Household filters for arsenic removal in the Nabigonj District (2020 – present)

Building on our SWAPNO and 1000 Household Filters research projects, we now have 2,000 household filters, which our project partner maintains and disinfects every three months. With small voluntary contributions from filter users, we will in future be able to provide filters to these people’s neighbours as well. This also strengthens the village community. Our contribution is to fund the staff who look after the maintenance and cleaning of the filters and who purchase and distribute new filters as soon as a budget has been accumulated for this purpose..

Operation of 200 cartridge-type household filters for arsenic removal (2020–2024)

This short film shows how our water filter works and how satisfied users are with it:

Development of household filters for arsenic removal (2019 - 2020

Household filters offer several advantages over large-scale filtration systems: families can continue to use their own household wells, even if they are contaminated with arsenic. This eliminates the need for large families to carry large quantities of drinking water – a task that falls mainly to women and children.

Building on the association’s decades of experience, several research projects have now been launched to investigate:

• Which filter systems are already available on the market and whether they are capable of removing arsenic.
• What characteristics a filter must have in terms of maintenance, flow rate, ease of use and price in order for people to use it.
• Which filter materials can be used to ensure sustainability and reusability.
• How a deposit scheme can be established so that used materials can be collected and recycled.

The first prototypes are based on filters from the Bengali brand ‘Drink it’. These filters feature a multi-layer filter that removes not only iron but also a range of other substances very effectively, which is why they are so widely accepted. However, according to research by the University of Heidelberg, the multi-layer filter cartridge offers no discernible benefit. To remove arsenic, we fitted these standard filters with a replaceable additional cartridge and tested various arsenic adsorbents: the filter media from the German manufacturers GEH, HeGo-Biotec and WatchWater, who provided us with their products free of charge.

We would like to take this opportunity to thank them and have, in return, agreed to share our results with the manufacturers. Following extensive testing, we opted for the Titansorb product from WachWater, Mannheim, as this proved to be the most stable during regeneration. By cleaning the material with caustic soda, it can be reused multiple times. This saves costs and is sustainable, as it does not need to be sent to landfill.

SONO household filters for villagers (2006 - 2013)

The SONO filters are based on a simple but very efficient operating principle. The high iron content is removed from the groundwater by a two-stage cleaning process. A layer of iron hydroxide and activated carbon also removes arsenic.

The filters must be regenerated with hot water at regular intervals. The service life of the filters is stated as 7 years on average. The problem with this figure is that the service life depends to a very large extent on the concentration of pollutants. This must be checked regularly or the filter must be replaced from time to time.

Major problems were caused by the ochre formation of the filters, i.e. the formation of calcareous iron precipitates which impair the permeability of the filter. The maintenance and repair of the filters was too complicated, so that these filters are now only operated sporadically.