Despite its potential, the bio-sand filter has not been extensively used during emergency projects. Our research has so far only identified two instances. One of them was successful; the other not. It is therefore interesting to make a comparison between the two in order to identify criteria for success or failure.
Unsuccessful – Mass distribution following Hurricane Mitch
In 1998, Nicaragua was hit by a hurricane, which affected an estimated 800,000 people. Apart from widespread destruction, many water treatment facilities were out of order while sanitary conditions had deteriorated. To address this emergency, thousands of bio-sand filters were distributed throughout the country in the hope of resolving the problem of polluted drinking water sources and avoiding the outbreak of epidemics.
However, this project was not as successful as had been planned. A number of problems arose in the inappropriateness of the design as well as the operation and maintenance aspects of the BSF. During an emergency it is not feasible to rapidly construct and transport large numbers of bulky concrete filters. A filter kit was therefore used that consisted of many separate parts that needed to be put together. The beneficiaries had great trouble to successfully assemble the filters. Furthermore, information on how to use and maintain the filter was not properly disseminated. The majority of people therefore did not know how to operate or clean the filter.
The suggestion has been made that the bio-sand filter is therefore not suitable for use during emergencies. This conclusion is incorrect, as it is possible to overcome the problems encountered in Nicaragua. There are now ready-to-use plastic filter available that are made as one integral unit needing no further assembly. On top of that, such filters are stackable and lightweight and are therefore easy to transport, which is an important consideration during emergencies. Click here to see an example. Secondly, a properly implemented information, education & communication (IEC) campaign using appropriate media channels can be used to inform the beneficiaries on the correct use and maintenance of the filter.
Successful – internally displaced people in the Sudan
In 2003, increased insecurity led to the displacement of thousands of local people in Darfur, West Sudan. The majority settled in temporary villages that relied on untreated surface water for drinking. Medair planned the construction of several boreholes and hand dug shallow wells; however, part of the budget was set aside to pilot the use of bio-sand filtration during this emergency. The decision proved to be well founded: increasing insecurity made the area inaccessible to NGO staff, severely hindering the construction of permanent clean water points. The introduction of filters however, continued successfully.
Difficult logistics and the slow rate of construction of concrete filters made the NGO decide to convert 200 litre metal fuel drums into filters. Click here to see how to make a drum filter.
Before the insecurity got too bad, humanitarian staff met with local authorities and installed a model filter at the compound of each village chief. Basic information on use and maintenance of the filters was spread as well. After the security situation deteriorated, filter materials and information leaflet were transported by local trucks instead of by NGO vehicles. In the villages, the filters were then assembled by previously trained people and distributed amongst the refugees. This way, some 1500 filters were distributed, providing clean water to between 7,500 and 10,000 people during a time when no other humanitarian activity could take place.
More information on the use of bio-sand filters following Hurricane Mitch can be obtained from:
Miller, B.; Murcott, S.; and Prestero, T. Appropriate Water Purification Technology for Nicaragua – the Biosand Filter. Design that Matters. Media Lab. Final Review Presentation. May 13, 2002.