Roof water collection systems in some Southeast Asian countries: status and water quality levels.

There is extensive use of simple and inexpensive roof water collection systems in some Southeast Asian countries. The collected runoff which flows off different types of roofs is affected not only by the inherent quality of the roofing material but also by the contamination of roofs by rodents, birds, etc. Consequently, bacteriological quality levels are excessive though the collected rainwater is still used extensively for potable purposes. From samples collected in most locations, there were positive Total and Faecal Coliform counts though, in terms of physico-chemical parameters, roof water appears to be of a higher quality. Various causes have been attributed to the frequent presence of Faecal Coliform but, mostly, pollution is of animal origin as the Faecal Coliform/Faecal Streptococci ratio is less than unity. It is proposed that the collected roof water be boiled, disinfected with household bleach or be subjected to radiation from sunlight which appears to have good potential to be an effective bactericide. It is recommended that simple testing methods be developed and health education imparted to the various aspects of utilising roof water collection systems.