Långsam sandfiltrering som vattenreningsmetod : En inventerande studie om långsamma sandfilters reningsgrad i landsbygdsområden i Colombia

Clean water is essential for health and the living in general for humans. For some people the access of clean and fresh water is a simplicity but for others, the lack of clean water, especially in rural areas creates one of the biggest humanitarian problems in the world today. For example a child under the age of five dies every 20 seconds today, due to water-related diseases. For areas with widespread poverty and poor living conditions it has shown that the access of clean water is a fundamental factor in order to increase the living situation and for the area to start develop. UNESCO claims that is possible to extinguish about 10 % of all diseases worldwide by implementing water treatment methods and sanitation facilities in vulnerable areas in order to improve the water quality. And reports from WHO and UNESCO shows that there is a clear connection between access to clean water and economic growth for a developing country. One of the oldest methods of water treatment is slow sand filtration (SSF) also known as biological sand filtration (BSF). The method is adapted from nature’s own way of treating water by filtration and has been used artificially by humans since the beginning of the nineteenth century. The SSFs in this study is a simple two-tank system where one tank is filled with sand and gravel and the other tank is working as a water reservoir tank. Under suitable circumstances this type of slow sand filters is a very effective water treatment method purifying the water with both mechanical and biological processes. In a rural area where Rio las Ceibas is flowing in the region Huila in Colombia, an environmental authority called La CAM is running a project where SSFs is implemented as a water treatment method at individual households. La CAM is in need of a pre-study in order to inventory some filters in the valley, to find out the purification rate of the filters and to get recommendations for further development of the SSF project. The purpose of this study was to examine the general status of the SSFs, find out about the households maintenance routines and knowledge of the SSF and to evaluate if the water quality produced by the SSFs is at drinking standard according to chemical and biological parameters. The methods used for achieving this purpose was by practical examinations, performing interviews and analysing water samples from the SSF system. In general the filters purified the water very poor and some filters even made the drinking water more contaminated than the raw water inlet. The study showed that many filters could reduce some of the chemical and biological parameters but no filter produced water according to the recommended drinking standard. The filters was most effective against turbidity and some filters reduced coliform bacteria very effectively. The filters general status was good but almost no filter had the required sand height or grain size. The interview study showed that the households considered clean water to be important in their homes and consider the SSF to have facilitated their lives. The households had some knowledge how the SSF function but had in general no routines on cleaning or maintaining the filter. For continued development of the SSF project it’s recommended to fill the filters with finer sand grains (0,2 – 0,45 mm), to at least a sand height of 40 cm, to spread more knowledge about maintenance of the filters and to continue to keep a regularly contact with the households to monitoring the status of the filters and also to maintain the relation between the household and the authority