China is one of the countries with 2 1 water shortage in the world. The total amount of fresh water resources ranks sixth in the world, but the per capita fresh water quantity ranks only at 108. Water resources have become one of the most serious resource problems in China. Beijing is a city that is seriously short of water. The utilization of water resources is related to the sustainable development of the capital economy and society, and it is one of the important factors to maintain Beijing's status as the capital. With the rapid development of Beijing's economy in recent years, people are more and more aware of the seriousness of environmental problems. Poor water saving and uncontrolled sewage discharge make the available fresh water resources less and less. The water storage capacity of several major reservoirs responsible for supplying Beijing water is shrinking year by year, and the largest Miyun reservoir can only supply water for another six years according to its current reserves. Beijing has sounded the alarm of the water crisis. In order to alleviate the current situation of water shortage, on the one hand, we should strive to open up new water sources and emphasize water conservation, on the other hand, we should make a fuss about sewage reuse. Therefore, scientific and rational use of water resources has become one of the first problems to be solved. As early as 1987, the municipal government put forward the Measures for Trial Operation of Reclaimed Water Project, which put reclaimed water instead of fresh water on the agenda.
The so-called reclaimed water refers to the municipal sewage such as domestic sewage, industrial wastewater and rainwater collected by the sewage treatment plant, which is treated by the traditional activated sludge method to remove organic matter and heavy metal ions. To make the sewage quality meet the discharge standard of rivers and lakes, and then send the water to the advanced treatment plant for coagulation, sedimentation, filtration and disinfection or advanced treatment by membrane technology, so the water obtained is called reclaimed water. About 40% of the water used in urban life and production is in close contact with people's lives, such as bathing and drinking. These aspects require high water quality, which is irreplaceable by reclaimed water. Up to 60% of the water is used for industrial water, agricultural irrigation, sanitation water, land washing and greening water, and some of them have low water quality requirements. If water is used, it will not only fully meet the water quality standards, but also save a lot of fresh water, which has excellent development prospects. Nowadays, the resource utilization of reclaimed water has risen to the height of newly opened water sources.
The reclaimed water reuse project of Gaobeidian Sewage Treatment Plant is a project to realize the purpose of reclaimed water reuse and is one of the 50 key projects in the city in 2000. The project takes the water treated by Gaobeidian Sewage Treatment Plant as the water source, starting from Gaobeidian Sewage Treatment Plant in the east and reaching Xibianmen in the west. After the completion of the first phase project, the water supply is 300,000 m3/d, the second phase project is 470,000 m3/d, and the first phase project is 300,000 m3/d, of which 200,000 m3/d is transported to Gaobeidian Lake by pipeline as supplementary water for cooling circulating water in the first thermal power plant. Another 654.38+100000 m3/d is used for municipal miscellaneous water after advanced treatment in the sixth water source plant. Among them, 50,000 m3/d is supplied to four parks, such as longtan lake, Tiantan, Taoranting and Daguan Garden, and the sanitation and garden departments downstream, which are used for park greening and road scouring and dust reduction along the Second Ring Road. Another 50,000 m3/d is supplied to the Eastern Suburb Industrial Zone for industrial production. The total investment of the project is 336 million. At present, the whole project has been completed in May according to the original design requirements, and has been put into trial operation under the auspices of the Municipal Urban Management Committee since June this year. Every day, 200,000 tons of water is supplied to Gaobeidian Lake to ensure the supplementary use of cooling water in the First Thermal Power Plant, and at the same time, 20,000-30,000 tons of water is supplied to the Sixth Water Source Plant as required.
In order to make the reclaimed water industry go to the market as soon as possible, on the basis of summarizing the recent work, we think the following problems are worth our study.
I. Use of reclaimed water
About 40% of urban domestic and production water is in close contact with people's life, and the water quality requirements are strict. Up to 60% of the water is used for industrial water, agricultural irrigation, sanitary water and greening water. If this part is replaced by reclaimed water, it is completely allowed in the water quality standard, and a lot of fresh water resources are saved. At present, industrial cooling water is closely related to factory operation, and the water consumption is relatively stable. With the continuous development of urban infrastructure construction, the corresponding municipal miscellaneous water such as sanitation, greening and landscape also increases, which puts forward higher requirements for the convenience of water use and the diversification of water supply forms, and has great potential for water use. We believe that the use of reclaimed water should be promoted in the following aspects:
1, green water includes the following aspects:
1. Greening water consumption is calculated according to the greening water consumption provided by the garden and greening departments, and the water consumption per square meter is 0.002m3 per day. The actual investigation water consumption of each park is estimated according to the multi-year average value of water meter measurement in the park. In fact, the water consumption standard for park greening can't reach the standard of 0.002 m3/d.m2 per square meter per day stipulated by the garden department. In summer, the water consumption is higher than this value in one month at the peak of water consumption, and lower than this value in other times, especially in winter, so the average actual water consumption is only 0.00153m3/d.m2. Because lakes or groundwater are used for greening at present, the price is lower. However, it is difficult to reduce the price of reclaimed water to the level of lake water or groundwater. Therefore, it is suggested that the government should effectively limit the use of rivers, lakes and groundwater for greening, and set a suitable water price to make reclaimed water used for greening is economic, reasonable, feasible and necessary.
Second, rivers and lakes should be replenished. In order to maintain the good water quality of parks and lakes and the flood control and storage capacity of Beijing, the moat should replenish water to the parks several times a year. According to the master plan of Beijing from 2000 to 20 10, the river is changed 6-8 times a year, and the water change depth is 1 m each time.
Every year, fresh water from Miyun Reservoir is used to replenish water to Beijing moat, and the water consumption is huge. Through the comparative analysis between the measured water quality of rivers and lakes and the Environmental Quality Standard for Surface Water, it is found that the current water quality of rivers and lakes can only meet the V-class standard. To make the water quality of rivers and lakes reach Grade IV, it is necessary to increase the fluidity of water, keep the water fresh during frequent replacement, and avoid the occurrence of anaerobic conditions in the lake. At present, the reclaimed water pipeline has been laid to the lakeside of each park, which provides the possibility of continuous water replenishment, so that the water replenishment amount of 6-8 times a year is evenly distributed to a week or less, and the lake body is constantly updated. On the other hand, the water supply of rivers and lakes can only come from the high-quality water bodies of Miyun and Huairou reservoirs in the upper reaches, and it is a great waste of water resources to supplement ornamental water in large quantities. If reclaimed water is used instead of fresh water to supplement the water used in rivers and lakes, the water quality can completely meet the requirements, and a lot of fresh water is saved for the country, and the water consumption is not affected by seasons. The use of reclaimed water is influenced by users. If there is no industrial water and rivers and lakes to replenish water, users will be useless in winter. Therefore, in the planning stage of reclaimed water project, it is necessary to supplement a certain amount of rivers and lakes to ensure the utilization efficiency of reclaimed water within one year and avoid idle assets.
Thirdly, another purpose of flushing water in the park is to flush toilets, which can realize two-way water supply to toilets. Flushing toilets with reclaimed water can save a lot of clean water. In order to change the poor sanitary conditions of public toilets in Beijing, and to meet the needs of hosting the 2008 Olympic Games in Beijing, it is suggested to vigorously promote the transformation of the second-class toilets (manual cleaning twice a day), especially in several major parks frequented by foreign friends, so that the water consumption of park toilets will continue to increase. If reclaimed water is used, it can fully meet the requirements.
4. Road washing in the park In order to realize road washing in the park, it is necessary to strengthen equipment investment and equip each park with facilities such as waterwheels. The landscaping department should formulate a perfect road washing plan to realize road washing with reclaimed water once a day and improve the road landscape level in the park.
2. With the comprehensive management of urban environment and the function of reclaimed water, the high dust content in the air is an important reason for the serious air pollution in our city. At present, inhalable particulate matter has become the primary pollutant of air pollution in Beijing, and according to the prediction of experts from the National Meteorological Administration, China has entered the stage of frequent sandstorms. Effective measures should be taken to effectively reduce inhalable particles in the air, and strengthen artificial dust suppression while controlling sand sources. At present, the method of artificial dust suppression is that the sanitation department regularly sends water trucks to spray the road surface. Due to the limited amount of water on the water carriage, the spraying range can not achieve the ideal purpose of dust suppression. Therefore, it is advisable to learn from foreign methods, lay reclaimed water pipelines along urban main roads and equip them with corresponding sprinklers. On the premise of ensuring sufficient water consumption, the existing waterwheel spraying can be changed into reclaimed water to wash the road surface, so as to improve the dust suppression effect. You can choose a specific road section to carry out the pilot project, and use the combination of waterwheel and sprinkler to gradually realize the dust suppression with reclaimed water. Really realize Beijing's clear water and sky blue, and provide guarantee for the 2008 Green Olympics. After the completion of the first phase of reclaimed water project, it mainly supplies water for environmental sanitation and park greening in the Second Ring Road, and the scope of reclaimed water is relatively small. With the start of the second phase project and the continuous development of cities in the future, we should extend the use of reclaimed water to areas along the Third Ring Road and the Fourth Ring Road. The total length of the Fourth Ring Road is about 65km, and the area along the line 100m is the green belt around the Fourth Ring Road 100m. Chaoyang Garden Bureau and Haidian Branch are mainly responsible for its greening and sprinkler irrigation work, in which Chaoyang Garden Bureau is responsible for the East Fourth Ring Road, Siyuanqiao to xiaohongmen is 20.5km long, with a total greening area of 3.8 million m2 and greening water consumption of 3,900 m3/d. This project passes through the East Fourth Ring Road in front of the sixth water source plant. We suggest adding a water intake at the junction of the pipeline and the fourth ring road, and laying an additional reclaimed water pipeline along the fourth ring road from the sixth water source plant to the north. At the same time, it is necessary to develop the reclaimed water reuse project of Jiuxianqiao Sewage Treatment Plant and lead it to the Fourth Ring Road to supply water for the sanitation and greening departments. Together with this project, reclaimed water will be supplied to the north and south at the same time, fully meeting the water demand of the Fourth Ring Road, and the water can be used freely. The 100-meter greening project of the Fourth Ring Road is a green barrier for Beijing's future, and it is also a part of the Olympic bid. Its completion will provide a strong proof for Beijing's spirit of bidding for the "Green Olympics". If reclaimed water is used for greening, Beijing's environmental image will be greatly enhanced, and it should be carried out simultaneously with the greening project of the Fourth Ring Road.
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