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A water filter for emergencies

Clean drinking water is a luxury. In many parts of the world water is polluted and full of harmful bacteria; the problem is particularly acute during humanitarian crises, such as in refugee camps. A simple short-term solution is a domestic water filter. There are many different types on the market, but their quality varies widely, so HLS researchers tested filters in three disaster areas. Working with the local population, they have made suggestions for product improvements.

Drought, floods or military devastation can all deprive people of access to a functioning clean water system, leading to humanitarian crises that aid agencies try to alleviate. But often there is neither time nor money to install entire water supply systems quickly. Household filters are an alternative way to supply clean water in the shortterm and have been used for many years with varying degrees of success. Maryna Peter and her team at the Institute for Ecopreneurship have therefore been commissioned by the Humanitarian Innovation Fund to investigate which filters work best in humanitarian emergencies.

In the joint project with Caritas Switzerland, Eawag and the Italian aid organisation Cesvi, the HLS researchers tested five pre-selected commercially available household filters. They wanted to know how easy the filters were to assemble and use, how robust they were and whether they reliably removed germs from the water. “First we tested the filters here in the HLS laboratories,” explains environmental engineer Peter. “They were then distributed to families living in refugee camps in Somalia, in rural areas in Kenya and in the West Bank. These families live in small households, often with their animals. In some places, the groundwater has a high salt content, in others, wells cannot be built for political reasons. Attempts are made to collect rainwater, but this stored water is of poor quality and household filters could help.” Household filters usually consist of two buckets, the upper containing a filter to remove bacteria and other microorganisms, the lower one to collect the clean water. Such a small, practical filter system can easily fit on a table. Peter and her team tested different models of ceramic and membrane filters, both of which work on the same principle, with small pores that trap bacteria when the water flows through. However, ceramic filters break more easily and have to be cleaned by hand whereas membrane filters should not be touched and have backwashing mechanisms.

The researchers tested three ceramic filters and two membrane filters – 150 filters each in Kenya and the West Bank and 120 in Somalia. Every family that wanted to could take part and the filter type was assigned at random. A special feature of the study was that each household was allowed to test a second filter after the first four months. Peter explains: “Many needy people in developing countries do not dare criticise anything; they are afraid that they will then no longer receive humanitarian aid or are very reluctant to criticise because of their culture. By trying out two filters, they found it easier to compare the advantages and disadvantages and to criticise. That worked very well.”

The researchers analysed the filters’ technical performance – their actual microbiological cleaning effect – at low cost on-site test stations. They found that the filters worked better in the lab than in practice. Water quality was certainly improved but not by as much as the manufacturers expected. Working with Eawag, the researchers developed a simple test for use in crisis regions, to enable aid organisations to see for themselves whether the filters work properly under real-life conditions. In addition to testing the filters’ performance, the researchers were interested in whether families could install a filter by themselves and use it regularly. They therefore filmed several documentaries and ran video interviews, giving people the chance to talk about their experiences and make suggestions for improving the filters. Of all the products examined, the best was found to be one of the ceramic filters. Nevertheless, although all the filters worked well technically, the research revealed that there is still room for improvement in the design. At three co-design workshops, the researchers and the users therefore developed ideas together on how to improve the filters. This could be done very simply, for example by using lids to stop insects getting into the water or fitting tougher hoses to protect against rats. “Only by running field tests could we see which products are both accepted and suitable,” says Peter. “As a research institute, we can help aid organisations invest in products that work well and reliably in specific situations.” The findings from this multinational project show how important household filters, their further development and practical test methods are for people in crisis regions.


  • Flow cytometry
  • Simple low-cost field methods for water quality analysis using bacterial plating (Nissui Compact Dry Plates) as well as turbidity, oxygen and conductivity analyses
  • Automated monitoring of water use and flow using Solinst Pressure Dataloggers
  • Mobile phone-based data collection and questionnaires
  • Human centered design (e.g. co-design workshop)


  • Low cost field laboratories established for the analysis of filter integrity, recontamination and microbial regrowth using plating methods for Enterococci, Escherichia coli and total coliforms


  • Humanitarian Innovation Fund


  • Caritas Switzerland
  • Eawag
  • Cesvi, IT
  • Italian Agency for Development Cooperation (AICS)
  • Palestine Polytechnic University
  • Jomo Kenyatta University of Agriculture and Technology, KE
  • Elrha’s Humanitarian Innovation Fund, UK

FHNW School of Life Sciences

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