China is a water resource-poor countries, is one of the world's 13 water-poor countries, per capita water resources is 1/4 of the world average. at the same time, China's vast area, water resources in time and regional distribution is very unbalanced, the south is more than the north is less in most parts of the northern part of the country, especially in Harbin, the per capita water resources are even lower. Haihe River, Huaihe River, Liaohe River, the Yellow River Basin per capita water resources for China's average level of 1/5, the Haihe River Basin, including Beijing and Tianjin, per capita water resources for China's average level of 1/7.
With the accelerated pace of economic development and urbanization, the problem of water shortage in urban areas is particularly prominent. Currently a considerable part of the city's water shortage, urban water supply is expanding, the degree of water shortage is becoming increasingly serious. According to statistics, China's 669 cities, 400 cities perennial water supply is insufficient, of which 110 cities are seriously short of water, the daily water shortage, the annual water shortage, due to the lack of water each year affects the industrial output value of more than 200 billion yuan, Tianjin, Changchun, Dalian, Qingdao, Tangshan, and Yantai and other large and medium-sized cities have been subjected to water shortages of a serious threat. According to statistics, the international extreme water scarcity line is 500 per capita water resources per capita, while the current per capita water resources per capita in the urban area of Baoding, Hebei is only 64, a serious shortage of water, resulting in insufficient water supply in the city, the groundwater overexploitation, triggering a series of environmental and geological problems.
In 2000, there was a 100-year drought in the northern region, so that many reservoirs and rivers have never been cut off and dry, 318 county-level cities in 13 northern provinces were forced to limit the water supply, the water shortage of more than 20 million people. 2001 drought, China's drought area of k.
In the shortage of water resources at the same time, China's water resources waste and pollution phenomenon is very serious, and the shortage of water.
In the meantime of water shortage, the phenomenon of water waste and pollution in China is very serious, and for this situation of shortage and waste coexisting, the traditional thinking is that we should administratively raise the price of water to limit the amount of water people use, but the problem of waste is never solved by administrative price, because when considering the problem of waste, we cannot neglect to limit the loss of utility brought by people's behavior itself. A survey by the Ministry of Construction shows that people will consider water conservation only when water expenses account for 2.0% of household income; when it reaches 5%, it will have a greater impact on people's lives; and when it reaches 10%, people will consider water reuse. In order to alleviate the contradiction between the supply and demand of water resources, sewage reuse within a certain range of use, provides us with an economical and reliable new water source, and can save high-quality drinking water source.
With the deepening of reform and opening up, China has entered a new period of economic construction, although in recent years vigorously advocating water conservation, but the strong increase in water consumption around the world, exacerbating the severity of water resources problems. The impact of water scarcity on the development of national economy has aroused the attention of leaders and experts. It is predicted that the century water crisis will rank first among all kinds of resource crises in the world. Therefore, it is imperative to study the utilization of urban water resources and water resources development, which is of far-reaching strategic significance to the healthy cycle of urban water use and guarantee the sustainable development of the city. Therefore, it is very important to realize sewage resource utilization, alleviate the contradiction between supply and demand of non-resources, and promote the sustainable development of national economy. Although China started to reuse sewage as early as the 1950s by using sewage irrigation. But the real depth of sewage treatment for urban life and industrial production is the development of recent decades, the Ministry of Construction in the "Sixth Five-Year Plan" special science and technology program was first included in the urban sewage reuse topics in Dalian, Qingdao, respectively, two places for experimental exploration. The results of these two places show that the sewage can be reused again through a simple depth treatment, is a very promising source of water.
From 1986 onwards, urban wastewater reuse has been included in the national "Seventh Five-Year Plan", "Eighth Five-Year Plan", "Ninth Five-Year Plan" key scientific and technological research program, began to wastewater reuse The exploration of sewage reuse technology and demonstration projects. The "Seventh Five-Year Plan" project, "Water Pollution Prevention and Control and Urban Sewage Resource Utilization Technology", conducted systematic research on sewage reclamation process, reuse technology for different reuse targets, and technical and economic policies for reuse. One of the studies include Qingdao Yan'an three-way sewage plant and other 14 sewage to different degrees or different objects to carry out sewage reuse projects, for the "Eighth Five-Year Plan" during the sewage reuse project research provides a large number of feasible relying on the project. "Eighth Five-Year Plan" research project "sewage purification and resource technology", respectively, Dalian, Taiyuan, Tianjin, Tai'an, Yanshan Petrochemical as a relying project, to carry out engineering experiments. Through a series of productive and practical engineering research, the "Eighth Five-Year Plan" has provided technical specifications and relevant water quality standards for the reuse of municipal wastewater for different purposes, such as industrial processes, cooling, chemicals, petrochemicals, iron and steel industry and municipal landscaping, etc. The "Eighth Five-Year Plan" has also provided technical specifications for the reuse of municipal wastewater for different purposes. The results of the "Eighth Five-Year Plan" have been improved to a practical level compared with the "Seventh Five-Year Plan", and the research content has been tested by the production disappointment, covering most of the fields of wastewater reuse. "Ninth Five-Year Plan" research project "urban wastewater treatment technology integration and decision support system construction", specific research on two parts: one is the integration of reuse technology research, the second is the urban wastewater underground recharge depth treatment technology research. These research studies, completed a large number of productive tests, has obtained a wealth of data, by the national expert-level identification and acceptance, many of the results were rated as international advanced or international leading level.
In the "21st Century International Urban Wastewater Treatment and Resource Development Strategy Seminar", the Ministry of Construction pointed out at the meeting that "China will start a comprehensive wastewater resource project, and in this field to strengthen the technical cooperation with foreign countries in a wide range of technical exchanges, and welcome financial institutions and enterprises in various countries to invest in China's municipal wastewater resources. Welcome financial institutions and enterprises from all over the world to invest in China's municipal wastewater recycling projects", indicating that China's investment in and demand for recycled water utilization in cities will heat up rapidly in the next few years. In order to alleviate China's water shortages and combat pollution of the water environment, China's recent construction of centralized wastewater treatment and reuse planning as shown in Table 1.
(1) sewage treatment and reuse as industrial water
The secondary treatment effluent from sewage treatment plants, depending on the use, can be directly or then further treatment to achieve higher water quality applied to the industrial process, which has the most common and representative of the use of industrial cooling water, China's secondary effluent in the sewage treatment plant or advanced secondary treatment effluent used as an industrial cooling, conducted a large number of experimental studies, and have run successfully. China has conducted a large number of experimental studies on the use of secondary effluent from sewage treatment plants or advanced secondary treatment effluent as industrial cooling, and there are examples of successful operation. The secondary treated effluent of Beijing Gaobeidian Wastewater Treatment Plant (BGWTP) provides cooling water to Huaneng Thermal Plant with a supply of 40,000 tons per day. At the same time, the sewage treatment plant also provides water for industrial enterprises such as Sanhe Thermal Power Plant.
Recycled water has now become Beijing's second largest water source. Statistics show that Beijing used 360 million cubic meters of reclaimed water in 2006 and is expected to reach 480 million cubic meters this year. Recycled water has been widely used in industrial manufacturing, agricultural irrigation, urban greening, river and lake environment and other fields. Of the 480 million cubic meters of recycled water used this year, 60 million cubic meters are used to supplement the use of water for urban landscaping and urban greening. Chaoyang Park, Grand View Garden, Tao Ran Pavilion, Wanquan River, South Moat, and the Olympic Center Area are all watered with recycled water. At the same time, 20 automatic water refilling machines have been built in the urban area of Beijing, which can provide 20 million cubic meters of renewable water for greening and municipal management every year.
(2) sewage treatment and reuse as miscellaneous domestic water
Treatment of sewage reuse of miscellaneous domestic water, Beijing is the most representative. 1984 Beijing sewage demonstration project construction, and in 1987, introduced the "Beijing municipal water construction and management of the implementation of the measures", in the management of the regulations, where the In the management regulations, all hotels, restaurants and apartments with a building area of more than one, as well as institutions and scientific research units with a building area of more than one and newly-built living quarters are required to set up water treatment facilities. To take this as an opportunity, the construction of water facilities in Beijing has been rapid development, so far, Beijing has been built and put into use more than 160 water facilities, most of these facilities are concentrated in hotels, restaurants and colleges and universities, they are bathing, washing and other daily miscellaneous water as a source of water, after treatment to the water quality standards, can be reused for flushing toilets, car washing, landscaping and so on. At present, the treatment capacity of these water facilities has reached 40,000, and the amount of water reuse is about. The construction of water has begun to take shape. In order to realize Beijing's 2008 "Green Olympics" commitment to urban wastewater reuse rate of 50%, Beijing will build nine new water plants to increase the reuse of sewage, promote the use of urban water.
Beijing has already built nine large-scale sewage treatment plants and related pipeline networks, and before the 2008 Olympic Games, five more similar sewage treatment plants will be put into operation. Meanwhile, sewage treatment in the suburbs has also been fully launched. The 14 small and medium-sized sewage treatment plants constructed in the new city handle nearly 170 million cubic meters of sewage annually.
(3) Reuse of Treated Sewage for Agricultural Irrigation
In the cities of northern China, municipal sewage and industrial wastewater have become one of the main sources of irrigation water for farmland (including vegetable, rice and wheat fields, etc.) in certain suburban areas. Some economic benefits have been achieved, which can improve soil structure, increase moisture and fertilizer, resulting in increased crop yields, on average, for every cubic meter of domestic wastewater, the yield of wheat or rice can be increased by about 0.5 kg. However, the sewage irrigation has also embodied a number of shortcomings, and some of the farmland, as a result of the deterioration of the farmland and the reduction of agricultural yields due to the use of toxic and hazardous industrial wastewater for irrigation, and the pollution of the groundwater, soil and agricultural products. The area of reclaimed water used for crop irrigation has been increasing year by year, with 300,000 mu of reclaimed water irrigation area formed in Daxing, Tongzhou and other areas. This year, the city's agricultural use of reclaimed water amounted to 230 million cubic meters. at the end of 2006, with the opening of the drainage gate of the Xiaohongmen Sewage Treatment Plant, clear reclaimed water gushed into the Liangfeng Irrigation Drainage Canal, and 200,000 acres of farmland in eight towns of Daxing District, such as Qingyundian, Changziying, and Caiyu, were irrigated with reclaimed water. Reclaimed water instead of clear water for farm irrigation, can reduce the exploitation of groundwater 60 million cubic meters per year. Beijing is a city with serious water shortage, and the per capita water resources possession is only 100 cubic meters, which is far lower than the internationally recognized water shortage warning line of 1,000 cubic meters. In recent years, the city adheres to the principle of "measuring water, supplying water to meet needs, adapting to the needs of water, and conserving water", and promotes the implementation of the most stringent water resource management system, and annually determines the total amount of water consumption, water use efficiency, and water functional areas to limit the pollution of the three red lines, so as to ensure the sustainable use of the capital's water resources.
Currently, recycled water has become the city's second largest water source, widely used in industrial water, agricultural irrigation, urban greening, community toilet flushing. In the past five years, a number of sewage treatment plants and reclaimed water plants have been built in Lugouqiao, Wujiacun, Shahe, etc., and the construction of reclaimed water pipeline network has been vigorously promoted, so the level of sewage resource utilization has been greatly improved. The daily sewage treatment capacity of the city's townships and above has increased from 3.29 million cubic meters in 2008 to 3.95 million cubic meters, and the sewage treatment rate has increased from 79% to 83%; the amount of reclaimed water has increased from 600 million cubic meters to 750 million cubic meters, and the utilization rate of reclaimed water has reached 61%. The sewage treatment rate and the utilization rate of reclaimed water are both at the leading level in the country.
This year, the city will further increase the amount of reclaimed water, plans to build Dongba, Fa Tou, Wulituo, Tongzhou Hedong, Fengtai Hexi, Changping Future Science and Technology City and other reclaimed water plant, the new reclaimed water pipeline 50 kilometers, complete the upgrading of Jiuxianqiao, Huangcun and other wastewater treatment plants, the city's wastewater treatment rate to 84%, the reclaimed water consumption of 800 million cubic meters, 0.5 billion cubic meters more than in 2012. billion cubic meters.
Currently, the city leads the nation in water conservation. In the past five years, the city has completed water-saving irrigation projects for 500,000 mu of farmland, orchards and vegetable fields, 185,000 mu of farmland are irrigated with reclaimed water, 1,830 water-saving units and districts have been created, and all the nine heat and power plants in urban areas are using reclaimed water to replace the new water source, and the industry's annual use of reclaimed water has reached 140 million m3. 2012, the city's total water consumption amounted to 3.65 billion cubic meters, of which 750 million m3 was reclaimed water. The water consumption of 10,000 yuan GDP dropped to 21 cubic meters, and the city's sewage treatment rate reached 83%.