1. Reconstruction background: Gongjiadao Waterworks in Yantai City is the only surface waterworks in Yantai City. There are three original water treatment systems in the water plant, among which the valveless filtration system has been abandoned. Accelerated clarifier and movable hood filter equipment are seriously aging, and the equipment failure rate is high. The backwashing water of filter is large, and the loss rate of filter material is high during backwashing. Although the system can barely run, it can't meet the requirements of water consumption and water quality during the peak period. Therefore, it is necessary to transform the original part to meet the requirements of Yantai's urban life and production and ensure the sustainable development of Yantai. Second, the water quality of menlou reservoir, the water source in the transformation process, basically belongs to the third class water standard in the Environmental Quality Standard for Surface Water, and the total nitrogen and petroleum indexes exceed the standard, but they can meet the relevant national requirements after routine treatment. Considering that the coming water in menlou reservoir will be the Yellow River water in the future, the source water quality will decline. After consulting other cities that use Yellow River water, the main indicators of source water quality are excessive oil and algae. Therefore, algae must be considered when selecting the process. According to the quality of raw water, the process flow is selected as: tubular static mixer, small-hole grid reaction tank, advection sedimentation tank and V-type filter. In this project, the process is built into two groups, which are interrelated and can run independently, and the possibility of direct filtration after mixing the liquid except coagulation and precipitation is considered. 3. Main production structure 1. Mixing is the premise of coagulation and sedimentation, and the mixing effect is directly related to the subsequent coagulation and sedimentation effect. At present, the mixing equipment used in newly designed waterworks in China is mostly tubular static mixer and rapid mechanical mixing. According to the relatively stable inflow situation of Gongjiadao Waterworks, this project adopts tubular static mixers, including two DN 1000 tubular static mixers, with a processing capacity of 0.67m3/s. The advantage is that there is almost no maintenance work and no operating cost. 2. The reaction is coagulation, which is very important to improve the precipitation effect. Flocculation can be basically divided into two categories, mechanical flocculation and hydraulic flocculation. According to the good effect of hydraulic flocculation in Gongjiadao Waterworks, this project adopts hydraulic flocculation, which is a small-hole grid reaction tank widely used in China at present. This project is divided into two groups, each group is equipped with two small-hole grid reaction tanks with a treatment capacity of 0.334m3/s and a total residence time of 20 minutes. The pinhole grid is divided into three sections, the first section 1900* 1400mm2, the second section 1900* 1600mm2 and the third section 1900* 1800mm2. The bottom of DN 150 tank is equipped with a perforated sludge discharge pipe, which is used to regularly discharge the sludge accumulated at the bottom of the tank and empty it. The mud discharge pipe is controlled by an electric mud discharge valve, which can be remotely and locally controlled electrically. 3. The commonly used sedimentation structures are advection sedimentation tank and inclined plate (tube) sedimentation tank. Advection sedimentation tank has the advantages of good water conservancy conditions, strong adaptability to raw water quality changes, strong impact load resistance, stable treatment effect, convenient operation and management, large potential tapping capacity, simple tank body structure and stable treatment effect, but the disadvantage is that it occupies a large area. The advantage of inclined plate (tube) sedimentation tank is small floor area, but the disadvantage is relatively poor impact load resistance and poor treatment effect on algae-containing water. Considering that the water quality of source water may deteriorate and algae may increase in the future, two groups of advection sedimentation tanks are selected for this project, each with a size of 108*4*3.5m3, a treatment capacity of 0.668m3/s, a retention time of t=2.5hr, a horizontal flow velocity of V= 12mm/s and an effective water depth. The sludge in the sedimentation tank is discharged by a vacuum sludge suction machine with a span of17.5m. The operation of the sludge suction machine is controlled according to time, and the sludge discharge time is set according to the change of turbidity in four seasons. The effluent of the sedimentation tanks adopts finger tanks, and each advection sedimentation tank is equipped with a stainless steel water collecting tank, and the overflow flow is170m3/m.h. For the convenience of maintenance, each sedimentation tank is equipped with a DN400 ventilation pipe. 4. Filtration is the most important process in the conventional water treatment process, which is used to remove flocs and impurities remaining after coagulation and precipitation of raw water. At present, the commonly used filters are common fast filter, double-valve filter, siphon filter, moving hood filter and V-type filter. V-type filter is adopted in this project. V-type filter is a constant water level filter. The automatic control of ultrasonic water level in the pool can adjust the water outlet valve to ensure the constant water level in the pool. Weir plates are set for the water intake and drainage of single pool, so that the water intake of each pool is uniform and is not affected by the water intake and drainage of other single pools. In this project, two groups of V-type filters are adopted, each group has four ponds, the filtration rate v=7.0m/h, the forced filtration rate V = 9m/h, the treatment capacity of each group is 0.67m3/s, the total filtration area is 720m2, the water depth is 3.85m, and the supporting layer of the filter is 4-8mm gravel with a thickness of150mm. ; The filter material is a single-layer quartz sand uniform filter material, with an effective particle size of 0.95mm, a uniformity coefficient of 1.2- 1.4, and a filter material thickness of 1.2m. The filter head is an ABS long-handle filter head, and the filter plate is a prefabricated concrete filter plate. In order to ensure the effect of filtration and backwashing, the flatness of filter plate must be very high during construction. The backwashing of filters adopts gas-water mixed backwashing, and the two groups of filters share a backwashing water pump room and a fan room. Three roots blowers are used, with air volume Q= 1950m3/h, lift H= 10m, two for use 1 standby; 3 pumps, flow rate Q=650m3/h, lift H= 10m, 2 for use 1 standby. When backwashing, firstly use air with the intensity of 55m3/h.m2 for 2 minutes, then use air and water to backwash for 4 minutes at the same time. The air flushing intensity is unchanged, and the water flushing intensity is 65438+ 100m3/h.m2, and then use water for 5 minutes, and finally the surface is washed. The backwashing period is 24-36h. The operation and backwashing of the filter are automatically controlled by PLC. In the process of filtration, the regulating valve on the outlet pipe automatically adjusts the opening according to the change of filter water level to realize constant water level filtration. When the filter reaches the set value of time or head loss, it will be backwashed automatically. In order to facilitate automatic control, valves and valve plates such as water inlet valve, backwashing drain valve, backwashing water inlet valve, air inlet valve and water outlet regulating valve are all pneumatically controlled. Fourth, the construction experience 1. The project bidding shall be prepared by the owner according to the performance indicators and boundary conditions required by the project; Tender is divided into commercial tender and technical specification tender. The main contents of the technical specification tender include the general requirements, design standards and performance requirements of equipment, pipelines, electrical instruments and civil installation. Then organize bidding in two steps. The first step is to bid for the technical scheme without quotation; The second step is to modify the technical scheme and commercial bidding. Only contractors who have passed the first bid can participate in the second bid. Finally, bid evaluation, determine the general contractor and sign the contract. 2. Quality control in the construction process Although the general contractor is fully responsible for the performance and quality of the project, the owner still needs to carry out all-round quality control in the construction process. After the construction drawing is completed, it must be reviewed by the owner, quality inspection and supervision unit before it can be put into construction, and quality supervision will run through the whole construction process. 3. Problems that should be paid attention to in the construction of automatic control Modern waterworks require high automatic control, with many imported equipment and many choices, but it is not easy to do it automatically or manually. So pay special attention. First, the positioning should be correct. The level of automation should be determined according to the demand and ability, and we should not blindly pursue full automation. Second, the choice of equipment should be based on me, first of all, it requires high reliability and high quality; It not only introduces foreign advanced equipment, but also excludes domestic advanced equipment. The third is to pay special attention to primary instruments. For the automatic control of waterworks, the reliability of PLC and computer is already quite high, so the selection of primary instrument is the key to the normal operation of automatic control system. 4. Debugging, acceptance and personnel training and debugging should be carried out in stages, and the general order is single machine idling, loaded operation and linkage trial operation. Manual first, then automatic. The completion acceptance shall be carried out in accordance with the relevant provisions of the state. Talent cultivation is the basis of building and managing modern factories. We realize that it is impossible to digest, absorb, innovate and improve foreign advanced equipment and technology overnight, and we must pay attention to personnel training. From the negotiation of project introduction to the installation and debugging of water plant design equipment, it is necessary to arrange technical personnel for water plant management. Without qualified and skilled managers, there will be no automation.

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