The characteristics of rural sewage: kitchen cooking water, bathing, washing water and toilet flushing water. These waters are scattered, and there is no collection facilities in the countryside. With the washing of rainwater, the surface flows into rivers, lakes, ditches, ponds, reservoirs, etc. Surface water bodies, soil water and groundwater bodies, of which the large content of organic matter is its main feature.
Rural sewage treatment methods:
Biological filter is a relatively new water treatment process, which is characterized by integrating biological oxidation and trapped suspended solids, saving subsequent sedimentation tanks. Anaerobic hydrolysis-high load biological filter treatment system integrates primary sedimentation tank and aeration Ponds, sludge return facilities and oxygen supply facilities are all in one, greatly simplifying the sewage treatment process. The operation and management of this process is very convenient and can withstand strong impact loads, which is of special significance for rural sewage treatment in China. Related research shows that the anaerobic acidification-high load biological filter treatment system has a cod removal rate as high as 75% to 85%, a bod removal rate as high as 85% to 95%, and an ss removal rate as high as 85% to 95%. (See Figure 1)
2. Artificial wetland
Constructed wetlands are a method of removing or reducing pollutants in water by using the dilution and degradation of multi-stage organisms in artificial water ecosystems. European and American countries have widely used artificial wetland systems to treat sewage in villages and towns and small communities, and have achieved significant results. As a new type of ecological wastewater treatment technology, artificial wetland has many advantages such as low investment and operating costs, strong impact load resistance, stable treatment effect, good effluent water quality, and aquatic plants have certain economic value. Submerged constructed wetlands are mainly used for rural domestic sewage treatment. (See Figure 2)
3.Unpowered underground sewage treatment plant
Domestic sewage first enters the anaerobic digester, and the suspended matter in the sewage settles down to become sludge. The sludge undergoes natural fermentation for a certain period of time, and the organic matter is degraded. (See Figure 3.) Underground anaerobic pipeline or baffled reactors with hollow spherical fillers as processing equipment have undergone small-scale, pilot-scale and practical applications. The average removal rates of uuar for rural cod, bod5, ss, tn, tp, coliform bacteria, total bacteria, and roundworm eggs reached 66% to 68.3%, 70% to 76.8%, 80% to 90.2%, 18% to 23.0%, 33% to 35.2%, 95% to 99.8%, 37% to 82.9%, and 78.7% to 100%. The quality of the effluent water has reached the national secondary discharge standard.
4. Domestic sewage purification biogas digester
The new domestic sewage anaerobic purification tank (also known as urban domestic sewage purification biogas digester) is a small decentralized sewage treatment device. The domestic sewage purification biogas digester is developed on the basis of septic tanks and biogas digesters, which solves the shortcomings of poor septic tank treatment effect, excessive sedimentation, and low biogas recovery rate. (See Figure 4)