Formation Of Disinfection By-products From The Monochloramination Of Chironomid Larvae Solution

In recent years, a large number of chironomid larvae breeding in reservoirs, lakes and water systems, and flowing into the water treatment system in the process of urban water supply with the water. This not only taken troubles and distress to people’s lives, but also caused adverseimpact to social. And it was difficult to inactivate chironomid larvae by traditional disinfection methods because of their strong antioxidant capacity, even if they were inactivated, their wreckage still will stay in the drinking water. The chironomid larvae which was not inactivated continued to multiply in the water supply network, and flowing into the user’s drinking water together with the wreckage of inactivated larvae, affecting the user’s sensory indicators and making unpleasant, even causing panic. In order to prevent the spread of diseases in water, disinfection has become an important technology in the water treatment process. However, the disinfection by-products (DBPs) which have been found to affect human health were brought in the disinfection process and they were got attention. There were varieties of kinds of disinfection by-products precursors (DBPFP), including humic acid, fulvic acid, protein, amino acids, polysaccharides, fatty acids, DNA and other substances, in recent years, scholars have found that algae will provide DBPFP. Compared with the algae, the volume and organic content of chironomid larvae were greater, but the research about whether chironomid larvae could produce DBPs was still fewer. Therefore, this study researched the formation of DBPs during the monochloramination of chironomid larvae metabolite solution and dead soluble substance solution and the formation influencing factors.The results showed that during the monochloramination, all chironomid larvae metabolite solution and dead soluble substance solution could produce DBPs including dichloroacetonitrile (DCAN), trichloroacetonitrile (TCAN), chloroform (TCM), dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), chloropicrin (TCNM) and chloral hydrate (CH).Increased monochloramine dosage and prolonged reaction time both made the concentration of DCAN, TCAN, TCM, DCAA and TCAA increasing, and TCNM concentrations had no obvious trend. Metabolites after disinfection brought the CH concentrations increased first and then decreased.During the monochloramination of chironomid larvae metabolite solution and dead soluble substance solution, different ph affected the DBPs formation greatly. When the precursor was metabolite solution, TCAN, DCAA, TCAA and CH concentrations were higher under acidic conditions than alkaline conditions, and the concentrations of TCAN and CH had lager gap between under acidic conditions and alkaline conditions, they did not generate at acidic conditions. While, the DCAN, TCM, and TCNM concentrations all increased with the increasing pH and then decreased. When the precursor was dead soluble substance solution, the TCAN, CH, DCAA and TCAA generated greater under acidic conditions, and concentrations of TCNM, DC AN and TCM were showing a increasing first and then decreasing trend with the increased pH.Different temperature also influenced the formation of these DBPs. The temperature was changed from10℃to30℃. When the precursor was metabolite solution, TCM, DCAA and TCNM concentrations were increasing with increased temperature, on the contrary, the concentration of DCAN and TCAA showed the opposite trend, TCAN and CH concentrations were increasing first and then decreasesd. When the precursor was dead soluble substance solution, DCAN and TCAN concentrations were higher at high temperature, and TCNM and DCAA concentrations were higher at low temperature, while too high or too low temperature both reduced the concentration of TCAN and CH.No matter the precursor was metabolite solution or dead soluble substance solution, the four typical DBPs (TCM, DCAN of DCAA and TCAA) concentrations were all decreased with the decline of C1/N.