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