Evaluation of the long-term sustainability of biosand filters in rural Ethiopia

Point-of-use water treatment is growing in popularity in the developing world, especially in rural areas where the costs of providing centralised treatment systems are higher than their low cost counterparts. One such technology, the biosand filter, has been shown to effectively remove turbidity and pathogens in laboratory and field research but the long-term performance of the filter and its sustainability are not well documented. An evaluation was therefore conducted to examine filters in rural Ethiopia installed more than 5 years previously. Filters were examined to assess filter performance, maintenance practices and the supporting environment. The working filters showed an average E.coli reduction rate of 87.9% with 75.7 % of filtrate samples achieving rates of <10cfu/100ml and 81.2% achieving turbidity values of <5NTU. The varied levels of usage in the three study villages, from 44% to 100%, also highlighted several risks and opportunities for continued active long term adoption.