Currently, China's sewage treatment rate is low, the discharge of pollutants, resulting in serious water pollution, eutrophication of water bodies is particularly prominent. State Environmental Protection Administration announced in 2001 the state of environmental quality shows that China's important water systems and lakes, although the pollution situation has improved, but the situation is still very serious. Among the 752 key monitoring sections of the seven major river systems in 2001, 27% of the sections met the standards of category 1 to 3, 14% of the sections met the standards of category 4, and nearly 59% of the sections had the water quality of category 5 or inferior category 5. The main pollutants are ammonia nitrogen, CODMn, BOD, volatile phenols and petroleum. Among them, the main nutrients causing eutrophication of water bodies are organic carbon, nitrogen, phosphorus, potassium, iron and so on. Organic carbon can be basically removed by general biological treatment, nitrogen and phosphorus in addition to other components relative to eutrophication in the process of occurrence of the demand is extremely low, does not constitute a limiting factor for eutrophication. The main factors causing algal blooms are nitrogen and phosphorus, and the demand for phosphorus by algae is about 1/20 of the demand for nitrogen, so controlling the source of pollution and reducing the nitrogen in the sewage, especially phosphorus, is the key to preventing eutrophication of the water body.
With the rapid development of the economy and the increasing urban population, especially in small and medium-sized towns and cities, the development of faster sewage treatment plants can not keep up with the needs of development, resulting in a large number of wastewater has not been fully processed and discharged into the water, and accelerate the process of eutrophication of the water body. Therefore, how to solve the small and medium-sized towns and cities sewage carbon, nitrogen, phosphorus discharge standards, control of eutrophication of water bodies is a priority. To this end, the relevant state departments promulgated a series of regulations and policies, in 1996 formulated the "Comprehensive Sewage Discharge Standards" (GB8978 - 1996), the provisions of the first level of discharge standards of ammonia nitrogen 15 mg / L, phosphate 0.5 mg / L, the second level of discharge standards of ammonia nitrogen 25 mg / L, phosphate 1.0 mg / L, in the water source protection areas and other key areas should be added to the phosphorus denitrification facilities, and on May 29, 2000, the State Administration of the United Nations Environment Programme (UNEP) issued the "Water Resources Management System", which is a comprehensive set of standards for the discharge of sewage. On May 29, 2000, the Ministry of Construction, the State Environmental Protection Administration and the Ministry of Science and Technology jointly promulgated the "Urban Sewage Treatment and Pollution Prevention Technology Policy", which puts forward China's recent sewage treatment goals: in 2010, the average sewage treatment rate of municipal cities and towns should not be less than 50%, the sewage treatment rate of municipal cities should not be less than 60%, and the sewage treatment rate of key cities should not be less than 70%, and stipulates that the sewage treatment rate of cities that cannot be integrated into the urban sewage collection system should not be less than 70%. Can not be included in the urban sewage collection system of residential areas, tourist attractions, resorts, sanatoriums, airports, railroad stations, economic development zones and other decentralized crowd of sewage discharged and independent industrial and mining areas of industrial wastewater should be treated locally to meet the standards of discharge. And China's environmental protection "Tenth Five-Year Plan" for the country and "3 rivers and 3 lakes" and other key areas of the total amount of ammonia and nitrogen emissions from sewage control, and Lake Taihu, Dianchi and Chaohu total phosphorus into the lake and the amount of emission targets. However, 80% of China's population is in rural areas, and there are also many places on the outskirts of cities where it is difficult to extend the urban pipeline network, and in many towns and cities, the penetration rate of sewers and the use of efficiency is very low. These are for the town of small domestic sewage treatment equipment application and development provides a broad space.
1 town small living sewage treatment equipment features and classification
The town small living sewage treatment equipment generally refers to the treatment capacity of 500 m3 / d below, set the sewage treatment process of the various parts of the function of the living sewage treatment device. The equipment is mainly used in:
(1) large amount of sewage, there is no urban sewage treatment plant areas and buildings.
(2) Remote urban areas and new areas outside the service area of the urban drainage system.
(3) Some industrial wastewater similar in nature to urban domestic sewage.
(4) Rural areas, townships, residential areas, tourist attractions, resorts, sanatoriums, airports, railroad stations, economic development zones and other dispersed crowded places.
At present, the main small domestic sewage treatment processes used in China are: septic tanks, stabilization ponds, land treatment of sewage, activated sludge and biofilm method. Septic tank can reduce the SS of 70% ~ 75% and BOD5 of 30% ~ 35%, but can not meet the discharge standards; the use of stabilization pond sewage treatment can make full use of the terrain, saving money, and can realize the resource of sewage, but covers a large area, the treatment effect is vulnerable to climate, so it is difficult to popularize; sewage land treatment system has slow percolation, rapid percolation, surface diffusion, wetlands, underground Infiltration and other forms, often used in combination with oxidation ponds, can make full use of natural conditions, simple structure, low cost, for the vast majority of rural and small town areas is very suitable; activated sludge and biofilm process is the most widely used small domestic sewage treatment process, with operational safety can be *, the investment province, construction and installation is convenient, short construction period, easy to operate and manage and so on. This type of process mainly includes physical treatment, biological treatment, disinfection of three major parts, of which the physical treatment process plays a pre-treatment role, usually using grating, sedimentation and other processes; biological treatment is the main part of the treatment process, the use of biofilter, bio-turntable, biological contact oxidation and activated sludge process; post-treatment is generally disinfected for reuse or discharge. Biological treatment process main design parameters are shown in Table 1.
Small sewage treatment equipment can be divided into indoor equipment and outdoor equipment according to the location of the treatment equipment, indoor equipment is usually placed in the basement of the building, mainly used for high-rise buildings, such as hotels, offices, but because of its small footprint, poor sanitation, operation and maintenance of inconvenience and other factors, and gradually replaced by outdoor equipment. Outdoor equipment is mainly used in outdoor open space such as green space, lawn, outdoor parking lot, etc., the equipment is buried in the ground, does not occupy the surface area. According to the operation of power, processing equipment can be divided into powered and unpowered 2 kinds.
2 Application Prospects
Existing activated sludge and biofilm processes generally do not consider the removal of phosphorus and nitrogen, as the development of activated sludge oxidation ditch method and SBR, although it can play a role in the removal of phosphorus and nitrogen, but the treatment of small-scale wastewater treatment effect is poor. Therefore, small sewage treatment equipment should consider the function of phosphorus and nitrogen removal. However, China's large-scale sewage treatment plant for the removal of phosphorus and denitrogen research, although many results have been achieved, and practical applications, but with the removal of phosphorus and denitrogen function of small-scale sewage treatment equipment research and development is still in the research stage. Therefore, in order to make China's urban sewage can meet the discharge standards, and can be completed in China's recent sewage treatment goals, research and development of small-scale sewage treatment equipment with phosphorus denitrification function is the urgent need to solve the problem. At the same time, with the improvement of environmental requirements and management level of the limitations of urban small-scale domestic sewage treatment equipment in the direction of phosphorus denitrification development at the same time, should be further developed in the direction of assembling the series, closed, automated, efficient treatment efficiency.
More about the engineering/service/procurement category of the tender writing production, to enhance the winning rate, you can click the bottom of the official website customer service free consultation:/#/?source=bdzd