Formation Of Disinfectant By-products During Chlorine Dioxide Preoxidation Followed By Chlorination Of Cyclops Metabolite

Some external nutrients such as nitrogen and phosphorus exceeded that could cause eutrophication resulting in algal blooms, the cyclops as the representative of zooplankton have been found in lakes, reservoirs and other water sources, because of the cyclops oxidation resistance were very strong, so if you want to kill it effectively that the regular disinfection of water treatment technology was difficult to remove it and cyclops often occur in the clean water tank and even pipe network. The cyclops was also an important medium for spread disease, this problem not only affected residents of the senses and psychological adversely,but also related to the quality of drinking water sources and water quality safety. Using an oxidizing agent to reduce its activity and inactivation has become a key step that may be related to whether the cyclops can be completely removed. Under the action of chemical oxidation can make algae cell density and surface morphology features changed effectively and also had been widely used. Different from the natural organic matter, the research about the preoxidation regular pattern of disinfection by-products during chlorination was still lacking. Therefore, this study researched the formation of disinfectant by-products during chlorine dioxide preoxidation followed by chlorination of cyclops metabolite solution and dead soluble substance solution and the formation influencing factors.The results showed that during the chlorine dioxide preoxidation followed by chlorination, all cyclops metabolite solution and dead soluble substance solution could produce DBPs including dichloroacetic acid (DCAA), trichloroacetic acid (TCAA),1,1,1-dichloropropanone (1,1-DCP),1,1,1-trichloropropanone (1,1,1-TCP), chloroform (TCM), chloral hydrate (CH) and dichloroacetonitrile (DCAN). In terms of the tested DBPs, preoxidation by chlorine dioxide could reduce the amount of DBPs obviously and compared to chlorination alone.Increased chlorine dioxide dosage made the concentration of DCAA, TCAA,1,1-DCP,1,1,1-TCP, TCM and CH decreasing, the most of DBPs decreased intensively when chlorine dioxide dosage was2mg/L. the yields of DCAA andTCAA were highest among the tested DBPs, but when the precursor was dead soluble substance solution, the concentration of them were higher than the previous quality as metabolites.With the prolonged preoxidation time, both made the concentration of DCAA, TCAA, TCM and1,1-DCP decreasing, whereas1,1-DCP and1,1,1-TCP changed in an opposite way. The concentration of CH increased continuously with increasing preoxidation time. when the precursor was dead soluble substance solution, CH concentration had no obvious trend. During the chlorine dioxide preoxidation followed by chlorination of cyclops metabolite solution and dead soluble substance solution, the influence of pH changed on DBPs:When the precursor was metabolite solution, DCAA, TCAA, CH,1,1-DCP and1,1,1-TCP concentrations were higher under acidic conditions than alkaline conditions, the yields of DCAA and TCAA decreased quickly as the pH from5to6, and TCAA then remained almost unchanged as the pH value increased. the yields of1,1,1-TCP decreased quickly as the pH from5to6. When the precursor was dead soluble substance solution, the DCAA、TCAA、CH、1,1-DCP and1,1,1-TCP concentrations all decreased with the increasing pH, the TCM and CH the concentrations had lager gap between under acidic conditions and alkaline conditions, the yields of TCM was higher under alkaline conditions than acidic conditions. CH showed the opposite trend.Different temperature also influenced the formation of these DBPs. The temperature was changed from10℃to30℃. When the precursor was metabolite solution, the yields of TCM, DCAA and TCAA increased continuously with increased temperature.When temperature changed from10℃to20℃, TCAA concentration trend exhibits a slight downward trend, the other DBPs concentrations had maximum yields at20℃. When the precursor was dead soluble substance solution, the amount of TCM, DCAA and TCAA were higher at high temperature, and1,1-DCP and1,1,1-TCP formation decreased continuously with increased temperature.