水污染处理文献综述英文

水污染的原因及防治措施英语作文Water pollution is a significant environmental issue that affects not only human health but also aquatic ecosystems. 水污染是一个重要的环境问题，影响了人类健康以及水生态系统。

There are several causes of water pollution, including industrial discharge, agricultural runoff, and improper waste disposal. 工业排放、农业径流和不当废物处置是水污染的几个原因。

Industrial discharge is a major contributor to water pollution, as factories often release harmful chemicals and toxins into water bodies. 工业排放是水污染的主要原因之一，因为工厂常常将有害化学物质和毒素排放到水体中。

Agricultural runoff, which includes pesticides and fertilizers, can also contaminate water sources, leading to eutrophication and harmful algal blooms. 农业径流包括农药和化肥，也可能污染水源，导致富营养化和有害藻类大量繁殖。

Improper waste disposal, such as littering and dumping waste into rivers and lakes, further exacerbates water pollution by introducing pollutants and pathogens into the environment. 不当的废物处置，比如乱扔垃圾和将废物倾倒入河流和湖泊，通过向环境中引入污染物和病原体，进一步加剧了水污染。

水污染及其措施英文作文Water Pollution and Mitigation Measures.Water, the elixir of life, is essential for thesurvival of all living organisms. However, the increasing prevalence of water pollution poses significant threats to human health, aquatic ecosystems, and the overall sustainability of our planet. This essay examines the multifaceted causes of water pollution and proposes comprehensive measures to mitigate its detrimental effects.Sources of Water Pollution.The primary sources of water pollution can be categorized into two main groups: point sources and nonpoint sources. Point sources, such as industrial discharge pipes and wastewater treatment plants, release concentrated pollutants directly into water bodies. Nonpoint sources, on the other hand, encompass a wide range of dispersed activities that contribute to water pollution.Examples include agricultural runoff carrying fertilizers and pesticides, stormwater discharge from urban areas, and septic tank seepage.Consequences of Water Pollution.The consequences of water pollution are far-reaching and multifaceted. Contaminated water poses serious health risks to humans who consume it, leading to diseases such as diarrhea, cholera, and typhoid fever. Aquatic ecosystems are also severely compromised by water pollution, as it disrupts food chains, reduces biodiversity, and impairs the ability of aquatic organisms to reproduce. Furthermore, water pollution can damage infrastructure, diminish aesthetic appeal, and hinder recreational activities.Mitigation Measures.Mitigating water pollution requires a multi-pronged approach that addresses both point and nonpoint sources.Point Source Control.Industrial Wastewater Treatment: Industries must implement effective wastewater treatment systems to remove pollutants before releasing waste into water bodies.Municipal Wastewater Treatment: Municipalities should upgrade and expand their wastewater treatment plants to meet the growing demand and improve treatment efficiency.Enforcement of Regulations: Strict enforcement of environmental regulations and penalties for non-compliance is crucial to deter polluters.Nonpoint Source Control.Agricultural Best Management Practices: Farmers should adopt sustainable agricultural practices, such as using cover crops, reducing fertilizer and pesticide application, and implementing erosion control measures.Urban Stormwater Management: Cities and towns need to invest in green infrastructure, such as rain gardens andpermeable pavements, to reduce stormwater runoff and capture pollutants.Septic Tank Management: Proper maintenance and inspection of septic tanks prevent leakage and ensure proper wastewater treatment.Other Measures.Public Awareness and Education: Raising awareness about the causes and consequences of water pollution is vital for encouraging responsible behavior and fostering a culture of water conservation.Research and Innovation: Ongoing research and development of new technologies and approaches can improve water treatment efficiency and reduce pollution sources.International Cooperation: Water pollution often transcends national boundaries, necessitating international collaboration to address transboundary issues and share best practices.Conclusion.Water pollution is a global crisis that demands urgent and comprehensive action. By implementing effective point and nonpoint source control measures, raising public awareness, and fostering international cooperation, we can protect this precious resource for future generations. The time for complacency has passed; the time for action is now. Let us work together to ensure that water, the source ofall life, remains a vital and sustainable asset for all.。

Wastewater treatment is a critical environmental process that plays a significant role in protecting our water resources and ensuring public health.Heres an essay on wastewater treatment suitable for middle school students:Title:The Importance of Wastewater TreatmentIntroduction:Water is the essence of life,and its purity is crucial for the health of our ecosystems and human beings.However,with the rapid industrialization and urbanization,the pollution of water bodies has become a pressing issue.Wastewater treatment is the process that helps in managing and purifying wastewater before it is released back into the environment.The Process of Wastewater Treatment:Wastewater treatment involves several stages to ensure that the water is clean and safe. The primary stages include:1.Screening:Large debris and solid materials are removed from the wastewater to prevent damage to the treatment equipment.2.Primary Sedimentation:This stage allows heavier particles to settle at the bottom of the tanks,forming sludge.3.Secondary Treatment:Microorganisms are used to break down the organic matter in the wastewater,reducing the biological oxygen demand BOD.4.Tertiary Treatment:This involves further processes such as filtration and disinfection to remove any remaining contaminants.Techniques Used in Wastewater Treatment:Various techniques are employed in wastewater treatment,including:Aerobic Processes:These involve the use of oxygen to break down organic matter. Anaerobic Processes:These processes occur without oxygen and are used for sludge treatment.Biological Filters:These filters support the growth of microorganisms that consume organic pollutants.Chemical Treatment:Chemicals are used to neutralize or precipitate contaminants.Significance of Wastewater Treatment:The significance of wastewater treatment is manifold:Environmental Protection:It prevents the pollution of rivers,lakes,and oceans, preserving aquatic life.Public Health:Clean water is essential for drinking and recreational activities,reducing the risk of waterborne diseases.Agricultural Use:Treated wastewater can be used for irrigation,supporting agriculture without depleting freshwater resources.Conservation of Water:By treating and reusing wastewater,we can conserve water and reduce the demand on natural water sources.Challenges in Wastewater Treatment:Despite its importance,wastewater treatment faces several challenges:High Costs:The construction and operation of wastewater treatment plants can be expensive.Technological Limitations:Some pollutants are difficult to remove completely.Lack of Infrastructure:In many developing countries,the lack of proper infrastructure hinders effective wastewater management.Conclusion:Wastewater treatment is a vital component of modern society,ensuring that our water resources remain clean and safe for future generations.By understanding and investing in this process,we can protect our environment and promote sustainable development. Words to Remember:WastewaterTreatment processEnvironmental protectionPublic healthBiological oxygen demand BODSustainabilityThis essay provides a comprehensive overview of wastewater treatment,its processes, significance,and challenges,making it suitable for middle school students to understand and learn about this important environmental issue.。

处理水污染英文作文Water pollution is a serious problem that affects the health of people and the environment. It is caused by the discharge of industrial waste, agricultural runoff, and untreated sewage into rivers, lakes, and oceans.The pollution of water can have devastating effects on aquatic life. Fish, plants, and other organisms can be harmed or killed by toxins and chemicals in the water. This can disrupt the delicate balance of the ecosystem and lead to a decline in biodiversity.In addition to harming the environment, water pollution can also have serious consequences for human health. Contaminated water can spread diseases such as cholera, dysentery, and typhoid, leading to illness and even deathin affected communities.Efforts to combat water pollution include implementing stricter regulations on industrial and agricultural waste,improving sewage treatment facilities, and promoting sustainable practices that reduce the amount of pollutants entering waterways.It is important for individuals to be aware of their own impact on water quality and take steps to reduce pollution in their daily lives. This can include properly disposing of household chemicals, minimizing the use of fertilizers and pesticides, and conserving water to reduce the strain on treatment facilities.。

Causes and Solutions to Water PollutionWater pollution is a global issue that threatens the sustainability of our planet. It arises from various sources and has devastating effects on aquatic life, human health, and the overall well-being of the environment.Causes of Water Pollution:Industrial Emissions: Factories and manufacturing units discharge harmful chemicals and toxins into water bodies, contaminating them. Urbanization: With the growth of cities, there's an increase in sewage and waste, often dumped into rivers and lakes.Agricultural Runoff: Fertilizers and pesticides used in farming wash off into waterways, causing eutrophication.Oil and Gas Spillages: Accidents during drilling and transportation of oil and gas can lead to massive pollution.Poor Waste Management: Insufficient waste treatment facilities lead to the direct discharge of untreated waste into water bodies.Solutions to Water Pollution:Strict Regulations: Governments should enforce strict laws and regulations on industrial emissions and waste disposal.Promote Sustainable Practices: Encourage industries to adopt eco-friendly practices and technologies.Invest in Wastewater Treatment: Build and upgrade wastewater treatment facilities to ensure proper waste disposal.Education and Awareness: Raise public awareness about water pollution and its consequences.Alternative Energy Sources: Develop and promote renewable energy sources to reduce dependency on fossil fuels.Research and Development: Invest in research to find innovative solutions to water pollution.In conclusion, water pollution is a complex issue that requires concerted efforts from all stakeholders. By addressing its root causes and implementing sustainable solutions, we can ensure clean and healthy water for future generations.水污染是一个全球性的问题，威胁着地球的可持续性。

水污染的原因及解决措施英语作文英文回答：Water is essential for life, but water pollution poses a significant threat to both human and environmental well-being. Several factors contribute to water pollution, including:Industrial waste: Factories and industries discharge harmful chemicals, heavy metals, and other toxic substances into waterways, contaminating water sources.Agricultural runoff: Fertilizers, pesticides, and animal waste from farms can leach into surface and groundwater, causing eutrophication, algal blooms, and harmful bacteria contamination.Domestic wastewater: Untreated or inadequately treated sewage from households and communities releases pathogens, nutrients, and organic matter into water bodies.Oil spills and accidental discharges: Tankers, pipelines, and offshore drilling activities can result in large-scale oil spills or leaks, releasing hazardous hydrocarbons into the marine environment.Climate change: Changes in precipitation patterns, sea-level rise, and extreme weather events can exacerbate water pollution by increasing runoff, eroding coastlines, and altering water temperature and salinity.Addressing water pollution requires a multi-pronged approach:Prevention: Implement strict regulations and enforce penalties for industrial and agricultural practices that contribute to water pollution. Promote sustainable practices such as reducing fertilizer use, employing water-efficient irrigation techniques, and adopting eco-friendly industrial processes.Wastewater treatment: Invest in infrastructure toimprove sewage collection and treatment systems, ensuring adequate disinfection and nutrient removal before discharge into waterways.Water conservation: Encourage water-saving practices in households, industries, and agriculture to minimize water consumption and reduce the amount of wastewater generated.Education and awareness: Conduct public education campaigns to raise awareness about the causes and consequences of water pollution. Encourage responsible water use and promote participation in water protection initiatives.Technological advancements: Develop innovative technologies for water purification and wastewater treatment. Explore advanced methods such as membrane filtration, reverse osmosis, and electrochemical processes to remove pollutants effectively.中文回答：水污染的原因：工业废水，工厂和工业排出有害化学物质、重金属和其他有毒物质进入水道，污染水源。

河水污染如何治疗英语作文Water pollution is a serious problem that affects many rivers around the world. Rivers are an important source of water for people, animals, and plants, and when they are polluted, it can have devastating effects on the environment and the health of those who rely on them. In this essay, we will discuss how to treat river water pollution.Firstly, prevention is key to reducing river water pollution. This can be achieved through strict regulations and enforcement of laws to prevent industries from dumping toxic waste into rivers. Additionally, individuals can take steps to reduce their own pollution, such as properly disposing of waste and using eco-friendly products.Secondly, physical treatments can be used to remove pollutants from river water. One effective method is sedimentation, where polluted water is allowed to settle in a tank or basin, allowing the heavier pollutants to sink tothe bottom. The clean water can then be removed from the top. Filtration is another method, where water is passed through a filter to remove impurities.Chemical treatments can also be used to treat river water pollution. One common method is chlorination, where chlorine is added to the water to kill harmful bacteria and viruses. However, this method can also create harmful byproducts, so it must be carefully monitored.Biological treatments are another option for treating river water pollution. This involves using natural organisms, such as bacteria or plants, to break down pollutants in the water. For example, wetlands can be used to filter water and remove pollutants.In conclusion, treating river water pollution requires a combination of prevention, physical, chemical, and biological treatments. It is important to take action to protect our rivers and ensure that they remain a safe and healthy source of water for generations to come.。

治理水污染英文作文Water pollution is a serious problem that needs to be addressed. It affects not only the environment but also human health. The discharge of industrial waste and untreated sewage into rivers and lakes is a major cause of water pollution. We need to take action to prevent further contamination of our water sources.One way to tackle water pollution is to enforcestricter regulations on industrial waste disposal. Companies should be held accountable for the pollution they cause and should be required to treat their waste before releasing it into the environment. This will help reduce the amount of harmful chemicals and toxins that end up in our waterways.Another important step in addressing water pollution is to improve sewage treatment systems. Many cities and towns around the world still do not have adequate sewage treatment facilities, leading to the direct discharge ofuntreated sewage into rivers and oceans. By investing in better sewage treatment infrastructure, we cansignificantly reduce the amount of pollutants entering our water sources.In addition to regulatory measures and infrastructure improvements, public awareness and education are also crucial in the fight against water pollution. People need to understand the impact of their actions on the environment and be encouraged to adopt more sustainable practices. This could include reducing the use of harmful chemicals, properly disposing of waste, and supporting initiatives aimed at protecting water quality.Furthermore, the preservation and restoration of natural habitats such as wetlands and mangroves can help mitigate water pollution. These ecosystems play a vital role in filtering out pollutants and maintaining water quality. By protecting and restoring these natural environments, we can help prevent further degradation of our water sources.In conclusion, addressing water pollution requires a multi-faceted approach that involves regulatory measures, infrastructure improvements, public education, and ecosystem preservation. It is a complex issue that requires collective effort and commitment from governments, industries, and individuals. By taking action to reduce water pollution, we can ensure the availability of clean and safe water for future generations.。

水污染处理文献综述英文Application of multi-soil-layer system (MSL) in ruralwastewater 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 environment 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, you 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 sewage; multi-soil-layering system; distributed1.IntroductionIn recent years, with the continuous development of economy, people's living standards continue to improve, rural economic development is also very rapid, but the rural economic development and environmental development is not synchronized, serious 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 communities in rural areas. While 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 overcomes the defects of the prior soil percolation which is easy to be blocked from the space structure.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 to 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 composed oflarger particles fillers such as gravel, pumice, perlite and zeolite.Higher porosity can effectively prevent 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 organic material added in the soil mixed layer can improve the biological decomposition 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, livestock wastewater and river water at home and abroad.Researchers in China, Ye Hai et al[1] studied the effect of surface load on polluted river water treated by multi-soil-layer system.Song Ying[2] had studied the treatment effect of multi medium soil infiltration system for turtle breeding wastewater.Zou Jun[3] 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 technology in sewage treatment in rural areas there is no comprehensive study,This article through to the MSL system technology processing rural domestic sewage research, inorder to provide some technical support for the MSL system in the practical application of rural sewage treatment.2.1characteristics of rural sewageFor a long time,China's 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 become one of the main reasons for the deterioration of water quality 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 China are:(1)The amount is huge and increases year by year.Statistics show that in 2002.There are 3.205 million tons of national 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 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 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 daily 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 of 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, laundry 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 China's rural living is scattered, rural domestic sewage showed a small amount and wide 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 of decentralized domestic sewage treatmentBeginning 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 began the construction of rural sewage treatment facilities, in 1972 promulgated the first complete 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 sewage 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 decentralized treatment in China began in late 1980s,Compared 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 puts forward somemature 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 development 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) technology2.4.1Structural characteristics of multi-media-soil layer systemMulti-soil-layer treatment (MSL) system is a kind of land sewage treatment system.Mainly composed of Permeable layer (PL) and a soil mixing layer block (SMB),From top to bottom are waterproof layer, gravel layer, soil layer and mixed layer (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 concentrations 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 decomposition of soil layer in microorganism, and phosphorus 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 reduced 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 shortcomings [12].The MSL system with "soil modular" as the core concept, its unique brick type internal structure can form a plurality of aerobic and anaerobic environment in order to promote the removal of pollutants,Among them, the permeable layer greatly improves the water permeability of the system to prevent clogging, adding natural materials in the soil increases the purification capacity of the system. 3.ConclusionsWith the economic reform and development, China's environmental awareness is also improving, water pollution in rural areas have also obtained more and more attention,The MSL system applicable to the small population, scattered in rural areas, the decentralized sewage treatment system can be widely installed and used in the rural society,especially in rural areas of developing countries such as Chinese, Chineseis in need of such technology, sustainable development can protect thepublic health and the environment.4.Reference[1] Ye Hai Ye et al. Effect of surface load on polluted river water treated by multi-soil-layer system[J]. China water supply and drainage, 2012,28 (19): 74-77[2]Ying Song et al.Treatment of turtle aquaculture effluent by an multi-soil-layersystem[J].Journal of Zhejiang University Science B.2015,16(2):145-154[3]Zou Jun, Chen Xin et al. Effect of material selection of multi-soil-layer system ondomestic wastewater treatment efficiency[J]. Journal of ecology and rural environment, 2010,26 (1): 14-18[4]Zhang Keqiang et al. Rural sewage treatment technology[M]Beijing: ChinaAgricultural Science and Technology Press, 2006.10[5] Chen Jinming et al.Policy and experience of managing decentralized wastewatertreatment systems in the United States [J]. China water supply and drainage, 2004,20 (6): 104-106[6] Hans B.Danish guidelines for small-scale constructed wetland systems for onsitetreatment of domestic sewage[C].Proceedings of the 9th International Conference on Wetland Systems for Water Pollution Control, Avignon, France,2004:1-8[7] Li Wushuang, Wang Hongyang. Status and treatment technology of ruraldecentralized domestic wastewater [J]. Tianjin Agricultural Sciences, 2008,14(6): 75-77[8] Zhang Jiawei, Zhou Zhiqin. Application of decentralized treatment technology forrural domestic sewage [J]. environmental science and management, 2011,36 (1): 95-99[9] Wang Xixi, Guo Feihong, et al. A new improved capillary infiltration ditch fordomestic wastewater treatment. [J].environmental chemistry,2011,30(3): 721-722[10] Zhang Xiaowei, Li Jianchao, et al. Experimental study on earthworm enhancedland treatment of rural wastewater [J]. Journal of agro environmental science,2009,28 (6): 1225-1229精品文档[11] Hu Hongqi, Yang Yong et al. Analysis of practical application of two efficientrural sewage treatment technologies [J]. Heilongjiang environmental bulletin, 2016, 40 (1): 20-24[12] Xin Chen et al.An introduction of a multi-soil-layering system:a novel greentechnology for wastewater treatment in rural areas[J].Water and Environment Journal.2009:255-262收集于网络，如有侵权请联系管理员删除。

Application of multi-soil-layer system (MSL) in ruralwastewater 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 environment 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, you 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 sewage; multi-soil-layering system; distributed1.IntroductionIn recent years, with the continuous development of economy, people's living standards continue to improve, rural economic development is also very rapid, but the rural economic development and environmental development is not synchronized, serious 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 communities in rural areas. While 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 overcomes the defects of the prior soil percolation which is easy to be blocked from the space structure.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 to 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 composed oflarger particles fillers such as gravel, pumice, perlite and zeolite.Higher porosity can effectively prevent 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 organic material added in the soil mixed layer can improve the biological decomposition 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, livestock wastewater and river water at home and abroad.Researchers in China, Ye Hai et al[1] studied the effect of surface load on polluted river water treated by multi-soil-layer system.Song Ying[2]had studied the treatment effect of multi medium soil infiltration system for turtle breeding wastewater.Zou Jun[3]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 technology in sewage treatment in rural areas there is no comprehensive study,This article through to the MSL system technology processing rural domestic sewage research, inorder to provide some technical support for the MSL system in the practical application of rural sewage treatment.2.1characteristics of rural sewageFor a long time,China's 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 become one of the main reasons for the deterioration of water quality 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 China are:(1)The amount is huge and increases year by year.Statistics show that in 2002.There are 3.205 million tons of national 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 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 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 daily 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 of 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, laundry 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 China's rural living is scattered, rural domestic sewage showed a small amount and wide 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 sametime, rural sewage production also poses a greater threat to the rural ecological environment.2.3main technologies of decentralized domestic sewage treatmentBeginning 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 began the construction of rural sewage treatment facilities, in 1972 promulgated the first complete 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 sewage 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 decentralized treatment in China began in late 1980s,Compared 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 puts forward some mature processing technology, including aerobic biological treatment, anaerobic biological treatment technology, soil infiltration technique andphysical and chemical processing technology etc.There are many scholars in the multi-soil-layer system improvement and application development 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) technology2.4.1Structural characteristics of multi-media-soil layer systemMulti-soil-layer treatment (MSL) system is a kind of land sewage treatment system.Mainly composed of Permeable layer (PL) and a soil mixing layer block (SMB),From top to bottom are waterproof layer, gravel layer, soil layer and mixed layer (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 concentrations 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 decomposition of soil layer in microorganism, and phosphorus removal is mainly through the soil layer of iron is oxidized toferric 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 reduced 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 shortcomings [12].The MSL system with "soil modular" as the core concept, its unique brick type internal structure can form a plurality of aerobic and anaerobic environment in order to promote the removal of pollutants,Among them, the permeable layer greatly improves the water permeability of the system to prevent clogging, adding natural materials in the soil increases the purification capacity of the system.3.ConclusionsWith the economic reform and development, China's environmental awareness is also improving, water pollution in rural areas have also obtained more and more attention,The MSL system applicable to the small population, scattered in rural areas, the decentralized sewage treatment system can be widely installed and used in the rural society, especially in rural areas of developing countries such as Chinese, Chinese is in need of such technology, sustainable development can protect thepublic health and the environment.4.Reference[1] Ye Hai Ye et al. Effect of surface load on polluted river water treated by multi-soil-layer system[J]. China water supply and drainage, 2012,28 (19): 74-77[2]Ying Song et al.Treatment of turtle aquaculture effluent by an multi-soil-layersystem[J].Journal of Zhejiang University Science B.2015,16(2):145-154[3]Zou Jun, Chen Xin et al. Effect of material selection of multi-soil-layer systemon domestic wastewater treatment efficiency[J]. Journal of ecology and rural environment, 2010,26 (1): 14-18[4]Zhang Keqiang et al. Rural sewage treatment technology[M]Beijing: ChinaAgricultural Science and Technology Press, 2006.10[5] Chen Jinming et al.Policy and experience of managing decentralized wastewatertreatment systems in the United States [J]. China water supply and drainage, 2004,20 (6): 104-106[6] Hans B.Danish guidelines for small-scale constructed wetland systems for onsitetreatment of domestic sewage[C].Proceedings of the 9th International Conference on Wetland Systems for Water Pollution Control, Avignon, France,2004:1-8[7] Li Wushuang, Wang Hongyang. Status and treatment technology of ruraldecentralized domestic wastewater [J]. Tianjin Agricultural Sciences, 2008,14 (6): 75-77[8] Zhang Jiawei, Zhou Zhiqin. Application of decentralized treatment technology forrural domestic sewage [J]. environmental science and management, 2011,36 (1): 95-99[9] Wang Xixi, Guo Feihong, et al. A new improved capillary infiltration ditch fordomestic wastewater treatment. [J].environmental chemistry,2011,30(3): 721-722 [10]Zhang Xiaowei, Li Jianchao, et al. Experimental study on earthworm enhancedland treatment of rural wastewater [J]. Journal of agro environmental science,2009,28 (6): 1225-1229[11]Hu Hongqi, Yang Yong et al. Analysis of practical application of two efficientrural sewage treatment technologies [J]. Heilongjiang environmental bulletin, 2016, 40 (1): 20-24[12] Xin Chen et al.An introduction of a multi-soil-layering system:a novel greentechnology for wastewater treatment in rural areas[J].Water and Environment Journal.2009:255-262。