Study On Coaguation-Microfiltration Process For Luan River Water Treatment

As water source quality gets worse and people's living standard becomes better, conventional treatment process is not suitable to the water source and the quality of drinking water. Coagulation-microfiltration process for drinking water production is promising, which has some advantages, such as simpler process and more convenient operation.Water from the Luan River was used as raw water for drinking water production by coagulation-microfiltration process. Two pilot-scale reactors have been operated stably in Yangliuqing Water Treatment Plant in Tianjin. Curtain-type membrane and cylinder-type membrane were used separately. Quality of the treated water was monitored. The organic matters in the raw water and the treated water were separated according to different molecular weight (MW) by ultrafiltration. DOC, UV254 and trihalomethanes formation precursor (THMFP) were compared in various MW fractions. The character of trihalomethanes (THMs) formation was studied.The results show that, the quality of the treated water can meet the requirements of Standards for Drinking Water Quality (GB 5749-2006). DOC and CODMn removal efficiencies are 26% and 35% separately. Ninety percent of the turbidity of the treated water is lower than 0.10 NTU. The total count of bacteria is below 15 CFU/mL while the total coliform is not detected. All species of THMs in the treated water comply with the water quality standards, when the concentration of free residual chlorine is no less than 0.3 mg/L after contacting with the disinfectant for 30 min. On the whole, the treated water form cylinder-type system shows some superior quality than that from curtain-type system. Sodium hypochlorite was added into the raw water along with coagulant when the concentration of algae was very high in the beginning of autumn. As a result, a superior water quality is gotten.The results of ultrafiltration test show that the organic matters with low MW are the major THMs precursors and the organic matters with MW between 3k-1k Da have the greatest THMFP in raw water. The organic matters with high MW are removed efficiently, and that with low MW even have minus-increase reversely. UV254 has a better removal than DOC in various MW fractions. THMFP removal efficiency of the two systems is nearly 40%.The mathematical predictive model for THMs formation rectified by Rodriguez was used in the raw water and the treated water. The results of statistic calculation show that, predicted values and measured values have a correlation coefficient of 0.945 when the level is 0.05. The two group of datas do not have significant difference (p=0.182>0.05). The model is applicable for the Luan River water.