How to start a Filter project

Hints and tips on how to start up your own Concrete Filter project.

The right approach

We believe that it is very important to have the right approach when starting up a biosand filter project – this is in order to ensure sustainability in the long-term after donor funds dry up, as well as creating livelihood opportunities. This entire website was started after we witnessed the success of a commercial-based project in Kenya in 1999-2000, financed by Medair. In this case, after only one year of very limited NGO funding and input, filters were being produced for a profit and there was a demand from people to buy them – at this time the NGO withdrew. However, filters are still being produced and sold in the same region of Kenya today, although the filter technician has also opened several seasonal sites for filter production, and sales tend to follow periods when villagers have money and when there is a demand for filters (e.g. after harvest). This project worked because there was a demand – people had a felt need for clean water since they only had access to muddy ponds – and the filters were produced cheaply enough that people could afford them (filters were sold for $10 which included profit for the producer).

Knowing that this approach works, we have since 2004 advocated this approach to filter production and distribution. By and large, we do not suggest distributing filters for free, which unfortunately appears to be the standard NGO approach yet which continues to create aid dependency and reduce empowerment of local people. Distributing non-food items can work in certain humanitarian situations (e.g. after a natural disaster), but biosand filters tend not to be in this category since they take time to set up and function – in this way they are much more of a longer-term intervention compared with other household water treatment products on the market that might be more suitable.

The Kenya commercial-based model of biosand filter production has been replicated in the complex emergency environment of Afghanistan by Tearfund (after being trained there by BushProof staff), demonstrating again that when done correctly, a demand-led approach to scaling up biosand filters is a sustainable approach to move away from aid dependency. Based on findings from an evaluation of the BSF project (Burt, 2012; {end-texte}Ref.01: Burt, M. (2012) Evaluation of a demand led biosand filter programme in the complex emergency context of Afghanistan. Tearfund, Teddington, UK.), it was recommended that, where the conditions are favourable, humanitarian agencies seriously consider demand-led commercialized approaches to BSF programming as a sustainable household water treatment solution in complex emergency situations. Some key points from this evaluation were:

  • Feedback from households using the BSF showed that overall perceptions were strongly positive, and 100% of the existing BSF filter owners said that they had “recommended the filter to others”. Specific perceived benefits included improved health (94%), and financial savings (70%). In the study area the rate of adoption was 96%, and the rate of sustained use was 94%. This is a high rate of sustained use for a new technology and will help create sustained demand for the product within the community. Of those surveyed without BSF, 100% stated that they would like to purchase a BSF, with the greatest barrier to purchase being stated as cost, 73%. At full cost recovery retail prices (average US$21.70) a BSF is affordable for the 55% middle to upper income households, but not for the 45% low income households. BSF manufacturers confirmed that low income buyers were only willing to pay US$7.00-$11.60, which is less than the actual production cost which ranges from US$14.00 – $17.40.
  • Of the households surveyed without a BSF, 47% of those fell into the middle to upper income bracket – but part of the reason why these households had not yet purchased a BSF, may be found in the cultural context. Of those that could, in theory, afford a filter, and stated that they would like to buy one, 57% were women. In the Afghan cultural context it is normally the responsibility of their husband to do the shopping and 27% actually stated that their husband either did not have time, or did not see a BSF as a priority.
  • Further investment in marketing would be required from external parties such as the government or NGOs in order to increase BSF demand to self sustaining levels. Despite this, it was evident that all BSF manufacturers were, at a minimum, able to supplement their income from their BSF manufacturing business.


There are several factors to consider before starting a bio-sand filter project. The most important considerations are discussed below. They apply to both micro and medium sized projects; however the design of a mass-introduction on a large scale falls outside the scope of this discussion. You will find more information on that topic elsewhere on this website

The following factors need to be considered:

  • Environmental;
  • Social;
  • Technical;
  • Programmatic.

Environmental factors

The effective application of bio-sand filtration is dependent on the quality of raw water used for filtration. While the filters are remarkably forgiving when over challenged for a short period, they do not cope well with the prolonged use of highly turbid water. This is because the high amounts of solids present in the turbid water settle in the top sand layer, leading to rapidly diminishing flow rates. This in turn requires that the filter is cleaned frequently, which involves disturbing the biological layer. This results in diminished performance for several days afterwards. An in-depth discussion on raw water turbidity and the way this affects bio-sand filtration can be found elsewhere.

Therefore, it is essential to obtain turbidity figures on raw water used by the people in the area where bio-sand filtration is proposed. When collecting this data, do not forget the effects of seasonal changes on surface water. During the rainy season, water might be much more turbid than during the dry period as flowing water erodes the soil. However, the opposite can also be true, for instance through the explosive growth of algae in stagnant water during the hot, dry season.

In general, communities that largely depend on surface water are obvious candidates for the introduction of household bio-sand filtration. However, since there is overwhelming evidence on the high level of contamination of clean water between the point of collection and point of consumption, bio-sand filters might be equally applicable where people draw water from wells, water vendors, public stand posts, boreholes or protected springs.

Social factors

The introduction of bio-sand filtration needs to be acceptable. Preferably, the people group targeted with the technology should have a concept of filtration, and have some understanding of the importance of clean water and the links between contaminated drinking water and disease. Informal discussions can often give a good indication.

Observation of traditional water collection methods may also give a hint. Many rural communities draw their water from rivers or dry river beds. Often, it is possible to observe people digging a shallow hole in the riverbank, just away from the main stream. Such a hole slowly fills up with water seeping through the sandy riverbed and is therefore cleaner than in the main stream. This habit provides an excellent example of sand filtration, which can be easily understood by most local people.

Another issue deals with water quantity and use changes. Before starting the project it is advised to measure the quantity and quality of water used on a daily basis by the average household. Choices of water sources and the patterns of home water use for different purposes should be analysed: drinking, personal hygiene (hand washing and bathing), food preparation and household cleaning. These factors will help determine the best selection of target population for the project.

Lastly, it needs to be stressed that while bio-sand filtration is a remarkably effective point-of-use water treatment, other solutions might actually be preferred under certain circumstances. This could include other forms of household water treatment, or traditional water programmes.

Technical factors

Where concrete filters are proposed, a ready supply of gravel and cement needs to be available in the project area, while the cost should be reasonable. Furthermore, a reasonably well equipped metal workshop needs to be found to fabricate the metal filter moulds. Another important consideration is the availability of sand: both for the construction of the actual filters and for the filter media. There are parts of the world, where sand is very hard to find and a proper source should be identified before the project is proposed. More details on sand selection can be found elsewhere on this site.

During the project design phase it is recommended to analyse the potential health impact that can be expected from the intervention. In order to do this, it is helpful to collect data on the incidence of water borne disease in the project area.

Programmatic factors

Several factors need to be considered.

Participation and ownership
During the project design phase, it is best practise to consult the target population in a meaningful manner. The use of Participatory Rural Appraisal techniques and the Logical Framework Approach are highly recommended.

Social marketing
At the same time, effective social marketing techniques need to be selected. Appropriate messages that are meaningful to the target population need to be prepared. For instance, messages that focus on the health benefits of drinking clean water might be appropriate only if the community in general has a reasonable understanding of the links between contaminated water and poor health. If this is not the case, other messages need to be selected. It is for instance perfectly possible to convince people to buy or use bio-sand filters because it is modern to do so. In other cases, the improved taste or temperature of filtered water can be used to generate interest in the filter. The bottom-line is that health benefits will become evident, regardless of the motivation for filter usage.

Social marketing in Kenya
The following method worked well in a Kenya project. Without much previous information, the owner of a hotel was asked to participate in a field test of a bio-sand filter. He was asked to put the filter in a prominent place in his restaurant, in full view of his clients. He was then asked to daily filter at least one 20 litre jerry can of dirty water. While he was told that the purpose of the exercise was to test the performance of the filter during several weeks, he was told that he could freely use the water it produced. No clean water source existed in this village and the water served during the meals was brown and quite contaminated. Naturally, the restaurant owner started serving filtered water to his guests. In fact, he gained several new regular customers during this period. After several weeks, project staff returned to the restaurant, declared the ‘test’ successful and declared their intention to take the filter away. By then, the restaurant owner – and his guests – had become quite used to their improved water supply and asked if the filter could stay. This resulted in some bargaining, and finally a deal was struck whereby the filter was sold. Not long after, several other restaurant owners approached the project, asking to buy their own. So did several of their customers and slowly demand for the filter began to grow. By now, thousands of filters are in use in this area, and demand continues to spread to adjacent areas. For more details on this project, read the following article, which appeared in WaterLines.

Sanitation and Hygiene promotion
While the benefits of improved drinking water supply are evident, it is also true that the effects on health are multiplied several times if combined with improved sanitation and especially hygiene promotion. It is therefore highly recommended to plan and budget for the implementation of a sanitation component (for instance focussing on environmental sanitation or the safe disposal of excreta) and a hygiene promotion campaign. Recommended topics include washing hands with soap and handling drinking water in the house.


Ref.01: Burt, M. (2012) Evaluation of a demand led biosand filter programme in the complex emergency context of Afghanistan. Tearfund, Teddington, UK.

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