1, urban sewage pollution and treatment status
Since 1985, the total annual wastewater discharge in China has been kept at about 35-40 billion m3/a .. 1996, 532 of the 666 cities in China have no sewage treatment plants, and 309 sewage treatment plants have been built in 134 cities. The total amount of urban sewage treatment is only 4.46 billion m3, of which only 6.9% is treated by secondary biochemical treatment, and 77.4% of urban sewage is directly discharged into water without any treatment. During the period of 1997, the wastewater discharge reached the highest value of 41600 million m3, including 22.7 billion t of industrial wastewater and 0.89 billion t of urban wastewater. From 65438 to 0999, the pollution load of urban sewage exceeded the pollution load of industrial wastewater for the first time, and the focus of water pollution in China has gradually changed from industrial point source-based control to urban sewage pollution-based control. According to the estimation of the Ministry of Construction, the wastewater discharge in 2000 was 48 billion cubic meters.
2. Prediction of urban sewage discharge
At present, there are more than 640 municipalities directly under the central government and10.6 million towns with a population of about 270 million. Since 1990s, China's gross national product has been growing at a high speed of 8 ~ 1 1%. It is predicted that in the first 20 years of the new century, China's economy will maintain a medium-high-speed and stable development of 6-9%. Based on the above factors, the increase of sewage volume is considered as 5%. By 20 10, the sewage volume will increase by 30 billion m3.
According to the development plan of small towns newly formulated by the relevant departments of our government, the development focus of new small towns in the future will be small towns along the highway, along the river, along the coast and along the border with good geographical location and traffic conditions, rich resources, a certain foundation of township enterprises or a certain scale of rural wholesale and professional markets; The construction target is a new small town with reasonable layout, complete facilities, convenient transportation, beautiful environment, prosperous economy, distinctive features and a population of about 30,000. By 20 10, China's urban population will reach about 560 million, and the level of urbanization will reach about 40%. In 20 10, there were about 1200 municipalities and 25,000-30,000 towns in China. By 20 10, the national tap water penetration rate will reach 65%, the per capita daily water consumption in small towns will be 180 liters, and that in villages will be 1 10 liters.
3, sewage treatment rate and investment estimation
Considering the current sewage volume, sewage increment and urban sewage volume, the total sewage discharge will be10.5 billion m3/a by 20 10. To sum up, considering the current sewage volume, sewage increment and urban sewage volume, by 2065.438+00, the total urban sewage discharge will be 654.38+005 billion m3. According to the requirements of the Ninth Five-Year Plan for National Economic and Social Development and the long-term target outline of 20 10, it is necessary to increase the treatment scale of 50 billion m3/a (10.40 billion m3/d) to 50% of that of 20 10. See table 1 for the predicted urban sewage volume and investment according to the growth rate. To achieve 50% sewage treatment rate, if the investment in sewage treatment per cubic meter is 2000-3000 yuan according to static investment (considering supporting pipe network), it will need 300-400 billion yuan. According to the degree of sewage treatment and the increase of sewage volume, the market share analysis of the main technical equipment (especially the secondary treatment related equipment) of urban sewage treatment plants is shown in Table 2. In order to expand domestic demand and promote economic development, the state has increased investment in infrastructure since 1998, and urban infrastructure has become an important part of it. At present, 30 billion of the10 billion national debt will be used for urban infrastructure construction. Among the local water supply and drainage construction projects reported to the Ministry of Construction, there are 322 water supply projects and 208 sewage projects, with a total investment of 1 1000 billion yuan. From 65438 to 0999, the state issued an additional 65 billion yuan, part of which was mainly used for projects under construction and some new projects from 65438 to 0998. Such huge investment and market share are both opportunities and challenges for the development of aquaculture in China.
In the above share, traditional industries such as mechanical processing (mechanical and electrical products such as pumps and fans) account for about 15-30%, and construction accounts for 35-45%. The sum of the two accounts for more than 60% of the total investment, and the market share will be about 20 billion in the next 10 year. The main body engaged in the above industries is the national large and medium-sized enterprises. It can be seen that for large-scale infrastructure projects such as urban sewage and urban water supply, state investment will drive the development of a large number of traditional industries such as electromechanical industry, machinery manufacturing and processing industry and construction industry. This can promote the development of related industries and increase the total consumption, which is conducive to the reform and economic development of large and medium-sized enterprises, which is also in line with the current national policy of invigorating large and medium-sized enterprises. Although the proportion of automatic control and instrument technical services in water pollution control is not high, about 8- 15%, the relative output value is high. This part of the market is valued at around 4-6 billion yuan/year. In addition, the general sewage treatment operation and management expenses account for about 10% of the investment, and the share of the operation service industry is about 4 billion/year.
Faced with such a huge environmental pollution control market in China, foreign companies began to enter. At present, many urban sewage treatment plants are built with foreign capital, such as 1996- 1998. There are dozens of large-scale urban sewage treatment plants with foreign loans, many of which are imported from abroad. Due to the mature technology, good quality and excellent service of foreign water treatment products, it poses a severe challenge to China's water treatment industry.
Second, the development of urban sewage treatment technology
1, urban sewage treatment process
China's urban sewage treatment technology was gradually studied from the "Seventh Five-Year Plan" national scientific and technological research. There are many researches on natural treatment technologies such as oxidation pond, land treatment and complex ecosystem in the key projects of the Seventh Five-Year Plan and the Eighth Five-Year Plan, and the design is based on these achievements. Some demonstration projects of oxidation ponds and urban sewage land treatment have been established. In terms of manual treatment technology, the "Eighth Five-Year Plan" has conducted in-depth research on high-load activated sludge, high-load biofilm and integrated oxidation ditch technology, and introduced and developed A/B, A/A/O, A/O, B/C, SBR and other treatment processes, and the research results have been applied to a large number of sewage treatment plants; During the Ninth Five-Year Plan period, the sludge treatment of urban sewage plants was paid attention to, and a complete sludge treatment process was developed. During the "Ninth Five-Year Plan" period, the focus of technical research was on simple and efficient complete sets of practical technologies for sewage treatment in small and medium-sized towns, which solved the problems of high energy consumption in manual treatment and large land occupation in natural treatment.
Through the efforts during the Seventh Five-Year Plan, the Eighth Five-Year Plan and the Ninth Five-Year Plan, China's urban sewage treatment technology has made great achievements and achieved fruitful results. As far as the breadth of technology is concerned, the gap with the international community has narrowed. At present, in the water pollution control technology, the following technical parameters can be provided. Traditional activated sludge technology includes traditional method, delay method, adsorption regeneration method and various new activated sludge processes, such as SBR, AB method and oxidation ditch technology. A-O method and A2-O technology; Acidification (hydrolysis)-aerobic technology; Various types of stabilization pond technology; Land treatment technology and so on. This can already meet the requirements of sewage treatment in most cities.
Second, the development of urban sewage treatment technology
1, urban sewage treatment process
China's urban sewage treatment technology was gradually studied from the "Seventh Five-Year Plan" national scientific and technological research. There are many researches on natural treatment technologies such as oxidation pond, land treatment and complex ecosystem in the key projects of the Seventh Five-Year Plan and the Eighth Five-Year Plan, and the design is based on these achievements. Some demonstration projects of oxidation ponds and urban sewage land treatment have been established. In terms of manual treatment technology, the "Eighth Five-Year Plan" has conducted in-depth research on high-load activated sludge, high-load biofilm and integrated oxidation ditch technology, and introduced and developed A/B, A/A/O, A/O, B/C, SBR and other treatment processes, and the research results have been applied to a large number of sewage treatment plants; During the Ninth Five-Year Plan period, the sludge treatment of urban sewage plants was paid attention to, and a complete sludge treatment process was developed. During the "Ninth Five-Year Plan" period, the focus of technical research was on simple and efficient complete sets of practical technologies for sewage treatment in small and medium-sized towns, which solved the problems of high energy consumption in manual treatment and large land occupation in natural treatment.
Through the efforts during the Seventh Five-Year Plan, the Eighth Five-Year Plan and the Ninth Five-Year Plan, China's urban sewage treatment technology has made great achievements and achieved fruitful results. As far as the breadth of technology is concerned, the gap with the international community has narrowed. At present, in the water pollution control technology, the following technical parameters can be provided. Traditional activated sludge technology includes traditional method, delay method, adsorption regeneration method and various new activated sludge processes, such as SBR, AB method and oxidation ditch technology. A-O method and A2-O technology; Acidification (hydrolysis)-aerobic technology; Various types of stabilization pond technology; Land treatment technology and so on. This can already meet the requirements of sewage treatment in most cities.
2. Discussion on the technical problems of urban sewage treatment.
In 1960s and 1970s, oxidation ditch and SBR process developed rapidly, and in recent years, they became the dominant processes of urban sewage treatment plants in China. Biological aerated filter (BAF) and primary enhanced process are newly developed high-efficiency urban sewage treatment processes with development potential in the late 1980s and early 1990s. Hydrolysis-aerobic biological treatment process is a new municipal sewage treatment process with independent intellectual property rights in China. In recent years, China has introduced many foreign new technologies and built quite a number of projects, which are precious wealth in the field of urban sewage in China and should be systematically summarized. However, the research of sewage treatment technology in China is mainly based on single research, focusing on process research, lacking sufficient systematicness and completeness, and lacking comprehensive comparative research and technical and economic evaluation system. This is also the reason why AB process is popular first, then three ditch oxidation ditch and other forms of oxidation ditch, and now SBR process is popular. Lack of comprehensive comparative ability, for a long time, foreign new technologies and new products will continue to impact the domestic market, and domestic technologies will never occupy a place in the market.
On the other hand, the activated sludge process, oxidation ditch process, SBR (intermittent activated sludge) process and AB process commonly used in urban sewage treatment plants in China are almost at the same level as those used in developed countries such as the United States and Germany, while China's gross national product is far lower than those in the above countries. The above technology has been proved to be an effective technology to control water pollution abroad. However, the above technologies are not necessarily advanced, especially not all of them are completely suitable for China's national conditions.
For example, at present, oxidation ditch and SBR process with extended aeration introduced from abroad are widely used in China. Extended aeration is a low-load process. For a developing country with insufficient resources and a large population, whether it is suitable to popularize this low-load activated sludge process is a question worthy of deliberation. First of all, the tank capacity and equipment of low-load aeration tank are several times that of medium-high load activated sludge process, so the corresponding investment is several times higher; Secondly, extended aeration is used to stabilize the sludge in an aerobic way, and the energy consumption is about 40-50% higher than that of medium and high load activated sludge. Of course, the increase in energy consumption has brought about an increase in direct operating costs and an increase in indirect investment. According to the data, at present, the power generation capacity per kilowatt needs to invest 1 000 USD, and the increased desulfurization investment per 10,000 tons of sewage needs 700,000 yuan. If the desulfurization investment is 10% of the power plant investment, the increased power plant investment is 7 million yuan, which is close to 50% of the sewage treatment unit investment. From the perspective of sustainable development, it is not suitable for China to adopt low-load processes with extended aeration, such as oxidation ditch process.
In the treatment and disposal of municipal sewage sludge, China has just started, and there is still a big gap compared with advanced foreign countries. With the commissioning of a large number of sewage treatment plants, the sludge output will greatly increase. The investment of sludge anaerobic digestion is high, and the cost of sludge treatment accounts for about 20-45% of the investment and operation cost of sewage treatment plant. Sludge anaerobic digestion technology is complex. Of the only dozen sludge digesters in China, only a few can operate normally, and some ponds don't operate at all. This is also the reason why oxidation ditch with expanded aeration function has been widely used in China in recent years. Therefore, one of the keys to adopt high efficiency (high load) and low consumption sewage treatment technology is to solve the sludge treatment technology of urban sewage plants. It can be said that the progress of urban sewage technology in China in the future depends largely on the progress of sludge treatment and utilization technology. Whether the sludge problem can be solved well is one of the decisive factors for the success of sewage purification. In order to solve this problem, it is necessary to strengthen the research on sludge treatment and utilization. From the way out of sludge final disposal, sludge agriculture is the most feasible and realistic disposal scheme according to the specific situation of our country. Combined with the final disposal of sludge and considering the utilization of sludge compost, it is another technically feasible and economic way for sludge treatment process suitable for China's national conditions.
Due to the low level of economic development, lack of funds, insufficient investment and many other factors, a large number of water treatment and environmental protection enterprises in developed countries have entered China's water treatment and environmental protection market on a large scale by means of loans. Since 1988, China has opened up about 200 foreign-funded water supply and drainage projects with a total amount of 7.8 billion US dollars. Due to the use of foreign capital, especially the government loans from developed European countries (which can only be used to buy equipment from the lending countries), although the construction of a number of modern sewage treatment plants has been promoted, the project investment (the price of foreign equipment is generally 4-6 times that of domestic equipment) and the daily maintenance expenses in the future (foreign exchange is needed to update accessories) have been increased. At the same time, it also seriously inhibited the development of domestic sewage treatment equipment manufacturing industry. Due to the lack of technology and capital investment, domestic sewage treatment equipment can not reach the international level. But on the whole, China's mechanical and electrical equipment manufacturing industry can produce complete sets of sewage treatment equipment after proper reorganization, adjustment and transformation. At present, about 90% of urban sewage treatment in China comes from various international loans, which are basically occupied by large international companies.
Third, the development trend of urban sewage treatment in China
Water pollution control technology involves the research and development of water treatment technology, engineering design, engineering implementation, equipment treatment and operation management. However, from the perspective of marketization and industrialization of water treatment technology, especially from the division of investment structure, water treatment technology industry can be divided into: 1) process technology; 2) Industrialization of engineering and equipment; 3) Facilities operation industrialization and other three parts. China's next major task is to focus on the above three aspects.
1, vigorously develop advanced water treatment technology.
For a country with serious pollution, resource shortage and in the primary stage of socialism, the standard of advanced water treatment technology should be a sewage treatment technology that is suitable for China's national conditions, efficient, low-consumption and low-cost. Various new technologies of urban sewage treatment with high efficiency and low investment can reach a certain depth of treatment, which will be of great significance to China, where the economy is not developed enough and the pollution needs to be treated urgently, especially to the vast majority of17,000 towns without sewage treatment facilities for a period of time. Therefore, there is an urgent need for a number of new sewage treatment technologies and processes that can meet the discharge requirements, have good treatment effect and low capital construction and operation costs. Therefore, the State Environmental Protection Administration proposes to establish an economical and practical advanced technology demonstration project suitable for China's current national conditions. The demonstration project should meet the following requirements: 65,438+0) The investment per ton of water is low, and the cost per ton of water should be controlled in 800 yuan; 2) The operating cost is low, and the operating cost per ton of water should be controlled below 0.3 yuan; 3) The project adopts domestic equipment and adopts the general contracting operation mechanism.
In order to achieve the above goals, we need to increase the application and demonstration of new technologies, new materials and high technologies. As we all know, efficient process can greatly reduce the capital investment of sewage treatment. For example, at present, the oxidation ditch and SBR process in extended aeration are generally 0.05-0.07kgBOD/m3.d, which is several times or even ten times different from the medium and high aeration tank load (0.3-0.5kgBOD/m3.d), so the investment of aeration tank is also increased several times or even ten times accordingly. From the perspective of new technology, the existing physicochemical-biochemical process, hydrolysis-aerobic process, biological aerated filter, medium and high load aerobic process and anaerobic-aerobic treatment technology are all promising new technologies, but they need to be further improved. In order to improve the sewage treatment rate in a short time, we must not only formulate reasonable and feasible industrial technical and economic policies and increase investment in the construction of urban sewage treatment plants, but also rely on technological progress to carry out some advanced sewage treatment technology demonstration and popularization as soon as possible.
Similarly, the use of new materials and new construction methods can reduce the project cost. For example, Biolack technology abroad in Germany uses high-density polyethylene as the impervious material of water treatment structures, which reduces the cost of water treatment structures. Advanced foreign tank-making technology, such as assembled reactor, can be popularized in sewage treatment structures. Equip treatment structures and provide complete sets of unit reactor equipment for urban sewage treatment in the form of fast and low-consumption equipment; Improve the complete sets and equipment of water treatment equipment, integrate complete process technology, mature automatic control technology and strict manufacturing technology, and design and produce complete sets of sewage treatment equipment with high-tech content;
In addition, the use of high technology, especially highly automated control system, makes electrical control, instrument and computer integrated, that is, monitoring, control and management integrated, which is the inevitable requirement and development trend of production process automation in environmental protection factories. The improvement of automation control in sewage treatment plant has brought a series of benefits to the transformation of operation management mechanism, the reduction of capital construction cost and operation cost. According to the international development trend, vigorously developing China's environmental protection automatic control technology and equipment is the fundamental guarantee to improve the management level of China's environmental protection projects and the stable operation of governance facilities.
2, vigorously promote the industrialization of water treatment technology and equipment.
The implementation of water pollution control is realized through engineering facilities and technical equipment. At present, water treatment engineering has the following characteristics: First, the content of equipment and construction technology and the proportion of investment in the project are constantly improving, which reflects the trend of equipment, industrialization and marketization of water treatment engineering technology. China needs to establish an industrial base of complete sets of sewage treatment equipment, and the implementation of water pollution control is realized through engineering facilities and technical equipment, while China needs to establish an industrial base of complete sets of sewage treatment equipment; Secondly, the engineering market has introduced the "turnkey" international general contracting operation mode from the traditional contracting mode. The "engineering company" involved in this kind of general contracting of engineering and equipment has become a cross-industry industry internationally. Engineering companies are generally large companies with comprehensive capabilities such as system design, project management, equipment integration, installation and debugging, and operation training. At present, there is no such large-scale professional engineering company with comprehensive ability in China.
The implementation of water pollution control is realized through engineering facilities and technical equipment. China needs to establish an industrial base of complete sets of sewage treatment equipment. For different scale and types of urban sewage treatment plants, the industrialization development goals are different.
1) construction of super-large urban sewage treatment plant
There are no more than 100 municipal sewage treatment plants with sewage volume ≥ 200,000 m3/d in China, but they account for 30% ~ 50% of the total sewage discharge. Although there were some super-large projects under construction in the early 1990s and now, due to the importance of the projects and the guarantee of funding sources, the focus of recent construction is still on such sewage treatment plants. According to the experience at home and abroad, most of the processes used in super-large urban sewage treatment plants are mature traditional activated sludge process, so the development of related equipment focuses on the single technical equipment of large sewage treatment plants (especially the secondary treatment related equipment). These include:
① Large automatic grid decontamination equipment;
(2) Various complete sets of desanding and flushing equipment;
(3) large sedimentation tank mud scraping and suction equipment;
④ Efficient aeration equipment;
⑤ General machinery and equipment for large-scale sewage, such as centrifugal fans and sewage pumps;
⑥ Large-scale concentration and dehydration integrated equipment;
⑦ Complete sludge digestion equipment;
(8) Complete biogas utilization equipment;
Pet-name ruby supporting automatic control system and instrument, etc.
Attending complete sets of sludge treatment and disposal equipment, such as composting and granulation devices.
2) Construction of sewage treatment plants in large and medium-sized cities
Because the sludge of urban sewage plants adopts anaerobic digestion treatment technology, the investment of sludge anaerobic digestion accounts for 30% ~ 40% of the investment of sewage treatment plants, and the sludge anaerobic digestion treatment technology is more complicated. This problem has not been well solved. The treatment, disposal and utilization of sludge in China started late, and both scientific research and development and engineering practice are far behind the needs of developed countries and domestic. Therefore, according to the characteristics of sewage treatment plants in large and medium-sized cities, many cities have recently adopted low-load oxidation ditch and SBR process, and adopted aerobic sludge stabilization method. For the development of medium-sized sewage treatment plants, the key point is to speed up the popularization of oxidation ditch method, SBR and other treatment technologies, and at the same time speed up the localization and large-scale production of these process-specific equipment to form the overall capacity from design, equipment manufacturing, engineering construction to operation management. Form the production capacity of the following equipment:
① Oxidation ditch aeration equipment: such as rotary brush, rotary table and surface aerator;
② Integrated equipment for sludge concentration and dehydration;
Decanter in SBR process;
Special aeration equipment for SBR;
⑤ SBR automatic control equipment.
3) Construction of sewage treatment plants in small and medium-sized towns
For a large number of small town sewage treatment plants in China, the sewage output of small and medium-sized towns is less than 50,000 m3/d, which is the focus and difficulty of water pollution control in China. Because our country is still in the primary stage of socialist development. Most small and medium-sized towns are located in underdeveloped rural areas, but the pollution caused by them is large and wide, which is the focus of the next phase of the control of three lakes and three rivers in China. According to this feature, it is necessary to develop a set of simple and efficient sewage treatment technologies suitable for small and medium-sized towns, focusing on solving the three high problems of high investment, high electricity consumption and high operating cost of urban sewage treatment plants. Low-consumption and high-efficiency processes, such as hydrolysis-aerobic biological treatment process and biological aerated filter, can meet this demand. Therefore, small urban sewage treatment plants need to do the following work:
① A complete set of simple and efficient urban sewage treatment devices;
② Full automation of simple and efficient urban sewage treatment device;
③ Complete technology of sludge composting and granulation. 3. Vigorously encourage the industrialization of water treatment facilities. According to the investment estimate of sewage treatment plant construction, the operating cost of urban sewage treatment plant will increase to 20 10 year by year, reaching 4 billion yuan/year ... The industrialization of sewage treatment facilities involves two aspects. First, the scope of traditional technical services continues to expand. Due to the improvement of environmental protection laws and regulations and the strengthening of law enforcement, the requirements for the compliance rate and integrity rate of water treatment equipment operation are higher, so the timeliness of technical requirements is constantly strengthened; At the same time, with the development of socialist market economy, the introduction of BOT mode in the field of water treatment will gradually break the traditional concept of Party A and Party B, leading to the exchange of roles between Party A and Party B, resulting in the demand for technical services similar to property management. This puts forward higher requirements for technical services. Therefore, a series of changes such as the expansion of technical service scope, the strengthening of requirements and the renewal of forms have led to the expansion of the connotation of technical service market. Secondly, with the role exchange between Party A and Party B, the way of raising funds has changed. Due to the planned economy, the current situation of most sewage treatment plants is that the government has invested heavily or used loans from foreign governments to build them. After the completion, most of them are compiled by public institutions, and the operating funds are approved and allocated by relevant government departments. A considerable number of sewage treatment plants have a serious shortage of operating expenses. This makes the good operation of sewage treatment plants, investment recovery, capital repayment and so on can not be guaranteed, and even if there is money to build, there is no money to support it. Adopting BOT investment mode is conducive to reducing project investment and improving the operation and management level of sewage treatment plants. At the same time, it can greatly reduce the economic pressure of local governments, speed up the pace of infrastructure construction and meet the needs of the whole society for public projects and infrastructure. The financial industry has also entered the water pollution control market. In the future, various funds, listed companies, investment companies and banks will accelerate their investment in this market, which will intensify the competition in this market, but it will undoubtedly promote the maturity and development of the water pollution control market. Therefore, the water pollution control market has the characteristics of equipment, specialization, capitalization and openness, and the research, design and production departments engaged in water pollution control should adapt to this industrialization form.