ABSTRACT
Most of the technology suitable for urban water supply in low and middle income countries is similar to that used in the high income countries and is described in conventional textbooks on water supply such as D. Ratnayaka et al. Treatment is usually necessary for surface water sources; it is particularly important for town water supplies because so many people are at risk. Treatment is of little use if it is only erratically applied and yet it is a major problem to ensure continuous and reliable operation of water treatment works in many countries. Various modifications and simplifications in the control of the filtration rate and of backwashing have been developed and are especially appropriate in low and middle income countries. In a typical urban water supply, the cost of the distribution system accounts for about one-third of the total construction cost. Water meters also permit the introduction of a ‘progressive’ tariff policy.
