Research And Application Of Slow Sand Biofiltration For Micro-polluted Water Drinking Safety In Rural Areas

Drinking water safety in rural areas is an important subject of people’s livelihood. In some rural area of China, Limited by natural factors、hydrogeological conditions and human activities, parts of the farmers live scattered, lack of water. As a result, the quality of drinking water can not meet safety standards. Especially in northwest arid and semi-arid regions, shortage of water resources get even worse, for example, many areas lack of safe drinking water sources there.The rain has been playing an important role in people’s life and yielding. Drinking water safety is a substantial problem and threatens people’s health and life.Slow Sand Biofiltration is the combination of traditional filtration and biological filtration.Under the condition of low filtration speed, slow biological filtration removes water pollutants by the metabolic activity of microbial groups(bacteria, algae, protozoa, and various small organisms) and physical- chemical adsorption in traditional filtration. For a long time, there has a bias to the role of algae. In fact, algae has the extremely vital significance and is indispensable in Slow Sand Biofiltration. Slow Sand Biofiltration is an economical and effective way to treat micro-polluted water and has many advantages such as no chemical dosage,good taste of filtered water, low cost, convenient operation and maintenance.However, the great drawback of this technology is that the filter clogging easily when treating the raw water with high turbidity and pollutants.The biological activity is influenced by the low temperature,leading to poor treatment effect. There is a need for further research in order to reduce the probability of clogging, improve the efficiency of removing pollutants, extend the operating cycle, optimize the operation and management.In this paper,this experiment adopts multistage filtration, consisting of roughing filtration followed by Slow biological filtration technology.There are two upward low roughing filters in the front of Slow biological filter. This paper studies the multistage biological slow filter on removal efficiency of pollutants in the micro-polluted water and various influencing factors. When the raw water turbidity around 10 NTU, removal rate of turbidity comes up to 92 % in the multistage filtration.The turbidity of the filtered water is less than 1NTU and meets the demands for drinking water. Removal rate of organic matter was 34.02% because of the microbial degradation, microorganism extracellular enzyme decomposition and biological flocculation.Under the action of nitrifier bacteria,the average removal rate of ammonia nitrogen was 74.26% through nitrification.When the influence factors were studied,the impacts of the thickness of filter bed and water temperature were analyzed. The results showed:there were a positive correlation between removal rates of the turbidity, ammonia nitrogen, organic matter and thickness of filter bed. Both the ammonia nitrogen removal rate and organic matte removal rate increased with rising temperature.In this paper, a kind of rural drinking water treatment installation is designed with The characteristics of security,stability,economical and practical,which could safeguard drinking water safety in rural areas.