In August 1988, IDRC and UNU cosponsored the first Workshop on Solar Water Disinfection. The workshop was hosted by the Brace Research Institute in Ste Anne de Bellevue (Quebec, Canada), which serves as the secretariat for INRESA. The original comprehensive technical report filed by Prof. Acra on completion of his IDRC-supported research project was presented at the workshop. This book is an edited version of that report.

It is hoped that researchers and field-workers alike will use Prof. Acra's findings to continue research and development in the field of solar disinfection of water meant for human consumption.

Alex Redekopp Senior Program Officer (formerly) Health Sciences Division International Development Research Centre