| Due to the unique features such as the elevation is high but the water-table is low, enough rain but missing in the ground, rock exposed without soil, thin soil and drought,karst rocky desertification areas develop unique karst engineering water shortage. Rainwater is the important source in some areas where water is scarce. Lots of resident drinking contaminated river water, pool water or even rain water without water purification equipment, most of those water can not reach the drinking water sanitary standard, drinking water safety is become the most important issue for the Karst Rocky Desertification. Local residents have the Urgent need to improve the water quality, bio-slow sand filtration technology, with the advantages such as little investment; simple skill; convenient management; good Water purification is suitable for Karst Rocky Desertification Rural Areas. Salaxi repair of Light – medium rocky desertification in karst plateau is Selected to be the research area.During April 2013 to Jan 2015, Through questionnaire investigation,water quality sampling survey, Critical review of literatures and indoor simulation experiment, technical system of the bio-slow sand filtration has been optimized to ensure that system is fitness in karst rocky desertification rural areas. We construct 7 bio-slow sand filtration cisterns, by means of analyzing the effluent from bio-slow sand filtration cisterns, state of results of purification to the cisterns, summarizing the Salaxi mode of bio-slow sand filtration, evaluation of the bio-slow sand filtration, at last,give a reasonable measure to generalize the bio-slow sand filtration.The following conclusions:(1)The main water sources for residents are the spring leaking from fissures and the rainwater harvesting in roof in which the physical indicators, microbiological index, sulphur index exceeding, water in the cellar, that from rainwater in roofs, is much higher over the standard, the pollutant is easy to access in the cisterns due to the lack of leakproofness, secondary pollution in the water taking and Free-range of poultry is the main reason to physical indicators, microbiological index exceeding. Due to minorcoal-mines near the Demonstration Area are excess emissions of coal washing wastewater, the sulfide index exceeding. Most of the villagers are not satisfied with the water quality, who are in urgent need of water treatment facility which has the advantages of easy operating, little investing and good purification results(2)The experimental results in indoor simulation show that the better effects on bio-slow sand filtration for removing the main pollutant in demonstration area. The rate for turbidity removal is Above 90% the removal rate of sulfide and coli is more than 60%,it found that cermsite has better effect on removing sulfide pollutant in the experiment. According to the experimental result, Bio-slow Sand Filtration can be used in purified water. Ceramsite should be put in filling to increasing of removal rate to sulfide pollutionwhen it is put into practice.(3)Optimize and improve the existing biological slow filtering technology usage patterns. Design the "Salaxi demonstration area" type biological slow filtering technology mode, namely the storage before physical water filter to adapt to the special circumstances of karst rocky desertification area. Design the rainwater harvesting slope, pebbles and the abandon rain devices to increase water collection, and prove this model is suitable for karst rocky desertification area. on-the-spot demonstrationing shows this mode is suit for Salaxi demonstration area. "Salaxi demonstration area" type biological slow filtering technology mode is also suit for the Karst Desertification engineering shortage of water areas.(4)The construction process of slow filter: Construction preparation→Casting the retainer plate→Casting the foundation→Masonry pool body→Loading filter material. The cost of one small slow filter for 4 to 6 people is about 2500 yuan. The construction should be paid attention to the connection between the retainer plate and the wall; setting a mesh on the slow filter to prevent mosquito flew into; it is convenient to clean filter material when constructing slow filter in the rainy season. Generally the biofilms has preliminarily formed on 45 days after running.The removal effect on pollutants is stable after biofilm mature.The removal rates of water colorless, tasteless, turbidity, chroma are stable at more than 95%. The sulfide removal is stable at around 60%.The removal rates of escherichia coli and the total numbers of colonies are stable at more than 90%. The quality of the water almost meets the GB5749-2006 regulations on hygienic standards of drinking water. Taken together, the construction of slow filter has the certain economic efficiency and the social benefit.(5) Through the analysis of demonstration results and detection, confirmed that Salaxi demonstration area type biological slow filtering technology system can effectively solve the problem of drinking water safety in rocky desertification area. Analyse the defects in the mode, pumping water when the site of the reservoir is lower than house;Set up plastic film surface of rainwater harvesting site to replace the Cement mortar rainwater harvesting site where is rugged terrain.The promotion of slow filtration technology system of biological Salaxi demonstration area type can be government guidance, demonstration sample support, participation of villagers, technology introduction, media publicity. |
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