[Optimal process combination for control of disinfection by-products and precursors during high algae laden period].

Traditional pre-chlorination process would lead to high yield of DBPs during high algae laden period. It had been compared that the efficiency of control disinfection by-products and their precursors by two classes and total 7 kinds of process combination. Algae were proven to be important DBP precursor and it contributed about 20% of HAA and THM precursor. Air floatation was key process to remove algae and it could also reduce the precursor concentration in some degree. Ozone or potassium permanganate also had good efficiency on algae removal, and precursor as well. The best process combination for DBPs and their precursor removal is pre-oxidation of ozone or potassium permanganate plus conventional process plus ozone-BAC process. Sequential chlorination can reduce 42.0%-45.9% HAA yield and 22.5%-71.4% THM yield of free chlorination.

[Simultaneous control of microorganism, disinfection by-products and bio-stability by sequential chlorination disinfection].

A new safe chlorination disinfection process, the sequential disinfection process with short-term free chlorine plus chloramines was investigated its efficiency on control of indices of microorganism, disinfection by-products and bio-stability. This disinfection process may take the advantage of free chlorine's quick inactivation of microorganism and chloramines' low DBP yield and long-term residual. Thus, both control of microorganisms and DBPs can be achieved effectively and economically. The pilot test results show that safe chlorination disinfection process has a little better efficiency on total bacteria count, HPC and total coliform count than free chlorination disinfection, which indicate that free chlorine and chloramines might have the synergetic disinfection effect for their different attacking targets. It also had the same inactivation efficiency on polio virus and coliphage f2 as free chlorination in 120 minutes contact time. Sequential chlorination disinfection process could reduce 35.8% - 77.0% yield of trihalomethane and 36.6% - 54.8% yield of haloacetic acids. The poorer quality the water had, the more advantage the safe-chlorination disinfection had than free chlorination disinfection one. Moreover, sequential chlorination had better efficiency on bio-stability control than free chlorination.