Nanyang, with a long history, is a water city, a green city and a famous historical and cultural city. At the end of last century, with the spring breeze of China's reform and opening up, the scale of Nanyang City has developed rapidly, the urban area has increased, the urban population has increased, and the production and life have increased the urban operation load, far exceeding the carrying capacity of urban infrastructure. Urban sewage cannot be effectively collected and treated, resulting in cross-flow of inland sewage and blackening of Baihe River. In the 1990s, the rubber dam on the Baihe River was built to store water, which increased the urban water area and effectively improved the climate environment. However, urban sewage treatment lags behind and is discharged into Hanoi at will. Clean water becomes turbid, sewage floats, rivers are overgrown with weeds, mosquitoes breed, and the smell is pungent, giving people the feeling of suffocation in the breeze. In some areas and some river sections, it is forbidden to discharge and discharge by blocking and intercepting, but it is difficult to achieve the purpose of regulation. Just like a city without public toilets, it is difficult to prohibit citizens from defecating at will. It is only a temporary measure to rely on the upper reaches of the Baihe River to flush the sewage, which only washes away the temporary sewage on the river surface and partially washes it away. The remaining sewage accumulated over time, and Baihe became a sewage river and a sewage pool, not to mention the inland river of the city. Sewage flows and accumulates, the temperature rises, the stench bursts, and the places with dense sewage are suffocating. The old city is already a "sewage city", and the newly developed cities do not take effective measures to eradicate sewage discharge. If this continues, it will soon become a "sewage city" from a "new city". It is urgent to effectively control sewage discharge. Qinhuai River in Nanjing is a famous inland river with rich historical stories, which adds civilization and beauty to Nanjing, but the sewage treatment is not good. Often due to the excessive inflow of sewage, dead fish and rotten shrimp overflow the river surface, rancidity is everywhere, which greatly destroys the urban landscape. We can't destroy the living environment for the sake of production and life, and we can't hurt others and future generations because of survival. It is the unshirkable responsibility of contemporary Nanyang people to effectively control sewage discharge and return Baihe and Nanyang to a clean, clean, green and elegant ecological environment!
1 Status of sewage discharge facilities
In 1990s, with the implementation of comprehensive improvement in the urban section of Baihe River, a special sewage drainage canal with a diameter of about 1m was built downstream of the entrance of Wenliang River, which reduced the amount of sewage discharged to Baihe River to some extent. But the specifications are low, the facilities are simple, the discharge is small, and dredging is difficult. After several years of operation, it was seriously damaged and blocked. Now it is almost abandoned, and the inland river has become a sewage river and sewage. The urban area develops rapidly along the banks of the Baihe River, and the production and domestic sewage in the newly developed urban area cannot be effectively collected, and it is out of control and directly discharged into the Baihe River. In recent two years, a sewage channel is being built in Binhe Road, Hebei Province, using reinforced concrete circular tubes with a diameter of less than 2 meters. The service scope is limited to the downstream area from Wenliang River to Baihe River, with small caliber and low discharge energy, and it is only used for sewage discharge in the old city. It is difficult to solve the problem of sewage discharge in the newly developed urban area in the upper reaches of Baihe River, and it is difficult to clean and dredge, which is easy to block and lose the sewage discharge capacity. Unreasonable wiring and improper construction method. After more than two years of construction, it is still in the critical stage. How to extend to the upper and lower reaches of Baihe River?
Two successful examples
Sewage discharge is an important part of urban survival and development and the main link of urban people's production and life. Many cities in many countries benefit from the effective implementation of sewage discharge, and many cities suffer from poor discharge and treatment measures. In Paris, France, the 300km underground sewage passage built 160 years ago is still a typical urban construction project in the world. It is a world-class metropolis, which discharges sewage and floods in the rainy season and is visited by hundreds of thousands of experts and scholars every year. Its underground passage is large enough for management and maintenance personnel and equipment to enter the operation and passage. Perfect function. In addition to sewage and flood discharge, pipe networks and cables can also be laid, and some sections can be visited by tourists (in the 1970s, a handwritten French detective novel circulating in China had the plot that the perpetrator escaped along the sewer, which was incredible at that time, and it was only realized when he occasionally had the opportunity to go to Paris to witness it with his own eyes). Over the years, many inland rivers such as the Seine River in Paris are still clear and unobstructed, and there is no phenomenon of inland river pollution and waterlogging in rainy season. In the former German Concession area of Qingdao, an underground sewage tunnel was built during the German occupation period. Qingdao citizens said, "those tunnels are big enough to drive cars in." It can be seen that the scale is large. In recent years, many cities such as Guangzhou, Wuhan, Hangzhou and Nanchang have repeatedly experienced urban waterlogging, underground buildings being flooded, cars floating and low-rise houses being flooded during the rainstorm season. Analysis of the reasons shows that the planning, design, construction and management of urban drainage channels are seriously backward, and the drainage capacity is low or cannot guarantee circulation. In contrast, in Qingdao's former German Concession, the underground drainage channel built by the Germans played a role and the drainage was smooth. There has been no cross-flow of sewage for many years, and the city is waterlogged.
The effective measures to control urban sewage and eliminate urban waterlogging are: building urban underground rivers and forming a drainage channel network all over the urban area. A network system that integrates sewage collection, circulation, treatment and discharge (or reuse) to assist urban flood drainage. Sewage disappears on the ground, realizing that sewage and river water go their own ways and do not commit crimes, creating a clean urban environment.
3 master plan
There are many rivers and their tributaries, such as Yong River, Wenliang River and Meixi River, on the north side of Baihe River in Nanyang City. It is planned to build underground sewage channels along the river (below the river bed, with shallow burial depth and low construction difficulty), with criss-crossing rivers and good foundation conditions. The main river is built along the Baihe River, the main canal is built along the urban inland river, and the branch canal is built along the tributaries of the inland river or some streets. The branch canal will extend to all production and living areas, and the canal along the river will be built under the river bed. The original river channel no longer undertakes the task of sewage discharge. After cleaning up, banks, green belts and pedestrian walkways will be built, and permanent buildings will be prohibited within 30-50 meters outside the bank, giving a green light to urban environmental construction. After the inland river regulation, clean water will be introduced from the upstream water source to restore the landscape of green grass, green water and sand, fish and shrimp playing in the water, birds and flowers. Urban sewage and quantitative rainwater in rainstorm period flow into branch channel, main channel, main channel and sewage treatment plant in turn through underground channel. In the south of Baihe River and the newly developed urban area, the original river channel is sparse, so the existing river bed is fully utilized to build drainage channels. At the same time, according to the development plan, an artificial river with a certain density will be built to introduce clean water into the city, and at the same time, the branch lines and trunk lines of underground drainage channels will be built simultaneously. According to the needs of density and emission, underground passages can also be planned and laid along some roads in the urban area to form a network, which is spread all over the new and old cities. Trunk lines, trunk lines and some branch lines have sewage discharge and drainage functions. At the same time, according to the needs of urban construction, the distribution of pipe network (water supply, gas supply, heating) and power grid (electric power, telecommunications cables, optical cables) can be comprehensively developed and fully utilized to realize various functions. Hook a river network on the ground to improve the urban environment; Construction of underground river network to discharge sewage and flood, and standardization of underground pipelines. Efforts will be made to maintain the ecology of inland river systems, solidly promote rain and sewage diversion and sewage pollution control projects, and improve the level of water environment infrastructure support.
4 architecture
Under the riverbeds on both sides of the Baihe River, trunk sewage channels will be built, with the upstream reaching the planned urban boundary and the downstream reaching the urban boundary to the sewage treatment plant. The main channel is built in parallel with the middle line of Baihe River, and the treatment of internal seepage and external seepage is strict. Interchange channels are arranged at intervals on both sides of the channel, which is convenient for adjusting flow and stopping single hole maintenance. Set entrances and exits at a certain distance to realize the management and maintenance of equipment and personnel in and out and the transportation of precipitated dirt. Sedimentation tanks are set at the entrance of each main canal into the trunk line, and mobile gates are built to remove solid floating objects, which can be removed at any time, stacked and transported to ensure unimpeded. The cross section of the main channel is arranged in an inverted pear shape, and the maximum inner diameter is not less than 6m. The upper section is semicircular or rectangular, which increases the flow at the peak, and the lower section is V-shaped. When the flow rate is small, the flow rate increases, effectively reducing sediment deposition and ensuring discharge capacity. In the passage, a pedestrian passage is set on one side or both sides to complete the management, maintenance and observation of the passage and the internal pipe network and power grid.
The main channel will be built along the urban river bed. In addition to making full use of the existing riverbed, the newly opened artificial riverbed and some roads will be used to build underground passages in the new urban area. The maximum inner diameter is not less than 4m. The cross-sectional shape is like the main groove, and the internal arrangement is similar to the main groove. The entrance and exit of people and machines within a certain distance. Sedimentation tank and electric gate are set at the entrance of each branch line into the main channel to reduce the solid flow into the main channel.
Underground branch lines of sewage channels are laid along the riverbed of inland river tributaries or some roads (green belts, pedestrian walkways and non-motor vehicle lanes), which are mainly rectangular channels with one side not less than 3 meters or pipe culverts with a diameter not less than 2 meters. The section setting should ensure that people and machines can effectively clean and dredge. In the underground of urban intersections, a rectangular channel with a single side of not less than 3 meters will be built to realize the sewage discharge function, and at the same time, the pipe network and line network will be laid through, so as to prevent the phenomenon that the urban areas dig ditches every day, often break the road, and the underground pipe network and line network are laid at will. Man-machine entrances and exits shall be set at appropriate positions within a certain length of the branch line, and automatic or manual rain water inlet shall be set in the rain collection area to ensure timely flood discharge during the rainstorm and prevent waterlogging in the urban area.
Branches are connected to the sewage branches of all streets in each district, and each branch is dominated by pipe culverts not less than 1 m to ensure sewage discharge and rainwater discharge in each district. Each entrance is equipped with sedimentation tank and movable grille to prevent solids from flowing in and ensure smooth pipeline. For the key control areas of sewage discharge, current limiting control devices are set to realize orderly management and quantitative discharge.
According to the industrial distribution, population density and other factors of urban planning, the maximum discharge amount is accurately calculated, and the maximum peak flow is accurately determined according to the geography, topography and historical peak value in the region. It is necessary to determine the distribution density, structural size and other data of sewage channels on the basis of several times the peak production and living flow and the maximum auxiliary flood discharge.
Video monitoring and dynamic monitoring of operation data are implemented in the construction of control center, main line, trunk line and branch line. The whole system realizes information management, observes the operation conditions of various places at any time, detects the operation data of each point at any time, transmits the information of water quality change in time, and dynamically monitors all parts of the sewage drainage channel to realize remote control of all electric grilles, gates, cleaning equipment and current limiting devices.
This project is a systematic and permanent project. We should adopt successful model experience, learn many lessons from poor governance, make full use of modern science and technology, and put them into practice with advanced thinking and careful planning. Can't blindly follow, can't rush, can't rush.
5 architecture
According to the order of trunk line before trunk line and branch line after branch canal, new trunk lines, trunk lines and branch canals can be built, and each branch canal can be rebuilt, expanded, restored and rebuilt on the basis of the original sewage facilities. From the downstream to the upstream, the main canal is built first, and the section is completed in the main canal, and the main canal is completed, and the branch canals and branch canals are completed. Build a section, put into use a section, and extend upstream in turn. It can also be completed by stages, segments and regions according to economic capacity. Until the entire sewage system construction in the planned urban area is put into use. Urban expansion can continue.
6 construction scheme
According to the whole sewage system planning and the geographical and geological characteristics of Nanyang city, the reasonable implementation scheme is determined and the appropriate construction method is selected to reduce the construction difficulty and project cost. The main channel and main canal are built along the river, and the buried depth is shallow. Cover excavation method and one-step forming construction method of steel plate cofferdam can be used, or both can be used in combination. The underground trunk passage along the urban road or street is deeply buried, and it is constructed by shield method and formed at one time.
Cover excavation method: a typical urban tunnel construction method, which is carried out in the order of side wall forming, roof sealing, seepage treatment, pore-forming and seepage treatment. All intersections, entrances and exits, etc. , are specially treated. Can be carried out simultaneously on a large scale.
Construction of steel sheet pile cofferdam: firstly, the construction area is closed with steel sheet pile cofferdam, and the closed area is cleaned, and the channel construction and seepage control treatment are carried out according to the design. The construction is simple and the cost is low, but the scale of synchronous construction is limited by the number of steel sheet piles.
Shield method: the tunnel is constructed by shield method, and the tunnel is formed at one time, which is fast but highly mechanized. It needs continuous operation, uninterrupted operation, concentrated investment and auxiliary operation. There are certain requirements for the construction environment and conditions.
7 construction funds
Perfecting the sewage drainage system of the whole city is a huge and long-term project, an important part of urban construction, and a permanent project that benefits the present and future generations. On the basis of one-time planning in place and perfect scheme, it will be implemented in a planned and step-by-step manner, and completed by stages and sections in the order of first tightening and then loosening, first tightening and then slowing down. How much money is invested and how many projects are completed each year? With the goal of "early completion and early production", a huge project is divided into stages and sections, and completed step by step, so as to reduce the difficulty of huge funds needed and ensure the continuous and efficient construction process.
Source of funds:
1) As an important part of urban construction, the government will inject part of the construction funds in stages according to the project implementation plan; 2) As a public welfare project for urban development, call on people from all walks of life in the city to donate money and set aside some funds from the society; 3) According to the affordability of enterprises, units and residents in the city, some construction funds will be included in the existing water charges. After the system is put into use, the funds used in the early stage are reduced; 4) The project is a long-term operation project, and the construction funds can be borrowed from social financial institutions. After it is put into operation, it will be repaid at a certain fee.
8 Operation management
The whole system adopts market-oriented operation mode and independent accounting.
Operating income: sewage treatment is organically combined with water supply and water use, and the sewage treatment fee is qualitatively and quantitatively borne by production and domestic water. According to the principle of "whoever uses water bears the cost", sewage treatment fees are charged in the water use link. Determine the benchmark unit price of sewage charges according to the nature of water use and the pollution degree of discharged water quality, and require "treatment first, then discharge"; Charge by segments, implement ladder unit price, advocate water conservation, and implement the charging method of "large quantity and high price"; For the pipe network and power grid laid along the underground sewage passage, relevant departments shall bear certain passage use fees. Expenditure: infrastructure investment; Maintenance fee for access facilities; Late renovation and expansion costs; Operating and management expenses. The whole operation process is subject to government supervision and social supervision to ensure benign and effective operation and achieve the purpose of serving the society for a long time and permanently benefiting the citizens.
This is a systematic urban construction foundation project and an effective measure to solve the problem of urban environmental water pollution. The completion of the sewage treatment system will not only benefit today, but also benefit people for decades, hundreds or even hundreds of years. Historical achievements are far more beneficial to a city and generations living here than a building, a road or a square. Nanyang is in a period of rapid development of old city reconstruction and new city development. It is urgent to transform and improve the sewage discharge facilities in the old city. The development of new towns and the construction of sewage channels should be put in the first place in urban construction, which is conducive to the improvement of construction and supporting facilities. After the completion of the new city, it will be a beautiful modern city, a new city with healthy ecology and elegant environment.
refer to
[1] Dai Yicheng. Building a Green City: Sewage Treatment Design Anhui People's Publishing House, 20 10.
[2] European Environment Agency. Guide to urban sewage management [M]. China Environmental Science Press, 2000.
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