Experimental Research And Comparison Of Chemical Pre-Oxidation Processes For Micropolluted Water Treatment

This research belongs to the projects of Tianjin Environmental Science andEngineering for Safe Drinking Water in 2002 and is the pre-research for the processesalteration of Tianjin Xin Kaihe Water Treatment Plant, China. Jar tests and pilot testswere taken in site. The removal efficiencies for organic matters, algae and DBPs wereinvestigated with different oxidants and combined processes in order to decide asafe and effective pre-oxidation technology and combined process, which can offer aadvanced technology for the processes alteration of Xin Kaihe Water Treatment Plantas well as some similar water treatment plants in China. It had been found that O3, ClO2 and Cl2 all can oxidize pollutants inmicropolluted water and aid to the coagulation-floculation process. Pre-ozonation wasmore effective to enhance removal efficiency of algae, bacteria, turbidity, chroma,odors and organic matters. Furthermore it could reduce the concentration of CHCl3precursors and CCl4 precursor and also produced a low concentration of disinfectionbyproducts, which guarantee the safety of the outlet. Consequently, ozonation was akind of better agents for pre-oxidation of micropolluted water. The optimum reactiontimes of O3, ClO2, Cl2 for pre-oxidation of micropolluted water were 15min, 30min,30min, and the doses of the three oxidants were 1.5mg/L, 4mg/L, 4mg/L, respectively. The combined processes composed of pre-oxidation, conventional treatmentprocess and GAC adsorption were studied in pilot test. Results indicated thatpre-oxidation could enhance the performance of conventional system andPre-ozonation was more effective than pre-chlorination. The concentration of CHCl3in the effluent of pre-chlorination process increased and could be removed effectivelyby GAC adsorption only. In order to meet the new Chinese National SanitaryStandard for Drinking Water and enhance the performance of conventional system andreduce DBPs, the integrated treatment system with pre-ozonation, conventionalprocesses and GAC adsorption should be used to treat micropolluted raw watercontained high concentration of algae.