A development and construction project in Wenshan covers an area of about 22,000 square meters, with a total construction area of about 6,543.8+200,000 square meters. The greening and roads of the project each cover an area of about 6,543.8+200,000 square meters. There is no centralized urban sewage treatment facility in the project area. According to the Functional Zoning of Surface Water Environment in Yunnan Province (revised draft), the affected surface water environment near the project is classified into three categories, which are subject to the three standards in the Environmental Quality Standard for Surface Water (GB3838-2002).
2 The necessity of setting up reclaimed water reuse system in the project
2. 1 Relevant local laws and regulations require that according to Article 15 of the Regulations on Urban Construction Management of Yunnan Province (revised in 2006), "the following projects shall be built, rebuilt and expanded in the urban planning area: hotels, restaurants, shopping malls, comprehensive service buildings and high-rise residential buildings with a building area of over 20,000 square meters; Institutions, scientific research institutions, institutions of higher learning and large-scale comprehensive cultural and sports facilities with a construction area of over 30,000 square meters; Residential areas and concentrated construction areas with a construction area of over 50,000 square meters.
Construction projects with exploitable capacity above 150m3/d; Other projects that should support the construction of reclaimed water utilization facilities: the construction unit should support the construction of reclaimed water utilization facilities at the same time, and the reclaimed water utilization facilities should be designed, constructed and put into use simultaneously with the main project. The required funds should be included in the total investment budget of the main project. Not included in the construction at the same time, the relevant departments shall not handle the relevant examination and approval procedures for construction projects. "According to its requirements, this example project belongs to a centralized building area with a building area of more than 50,000 m2, which meets the relevant requirements in the Regulations on Urban Construction Management of Yunnan Province (revised in 2006). In the process of environmental impact assessment of construction projects, it is necessary to put forward the setting of reclaimed water reuse system.
2.2 Imperfect factors of sewage collection and treatment facilities in small towns There are many imperfect factors in sewage collection and treatment facilities in small towns. In the past, small towns had a small population and little domestic sewage. Coupled with economic constraints and insufficient awareness of environmental protection, there is no centralized collection and treatment facility for domestic sewage in small towns, and domestic sewage is directly discharged into surface water bodies after being pretreated by septic tanks.
This not only has a certain impact on the surface water environment, but also has a certain impact on the atmospheric environment because it cannot be diluted in time in dry season. Later, with the development of economy and the improvement of environmental awareness and requirements, some small towns improved the centralized collection and treatment facilities for domestic sewage. However, due to the lack of consideration of regional development planning and the unpredictability of urban development, there are many disadvantages in sewage collection and treatment facilities in small towns. For example, the treatment capacity of sewage treatment plants in small towns is too small to accommodate the treatment of new domestic sewage in towns; The diameter of the main sewage collection pipe in small towns is small, which can not meet the collection of new sewage in urban areas, resulting in the centralized collection and further treatment of domestic sewage generated by development and construction projects in small towns.
For example, there is no centralized municipal sewage treatment facility in the project construction area at present, and the affected surface water in the project area belongs to Class III water body. The domestic sewage generated by this project is discharged only through septic tank pretreatment, which cannot meet the requirements of the first-class standard in the Integrated Wastewater Discharge Standard (GB 8978- 1996). The project must build sewage treatment facilities to treat domestic sewage. In addition, the greening area and road area set by the project are large, and the water supply project of the town where the project is located is not perfect. In the process of environmental impact assessment of construction projects, it is necessary to put forward that construction projects should set up reclaimed water reuse systems.
2.3 Environmental Protection Requirements for Total Emission Reduction The wastewater generated during the operation period of small town construction projects is mainly domestic sewage, and the total control indicators in wastewater are COD and ammonia nitrogen. According to the "Twelfth Five-Year Plan" of national environmental protection, by 20 15, the total chemical oxygen demand will be reduced by 8% on the basis of 20 10, and the total ammonia nitrogen emission will be reduced by 10%. Urban pollution source is one of the main factors affecting chemical oxygen demand and total ammonia nitrogen. In small towns with imperfect sewage collection and treatment facilities but rapid development and construction, the project party establishes a reclaimed water reuse system in the project area to collect sewage nearby and reuse it after treatment nearby, which is a measure that meets the requirements of total emission reduction and environmental protection.
2.4 By analyzing the building foundation of an example project as a parameter, the benefits of reclaimed water reuse are reflected. The construction area of the example project is about 65438+200,000 m2, and the sewage generated during the operation period of the project is about 360m3/d, and the reclaimed water reuse system with a treatment capacity of 360m3/d is built. Considering that there is less reclaimed water used for greening and watering in rainy season, the actual available reclaimed water is calculated as 80%. According to the construction budget, the construction and installation cost per unit building area is 1.5 million yuan /m2, and the cost of reclaimed water recycling system in the building is considered as 1.0% of the total cost. According to relevant data, the maintenance cost of reclaimed water reuse system is calculated as 65,438+00% of its cost. Operating costs of reclaimed water reuse system (including equipment depreciation and maintenance, labor, electricity, chemicals, etc. ) Calculated by 0.7 yuan /m3. According to the calculation, the total investment for establishing and maintaining the reclaimed water recycling system in this project is (1500×12×1.0 %× (1+65438+). At present, the water price in the project area is 2.0 yuan /m3, and the project can save (2.0-0.7) = 1.3 yuan /m3, and the annual cost saving is (1.3× 360× (1-20% )× 365) =/kloc-. In addition, the establishment of reclaimed water reuse system can save the construction and operation costs of urban drainage facilities in the project area, as well as the construction and operation costs of long-distance water transfer and water purification projects in the project area. In a word, reclaimed water reuse system is a systematic project, and the benefits of building reclaimed water reuse system are not only reflected in the project itself, but also in the establishment and operation of water supply and drainage facilities in the region.
3 Constraints on the setting of reclaimed water reuse system
3. 1 The management mechanism is not perfect. China only started the research of reclaimed water reuse in the late 1970s. Although the reclaimed water reuse facilities in Beijing, Shanghai, Dalian and other big cities have achieved fruitful results, on the whole, the reclaimed water reuse in buildings in China is still in its infancy. The relevant national policies, regulations and technical specifications are not perfect, the supporting industrial policies and regulations system has not been formed, and local governments also lack relevant restrictive laws and regulations and relevant supervision and supervision standards and requirements, which makes the setting of water reuse system in small town construction projects only appear in the text as an indispensable sewage treatment measure, and the actual operability is poor.
3.2 Lack of contact between departments involved in construction projects. At present, the initial design description of most construction and development projects mentions the setting of reclaimed water reuse system. In the concrete water supply and drainage design of the construction project, the design department only designed the water supply and drainage pipe network, but did not design the reclaimed water reuse system. In the process of environmental impact assessment of construction projects, although the EIA unit put forward the requirement of setting up water reuse system in construction projects according to environmental protection requirements and local laws and regulations, due to the disconnection between design department, EIA department and environmental protection engineering design department, it is impossible to design the pipe network of water reuse system in construction projects specially, and the construction of water reuse system in construction projects cannot be implemented in the actual construction process.
3.3 Technical strength and operation management are not in place. Because the research on water reuse technology in buildings in China started late, the market mechanism has not yet formed. In the actual implementation process, due to the weak technical force and lack of design experience, there are often problems such as the project can not run normally after being put into use, the effluent quality is not up to standard or the operating cost is high. In addition, due to inadequate operation management, secondary pollutants such as sludge and odor generated during the operation of the reclaimed water recycling system cannot be properly treated and disposed of, which makes some built reclaimed water recycling systems semi-paralyzed, which has a certain negative impact on the setting of reclaimed water recycling systems in small towns.
3.4 Due to economic constraints, the one-time investment of reclaimed water reuse system is relatively large. Roughly estimated, the initial investment of water system in an example project is about 6.5438+0.98 million yuan, which is a large environmental protection investment in the development and construction of small town construction projects. Investors and builders are unwilling to consider part of their environmental protection investment in the total investment of the project. The cost of reclaimed water is obviously higher than the price of tap water in the initial operation of reclaimed water reuse system, which makes economic factors one of the restrictive factors in the setting of reclaimed water reuse system in small towns.
In addition, in the process of building development and construction in small towns, due to the limitation of regional topography and landform and in order to reduce the construction cost of "three links and one leveling", general construction projects are laid out according to topography, which leads to relatively large topographic differences between plots of construction projects, which is another restrictive factor for the reasonable setting of reclaimed water reuse system: if a centralized reclaimed water reuse system is set within the scope of the project, the operation cost will increase due to the use of sewage lifting pumps or reclaimed water delivery pumps; If multiple reclaimed water reuse systems are built in different areas, not only the initial construction investment is large, but also the unit cost of sewage treatment operation will increase, so it is difficult to manage them in a unified way.
Four suggestions
In the process of building development and construction in small towns, it is necessary to set up reclaimed water reuse system, and there are many factors restricting the setting and implementation of reclaimed water reuse system, thus reducing the operability of setting up reclaimed water reuse system proposed in EIA. In order to solve the above contradictions, the following suggestions are put forward:
(1) Improve relevant national and local policies, regulations and technical specifications, and form a top-down supporting industrial policy and regulation system.
(2) The rapid development of small towns should first improve the municipal engineering of centralized sewage collection and treatment, so that the fecal sewage generated during the operation period of development and construction projects can be pretreated by septic tanks and then discharged into municipal sewage treatment facilities for treatment to meet the relevant environmental protection requirements. The development and construction of water reuse system in buildings can make use of high-quality miscellaneous drainage (bathing, washing, etc.). ) as raw water, it can meet the water requirements of toilet flushing, greening and road washing in development and construction projects after treatment. So as to reduce the investment of reclaimed water reuse system.
(3) Environmental management departments, environmental design departments, engineering design departments and other departments should strengthen coordination, form a systematic market operation mechanism, and organically combine engineering facilities such as the source, collection, treatment and water supply of raw water in the reclaimed water recycling system.
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