Research On The Optimization Of Coagulation And Filtration On Polluted River Raw Water

With the rapid development of China social economy, the quality of water resource becomes worse and worse, what’s more, the implementation of Standards for Drinking Water Quality(GB5749-2006) in China presents a challenge for the conventional water treatment process. In this study, the optimization of coagulation and filtration was studied based on the raw water and effluent of some parts of process of a DWTP, which located in Jiaxing. The paper mainly research on the effect of different hydraulic conditions on the performance of coagulation and determined the optimal operation parameters of coagulation beaker test and efficient sedimentation tank. At the same time, the performance of filtration with the influent turbidity below 0.5 NTU was monitored by Turbidmeter and Particle Counter. The best backwashing process was investigated as well. Above research provided a realistic basis for the energy saving operation in the modern DWTP.The optimal kinetic parameters should be: rotating speed of rapid stirring was 500r/min, time was 1min; rotating speed of slow stirring was 60r/min, time was 15 min, which determined by an orthogonal experiment, during the static beaker test. Based on these parameters, the numerical simulation of the coagulation beaker test was simulated by fluent 6.3, and the results showed that the most suitable form of beaker and paddle in the experiment DWTP should be square and flat, respectively. The best dosage of PAC was 50 mg/L, which determined by analysis the value of turbidity, CODMn, UV254 and NH4+-N under different PAC dosage conditions. Activated silica and PAM can reduce the turbidity of the water by cooperated with PAC under low temperature and turbidity condition, for example, large and dense alum particles can be observed when the dosage of PAM reached 0.06 mg/L, however, activated silica should reached 3mg/L can meet the requirements.The pilot-scale efficient sedimentation tank has some problems, such as effluent turbidity high and unstable operation. In order to solve those problems, a pilot-scale experiment was studied. By adjusting the agitation frequency(speed), standardized dosing position, optimize mud, filling alternative approach ramp to ensure the efficient operation of the sedimentation tank under design flow rate, and concluded the following conclusions: the G value of flocculation area under different speed was determined through numerical simulation method and analyzed the problems of the flocculation tank. By compared 8 working conditions, the optimal speeds of mixing and flocculation area were 130 r/min and 40 r/min, respectively. According to actual operation, debugged and transformed the sludge area of the sedimentation tank to ensure sludge removal. The sedimentation tank can effectively remove turbidity and organic pollutants during different inflow efficiency after optimized. The hydraulic shock loading resistance of this tank was increased as well.The online Particle Counter and Turbidmeter was used to determine the optimal backwashing strength and the operation of the filter in a running circle was studied as well, in order to save the energy of DWTP, and concluded the following conclusions: low backwashing strength would make the effluent quality more better and ensure the stable operation of filter. Replaced the high backwashing strength to low backwashing strength would benefit for the energy-saving of the DWTP, and the calculation data indicated that it can save water and electricity were 5173.88 tons and 5173.88 kWh a year, respectively.