A small town sewage characteristics and processing requirements 1.1 small town sewage characteristics The characteristics of small town sewage is determined by various factors. Due to the small population of small towns and the low popularization rate of tap water, the discharge of sewage in small towns is generally between 3,000 and 30,000 m3 / d. However, the development level of industry and agriculture in small cities and towns determines that more than 50% of the sewage is domestic sewage, and the industrial wastewater is mainly treated by the wastewater from agricultural products. Therefore, the content of nitrogen and phosphorus in the water is high, the water basically does not contain heavy metals and toxic and harmful substances, and the water quality and quantity of the sewage fluctuate relatively. Most of the small towns have little difference in the nature of the sewage, of which the BOD5 is between 100 and 150 mg / L, the COD is between 250 and 300 mg / L, and the SS is around 200 mg / L. 1.2 small town sewage treatment process requirements The requirements for wastewater treatment in small towns are determined by the characteristics of their wastewater and the conditions in small towns themselves. First, due to the small town water quality fluctuations in water quality is relatively large, the size of the sewage treatment plant is also small, the coefficient of change is large, so the town of sewage treatment process stronger anti-shock load capacity. Second, due to the weak economic strength of small towns, the sewage treatment process should be selected as little as possible to run the cost, low cost, basically no dosing or dosing less. At the same time, the process of sludge production as little as possible to reduce secondary pollution, reduce sludge handling costs. Third, small towns lack professional wastewater treatment workers, so the treatment process should be simple and easy to maintain and manage. 2 suitable for small town sewage treatment process The sewage treatment process in the big cities of our country has developed quite maturely. Compared with the big cities, the small towns are limited by the economic strength and their own geographical area, and are relatively slow in the development of the sewage treatment technology. We can see from the above situation, the core of small town sewage treatment is: the process is simple, easy to maintain. Now introduce several suitable for small town sewage treatment process, and put forward the development trend of small town sewage treatment process in our country. 2.1 Sewage natural purification system Common natural sewage treatment systems include stabilization ponds, land treatment systems and wetland treatment systems. 2.1.1 stable pond. Stabilization pond, also known as oxidation pond or biological pond, is a kind of natural or certain artificial sewage purification system with the advantages of less investment, simple operation and management and energy saving. Since the beginning of the 20th century, all countries in the world started their studies on Stabilization Ponds and developed rapidly after the 1950s. The study on Stabilization Pond in our country began in the late 1950s. So far, Stabilization Ponds have been built and put into operation in almost all parts of the country. Stabilization ponds in accordance with the type of microorganisms in the pond can be divided into: aerobic ponds, facultative ponds, anaerobic ponds, aeration ponds, deep ponds. Compared with other processes, stabilization pond has the following advantages: First, the processing cost is low. Stabilization ponds are simple in structure, short in construction period, low in energy consumption, convenient in operation and maintenance and low in cost because of low sewage treatment cost in stability ponds. Second, due to the large volume of the stability pond, it can withstand fluctuations in the amount of sewage water, adaptability and impact load. Suitable for small town sewage treatment process requirements. Third, Stabilization Pond can make full use of the existing lakes and ponds in the area. Therefore, according to local conditions, to achieve the purpose of sewage treatment. Fourth, Stabilization pond less sludge production, thereby reducing the secondary pollution, reducing the sludge disposal costs. As the oxidation pond has the above advantages, oxidation pond technology has been widely used. Oxidation ponds, however, also have some shortcomings and limitations. They cover a large area and are relatively inefficient in handling and may cause odor breeding mosquitoes and flies. They should not be built near residential areas. 2.1.2 Land Processing System. The sewage land treatment system [4] refers to the ecological engineering that uses the terrestrial ecosystem composed of soil microbial plants such as farmland and woodland to comprehensively purify the pollutants. It can treat the urban sewage and realize the resource recycling and harmlessness The At present, commonly used processes are slow infiltration system, rapid infiltration system, surface flow system, wetland treatment system and underground infiltration system. In the land treatment system is the most widely used, the most mature research is constructed wetland treatment system. The five indispensable components of a constructed wetland system are permeable matrices, plants, water bodies, invertebrates or vertebrates that can grow in saturated water and anaerobic matrices, and aerobic or anaerobic microbial populations, respectively. The land treatment system uses these parts to process pollutants through physical filtration, physical adsorption and deposition, physicochemical adsorption, chemical reaction and precipitation, microbial metabolism and organic biodegradation. The advantages of sewage land treatment system are: First, sewage land treatment system can promote the recycling of plant nutrients in wastewater, and the useful substances in sewage water can be reused by the growth of crops. Second, the sewage land treatment system has less capital costs and can make full use of land and depressions. Third, sewage land treatment system operation and management convenience, and low energy consumption. Fourth, sludge is fully utilized, secondary pollution less. Sewage land treatment system has some of the above, at the same time, there are some shortcomings, if not properly designed, will pollute the soil and groundwater, especially caused by heavy metal pollution, organic poison pollution, resulting in decline in the quality of agricultural products. Will also emit odor, breeding mosquitoes and flies, and even affect the health of the human body. 2.1.3 Wetland treatment system. Similar to the above-mentioned natural purification system, the main advantage of constructed wetlands is simple operation, low investment and low energy consumption. However, its area is relatively large. Therefore, the constructed wetland treatment system is more suitable for small towns in agricultural areas where land use is not too tight. 2.2 oxidation ditch process Oxidation ditch is a new type activated sludge method invented by Dutch engineers in the 1950s on the basis of delayed aeration activated sludge process. Depending on the structural characteristics of the oxidation ditch and the inventors and patents, it is possible to classify the oxidation ditch into different types. Commonly there are Carrousel oxidation ditch, alternating oxidation ditch, phosphorus and nitrogen removal double ditch oxidation ditch, triple ditch oxidation ditch, ObraI oxidation ditch and integrated oxidation ditch. On the basis of the traditional oxidation ditch for removing COD and BOD, the second generation oxidation ditch also has the function of nitrogen and phosphorus removal, which greatly improves the application prospect of the oxidation ditch. Oxidation ditch process has the following advantages: First, due to the structure of the oxidation ditch less, do not build the first sedimentation tank and sludge digestion tank, so the process is simple, easy operation and management. Second, the oxidation ditch is suitable for high-concentration industrial wastewater and can withstand the impact load of water quality and quantity, and overcomes the shortcomings that the high-concentration industrial wastewater inhibits the activity of the activated sludge. Third, when the need for nitrogen and phosphorus removal, the relatively traditional nitrogen and phosphorus removal process, the oxidation ditch has the advantages of reducing operating costs and energy consumption. Fourth, the water quality is good, stable operation. However, because the primary sedimentation tank and the sludge digester are not built, the oxidation ditch process increases the load on the reaction tank, which increases the energy consumption to a certain extent. At the same time, due to the oxidation ditch aeration device such as surface aerator Or aeration brush and other mechanical parts to be regularly repaired, so overhaul workload. 2.3SBR process < 1 2 > NINGBO PAPER GAMES KINGDOM CO.,LTD , https://www.papergameskingdom.com
October 08, 2021