Discussion on the application of rural sewage treatment technology in different regions of China

Central and southern region

The central south region refers to most areas on both sides of the Qinling-Huaihe River line. The terrain and geomorphology in the region are highly complex, with mountains, hills and plains ubiquitous, dense river networks, and most of them are located in important water systems. The whole is located in the warm temperate zone to the middle temperate monsoon climate zone, with high temperature and rain in summer and little rain in winter. The level of rural economic development in the region is not balanced, and because it is located in the customary border between the north and the south, the difference of rural living habits is obvious. The villages on the northern side of the Qinling-Huaihe River line often have dry latrines and composting habits, and the amount of sewage produced is small, and simpler treatment technologies such as septic tanks can be used. The villages on the south side of the Qinling-Huaihe River line are mostly built near water, and the sewage is often directly discharged into ponds and other water bodies, which is suitable for using constructed wetlands or multi-pond technology of existing ponds.

Southwest China

The southwest region includes Sichuan, Guizhou, Yunnan, Chongqing, Tibet, Guangxi and other provinces and cities, with a large regional span, and the terrain is dominated by plateaus, mountains and hills. There are various climatic conditions in the region, such as monsoon climate, plateau climate and alpine cold zone climate. Except for the gentle terrain of Sichuan Basin, which has been an important agricultural area since ancient times, other regions are mainly mountainous rural areas with relatively backward economic development level, and residents' traditional awareness of sewage treatment is relatively weak. With the development of rural tourism in recent years, the sewage production in rural areas in southwest China has increased rapidly, and the demand for supporting construction of sewage treatment infrastructure in rural areas is also increasing. It is suitable to adopt corresponding decentralized or centralized treatment facilities according to the scale of personnel gathering and topography.

At present, the sewage treatment modes in villages and towns in China include scattered treatment, centralized treatment in villages and treatment in urban drainage network. Generally, small settlements of single or several households are suitable for decentralized small sewage treatment equipment or natural treatment mode, larger villages can build village-level sewage treatment stations for centralized treatment, and rural villages can discharge sewage into the urban sewage network and transport it to the urban sewage treatment plant.

China's rural distribution area is wide, but with the gradual rise of urbanization rate, the future rural population will be significantly reduced, rural sewage treatment technology is bound to develop in the direction of decentralization, small, low cost and high efficiency. Using the existing natural conditions as much as possible and integrating the ecological sewage treatment technology with the environment will be the main trend of the future construction of rural sewage treatment facilities in China. According to the characteristics of decentralized and centralized sewage treatment technology, this paper discusses the differences of technical routes in six regions in China.

Distributed processing technology

The distributed sewage treatment technology includes small constructed wetland, land treatment, stabilization pond, purification biogas digester, and small integrated treatment equipment. According to the "Rural domestic sewage treatment Project construction and investment Technical Guide" issued by the Ministry of Ecology and Environment, the capital construction cost of commonly used distributed treatment technology is mainly 1500 yuan/T-3000 yuan /t, but the construction cost of small integrated treatment equipment can reach 10,000 yuan /t or more. The treatment scale of most distributed treatment facilities is less than 10t/d, and the stabilization pond technology is more suitable for large-scale distributed sewage.

In the engineering practice in different areas of our country, the choice of distributed sewage treatment technology should consider the local terrain and climate conditions. In northern China, the climate is generally dry, water resources are scarce, and sewage discharge is small, which is suitable for ecological treatment technology such as land percolation, constructed wetland and stabilization pond. However, considering the cold winter in the northern region, especially in the northeast, the effect of conventional ecological treatment technology will be affected to a certain extent, and it is necessary to improve the technical facilities such as constructed wetlands and stabilization ponds according to the regional climate characteristics. In northwest China, perennial drought, poor water resources, fragile ecological conditions, less water consumption for residents, suitable for septic tank or biogas pond treatment, larger villages can use upflow anaerobic biological filter, ditch land treatment, low temperature oxidation pond and other processes, but also make full use of abandoned ponds or swallowlands in arid areas for transformation.