Study on reuse scheme of Gaobeidian sewage treatment plant.

Beijing is located at the northern end of North China Plain, in the north of China, where water resources are very poor. It is a city with serious water shortage. The per capita water resources in Beijing are only about 300m3, which is 1/8 of the national water resources and 1/32 of the world water resources. The water resources in normal years are about 4.2 billion m3, including 2.4 billion m3 of groundwater, 65.438+0.8 billion m3 of surface water and 3.3 billion m3 in dry years. At present, the annual water consumption has reached the level of normal years of water resources. Up to now, the groundwater has been seriously over-exploited, and a funnel area of over 1000 km2 has been formed in the urban area. The groundwater level has dropped year after year, and the groundwater exploitation has been restricted.

According to the long-term target outline of Beijing's national economic and social development and the overall urban planning, the environmental water demand of Beijing's life, industry, agriculture and urban rivers and lakes is predicted. In 2020, the city's water demand will reach more than 6 billion cubic meters, with an annual water shortage of about 2 billion cubic meters. Therefore, the imbalance between supply and demand of urban water resources and the shortage of water resources have become an important factor restricting Beijing's social and economic development. In order to realize the sustainable development strategy of Beijing's national economy and alleviate the contradiction between urban development and available water resources in the 2 1 century, Beijing municipal government decided to develop urban sewage resources as the second water source of the city. The wastewater reuse project of Gaobeidian Sewage Treatment Plant has been listed in the Beijing Municipal Government's "Beijing Environmental Pollution Control Objectives and Countermeasures" (Beijing Zhengban Letter [1999])11999. The preliminary research work and feasibility study of this project were completed from March to August 2009. 1999. In June 5438 +2000 10, the preliminary design and approval of the project were completed, the construction drawing design was completed in February, and the construction began in April. At present, the project construction has been basically completed, and it is expected to be officially put into use in the first half of this year. In this project, the secondary effluent of Gaobeidian Sewage Treatment Plant is upgraded to industrial water for river water intake, replacing clean water and improving river landscape, and some secondary effluent is used for municipal miscellaneous purposes (such as road spraying, green space watering, etc.). After advanced treatment, it can replace tap water, thus achieving the purpose of recycling urban sewage and improving river water quality. The areas involved in reclaimed water reuse are East First Ring Road, West Third Ring Road, South Fourth Ring Road and North Chang 'an Street. Area 14 1km2. Users of reclaimed water involve industry, park greening, river and lake water replenishment, road spraying and so on. This paper mainly analyzes the technical scheme and research results of this project.

Gaobeidian sewage treatment plant

Gaobeidian Sewage Treatment Plant is the largest sewage treatment plant in China at present. The first phase of the project was completed and put into operation on June 24th 1993, with a processing capacity of 500,000 m3/d. The second phase was completed and put into operation at the end of 1999. At present, the treatment capacity is 6.5438+100,000 m3/d, and the sewage system of Gaobeidian Sewage Treatment Plant covers an area of 96 square kilometers, serving 2.4 million people. It collects most of the domestic sewage in the southern urban area of Beijing, and all the sewage in the industrial zone, embassy zone and chemical road in the eastern suburbs. The treatment plant adopts the activated sludge process with pre-anoxic section, that is, an anoxic section is set in front of the plug-flow aeration tank, in order to improve the properties of sludge and prevent sludge from swelling. At present, the secondary effluent from Gaobeidian Sewage Treatment Plant is directly discharged into the lower reaches of Tonghui River. In addition to about 55 million m3 used for agricultural irrigation every year, the remaining treated water exceeds 300 million m3 every year. According to our many measurements of the effluent from the factory and the analysis results of the effluent quality provided by the factory in 1999, the effluent meets the design requirements, and the effluent quality and quantity are stable. Most parameters of secondary effluent are close to the relevant reuse water quality standards, but the content of ammonia nitrogen and phosphorus in secondary effluent of Gaobeidian Sewage Treatment Plant is still high, mainly because the project was established earlier, and there was no requirement for nitrogen and phosphorus removal in the discharge standards of national urban sewage treatment plants at that time. Therefore, there is no phosphorus and nitrogen removal facility in the first phase treatment process of this plant.

Object analysis can be applied.

The wastewater treatment plant in Gaobeidian, a potential industrial user, has completed the reclaimed water reuse project with the scale of 65438+100000 m3/d, which is mainly used for sludge dewatering, filter cloth washing, maintenance, spraying, watering green space, car washing water source, etc. This water must be guaranteed first. Huaneng Thermal Power Plant Huaneng Thermal Power Plant is located opposite Gaobeidian Sewage Treatment Plant. Two pipelines with a diameter of 800 mm have been laid between Gaobeidian Sewage Treatment Plant and Huaneng Thermal Power Plant, and the advanced treatment station in the plant has also been built. According to the latest data provided by Huaneng Thermal Power Plant, the secondary effluent of Gaobeidian Sewage Treatment Plant is intended to be used as the cooling water supply source for four units, which will be reused after being treated by the advanced treatment station of the power plant to ensure the quality of cooling water. The actual available secondary effluent of Gaobeidian Sewage Treatment Plant is 76,800 m3/d, which should be given priority. Beijing No.1 Thermal Power Plant Beijing No.1 Thermal Power Plant is a high-temperature and high-pressure thermal power plant, located on the north side of Tonghui River, only a few kilometers away from Gaobeidian Sewage Treatment Plant. There are 4 circulating pumps in our factory, each with a circulating water volume of 4. 15m3/s, the circulating pump house is located on the north bank of Tonghui River, and the cooling water is in open circulation. Under normal production conditions, with three pumps running, the required water amount is about 12 m3/s (i.e. 104m3/d). Its water supply is about 260,000-346,000 cubic meters/day, and the average water supply is 303,000 cubic meters/day ... Considering the current situation of river water quality, in order to maintain the upstream water quality, part of the backwater of Beijing No.2 Thermal Power Plant can still be used for the No.1 Thermal Power Plant. Recently, only 200,000 m3/d of treated water from Gaobeidian Sewage Treatment Plant is used for the first thermal power plant ... In the long-term engineering scheme, the second thermal power plant will operate in closed circulation cooling mode, and the water consumption will be greatly reduced, so there will be no inertial flow for the first thermal power plant to return water. Therefore, in the long-term project plan, the water consumption of the first thermal power plant to reuse the treated water of Gaobeidian Sewage Treatment Plant will increase by 654.38+ 1 100 million m3/d on the basis of the recent project scale. Beijing No.6 Water Source Plant Beijing No.6 Water Source Plant is only a few kilometers away from Gaobeidian Sewage Treatment Plant. This plant is a river water plant with advanced treatment facilities, with a scale of 654.38+700,000 m3/d, while the water supply of the sixth water source plant 1998 is only 47,000 m3/d, including the Chemical Experiment Plant 15000 m3/d, the Organic Chemical Plant 66,000 m3/d and the Chemical Plant II. The inlet water of this factory comes from Tonghui River. The secondary effluent from Gaobeidian Sewage Treatment Plant can be directly used by the Sixth Water Plant. In the near future, it is planned to use Gaobeidian Sewage Treatment Plant to treat 50,000 m3/d water and 50,000 m3/d urban miscellaneous water in the eastern suburb industrial zone and coking plant. In the long-term planning, the sixth water source plant will be expanded by 70,000 m3/d ... Tongzhou Water Plant is about eight kilometers away from Gaobeidian Sewage Treatment Plant. Tongzhou has more than 120 factories, including chemical industry, machinery, textile, papermaking, food and other industries. The factories that consume a lot of water include Paper Mill No.7, Dongfang Chemical Plant, Tongzhou Nitrogen Fertilizer Plant and Beijing No.2 Daily Chemical Plant. Tongzhou factory can reuse 70,000 cubic meters of water every day. Urban miscellaneous water in the study of sewage comprehensive utilization in Beijing, urban miscellaneous water has not attracted people's attention. This study investigated the greening area of main parks along Tonghui River and south moat, urban greening and spraying water consumption of urban roads, and visited municipal gardens and sanitation management departments many times. The specific investigation results are as follows: 3.2. 1 Park Greening and Water Use for Rivers and Lakes The main parks along the river include longtan lake Park, beijing amusement park, Tiantan Park, Taoranting Park, Daguan Garden and Wanshou Park. The total area of main parks is about 2.67 million m2, and the water consumption for park greening is about 534,000 m3/d. Besides the above parks, the water supply for rivers and lakes is about 23,000 m3/d, and the toilet flushing is about 460 m3/d.. Therefore, the total water consumption of major parks is about 28,800 m3/d. There are many urban concentrated green spaces in the water supply range of urban greening, and it is difficult to strictly calculate the reuse water of urban greening under the current situation because of their scattered locations. Therefore, it is mainly considered to focus on the isolation belt on both sides of the road and the green space on both sides of the river. According to the overall planning of Beijing, the water consumption for urban greening is estimated to be about 2000 m3/d, and according to the planned road network index of Beijing, the road area of main roads and secondary roads is about 58.68 million square meters. At present, it can spray 33.89 million square meters. At present, the municipal and district sanitation departments are responsible for urban road spraying. All water sources are tap water, and the water intake points are fixed tap water. However, according to the water intake radius of the road spraying waterwheel of the sanitation department, not all the roads that can be sprayed can be replaced by the treated water of Gaobeidian Sewage Treatment Plant. In this scheme, urban miscellaneous water will be deeply treated in the sixth water source plant, and the treated effluent will be transported from the sixth water source plant to Xibianmen and Guang 'anmen along the moat. If a water intake is added to the water supply network of the original Sixth Water Source Plant, the road sprayed by the treated water from Gaobeidian Sewage Treatment Plant is about 23.5km long from east to west, from the first ring road to the west of the third ring road. According to the water intake radius of road sprinklers in sanitation department of 3km, the north-south length can reach 6km, and the sprayable area is 14 1km2. According to the research results of Beijing Urban Planning and Design Institute 1992 Beijing Master Plan, the land utilization rate of the First Ring Road was 3.82% before 199 1 year, and will reach 13.43% by 20 10/year. If the land utilization rate of roads in the recent scheme is calculated as 10%, the road area sprayed with treated water from Gaobeidian Sewage Treatment Plant is about 14. 1 km2. According to the water consumption index of spraying roads provided by the sanitation department, the road area can be sprayed with 2,500m2 of water, so the water demand for spraying roads once a day is 564,000m3/d ... At present, many roads in Beijing are sprayed twice a day. According to the requirements of the municipal government to control air pollution and reduce the amount of urban air dust, road spraying in Beijing will be required to reach three times a day in the future. Therefore, if roads are sprayed twice a day in the near future, the water demand will be about 1. 1.3 million m3/d, and the planned scale of municipal miscellaneous water consumption in the near future is about 42,654.38+0.00 m3/d, of which the water consumption for urban greening and road spraying is1.30 m3/d; The water consumption of the park is 28,800 m3/d. Considering the unpredictable water quantity and the leakage rate of the pipe network, the scale of municipal miscellaneous water in the near future plan is 50,000 m3/d.. 3.3 Agricultural Irrigation Water The agricultural irrigation area of Gaobeidian Sewage Treatment Plant includes four irrigation areas, namely, southeast suburb, Chaoyang, Shuangqiao and Tongzhou, which are distributed in 14 towns and 2 farms on both sides of Tonghui River in Chaoyang and Tongzhou. At present, the irrigation area is 20,265,438. The crops are mainly grain and vegetables, of which the grain field area is169,000 mu, accounting for 83%. Vegetable area 1.72 million mu, accounting for 9%; The area of fruits and other crops is 1.59 million mu, accounting for 8%. The water demand for agricultural irrigation is about 480,000 m3/d. At present, the index water supply and industrial backwater supply of Guanting and Miyun Reservoir are about 654.38+10,000 m3/d, the groundwater consumption is about190,000 m3/d, and the water intake of Tonghui River is about190,000 m3/d ... The downstream replenishment of Gaobeidian sluice and the evaporation and leakage from Gaobeidian sluice to the North Canal in the downstream of Tonghui River for one year.

Multiplexing technical scheme

Optimal allocation of water for users

The treatment water of Gaobeidian Sewage Treatment Plant gives priority to the reuse water in the plant 1 10,000 m3/d, the cooling water of Huaneng Thermal Power Plant is 76,800 m3/d, and the municipal miscellaneous water is 50,000 m3/d, which is supplied to the eastern suburb industrial zone and coking plant through the sixth water source plant 50,000 m3/d and the first thermal power plant 200,000 m3/d, totaling 386,800 m3/d before the implementation of the long-term project. The remaining treated water of Gaobeidian Sewage Treatment Plant can be used for agricultural irrigation of 480,000 m3/d, another 36,000 m3/d for greening from Gaobeidian Gate to both sides of the North Canal, and the last 70,000 m3/d for Tongzhou Plant, totaling 972,800 m3/d. After the implementation of the long-term project, the first thermal power plant will expand the water consumption by 654.38+ 1 100 million m3/d, and the sixth water source plant will The remaining treated water from Gaobeidian Sewage Treatment Plant is used for greening, river water supply of 36,000 m3/d and agricultural irrigation of 407,200 m3/d, totaling 6,543,800 m3/d, and the project scale mainly considers the users of reclaimed water in the upstream of Gaobeidian Sluice. After the implementation of the recent project planning, the users who can use Gaopaidian Sewage Treatment Plant to treat water are: 200,000 m3/d for the first thermal power plant and 50,000 m3/d for municipal miscellaneous water, and 50,000 m3/d for the eastern suburb industrial zone and coking plant through the sixth water source plant. Therefore, the planned scale of the project in the near future is 300,000 m3/d. The planned scale of the long-term project will be expanded from 300,000 m3/d in the recent project to 470,000 m3/d. The main new users are: the water consumption scale of the first thermal power plant will be expanded by 654.38+ 1 100 million m3/d, and the water consumption of the sixth water source plant will be expanded by 70,000 m3/d. The effluent from the secondary sedimentation tank of Gaobeidian Sewage Treatment Plant will be transported to Gaobeidian after being upgraded by a newly-built pumping station (scale of 470,000 m3/d). The treated water sent to Gaobeidian Lake is used in Beijing No.1 Thermal Power Plant. After advanced treatment, part of the treated water sent to the sixth water source plant is supplied to the eastern suburb industrial zone and coking plant through the existing water supply system of the sixth water source plant. Part of it is transported to Xibianmen and Dongbianmen through new pipelines. Water intakes are set along the existing water supply pipelines and newly-built pipelines of the Sixth Water Source Plant for urban miscellaneous water intake.

Technical guarantee measures for reuse water quality

Reconstruction of Gaobeidian Sewage Treatment Plant Because of the high content of nitrogen and phosphorus in the effluent of Gaobeidian Sewage Treatment Plant, it will directly affect the quality of recycled water, so it is necessary to carry out technical transformation to further improve the effluent quality of this plant. In May 2000, the feasibility study of the renovation project of this factory was completed. The transformation scale is 500,000 m3/d, that is, the first phase of Gaobeidian Sewage Treatment Plant (500,000 m3/d). The renovation project is carried out in two steps. After the first stage, the effluent quality is better than that of Gaobeidian Lake, the cooling water intake source of the First Thermal Power Plant. The effluent BOD, COD, total phosphorus and ammonia nitrogen reached 65438 00 mg/L, 40mg/l, 65438 00 mg/L and 65438 00 mg/L respectively. The second step is to make the plant 500,000 m3/d meet the water quality requirements of Class IV water body in Gaobeidian Lake. The main transformation workload includes the transformation of aeration tank and sludge treatment system. The original aeration tank112 is an anaerobic zone, and the rest is an aerobic zone. After modification, 2/9 of the original tank was divided into anoxic zone and anaerobic zone (hydraulic retention time was 2h), and an enhanced adsorption zone with retention time of 15min was separated at the water inlet. The rest is still an aerobic zone (hydraulic retention time 7.25h). The surplus sludge of raw sludge system is pumped into the primary sedimentation tank, and its mixed sludge is concentrated in the sludge concentration tank, and then digested and dehydrated. Because the retention time of the concentrated sludge tank is too long (3d) and it is in an anaerobic state, phosphorus is released and returned to the sewage through the supernatant, so the purpose of phosphorus removal cannot be achieved. After the transformation, the original concentration tank was changed into a concentrated acidification tank, and the supernatant of the concentrated acidification tank was discharged into the water treatment system as a carbon source. The supernatant of digester, filtrate of dehydrator and washing water were collected for chemical dephosphorization. At present, the renovation plan of Gaobeidian Sewage Treatment Plant is in the process of approval, and the municipal government will set up a separate project for the renovation project, and its investment (about 25 1 654,38+0,000 yuan) is not included in the sewage reuse project. Advanced treatment measures The secondary effluent quality of Gaobeidian Sewage Treatment Plant is stable and meets the design requirements, but it cannot meet the urban miscellaneous water standard. The water quality of municipal miscellaneous water such as greening water and road spraying will have an impact on human health and urban environment. Therefore, urban miscellaneous water must be treated in depth before reuse to meet the corresponding standards. In the scheme determination, through the comparison of different sites, the sixth water source plant is selected for advanced treatment. The sixth water source plant has advanced treatment facilities, with a daily treatment capacity of 6.5438+0.7 million m3/d, and mainly adopts mechanical accelerated clarification, sand filtration and disinfection. According to the effluent quality provided by the factory, the effluent can meet the requirements of corresponding users. Due to the adjustment of industrial structure in Beijing, the average actual water supply of this factory is less than 50,000 m3/d at present, and the treatment capacity of 65,438+200,000 m3/d has not been utilized. In addition, the sixth water source plant is close to urban miscellaneous water users, and the advanced treatment of urban miscellaneous water is located in the sixth water source plant, which can use its remaining treatment capacity to meet the short-term and long-term scale demand of urban miscellaneous water, and the water quality after advanced treatment in this plant can meet the water quality requirements of urban miscellaneous water.

Main project content and investment

The total investment of this project is 336.68 million yuan (excluding the renovation cost of Gaobeidian Sewage Treatment Plant), including land acquisition and demolition100000 yuan and project192.6 million yuan. The main contents of the project are: (654.38+0) 470,000 m3/d pumping station of Gaobeidian Sewage Treatment Plant. (2) pipeline from Gaobeidian sewage treatment plant to Gaobeidian lake water: DN 1800mm, length 1480m..(3) pipeline from Gaobeidian sewage treatment plant to the sixth water source plant: DN 1400mm, length 4766m..(4) municipal miscellaneous water distribution pipe:. ; DN 1000mm, length1431m; DN800mm, length 4615 m; DN600mm, length 2845 m; D=500mm, with a length of 2880m. (5) Reconstruction of the sixth water source plant: including reservoir dredging and masonry, sludge pond expansion, water pump reconstruction, water inlet and outlet reconstruction, and adding automatic control and electrical equipment. Garden water supply branch pipe.

Analysis of engineering economic benefit

The total investment of this project is 336.68 million yuan, of which the government grants/kloc-0.0 million yuan, and the rest is loans (corporate financing). Considering the sewage resource fee of 0.20 yuan /m3 and the original asset cost and profit tax of the sixth water source plant of 0.73 yuan /m3, the calculation and analysis results of water price are as follows: the water price of the first thermal power plant is 0.3 1 yuan /m3, the municipal miscellaneous water price is 1.92 yuan /m3, and the water price of the eastern suburb industrial zone is1.2/kl. After the completion of this project, clean water resources of 6.5438+0.6673 million m3 and tap water of 36.5 million m3/a can be saved every year, which is equivalent to saving 400 million yuan by building a waterworks with 6.5438+0.00 million m3/d, which can achieve the purpose of increasing revenue and reducing expenditure, create conditions for the expansion of urban greening area and spraying dust on roads in Beijing, and play a greater role in comprehensive environmental management. Environmental improvement will also bring about land appreciation in the surrounding areas.

Conclusion and discussion

(1) Beijing is a city that is seriously short of water. Rational utilization of Gaobeidian sewage treatment plant to treat water resources is of great significance to realize the sustainable development of Beijing's national economy and to alleviate the contradiction between urban development and available water resources in the 2/kloc-0 century. (2) The reuse project of Gaobeidian Sewage Treatment Plant fully considers the present situation of Beijing's urban water system, gardens, roads and industrial layout, which is feasible. (3) The wastewater reuse project of Gaobeidian Sewage Treatment Plant can achieve the purpose of increasing income and reducing expenditure, alleviate the shortage of urban water resources in Beijing to a certain extent, create conditions for the expansion of urban green area and the spraying of dust on roads in Beijing, and play a great role in comprehensive environmental management. (4) The total investment of this project is 336.68 million yuan, and the project cost is192.6 million yuan. According to the government investment of 654.38 billion yuan, the rest is company financing. Considering the water resource fee of 0.20 yuan /m3 and the water production cost of the sixth water source plant, the reuse water price is 0.365.438+0 yuan /m3, the municipal miscellaneous fee is 65.438+0.92 yuan /m3, and the eastern suburb industrial zone is 65.442 yuan /m3. (5) It is suggested to formulate relevant laws and policies to promote the development of urban sewage reuse facilities. The development plan of reuse facilities in Beijing should be formulated as soon as possible, and reuse pipelines and other facilities should be laid in corresponding municipal projects to gradually improve urban sewage reuse facilities.

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