Water disinfection for developing countries and potential for solar thermal pasteurization

Water-borne disease in developing countries leads to millions of deaths and billions of illnesses annually. Water disinfection is one of several interventions that can improve public health, especially if part of a broad program that considers all disease transmission routes and sustainably involves the community. Considering water volumes less than or similar to 30 m(3)/day, appropriate disinfection methods include chlorination, slow sand filtration, ultraviolet (UV) radiation and pasteurization. Pretreatment with a coarse roughing filtration is generally used with the first three of these technologies to reduce turbidity and maintain high effectiveness. Cysts and worm eggs are resistant to chlorination and UV but can be filtered relatively easily. Chlorination is widely used and inexpensive but requires a continual supply of chemicals. Slow sand filtration is lowest in cost but requires high investment in labor. Household filtration using indigenous devices requires little capital investment but is relatively ineffective and difficult to properly maintain. Batch treatment with solar UV is very easy to implement but effectiveness in practice is uncertain since temperatures above 50 degrees C should be attained. UV lamp devices are inexpensive and easy to use but require power and access to maintenance infrastructure. Boiling of water requires no initial expense but fuel and labor costs are very high. Solar pasteurization devices (batch and flow-through) are effective and relatively maintenance-free, but existing products yield high treatment cost. Flow-through systems with selective Rat plate collectors become cost-competitive with UV technology at costs of about $380/m(2) and $80/m(2) for home-scale and village-scale use, respectively. These cost goals might be attained with polymer thin film designs if durability issues are adequately resolved. Published by Elsevier Science Ltd.