Study On The Application Of Particle Counting Technology On The Performance Optimization Of Water Treatment Plant

With the improvement of living standard and the increasing of population in Shanghai, higher demands for drinking water quantity as well as quality have been raised. How to modify or upgrade the conventional water treatment plant as to improve the production capacity and quality of treated water has become an urgent task in many water treatment plants.The study made use of particle counting technology, combining with conventional monitoring methods, to optimize the performance of coagulation, sedimentation and filtration, etc. Researches were undertaken in two plants of Shanghai Pudong Veolia Water Co., Ltd. by full-scale experiments and jar tests.Jar tests showed that, based on Huangpu river raw water, temperature had an influence on the coagulation efficiencies of aluminum sulfate. Under the condition of middle and high temperatures, the dosage of coagulant can be controlled at 40～50 mg/L; under low temperatures, the coagulation efficiencies was not good, so polymer coagulant or coagulant aid was recommended as a substitute. Pre-chlorization had some positive effect for coagulation, which could decrease the particle number of settled water by 5～10 %. Experiments for Yangtze raw water showed that, in summer, PAC dosage for Chenhang raw water and in-situ raw water could be controlled at 6.5～7.5 mg/L and 11～12 mg/L separately.Experiments for clarifier optimization in winter showed that, the optimized rotation speed for low, middle and high treatment capacities was 3.0～4.0 r/min, 4.0～5.0 r/min and 5.5 r/min separately. Under low treatment capacity, the sludge discharging cycle could be prolonged to 24 h.Full-scale experiments for bivalve filter showed that, the operational difference between direct filtration plate and short stem diffuser is not obvious. Fluctuation of filtration speed and settled water quality could both influence the interception efficiency of particles, so effective counter measures should be taken to avoid it. By prolonging the filtration circle in both plants, it was found that, the filtration efficiency of V-type filter is better than bivalve filter, but the interception efficiency of minor particles were low in both cases.Filtered water quality in the initial period was mainly influenced by influent quality and backwashing performance. The initial filtered water quality of V-type filter was good because of the thorough backwashing. To bivalve filter, there was a short time breakthrough of 2～5μm particles in the initial filtration period, so controlled filtration speed and reasonable backwash parameters were recommended to improve the water quality.In conclusion, particle counting can be applied in the treatment processes of coagulation, sedimentation and filtration. Its advantage of accuracy and sensitivity in filtered water monitoring can assist the conventional water quality monitoring methods. With a higher demand for drinking water quality and the development of direct drinking water, the application of particle counting method can play a positive role in ensuring water-supply safety.