In the early days of liberation, because industrial and agricultural production just started and sewage pollution was very low, it was advocated to use sewage for agricultural irrigation, especially in the water-deficient areas in the north, such as the famous Shenfu irrigation canal, so nearly ten sewage treatment plants were built in only a few cities in China (including three sewage treatment plants built by foreigners between 192 1 ~ 1926). Some treatment processes are primary treatment, and the treatment scale is very small, only a few thousand cubic meters/day, and the largest is only about 50 thousand cubic meters/day, which makes the sewage treatment technology and management level in a relatively backward state.
China began to solve the problem of urban sewage purification in 1970s. In some cities, pits, ponds, depressions, abandoned rivers and swamps in the suburbs have been slightly renovated or dams have been built to purify urban sewage. According to the survey, 38 stabilization ponds of various types have been built in China during this period, and the daily treatment of urban sewage is about 6.5438+0.73 million cubic meters. Among them, domestic sewage accounts for half, and the rest includes various industrial wastewater such as petroleum, chemical industry, paper making, printing and dyeing. At this stage, we began to pay attention to the introduction of foreign advanced technology and equipment, carry out technical exchanges with foreign countries, and gradually explore engineering technology and design suitable for China's national conditions to lay the foundation for future construction.
1970s and 1980s: Tianjin Ji Zhuangzi Sewage Treatment Plant was put into operation, which led to dozens of new sewage treatment plants.
With the continuous development of industrial and agricultural production and the gradual improvement of people's living standards, urban sewage has also changed, and the pollution level has gradually evolved from low to high. Some developed capitalist countries have learned the painful lesson that sewage pollution threatens people's health (such as the appearance of Japanese osteopathy and Minamata disease), which has aroused people's attention and our government's great attention, and established a national environmental protection organization (the State Council Environmental Protection Office). Universities have also set up environmental engineering departments or majors. The State Council Environmental Protection Office invested and built a pilot sewage treatment plant in Tianjin (Tianjin Ji Zhuangzi Pilot Sewage Treatment Plant), which started in the late 1970s. Treatment scale: primary treatment is 0. 1 m3 /s, secondary treatment is 0.025 m3 /s, and Beijing Gaobeidian sewage treatment pilot plant has also been operated successively. The state and local governments have done the preparatory work for the construction of large-scale domestic sewage treatment plants. At this moment, Tianjin Municipal Government, Ministry of Construction and relevant ministries and commissions took the lead in deciding to build Tianjin Ji Zhuangzi Sewage Treatment Plant, which broke ground on 1982 and was completed and put into operation on April 28th, 1984, with a treatment scale of 260,000 cubic meters per day.
Tianjin Ji Zhuangzi Sewage Treatment Plant, the first large-scale urban sewage treatment plant in China, broke ground on 1982, and was completed and put into operation on 1984 on April 28th, with a treatment scale of 260,000 cubic meters/day. Zhuangzi Sewage Treatment Plant reached the designed effluent quality standard for many years after it was put into operation, which turned black and smelly sewage into clean water. Its birth fills the gap in the construction of large sewage treatment plants in China. Driven by this successful experience, Beijing, Shanghai, Guangdong, Guangxi, Shaanxi, Shanxi, Hebei, Jiangsu, Zhejiang, Hubei, Hunan and other provinces and cities have built dozens of sewage treatment plants of different scales according to their specific conditions.
During the Ninth Five-Year Plan period, water pollution control in the Three Rivers and Three Lakes basins was officially launched.
During the Ninth Five-Year Plan period, China officially began to control the water pollution in the three rivers (Huaihe River, Haihe River and Liaohe River), the three lakes (Taihu Lake, Chaohu Lake and Dianchi Lake) and the Bohai Rim region, and the state gave corresponding financial and technical support. From 1996 to 1999, 22 urban sewage treatment projects were completed and put into operation, with an investment of 5.958 billion yuan and a daily treatment scale of 37 1.7 million cubic meters. Projects under construction 109, planned investment1665438+83 million yuan, daily processing capacity of 8.32 million cubic meters.
The establishment of national key scientific and technological projects in the Seventh Five-Year Plan, the Eighth Five-Year Plan and the Ninth Five-Year Plan has made gratifying scientific research achievements in new technologies such as sewage treatment, sludge treatment and reclaimed water reuse in China, and some projects have reached the international advanced level. New technologies, new processes and new equipment for sewage treatment from abroad have been introduced to China. While adopting the activated sludge method, AB method, A/O method, AA/O method, CASS method, SBR method, oxidation ditch method, stabilization pond method and land treatment method are also applied to the construction of sewage treatment plants. Open up the industry market from the sewage treatment technology that only has the function of removing organic matter in the past. Such as grid machine, submersible pump, desander, mud scraper, aerator, blower, sludge pump, dehydrator, biogas generator, biogas boiler, sludge digestion and stirring system and other large equipment.
Due to the large investment in the construction of large-scale urban sewage treatment plants, the construction funds in China are limited, which can not meet the needs of water pollution control. Therefore, the introduction of foreign capital to build sewage treatment plants has become an important part of construction funds, which has also accelerated the construction speed of urban sewage treatment plants in China. A number of large-scale urban sewage treatment plants have been built and put into operation with foreign loan projects. For example, the largest sewage treatment scale in China in the 20th century was 600,000 cubic meters/day; The treatment scale of Tianjin Dong Jiao Sewage Treatment Plant, Chengdu Sanwayao Sewage Treatment Plant, Shenyang North Sewage Treatment Plant and Zhengzhou Wangxinzhuang Sewage Treatment Plant is 400,000 cubic meters per day. ..
According to statistics, by the end of 2000, 427 urban sewage treatment plants had been built in China, including 282 secondary treatment plants, and the secondary treatment rate was about 15%. In 2000, the total investment of urban sewage treatment project construction was about 654.38+0.5 billion yuan. But at present, most small towns have not built sewage treatment facilities. Seven serious injuries restrict the development of urban sewage treatment
According to Zhu Yanbo, an expert in sewage treatment, there are seven major problems in urban sewage treatment in China, which restrict the development of urban sewage treatment in China.
First, there is a shortage of funds for the construction of sewage treatment plants.
Although more than 100 sewage treatment plants have been built in China, they are still far from meeting the needs of urban industrial and agricultural production and people's lives. This is reflected in the low treatment rate of a city, that is, the sewage treatment capacity is not enough. It is also reflected in the fact that big cities have begun to plan and plan the construction of sewage treatment plants. However, in small and medium-sized cities, especially in the northwest, the planning and construction of sewage treatment has not been included in the agenda of urban development. One of the main reasons is that there is no special construction fund, and water pollution in some areas is becoming more and more serious. If the capital is invested to build a sewage treatment plant, the environment will deteriorate, bringing inconvenience to people's lives and endangering people's physical and mental health. Therefore, we should raise funds from various channels to speed up the control of water pollution and leave a beautiful living environment for future generations.
Second, the operating funds of the sewage treatment plant cannot be put in place.
At present, there are more than 100 sewage treatment plants built and put into operation in China, of which less than13 can operate at full capacity. Most of them are caused by insufficient operating funds. Some provinces and cities do not charge sewage treatment fees, some only charge factories, enterprises and residents, and some all of them. It is far from the lowest cost of normal operation of sewage treatment plants, which makes some sewage treatment plants have the practical problem of treating as many tons of sewage as they can. In the long run, it will not give full play to the benefits of building sewage treatment plants, but will also damage instruments and equipment, and at the same time it will not play the role of professional managers of sewage treatment plants.
Third, the maintenance of imported equipment and the development of equipment accessories.
Due to a large number of imported equipment entering the sewage treatment industry, after several years of operation, the equipment will be damaged one after another, especially after the claim period for maintenance and normal overhaul. This requires technicians with professional skills. If foreign experts are invited to repair, the maintenance cost will increase greatly, which is really unacceptable, and the imported equipment can maintain normal operation. It is necessary to train domestic imported equipment maintenance professionals so that they can master maintenance skills and meet the maintenance standards of imported equipment. With maintenance professionals, there must be enough spare parts, especially some equipment that will be eliminated will be introduced to China, and spare parts will not be produced abroad, so it is necessary to carry out domestic mapping, processing and manufacturing. Only in this way can imported equipment play its role, otherwise the damage of equipment and the lack of spare parts will affect the normal operation of sewage treatment plants.
Fourth, the sewage treatment process should follow the trend and cannot be combined with the actual situation.
Choosing popular technologies is simply pursuing new and fashionable technologies when choosing sewage treatment technologies, without considering the problems of influent quality, treated water quantity and effluent use in this area. Some sewage treatment plants built in China have low influent quality, so AB method is chosen, which can not be fully utilized, resulting in idle facilities and equipment. In some areas, the treated reclaimed water is directly used for agricultural irrigation, with too much emphasis on phosphorus and nitrogen removal. The adoption of A/A/O method increases the construction investment and daily operation cost. When building sewage treatment plants in other areas, what technology to adopt depends on the wind blowing at that time.
Fifth, the reclaimed water after sewage treatment can not be fully utilized.
The construction investment of sewage treatment plant is huge, and the treated reclaimed water can not be fully utilized. Even in some areas, treated reclaimed water is mixed with untreated sewage, and in some areas, reclaimed water is discharged into the sea, resulting in a waste of fresh water resources. At present, the world's fresh water resources are extremely scarce. China ranks 12 1 in the world, with only 2,000 cubic meters of fresh water per capita.
Sixth, sludge is not really harmless, and there is no way to finally dispose of it.
After the sewage is treated by various processes, the effluent reaches the national discharge standard. However, the reward and punishment sludge in the sewage treatment process is not properly disposed, which will also cause secondary pollution to the environment. In some areas, sludge is piled up outside the site without harmless treatment and taken away at will. In some areas, sludge is used as agricultural fertilizer after drying, and it is seldom considered whether the content of heavy metals reaches the standard, which is not harmful to crops. The national environmental protection department prohibits sludge from being used as fertilizer for vegetable fields and rice fields. As an agricultural fertilizer in dry land, sludge needs to be analyzed, and heavy metals and toxic substances should not exceed the standard before use. Sludge, as a fertilizer for green space, must be recognized by the garden department and can only be used after being tracked and analyzed by the monitoring department. In short, if there is no final disposal method for sludge, it will bring hidden dangers to the environment.
Seventh, the sewage treatment plant has no deodorization device.
The water intake tank, grille room, grit chamber, primary sedimentation tank, sludge storage tank of sludge treatment system and dewatering machine room (except centrifuges) of sewage treatment plants will all produce serious odor, which will not only affect the health of operators, but also pollute the living environment of surrounding residents, especially some sewage treatment plants that were built earlier, used to be farmland and pools, and were far away from urban areas. Now they are all urban areas, and residential areas have been built around the sewage treatment plant.
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