The long-term sustainability of household bio-sand filtration

The introduction of intermittently operated slow sand filters, suitable for use at household level, is gaining momentum in the developing world. An estimated 100,000 bio-sand filters are already in use, providing improved drinking water to more than half a million people. Laboratory and field research has shown that bio-sand filters are capable of impressive reductions of turbidity and pathogen levels. However, long-term sustainability, social acceptance and appropriateness have not been well documented. An evaluation was therefore conducted in rural Kenya to measure the performance of filters introduced 4 years previously. Measuring turbidity and E.coli removal rates, maintenance practices and user perceptions, the study found all but one filter were still in use with over 70% producing water of good quality. Underperformance of some filters pointed at poor maintenance habits. As a ‘point-of-use’ water treatment solution, bio-sand filtration seems to be very appropriate, effective and cheap. Strategies to introduce this promising technology at a large scale need to be seriously investigated.