| The first water treatment plant in M city was built in 1959, the water comes from underground sources, and its designed supply capacity is 86000m3/d. The water from wells is only disinfected with chlorine in the plant. In recent year, as a result of contamination from municipal sewage and industrial wastewater, agricultural runoff from chemical fertilizers and garbage, the quality of water from 3 ones of all wells declined and ammonia nitrogen and nitrate nitrogen were found exceeding the standard. Thus, the 3 wells are out of use currently, and the water supply from this plant fell to 56000m3/d. The water qualities from the 3 wells are described as follows: total hardness is 461-616mg/L; nitrate from first well is 14.73-28.56mg/L, ammonia nitrogen is 0.4-1.0mg/L, nitrite nitrogen is 0.23-0.30mg/L, while the nitrate of 4th well is 19.88-26.85mg/L, ammonia nitrogen is 0.3-1.1mg/L, nitrite nitrogen is 0.21-0.28mg/L, and for the 5th well, nitrate is 12.42-31.15mg/L, ammonia nitrogen is 0.5-1.1mg/L, nitrite nitrogen is 0.19-0.30mg/L. Because the raw water plant only has liquid chlorine disinfection process, so the indicators of nitrate nitrogen, ammonia nitrogen and total hardness have been unable to meet the requirement of drinking water sanitary standard.According to M city master plan, the total water requirement should be 199300m3/d in 2020, while the current water supply capacity is 121000m3/d, the gap between water supply and demand is 78300m3/d.Considering the water resource distribution on water department and regulations of provincial government which control exploiting the groundwater strictly and new water-taking facility is not allowed to be built, the nearby Y reservoir is the only available water resource in M city, there still has about 50000m3/d water yield support the city's water. M city plans to construct one surface water treatment plant in 2017, the water supply is designed for 50000m3/d. Thus, the difference between the demand and supply will be 28300m3/d in 2020. In order to meet the demand of urban water supply, the 3 wells will be used again. But due to the water contamination the technical transformation will be done for the water works, and the transformation scale is 30000 m 3/d.The transformation plan is utilizing the office buildings, treated water reservoirs, chlorinating room, garages and so on, building a new water treatment workshop, and updating the facilities in chlorinating room.Comparing the water source quality and the standard for drinking water, nitrate nitrogen, ammonia nitrogen and total hardness are the main index exceeding the standard. The water treatment process is as the following, raw water-filtration-Micro-hole precision filtration-reverse osmosis-chlorine disinfection.The filtration is remove sands and tiny suspended substance from water. The micro-hole precision filtration helps to remove above 5?m tiny particulates and other impurities and reduce the raw water pollution index, to protect reverse osmosis membrane. Taking use of 8 40 PP melting & spraying 8 filter machines, 6 of them will general operation, the other two for backup. The thickness of this filter is 4mm, and it is ?1100mm×2400mm stainless steel tank.The role of reverse osmosis unit is to remove soluble substances in water, for nitrate nitrogen, ammonia nitrogen and hardness. With CPA membrane, 8 inch CPA3-LD and the water treated by single-stage. The average the desalinization rate is 95%, and water productivity rate is 75%. The operating pressure of membrane is 1.05 MPa, available membrane is 37.2m2 each unit and water flux is 1.7m3/h. The number of membrane module is 168 totally.The agent used for membrane cleaning is in food-grade security, which is 35% citric acid, sodium hydroxide, sodium bisulfate respectively.The scale inhibitor is AMEROYAL 428, and its dosage is 2-4mg/L.As the main component of reverse osmosis concentrated water ions, the water content of the particulate matter is less, so, the concentrated water generated by reverse osmosis would flow into concentrated water regulation pond, At the same time, using the control system to make the concentrated water used in the back flushing of general fast filter and precision filtering device. The function of the concentrated water regulating pond is to regulate the discharge and reuse of the concentrated water, and to act as an backwash tank.Filtered water is feed into the treated water reservoir to sterilize with chlorine, which aims to zap pathogenic microorganisms in water. By using the chlorinating room, chlorination equipment will renew. The designed maximum chlorine dosage is 1.5mg/L, meanwhile by using 2 vacuum chlorinators to support whole work, one for normal and the other for backup.The project cost is 29.9165 million, among which engineering cost is 23.6605 million, other engineering construction cost is 3.3827 million, reserve fund is 2.1635 million and initial working capital is 0.7098 million.The total cost of this project is 24.0575 million, and operation cost is 22.7105 million, water production cost per unit is 2.64 yuan/ton. |
PDF Full Text Request