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Biosand filters in Ghana contribute to a 60% overall reduction in diarrhoeal disease

Eric Fewster

An 8-month randomized controlled trial of the plastic biosand filter was performed in 6 rural communities in Tamale, Ghana, during 2008 by Stauber et al (2012). The trial was carried out in order to assess reductions in diarrheal disease and improvements in household drinking water quality. During the study, the longitudinal prevalence ratio for diarrhoea comparing households that received the filter to households that did not receive it was 0.40 (95% confidence interval: 0.05, 0.80), suggesting an overall diarrheal disease reduction of 60%. Further details are available here.


Over 47% reduction in diarrhoea risk: new health impact studies on the BSF

Eric Fewster

A few health impact studies are starting to emerge on the biosand filter. These look at how much impact the filters have on diarrhoea in real life situations. So far, results are encouraging and confirm the anecdotal evidence that many of us hear from sand filter users in the field. Two studies carried out in the Dominican Republic and Kenya showed a reduction in diarrhoea risk of 47% and 54%, indicating a significant protective effect of the BSF against waterborne diarrheal disease. More information here.

The effect of pause time on water quality: new research out

Eric Fewster

Research published by the University of North Carolina has confirmed the importance of residence time of water in a filter. Regarding the daily amount of water put through the filter, they found that microbial reductions were greater with a greater residence time within the filter, especially for water retained in the filter bed overnight. The researchers showed this through taking samples of filtered water at various stages when the filter was re-started after pause time – a significant drop in filtrate quality was noted after the pore volume threshold had been filtered. This showed that water that had been sitting in the filter during pause time had a much better quality, and this seems to be largely due to the increased contact time for biological and chemical processes in the sand. More information here.


The effect of hydraulic loading on microbial removal: new research out

Eric Fewster

Following a call for research by, researchers at the University of California, Davis, answered the challenge to look at the effect of hydraulic loading on filter efficiency. Lab and field research looked at the effect of pause time on efficiency at removing viruses, bacteria and turbidity, as well as other parameters that influence flow rate and therefore residence time, namely hydraulic loading and sand size. They confirmed previous findings about the impact of pause time on water quality, but they also tested filters with varying levels of hydraulic loading above the sand surface (10, 20 and 30 cm) and two sand sizes (0.17 mm and 0.52 mm). They found that bacteria and virus removal was significantly better for filters with finer sand and those with lower head, independently from each other and for both short and long term residence times, but that results were enhanced with longer residence times. The best combination was 0.17 mm sand with 10 cm head over longer residence times. More information available here.


On-site trainings carried out in Afghanistan and Somaliland

Eric Fewster

BushProof carried out biosand filter trainings for Tearfund in Kabul, Afghanistan in November 2008 and for Caritas in Hargeisa, Somaliland in March 2009. Over 30 NGO and government staff were trained as a result, and the trainings were well received.


Training successfully carried out in Kenya from 17 - 21 December 2007

Eric Fewster

BushProof successfully held a training in household biosand filtration for 5 participants in Machakos, Kenya between 17 - 21 December 2007.
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