1, urban sewage pollution and treatment of the status quo
Since 1985, China's total annual discharge of wastewater has been maintained at 35 to 40 billion m3 / a. In 1996, the country's 666 municipal cities, 532 cities have no sewage treatment plants, 134 cities built 309 sewage treatment plants, only 4.46 billion m3 of total urban sewage treatment, of which only 6.9% by the secondary biochemical treatment, 77.4% of the urban sewage treatment total of only 4.46 billion m3. 309 sewage treatment plants, the total amount of urban sewage treatment is only 4.46 billion m3, of which only 6.9% by the secondary biochemical treatment, 77.4% of the urban sewage is directly discharged into the water body without any treatment. 1997 wastewater discharges reached a maximum value of 41.6 billion m3, of which 22.7 billion tons of industrial wastewater discharges, municipal sewage discharges of 18.9 billion t. In 1999, the urban sewage pollution load for the first time exceeded the industrial wastewater pollution load, and the municipal sewage discharges of 18.9 billion tons. In 1999, the pollution load of municipal sewage exceeded the pollution load of industrial wastewater for the first time, and the focus of water pollution in China has been mainly from industrial point sources of control, and gradually transformed into the control of municipal wastewater pollution. According to the Ministry of Construction estimated wastewater discharge in 2000 for 48 billion m3.
2, urban wastewater discharge forecast
At present, the country has more than 640 municipal cities, more than 16,000 formed towns, with a population of about 270 million people. Since the 90's, China's gross national product continuously to 8 ~ 11% of the high rate of growth, it is expected that the first 20 years of the new century, China's economic growth will remain at 6 ~ 9% of the high and medium rate of steady development. Sewage volume increase taking into account the above factors by 5% of the rate of consideration. By 2010, an increase in the amount of sewage 30 billion m3.
The amount of sewage generated by the established towns, in accordance with the relevant departments of the Government of China's newly formulated small town development plan, the future focus of the development of new small towns along the road, along the rivers and rivers, the coast, along the border and other geographic location and transportation conditions, rich in resources, townships and townships have a certain basis for enterprise or rural wholesale and professional markets have taken shape of the townships; The goal of construction is to build new types of small towns with a reasonable layout, matching facilities, convenient transportation, a beautiful environment, economic prosperity, and distinctive features, with a population of about 30,000 people. By 2010, the population of cities and towns nationwide will have reached about 560 million, and the level of urbanization will have reached about 40 per cent; in 2010, the number of cities with municipalities will have reached about 1,200, and the number of towns and towns will have reached 25-30,000, and by 2010, the penetration rate of piped water in villages and towns nationwide will have reached 65 per cent, and the daily per capita water consumption in small towns will be 180 liters, and in villages will be 110 liters, according to which Calculation of annual wastewater in villages and towns may reach 27 billion tons.
3, sewage treatment rate and investment estimates
Taking into account the current sewage volume, sewage increment and sewage volume of the townships, the total amount of sewage discharged by 2010 is 105 billion m3/a. To sum up, taking into account the current sewage volume, sewage increment and sewage volume of the townships, the total amount of sewage discharged by the city in 2010 is 105 billion m3. According to the "Ninth Five-Year Plan", the total amount of sewage discharged by the city is 10 billion m3, which is the same as the total amount of sewage discharged by the townships. According to the requirements of the "Ninth Five-Year Plan and the Outline of the Visionary Goals for 2010", the urban sewage treatment rate should reach 50% by 2010, which requires an additional treatment scale of 50 billion m3/a (140 million m3/d day). Urban sewage sewage volume and investment according to the growth rate forecast in Table 1. 50% of the sewage treatment rate, according to the static investment (taking into account the supporting pipeline network) to deal with each cubic meter of sewage investment of 2,000 - 3,000 yuan, then the need for investment of 300 - 400 billion yuan. According to the degree of sewage treatment and sewage volume growth, for urban sewage treatment plant for the main technical equipment (especially the secondary treatment-related equipment) market share analysis in Table 2. in order to expand domestic demand, drive economic development, since 1998, the country has increased investment in infrastructure, urban infrastructure has become an important part of the current issuance of 100 billion of the national debt will be used for the construction of urban infrastructure, there will be 30 billion. Urban infrastructure construction. In the local water supply and drainage construction projects reported to the Ministry of Construction, water supply projects, 322 projects, 208 sewage projects, with a total investment of 110 billion yuan. 1999, the State issued an additional 65 billion of which a part of the national debt is mainly used for the 1998 projects under construction and some new projects. Such a huge investment and market share, which is the development of China's water industry is both an opportunity and a challenge.
In the above share of traditional industries such as mechanical processing (electromechanical products: such as pumps, fans, etc.) accounted for about 15-30% of the share of the construction industry accounted for 35-45% of the share. The sum of these two accounted for more than 60% of the total investment in the next 10 years there is an annual market share of about 20 billion. Engaged in the main body of the above industry for the country's large and medium-sized enterprises. Thus, it can be seen for the city sewage and urban water supply this large-scale infrastructure projects, national investment will lead to a large number of such as mechanical and electrical industry, machinery manufacturing and processing industry and construction industry and other traditional industries. This can lead to the development of related industries and the increase in total consumption, in favor of large and medium-sized enterprise reform and economic development, which is also consistent with the country's current policy of revitalizing large and medium-sized enterprises. In the water pollution control in the automatic control and instrumentation and technical services accounted for a small proportion of 8-15% or so, but the relative value of higher. This part of the market rated at about 4-6 billion yuan / year. In addition, the general operation and management costs of sewage treatment accounts for about 10% of the investment, the share of the operation service industry is about 4 billion / year.
Faced with such a huge market for environmental pollution treatment in China, foreign companies have begun to enter. At present many urban pollution treatment plants using foreign capital construction, such as 1996-1998 dozens of foreign loan projects to build large-scale urban sewage treatment plants, many of the key equipment and supporting products imported from abroad. As foreign water treatment products, mature technology, better quality, superior service, water treatment industry in China has posed a serious challenge.
Second, the development of urban sewage treatment technology
1, urban sewage treatment process
China's urban sewage treatment technology from the "Seventh Five-Year Plan" national scientific and technological research gradually. "Seventh Five-Year Plan" and "Eighth Five-Year Plan" research projects in the oxidation ponds, land treatment and composite ecosystems and other natural treatment technologies, more research, based on these results as the basis for design. A number of demonstration projects on oxidation ponds and land treatment of urban wastewater have been established. In terms of artificial treatment technology, the "Eighth Five-Year Plan" has carried out 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 results of the research have been applied to a large number of wastewater treatment plants; the disposal of sludge from municipal sewage plants has also been carried out. The issue of sludge disposal in urban sewage plants has been emphasized in the "Ninth Five-Year Plan" scientific and technological research, and supporting the development of complete sets of sludge treatment. During the "Ninth Five-Year Plan" process technology research focus on small and medium-sized towns and cities for simple and efficient sewage treatment of practical sets of technology to solve the problem of artificial treatment of high energy consumption, natural treatment occupies a large area.
After the "Seventh Five-Year Plan", "Eighth Five-Year Plan" and "Ninth Five-Year Plan" period of effort, China's urban wastewater treatment technology has made greater achievements, the research results are fruitful. In terms of the breadth of technology, the gap with the international community has been narrowed. At present, in terms of water pollution treatment technology, the process parameters of the following technologies are available. Traditional activated sludge method technology including traditional method, delayed method, adsorption regeneration method and various new activated sludge processes, such as: SBR, AB method and oxidation ditch technology, etc.; A-O method and A2-O technology; acidification (hydrolysis)-aerobic technology; various types of stabilization pond technology; land treatment technology and so on. This has been able to meet the requirements of most urban sewage effluent treatment.
Second, the development of urban sewage treatment technology
1, urban sewage treatment process
China's urban sewage treatment technology from the "Seventh Five-Year Plan" national scientific and technological research began to progressively carry out research. "Seventh Five-Year Plan" and "Eighth Five-Year Plan" research projects in the oxidation ponds, land treatment and composite ecosystems and other natural treatment technologies, more research, based on these results as the basis for design. A number of demonstration projects on oxidation ponds and land treatment of urban wastewater have been established. In terms of artificial treatment technology, the "Eighth Five-Year Plan" has carried out 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 results of the research have been applied to a large number of wastewater treatment plants; the disposal of sludge from municipal sewage plants has also been carried out. The issue of sludge disposal in urban sewage plants has been emphasized in the "Ninth Five-Year Plan" scientific and technological research, and supporting the development of complete sets of sludge treatment. During the "Ninth Five-Year Plan" process technology research focus on small and medium-sized towns and cities for simple and efficient sewage treatment of practical sets of technology to solve the problem of artificial treatment of high energy consumption, natural treatment occupies a large area.
After the "Seventh Five-Year Plan", "Eighth Five-Year Plan" and "Ninth Five-Year Plan" period of effort, China's urban wastewater treatment technology has made greater achievements, the research results are fruitful. In terms of the breadth of technology, the gap with the international community has been narrowed. At present, in terms of water pollution treatment technology, the process parameters of the following technologies are available. Traditional activated sludge method technology including traditional method, delayed method, adsorption regeneration method and various new activated sludge processes, such as: SBR, AB method and oxidation ditch technology, etc.; A-O method and A2-O technology; acidification (hydrolysis)-aerobic technology; various types of stabilization pond technology; land treatment technology and so on. This has been able to meet the requirements of most urban sewage effluent treatment.
2, urban wastewater treatment technology issues discussed
From the 1960s-70s, oxidation ditch and SBR process development has been rapid, in recent years to become China's urban wastewater treatment plant dominant process. And aeration biofilter and primary intensification process is a new international development in the late 1980s and early 1990s, with the potential for development of efficient municipal wastewater treatment process. The new process of municipal wastewater treatment --- hydrolysis - aerobic biological treatment process is our own intellectual property rights of the process. China has introduced a lot of new foreign processes and established quite a lot of projects in recent years, and these works are the valuable wealth of China in the field of urban wastewater, which should be summarized systematically. However, China's wastewater treatment technology research is dominated by single research, and favors process research, lack of sufficient systematic, complete, and lack of comprehensive comparative research and technology and economic evaluation system. This is also in recent years, the first popular AB process, then popular three ditch oxidation ditch, as well as other forms of oxidation ditch, and currently in the popular SBR process is the reason. Lack of comprehensive and integrated comparison ability, in a long period of time foreign new technologies and new products on the domestic market, domestic technology is always unable to occupy a place in the market.
On the other hand, at present, China's urban sewage treatment plants commonly used process for ordinary activated sludge, oxidation ditch method, SBR (intermittent activated sludge) method, AB method, etc., which is the United States, Germany and other developed countries and the technology and process is almost at the same level, and China's gross domestic product is much lower than that of the above countries. The above technology is abroad in the water pollution control, has been proved to be effective technology. But the above technology is not necessarily advanced technology, especially not always fully suitable for our national conditions.
For example: at present, most of the domestic oxidation ditch introduced from abroad, delayed aeration of the SBR process. Delayed aeration is a low load process, for China such a lack of resources, populous developing countries, whether it is suitable to promote this low load of activated sludge process is worthy of scrutiny of the issue. First of all, the low load aeration tank capacity and equipment is in the high load activated sludge process several times, so the corresponding investment to be several times higher; Secondly, the delayed aeration of sludge is the use of aerobic stabilization methods, its energy consumption than in the high load activated sludge to be higher than 40 to 50% or so; increase in energy consumption certainly brought about by an increase in the direct operating costs, while also increasing the indirect investment. According to the information reported that at present each kW of generating capacity desulfurization needs to invest 1000 U.S. dollars, then each million tons of sewage to increase the investment in desulfurization needs 700,000 yuan. If the investment in desulphurization is 10% of the investment in the power plant, the increase in investment in the power plant is $7 million, which is close to 50% of the investment in the sewage treatment unit. From the point of view of sustainable development, the use of delayed aeration of low load process, such as oxidation ditch process, etc. is not suitable for China's national conditions.
From the municipal sewage sludge treatment and disposal, in our country has just started with foreign advanced countries compared to a large gap. With a large number of sewage treatment plants in operation, sludge production will have a substantial increase. Sludge anaerobic digestion of high investment, sludge treatment costs account for about 20-45% of the investment and operating costs of sewage treatment plants. And sludge anaerobic digestion treatment technology is more complex. In our country there are only a dozen of sludge digestion pools, can be normal operation of the few, some pools are not running at all. This is also the reason that led to a large number of oxidation ditch with delayed aeration and other technologies in recent years in China. So one of the keys to the use of efficient (high load), low-consumption sewage treatment process is to solve the urban sewage plant sludge treatment technology, it can be said that the future progress of China's urban sewage process depends largely on the progress of sludge treatment and utilization technology. Can solve the sludge problem 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 point of view of the final disposal of sludge, the agricultural use of sludge is the most feasible and realistic disposal program in terms of the specific situation of our country. Combined with the final disposal of sludge to consider sludge composting and utilization, is suitable for China's national conditions of sludge treatment process another technically feasible, economically advantageous technology pathway.
Because of China's economic development level is still low, lack of funds, lack of investment and many other factors, resulting in a large number of developed countries, water treatment and environmental protection enterprises to take loans, a large-scale entry into China's water treatment and environmental protection market. 1988, China opened up the construction of urban infrastructure, water supply and drainage using foreign investment in the construction of projects **** about 200, with a total of 7.8 billion U.S. dollars. As a result of the use of foreign capital, especially the use of government loans from developed European countries (can only be used to buy equipment from the lending countries), although it promotes the construction of a number of modern sewage treatment plants, but increased investment in the project (the price of foreign equipment is generally 4-6 times the price of the domestic equipment) and the future of routine maintenance costs (the need for foreign exchange to update the accessories). Also seriously inhibit the development of domestic sewage treatment equipment manufacturing industry. Due to the lack of technology and capital investment so that the domestic sewage treatment equipment can not reach the international level. But overall China's electromechanical equipment manufacturing industry after appropriate reorganization, adjustment and transformation is able to manufacture the required sewage treatment equipment. At present, about 90% of China's urban sewage treatment from a variety of international loans, basically occupied by major international companies.
Third, China's urban sewage treatment development trend
Water pollution control technology involves all aspects of water treatment technology research and development, engineering design, engineering implementation, equipment processing and operations management. However, from the point of view of marketization and industrialization of water treatment technology, especially from the division of the investment structure, the water treatment technology industry can be divided into: 1) process technology; 2) engineering and equipment industrialization; 3) industrialization of facility operation and other three parts. China's next major task is to focus on the development of the above three aspects.
1, vigorously develop advanced water treatment process technology
For a country such as China's serious pollution, resource scarcity, and the primary stage of socialism, the standard of advanced water treatment process should be suitable for China's national conditions, high efficiency, low consumption and low-cost sewage treatment technology. Various types of high efficiency, low investment, can achieve a certain depth of treatment of urban sewage treatment technology, the economy is not developed enough and pollution in need of urgent treatment of our country, especially the vast majority of no sewage treatment facilities in more than 17,000 towns, in a period of time will be of great significance. Therefore, there is an urgent need for a batch of new sewage treatment technologies and techniques that can meet the discharge requirements, have good treatment effects, and have low capital and operation costs. Therefore, the State Environmental Protection Administration put forward the need to establish with China's current stage of national conditions, economic and practical advanced technology demonstration projects, demonstration projects should meet: 1) low investment in tons of water, tons of water cost should be controlled at 800 yuan; 2) low operating costs, tons of water running costs should be controlled at 0.3 yuan below; 3) the use of localized equipment in the project, and the use of general contracting and implementation of the operation of the mechanism. mechanism.
To achieve the above goals, we need to make more efforts in the application and demonstration of new processes, new materials and high technology. It is well known that efficient processes can significantly reduce the infrastructure investment in sewage treatment, such as the current domestic delayed aeration of oxidation ditch and SBR process is generally in the 0.05-0.07kgBOD/m3.d, with medium and high aeration pool load (0.3-0.5kgBOD/m3.d) difference of a few times or even up to ten times so that the aeration pool of the investment is also correspondingly increased by a few times or even up to ten times. From the point of view of the new process, the existing physical - biochemical process, hydrolysis - aerobic process, aerated biofilter and high and medium load aerobic process and anaerobic - aerobic treatment technology and other processes are promising new process, but need to be further improved. To increase the sewage treatment rate in the short term, in addition to the development of reasonable and feasible industrial technology and economic policy, increase the construction of urban sewage treatment plant investment, must rely on technological progress, as soon as possible to carry out some of the advanced sewage treatment process demonstration and promotion work.
Likewise, the utilization of new materials and new construction methods can reduce the project cost. For example, Germany abroad Biolack card (Biolack) technology, the use of high-density polyethylene for water treatment structures impermeable materials, reducing the cost of water treatment structures. In the sewage treatment structures can promote advanced foreign tank technology, such as assembled reactor. Treatment structures equipment, fast and low-consumption equipment type, complete sets of unit reactor equipment to provide urban wastewater treatment; improve the complete sets of water treatment equipment and equipment, the complete process technology, mature automatic control technology, as well as rigorous manufacturing technology combined into one, design and production of high-tech content of wastewater treatment equipment;
In addition, the use of high-tech, especially a high degree of Automatic control system, so that the integration of electrical control, instrumentation, computer integration, that is, monitoring, control, management integration is the inevitable requirements and development trend of the automation of the production process of environmental protection plant. Sewage treatment plant to improve the degree of self-control, to the operation and management mechanism to change, the reduction of infrastructure costs and operating costs to reduce a series of benefits, according to the trend of international development, and vigorously develop China's environmental protection and self-control technology and equipment is to improve China's environmental protection project management level and stable operation of the treatment facilities of the fundamental guarantee.
2, vigorously promote the industrialization of water treatment technology and equipment
The implementation of water pollution control is achieved through engineering facilities and technical equipment. The current water treatment works have the following characteristics: First, the project in the technical content of equipment and construction and the proportion of investment continues to increase, thus reflecting the trend of water treatment engineering technology equipment, industrialization and marketization. China needs to establish a sewage treatment equipment industrial base, the establishment of sewage treatment equipment industrial base, the implementation of water pollution control is realized through engineering facilities and technical equipment, China needs to establish a sewage treatment equipment industrial base; Secondly, the engineering market has been introduced by the traditional contracting method of the international common "Turnkey Secondly, the engineering market has been introduced from the traditional contracting method to the international common "Turnkey" operation mode. Participate in this kind of engineering and equipment general contracting "engineering company" in the international has been a cross-industry industry. Engineering company is generally a system design, engineering management, equipment integration, installation and commissioning and operation of the training of the comprehensive ability of large companies, China currently lacks such a comprehensive ability of large-scale specialized engineering companies.
The implementation of water pollution control is realized through engineering facilities and technical equipment. China needs to establish a sewage treatment equipment industry base. For different sizes and types of urban sewage treatment plants, industrialization and development goals are different.
1) Super-large urban sewage treatment plant construction
The volume of sewage ≥ 200,000m3 / d of this type of urban sewage treatment plant in the country's total **** no more than 100, but accounted for 30% to 50% of the total amount of sewage discharge. Although in the early 1990s and is currently under construction in the mega-projects have been part of the project, due to the importance of the project and funding sources are guaranteed, the focus of the recent construction is still the focus of this type of sewage treatment plant. According to domestic and foreign experience for large-scale urban sewage treatment plants using the process is mostly more mature traditional activated sludge process, so the development of related equipment focuses on large-scale sewage treatment plants, a single technology equipment (especially the secondary treatment-related equipment). These include:
① large-scale automatic grating decontamination equipment;
② a variety of complete sets of sand, sand washing equipment;
③ large-scale sedimentation tank scraping and suction equipment;
④ high-efficiency aeration equipment;
⑤ large-scale general sewage machinery and equipment, such as centrifugal fans, sewage pumps, etc.;
⑥ large-scale thickening, dewatering integrated equipment;
⑦ large-scale sewage treatment plant.
7 sludge digestion equipment;
8 biogas utilization equipment;
9 supporting automatic control systems and instrumentation, etc.;
⑩ sludge treatment and disposal equipment, such as composting, granulation devices and so on.
2) Construction of large and medium-sized urban sewage treatment plants
Since the city sewage plant sludge using anaerobic digestion treatment technology, anaerobic digestion of sludge investment accounted for 30% to 40% of the investment in sewage treatment plants, and anaerobic digestion of sludge is more complex treatment technology. This problem has not reached a good solution, China's sludge treatment and disposal and utilization of late start, whether it is scientific research and development, or engineering practice, are far behind the developed countries and domestic demand. Therefore, according to the characteristics of large and medium-sized urban sewage treatment plants, many cities have recently adopted low load oxidation ditch and SBR process using aerobic stabilization of sludge. For the development of medium-sized sewage treatment plant focuses on the basic mastery of the oxidation ditch method and SBR and other treatment processes to accelerate the promotion of technology, at the same time to accelerate the special equipment for these processes of localization, large-scale production, the formation of the overall capacity from the design, equipment manufacturing, project construction to the overall ability to operate and manage. The formation of the following equipment production capacity:
① oxidation ditch aeration equipment: such as rotary brush, turntable and table aeration machine;
② sludge thickening, dewatering integrated equipment;
③ SBR process decanter;
④ SBR special aeration equipment;
⑤ SBR automatic control equipment.
3) Construction of sewage treatment plants in small and medium-sized towns
For a large number of small and medium-sized towns in our country, small municipal sewage treatment plants with sewage volume of ≤50,000m3/d are the focus and difficulty of water pollution control in our country. As China is still in the primary stage of socialist development. Most of the small and medium-sized towns are in less developed rural areas, but the pollution caused by its is a large amount of surface, is the next stage of China's three lakes and three rivers management focus. According to this feature must develop small and medium-sized towns applicable to simple and efficient sewage treatment technology, focusing on solving the three high problems of urban sewage treatment plant, namely, high investment, high power consumption and high operating costs. Hydrolysis - aerobic biological treatment process, aeration biofilter, etc. as a representative of the low-consumption, high-efficiency process can meet this demand. Therefore, for small municipal wastewater treatment plants need to do the following:
① applicable simple, efficient municipal wastewater treatment plant sets;
② simple and efficient municipal wastewater treatment plant full automation;
③ sludge composting, granulation and fertilizer technology sets.3, vigorously encourage the industrialization of the operation of water treatment facilities according to the construction of wastewater treatment plant investment estimates, the future Urban sewage treatment plant operating costs increase year by year to 2010 can reach 4 billion yuan / a. Operation of sewage treatment facilities industrialization involves two levels of problems, one of which is the expansion of the scope of traditional technical services. Due to the sound environmental regulations and the strengthening of law enforcement efforts, for water treatment equipment operation of the standard rate and the completion rate of higher requirements, so the timeliness of the technical requirements continue to strengthen; at the same time, with the development of the socialist market economy, the introduction of BOT in the field of water treatment will gradually break the traditional concept of A, B, resulting in the role of A, B interchangeable, resulting in a similar property management-type demand for technical services. This puts forward a higher level of requirements for technical services. Therefore, a series of changes such as the expansion of the scope of technical services, the strengthening of the requirements and the updating of the form, resulting in the expansion of the connotation of the technical services market. Secondly, with the role of party A and party B interchangeable, the financing method has changed. The planned economy led to the current situation of the vast majority of sewage treatment plants is: by the government to invest huge sums of money or the use of foreign government loans to build, after the completion of most of the establishment of institutions, operating funds approved by the relevant government departments to allocate a considerable portion of the sewage treatment plant operating costs are seriously inadequate. This makes the good operation of the sewage treatment plant, investment recovery, capital repayment is not guaranteed, and even appeared even if the "money to build" but also "no money to raise" situation. The use of BOT investment is conducive to reducing project investment, improve the operation and management of sewage treatment plants, but also can greatly reduce the economic pressure on local governments, and accelerate the pace of infrastructure construction, to meet the needs of the whole society on the public **** engineering and infrastructure. The financial industry has also entered the water pollution control market, the future of a variety of funds, listed companies, investment companies and banks will accelerate the investment in this market, in will intensify the competition in this market, but at the same time will undoubtedly promote the maturity and development of the water pollution control market. Therefore, the water pollution control market has equipment, specialization, capitalization and openness characteristics, engaged in water pollution control research, design and production departments to adapt to this form of industrialization.