Reclaimed water refers to the water that can be used profitably after the sewage is properly treated, reaches a certain water quality index and meets certain use requirements. Compared with seawater desalination and inter-basin water transfer, reclaimed water has obvious advantages. From the economic point of view, the cost of reclaimed water is the lowest. From the environmental point of view, the recycling of sewage is helpful to improve the ecological environment and realize a virtuous cycle of water ecology.
Edit the introduction of this paragraph.
Reclaimed water is also the standard water treated by sewage treatment plants, which is generally secondary treatment and is not affected by climate. Reclaimed water is not used near Beijing.
It has the advantages of competing for water nearby, taking it locally, being stable and reliable, and having high guarantee rate. Reclaimed water, the so-called reclaimed water, follows the name of Japan. Usually people call tap water "water supply" and sewage "sewer", and the water quality of reclaimed water is between water supply and sewer, so it is called reclaimed water. Although reclaimed water is not drinkable, it can be used in some occasions with low water quality requirements, such as flushing toilets, washing cars, spraying roads and greening. Reclaimed water engineering technology can be considered as a miscellaneous water technology between domestic water supply system and building drainage system. The water quality index of reclaimed water is lower than that of drinking water in urban water supply, but higher than the discharge standard of polluted water allowed to be discharged into surface water. Reclaimed water is the second water source of the city. Recycling of urban sewage is one of the effective ways to improve the comprehensive utilization rate of water resources and reduce water pollution. Rational reuse of reclaimed water can not only reduce water pollution, but also alleviate the contradiction of water shortage, which is an important measure to implement sustainable development. The recycling of sewage has considerable social, environmental and economic benefits and has become the only way to solve water problems in all countries of the world.
The feasibility of editing this paragraph.
Advantages of sewage reuse
Reclaimed water, also known as reclaimed water, is between sewage and tap water. It is non-drinking water that can be used in a certain range after the purification of urban sewage and wastewater, and can be used in many aspects of urban landscape and people's life. In order to solve the problem of water shortage, the reuse of urban sewage has become more and more important, which has advantages compared with the development of other water sources. First of all, the amount of urban sewage is huge and stable, not limited by natural conditions such as climatic conditions, and can be recycled. Sewage as reclaimed water
Source and sewage can occur at the same time, that is, as long as urban sewage is produced, there will be reliable renewable water sources. At the same time, the sewage treatment plant is a reclaimed water source, which is close to urban reclaimed water users and convenient for water supply. The scale of sewage reuse is flexible, and large reclaimed water plants can be built on the edge of cities, and small reclaimed water plants or integrated treatment equipment can also be built in various residential quarters and public buildings. The scale can be large or small, according to local conditions.
technical feasibility
Technically, there is no technical problem in the utilization of urban reclaimed water, and the current water treatment technology can treat sewage to the water quality standard that people need. The impurity content of urban sewage is less than 0. 1%, and the conventional advanced treatment of sewage is adopted, such as filter media filtration, microfiltration, nanofiltration, reverse osmosis and other technologies. After pretreatment, the effluent of the filter material filtration treatment system can meet the requirements of domestic miscellaneous water, including domestic toilet flushing, green space watering, road flushing and general industrial cooling water. The effluent of microfiltration membrane treatment system can meet the requirements of landscape water use. The effluent quality of reverse osmosis treatment system is far better than the tap water quality standard. A large number of successful examples of sewage reuse projects at home and abroad also show that it is technically feasible to reuse sewage for industry, agriculture, municipal and miscellaneous uses, river replenishment, domestic and miscellaneous uses, and groundwater recharge. In order to cooperate with the urban sewage recycling in China, the Ministry of Construction and the National Standardization Administration Committee have compiled a series of sewage recycling standards, such as the Code for Acceptance of Urban Sewage Treatment Plant Engineering Quality, the Code for Design of Sewage Recycling Engineering, the Code for Design of Reclaimed Water under Construction, and the Quality of Urban Sewage, which provide technical data for effectively utilizing urban sewage resources and ensuring the quality and safety of sewage treatment.
economic viability
Compared with other water resources, the economic advantage of urban sewage is that (1) is cheaper than long-distance water transfer. The recycling of urban sewage means that after secondary treatment, it is further treated in a suitable place and reused as a renewable resource. Infrastructure investment is far more economical than long-distance water transfer. The data show that after advanced treatment, urban sewage can be used as reclaimed water for miscellaneous water.
Degree, infrastructure investment is equivalent to water diversion from 30 kilometers away. If it is treated and reused as high-demand process water, its investment is equivalent to drawing water from 40 to 60 kilometers away. The middle route project of South-to-North Water Transfer Project has an annual water regulation capacity of over 654.38+000 billion cubic meters, the main project investment of over 654.38+000 billion yuan, and the basic unit investment of about 3500-4000 yuan/t. Therefore, many countries regard the utilization of urban reclaimed water as one of the options to solve the water shortage problem and one of the ways to save water, which is very valuable from the economic point of view. In the United States, there are 300 reclaimed water projects, including China International Trade Center and Lugang Sewage Treatment Plant in Baoding. Practice has proved that the popularization and application of sewage treatment technology is imperative, and it is also an inevitable development trend to use reclaimed water as the second water source in the city. (2) Compared with seawater desalination, the impurities in economical urban sewage are less than 0.65438 0%, which can be removed by advanced treatment. However, seawater contains 3.5% dissolved salt and a lot of organic matter, and its impurity content is more than 35 times that of secondary treatment sewage, which requires complex pretreatment, reverse osmosis or flash evaporation and other expensive treatment technologies. Therefore, whether it is capital cost or unit cost, seawater desalination is higher than the utilization rate of reclaimed water. The cost of seawater desalination in the world is mostly between $1 ton 1. 1-2.5, which is equivalent to its consumption water price. The cost of seawater desalination in China has dropped to about 5 yuan, and it is more likely to drop to about 3.7 yuan if large-scale facilities are built. Even so, the price is much higher than the reclaimed water recovery price of less than one yuan. The prospect of breakthrough in urban reclaimed water treatment technology is still very broad. With the progress of technology and the continuous innovation of equipment and materials, the safety and reliability of reclaimed water supply will be continuously improved and the treatment cost will be reduced day by day. (3) It can achieve remarkable social benefits. In today's increasingly scarce water resources, the treated water can be reused for greening, car washing and toilet flushing, which reduces the discharge of pollutants, thus reducing the impact on the water environment around the city and increasing the available reclaimed water. This change is conducive to protecting the environment and strengthening the self-purification of water bodies, and will not adversely affect the hydrological environment of the whole region. Its application prospect is broad. Sewage reuse provides a very economical new water source for people, reduces the social demand for fresh water resources, and maintains a high-quality drinking water source. This optimal allocation of water resources is undoubtedly a measure to benefit the country and the people and realize the sustainable development of water resources. When countries around the world solve the problem of water shortage today. Urban sewage has been selected as a reliable and reusable second water source, and the reuse of urban sewage has been a research hotspot at home and abroad for many years. Solving the shortage of water resources has become a strategic countermeasure for many countries in the world.
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Reclaimed water is a very valuable water resource, with large water quantity and stable water quality, which is less affected by seasons and climate. There are many ways to use reclaimed water, which can be divided into direct use and indirect use according to the relationship with users, and direct use can be divided into local use and centralized use. Reclaimed water in most countries is mainly used for farmland irrigation, mainly indirect irrigation; Reclaimed water in a few countries such as Japan is mainly used for urban non-drinking water, mainly for local use; Environmental water use has become a new trend of urban environmental "water landscape". Reclaimed water has many uses, which can be used for farmland irrigation and landscaping (parks, campuses, highway green belts, golf courses, cemeteries, green spaces, residential areas, etc.). ), industry (cooling water, boiler water process water), large-scale building washing, entertainment and environment (improving lakes, ponds and marshes, increasing river flow and raising fish, etc. ), as well as fire fighting, air conditioning, flushing toilets and other municipal miscellaneous uses. According to the use of reclaimed water, reclaimed water can be reused for groundwater recharge, industrial water, water for agriculture, forestry and animal husbandry, urban non-drinking water and landscape environment water. Reclaimed water can be used for groundwater recharge, groundwater recharge, seawater intrusion prevention and land subsidence prevention. Reclaimed water can be reused as cooling water, washing water and boiler water in industry. regenerated water
Water for agriculture, forestry and animal husbandry can be used for irrigation, planting and seedling raising of food crops and cash crops, irrigation, planting and seedling raising of trees and ornamental plants, and livestock and poultry breeding.
In this section, edit the usage of reclaimed water in China.
condition
After entering the 2 1 century, under the background that water resources in China are increasingly scarce, the utilization of reclaimed water has begun to be paid attention by the China municipal government. By 2009, China's sewage reuse rate (sewage reuse rate/sewage treatment rate) is about 15%, while the ratio of sewage reuse rate/sewage discharge is only about 5%.
Necessity
China is a water-poor country, belonging to one of 13 water-poor countries in the world. The per capita water resource is 65438+ 0/4 of the world average. At the same time, China has a vast territory, and the distribution of water resources is uneven in time and region, with more in the south and less in the north, and the per capita water resources in most parts of the north, especially Harbin, are even lower. The per capita water resources in Haihe River, Huaihe River, Liaohe River and Yellow River basins are about 1/5 of the national average, while the per capita water resources in Haihe River basin including Beijing and Tianjin are only 1/7 of the national average. With the acceleration of economic development and urbanization, the problem of urban water shortage is particularly prominent. At present, quite a few cities have reclaimed water.
Water resources are in short supply, the scope of urban water supply is expanding, and the degree of water shortage is becoming more and more serious. According to statistics, among the 669 cities in China, 400 cities are short of water for a long time. Among them, 1 10 cities are seriously short of water, with daily water shortage and annual water shortage. Due to water shortage, the annual industrial output value is more than 200 billion yuan, and large and medium-sized cities such as Tianjin, Changchun, Dalian, Qingdao, Tangshan and Yantai have been threatened by serious water shortage. According to statistics, the international extreme water shortage line is 500 per capita water resources, while the current per capita water resources in Baoding City, Hebei Province is only 64. Serious water shortage leads to insufficient urban water supply and over-exploitation of groundwater, which leads to a series of environmental geological problems. In 2000, the worst drought in 100 years occurred in northern China, which caused many reservoirs and rivers to be cut off and dried up. North of China 13 provinces18 cities above the county level were forced to supply water within a limited time, and the water shortage population reached more than 20 million. 200 1 drought, the drought-affected area in China reached K. At the same time of water shortage, water resources waste and pollution in China are very serious. In view of the coexistence of shortage and waste, the traditional thought is that people's water consumption should be limited by raising water price by administrative means, but the waste problem has never been solved by administrative price, because when considering the waste problem, the utility loss caused by restricting people's behavior itself cannot be ignored. According to a survey conducted by the Ministry of Construction, people will only consider saving water when water charges account for 2.0% of household income. When it reaches 5%, it will have a great impact on people's lives; When it reaches 10%, people will consider water reuse. In order to alleviate the contradiction between supply and demand of water resources, sewage reuse in a certain range of use provides us with an economical and reliable new water source, which can save high-quality drinking water sources. With the deepening of reform and opening up, China has entered a new era of economic construction. Although water conservation has been strongly advocated in recent years, the water consumption in various places has increased strongly, which has aggravated the seriousness of water resources problems. The influence of water shortage on national economic development has attracted the attention of leaders and experts. It is predicted that the water crisis in 2 1 century will rank first among all kinds of resource crises in the world. Therefore, it is imperative to study the utilization and development of urban water resources, which has far-reaching strategic significance for the healthy circulation of urban water and the guarantee of urban sustainable development. Therefore, it is of great significance to realize the recycling of sewage, alleviate the contradiction between supply and demand of non-resources and promote the sustainable development of national economy.
service condition
Although our country began to reuse sewage through sewage irrigation as early as 1950s. However, it is not until recent decades that wastewater can be reused for urban life and industrial production after advanced treatment. For the first time, the Ministry of Construction included the topic of urban sewage reuse in the "Sixth Five-Year Plan" and conducted pilot exploration in Dalian and Qingdao respectively. The research results of these two places show that sewage can be reused after simple advanced treatment, and it is a promising water source. Since 1986, urban sewage reuse has been included in the national key scientific and technological projects in the seventh, eighth and ninth five-year plans, and the exploration of sewage reuse technology and the experiment of demonstration projects have begun. The key project of the Seventh Five-Year Plan, "Water Pollution Prevention and Urban Sewage Recycling Technology", systematically studied the sewage recycling technology, the recycling technology of different recycling objects, and the technical and economic policies of recycling. Among them, the study includes 14 sewage reuse projects with different degrees or different objects, such as Qingdao Yan 'an No.3 Road Sewage Treatment Plant, which provides a large number of feasible supporting projects for tackling key problems of sewage reuse projects during the Eighth Five-Year Plan period. The key project of the Eighth Five-Year Plan "Sewage Purification and Resource Utilization Technology" used a lot of reclaimed water respectively.
Based on the petrochemical projects in Lian, Taiyuan, Tianjin, Tai 'an and Yanshan, engineering tests were carried out. Through a series of productive and practical engineering studies, the Eighth Five-Year Plan provides technical specifications and relevant water quality standards for the reuse of urban sewage for different purposes such as industrial technology, cooling, chemical industry, petrochemical industry, steel industry and urban landscape. Compared with the Seventh Five-Year Plan, the achievements provided by the Eighth Five-Year Plan have been improved to a practical level, and the research content has passed the production test, covering most fields of sewage reuse. The key project of the Ninth Five-Year Plan "Urban Sewage Treatment Technology Integration and Decision Support System Construction" includes two parts: one is the research on the integration of reuse technology, and the other is the research on the advanced treatment technology of urban sewage underground recharge. These key research projects have completed a large number of productive experiments and obtained rich data. After the appraisal and acceptance by national experts, many achievements have been rated as international advanced or international leading level. The Ministry of Construction pointed out at the "International Symposium on Urban Sewage Treatment and Resource Development Strategy in the 265438+20th Century" that "China will comprehensively launch sewage recycling projects, and extensively strengthen technical cooperation and exchanges with foreign countries in this field, and welcome financial institutions and enterprises from all over the world to invest in urban sewage recycling projects in China", which indicates that the investment and demand for reclaimed water utilization in China will increase rapidly in the next few years.
plan
In order to alleviate the shortage of water resources in China and control the pollution of water environment, the recently built centralized sewage treatment and reuse scheme in China is shown in table 1. (1) After sewage treatment, it can be reused as the secondary effluent of industrial wastewater treatment plant. According to different uses, it can be used in industrial processes directly or after further treatment to achieve higher water quality. The most common and representative use is industrial cooling water. In China, a large number of experimental studies have been carried out on the secondary effluent or advanced secondary effluent from sewage treatment plants as industrial cooling, and there are examples of successful operation. The secondary treated effluent from Beijing Gaobeidian Sewage Treatment Plant provides Huaneng Thermal Power Plant with 40,000 tons of water supply every day. At the same time, the sewage treatment plant also provides water for industrial enterprises such as Sanhe Thermal Power Plant. Reclaimed water has become the second largest water source in Beijing. Statistics show that in 2006, Beijing used 360 million cubic meters of reclaimed water, which is expected to reach 480 million cubic meters this year. Reclaimed 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 reclaimed water used this year, 60 million cubic meters are used to supplement urban landscape and urban greening water. Chaoyang Park, Grand View Garden, Taoranting, Wanquan River, South Moat and Olympic Center are all irrigated by reclaimed water. At the same time, 20 automatic reclaimed water adding machines have been built in Beijing urban area, which can provide 20 million cubic meters of reclaimed water for greening and municipal management every year. (2) After being treated, sewage can be reused as domestic miscellaneous water, and Beijing is the most representative. 1984 Beijing carries out sewage demonstration project construction, 1987 "Beijing Reclaimed Water Building Management Implementation Measures" was issued. In this management regulation, all hotels, restaurants and apartments with a building area of above, government scientific research units with a building area of above and newly-built living quarters should establish reclaimed water facilities. Based on this, the construction of reclaimed water facilities in Beijing has developed rapidly. Up to now, more than 160 reclaimed water facilities have been built and put into use in Beijing. Most of these facilities are concentrated in hotels, restaurants and universities. They use daily miscellaneous water such as bathing and washing as water source, and after treatment, it can be reused for flushing toilets, washing cars and greening. At present, the treatment capacity of these reclaimed water facilities has reached 40 thousand, and the repeated water consumption is about. The construction of reclaimed water has begun to take shape. In order to realize Beijing's promise of "Green Olympics" in 2008 and make the reuse rate of urban sewage reach 50%, Beijing will build nine new water plants to increase the reuse of sewage and promote the use of urban reclaimed water. Nine large sewage treatment plants and related supporting pipe networks have been built in Beijing, and five similar sewage treatment plants will be put into operation before the 2008 Olympic Games. At the same time, sewage treatment in the suburbs has also been fully launched. The 14 small and medium-sized sewage treatment plant built in Xincheng has an annual sewage treatment capacity of nearly10.70 billion cubic meters. (3) Sewage is reused for agricultural irrigation. In the northern cities of China, urban sewage and industrial wastewater have become one of the main sources of irrigation water for some suburban farmland (including vegetable fields, rice fields and wheat fields). It has achieved certain economic benefits, which can improve the soil structure, increase the content of water and fertilizer, and lead to an increase in crop yield. The average domestic sewage per cubic meter can increase the yield of wheat or rice by about 0.5 kg, but sewage irrigation also shows some shortcomings. Due to the use of toxic and harmful industrial wastewater for irrigation, some farmland is degraded, agricultural production is reduced, and groundwater, soil and agricultural products are polluted. The area of reclaimed water used for crop irrigation has increased year by year, and 300,000 mu of reclaimed water irrigation areas have been formed in Daxing, Tongzhou and other areas. This year, the agricultural utilization of reclaimed water in this city reached 230 million cubic meters. At the end of 2006, with the opening of the drainage gate of xiaohongmen Sewage Treatment Plant, clear reclaimed water poured into the cool air irrigation canal, and the reclaimed water was used to irrigate 200,000 mu of farmland in eight towns, including Qingyundian, Zhangziying and Cai Yu in Daxing District. Reclaimed water can replace clean water for farmland irrigation, which can reduce the exploitation of groundwater by 60 million cubic meters every year.
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Effective ways to alleviate the shortage of water resources
According to relevant statistics, 80% of urban water supply is converted into sewage, and 70% of reclaimed water can be recycled after collection and treatment. This means that through sewage reuse, the available water in the city can at least be reclaimed water without changing the existing water supply.
Increase by more than 50%. Countries all over the world attach great importance to the utilization of reclaimed water. As a legal alternative water source, reclaimed water is being widely used and has become an important part of urban water resources.
An important link to realize the sustainable utilization of water resources
Water is the basic resource and strategic economic resource for urban development. With the process of urbanization and economic development, as well as the increasingly serious environmental pollution, water resources are increasingly tense, which has become a bottleneck restricting urban development. Promoting the advanced treatment of sewage and promoting the utilization of reclaimed water are important measures to coordinate the development of man and nature, create a good water environment and promote the development of circular cities. Great changes have taken place in the international management objectives of water resources, that is, from water control, development and utilization to "recycling water" and "restoration and restoration of water ecology" with water quality regeneration as the core, so as to fundamentally realize a virtuous cycle of water ecology and ensure the sustainable utilization of water resources.
Can bring considerable benefits.
The rational utilization of reclaimed water not only has good economic benefits, but also has great social and ecological benefits. First of all, with the increase of urban tap water price, the operation cost of reclaimed water is further reduced, and the economic benefits will become more and more prominent with the increase of reclaimed water consumption; Secondly, the rational utilization of reclaimed water can maintain ecological balance, effectively protect water resources, change the traditional mining mode of "exploitation-utilization-discharge", realize a virtuous cycle of water resources, play a positive role in alleviating the shortage of urban water resources and have long-term social benefits; Thirdly, rational use of the ecological benefits of reclaimed water can not only eliminate the adverse effects of wastewater on the urban environment, but also further purify and beautify the environment.