Structure Optimization And Technology Demonstration Of Bio-slow Sand Filtration In Karst Rocky Management Areas

Water is an essential material for human life, however, the current water supply in rural of karst rocky desertification areas is low, in which areas the main source of water supply is rain and spring water. Therefore, people tend to pay more attention to the problem of water supply but not the issue on water quality enough. Combined with the requirements of national ‘Twelfth Five Year Plan" Technology Support Program for rural drinking water safety, the author summarized the research status of bio-slow sand filtration technology through literature review and understood the principle and technical method of bio-slow sand filtration. Taking salaxi area of Bijie in Guizhou province as the sample, this paper aims at achieving the structure optimization and Demonstration of bio-slow sand filtration technology in rural karst rocky desertification areas. Combined with the indoor simulation experiment and on-the-spot application, this paper try to construct a series of bio-slow sand filtration models suitable for the rural rocky desertification area, optimize the bio-slow sand filtration technology and carry out technical demonstration and comprehensive benefit evaluation, optimizate the bio-slow sand filtration models and extension of application.(1)So far the theoretical research has been more comprehensive and it’s purifying effect has been widely recognized at home and abroad. The water purification technology of the combination of coarse filter and slow filter, ozone treatment before filter, activated carbon addition and other technologies have been applied in Fujian, Hubei, and other places, but less in karst desertification areas. Therefore, combining with the topography, hydrology, rocky desertification and so on, this paper made a study and designed the bio-slow sand filtration technology suitable for this area.(2)Field investigation the drinking water situation of demonstration area, found that there is no running water and disinfection treatment measures, mainly drink stored fissure water and rain water. In the demonstration area of every family built a small cellar, but the cellar inside and outside can be seen insects, leaves, animal faeces and other sundries everywhere. Selected and test water samples were collected during dry and wet seasons, the main pollutants are the chroma, turbidity, odor and taste, visible material by bare eye, sulfide and Escherichia. This shows that the water shortage and quality problems seriously plagued the daily lives of local residents, endanger the physical and mental health of the residents.(3)For the willingness of water quality improvement, most residents supported and participated in the construction of bio-slow sand filtration. Considering the actual situation of demonstration area, the large-scale centralized filter-first structure of bio-slow sand filtration has been changed to the storage-first structure of single-family scale. Water harvesting and pre-processing technology has been adopted on the basis of traditional bio-slow filtration. According to different water sources and water yield, two kinds of coupled model are built: one is roof rainwater-reservoir- bio-slow sand filtration and the other is spring- reservoir-bio-slow sand filtrationn.(4)Through the indoor simulation experiments, it was found that the formation of biofilm greatly improved the removal efficiency to sulfide. The second scheme of filter material filling(pebble bearing+ quartz sand+ activated carbon+ ceramic) was better than the first scheme(pebble bearing+ quartz sand+ activated carbon+ ceramic quartz sand). The thickness of filter material is proportion to the removal efficiency. The removal efficiency is the best while filtering speed was controlled within 0.1- 0.3m/h. When applied on the field, it combined roof set rain technology with bio-slow sand filtration technology, used brick and concrete to pour two structures, selected the ratio of pebble bearing, quartz sand, activated carbon and ceramic as 8:1:1.(5)Through regularly testing water samples, it was proved that bio-slow sand filtration had a good removal effect for turbidity, chroma, sulfide and lead and mercury pollutants. But for Escherichia coli and the total colonies number, it was still unable to be controlled within the national drinking water standards. The results show that the removal rate of odor,taste and visible material is 100%. The removal rate of turbidity is higher than 97.1%. The chroma removal rate is higher than 83.3%. The removal rate of sulfide is higher than 77.8%. And the highest removal rate of total bacteria colony and Escherichia is higher than 95%. The costs of two kinds of bio-slow sand filtration are both about 2000 yuan while the cost of brick structure is 300 yuan higher than cement. After a comprehensive benefit analysis of the bio-slow sand filtration, it was proved that the bio-slow sand filtration could improve the drinking water condition of local people and animals.