1、水污染处理文献综述英文Application of multi-soil-layer system (MSL) in rural wastewater treatmentAbstract: with the continuous improvement of living in rural farmers, the water consumption of residents is increasing, rural sewage emissions will continue to increase, if not treat effectively, the water environme
2、nt in rural areas will be serious deteriorated, and influence the life quality of rural residents. In this case this paper presents a decentralized sewage treatment system, multi-soil-layer system technology (MSL) application in the rural sewage treatment, this paper summarizes the new technology, y
3、ou can better understand and practice, especially in the developing countries where is in need of this technology. In the foreseeable future, it can protect public health and the sustainable development of the environment, and it also provides a new way for rural sewage treatment.Key words: rural se
4、wage; multi-soil-layering system; distributed1.IntroductionIn recent years, with the continuous development of economy, peoples living standards continue to improve, rural economic development is also very rapid, but the rural economic development and environmental development is not synchronized, s
5、erious rural water pollution.While high technical sewage treatment plants, such as centralized sewage treatment plants are involved in large investment costs, high operating costs,Because of economic constraints, such systems are less suitable for livestock farms and small munities in rural areas. W
6、hile the multi-media-soil layer system(MSL) sewage treatment system, this decentralized sewage treatment system, it has less investment, low operating costs, high handling load. Besides, the utility model overes the defects of the prior soil percolation which is easy to be blocked from the space str
7、ucture.The sewage treatment system is one kind of the purification technology of sewerage treatment soil developed in Japan in twentieth Century, the soil system will be modularized, and the module is set up around the water in the soil layer to avoid clogging, and adding natural organic materials t
8、o soil modules can improve the purification ability of the system.The MSL system consists of a Permeable layer (PL) and a soil mixing layer block (SMB),The Permeable layer is usually posed of larger particles fillers such as gravel, pumice, perlite and zeolite.Higher porosity can effectively prevent
9、 clogging of the soil water layer.At the same time, the formation of aerobic environment is conducive to organic degradation.The mixed layer soil is mainly packing soil mixed with other 20%-30% other materials such as activated carbon, wood, iron and other material or soil with local resources.The o
10、rganic material added in the soil mixed layer can improve the biological deposition and adsorption capacity of the system, and can also improve the supply of hydrogen in the process of nitrogen removal and promote the removal of nitrogen.There are many researches on MSL system treating urban sewage,
11、 livestock wastewater and river water at home and abroad.Researchers in China, Ye Hai et al1 studied the effect of surface load on polluted river water treated by multi-soil-layer system.Song Ying2 had studied the treatment effect of multi medium soil infiltration system for turtle breeding wastewat
12、er.Zou Jun3 also pointed out that multi-soil-layer material selection will have a certain impact on the domestic sewage treatment efficiency.In foreign countries, especially in Japan, Thailand and Indonesia, MSL systems have been used to handle various types of wastewater, but the domestic of this t
13、echnology in sewage treatment in rural areas there is no prehensive study,This article through to the MSL system technology processing rural domestic sewage research, in order to provide some technical support for the MSL system in the practical application of rural sewage treatment.2.1characteristi
14、cs of rural sewageFor a long time,Chinas pollution control on rural attention and investment far less than the city,96% of the villages without drainage pipe network and sewage treatment system,The random discharge of domestic sewage has bee one of the main reasons for the deterioration of water qua
15、lity in the basin, and is also an important factor causing the rural water environment pollution and lake eutrophication.At the same time, it seriously affects the safety of production and living in the rural areas, and seriously affects the economic development.The main features of rural sewage in
16、China are:(1)The amount is huge and increases year by year.Statistics show that in 2002.There are 3.205 million tons ofnational rural domestic sewage daily emissions.The total nitrogen emission is about 283.1t, total phosphorus daily emission is about 56.6t, basically without any treatment directly
17、discharged.(2)Water quality and water quantity fluctuation are huge.Rural sewage water is not stable, different periods have different water quality,generally do not contain heavy metals and toxic and harmful substances, but contains more synthetic detergent and bacteria, viruses.(3)More sources.In
18、addition to human feces, kitchen generated sewage, there are household cleaning, domestic waste landfill leachate generated sewage, which will then enter the river part of the sewage, will cause greater pollution.(4)Low treatment rate.Part of the system can not run low temperature, rural sewage dail
19、y variation coefficient and seasonal variation coefficient, the system a few time high load operation, if there is little sewage, it will stop running 4.(5)Wide and scattered.Scattered geographical distribution of villages caused sewage dispersion and it is difficult to collect.2.2 the main source o
20、f rural sewageRural sewage refers to the formation of sewage of the rural areas in the life and production process, including rural production wastewater and rural domestic sewage two aspects.Rural domestic sewage refers to the residents living in the process of toilet discharge of sewage, bath, lau
21、ndry and kitchen sewage, etc.Rural production sewage refers to livestock and poultry breeding, aquaculture, agricultural products processing and other high concentration of organic wastewater.Because Chinas rural living is scattered, rural domestic sewage showed a small amount and wide dispersion.La
22、ck of appropriate sewage collection, treatment facilities, domestic sewage without treatment will be free to discharge, the health of rural residents to bring greater harm.At the same time, rural sewage production also poses a greater threat to the rural ecological environment.2.3main technologies o
23、f decentralized domestic sewage treatment Beginning in 1970s, Japan, the United States, Europe and other developed countries on the use of decentralized sewage treatment of rural sewage treatment, has accumulated a lot of experience, achieved good results.The United States since the mid-20th century
24、 began the construction of rural sewage treatment facilities, in 1972 promulgated the first plete clean water, then according to the distributed processing technology in 2002 promulgated the decentralized sewage treatment system application manual 5.1987, In Denmark promulgated a decentralized sewag
25、e treatment guidelines 6.Germany from 2003 to implement the decentralized needle infrastructure system project research, use membrane bioreactor purification to treat remote rural sewage 7.Australia proposed a sewage treatment land use system 8.While research and application of rural sewage decentra
26、lized treatment in China began in late 1980s,pared with developed countries and regions, there are still many gaps in laws and regulations system, technical standard system and management and service system.In recent years, domestic scholars have done a lot of research on rural domestic sewage,and p
27、uts forward some mature processing technology, including aerobic biological treatment, anaerobic biological treatment technology, soil infiltration technique and physical and chemical processing technology etc.There are many scholars in the multi-soil-layer system improvement and application develop
28、ment of the Japanese, it has also done a lot of research, some scholars found through experiments: to earthworm soil infiltration layer can also solve the problem of blockage of MSL system, but also can guarantee the winter operation effect in winter 9-10.2.4 Multi-soil-layer system (MSL) technology
29、2.4.1Structural characteristics of multi-media-soil layer system Multi-soil-layer treatment (MSL) system is a kind of land sewage treatment system.Mainly posed of Permeable layer (PL) and a soil mixing layer block (SMB),From top to bottom are waterproof layer, gravel layer, soil layer and mixed laye
30、r (two alternately arranged), in addition, the MSL technology has a certain terrain fall from the inlet to the outlet, mainly by the drop let water can automatically flow in the system, at the same time to purify 11.2.4.2Purification mechanism of multi-soil-layer systemWastewater contains high conce
31、ntrations of BOD, COD, ammonia nitrogen, phosphate ions and organic matter.When the wastewater into the MSL system, the organic matter in wastewater can be adsorbed on the surface of zeolite and soil through physical and chemical effects, followed by deposition of soil layer in microorganism, and ph
32、osphorus removal is mainly through the soil layer of iron is oxidized to ferric hydroxide after the formation of insoluble iron, then adsorption in wastewater the formation of phosphate coprecipitation.Nitrogen removal is mainly through nitrification and denitrification by ammonia ion, and finally r
33、educed to nitrogen discharge system.2.4.3Advantages of multi-soil-layer systemMulti-media-soil layer system is used to treat wastewater from traditional soil infiltration system.It has the disadvantages of low treatment load, large ground, easy to block nitrogen and phosphorus removal and other shortings 12.The MSL syste
