engleski

Disinfection byproduct formation according to type of disinfectant used

Results of the Petrinja-Sisak water supply system safety testing for potentially harmful disinfection by-products collected over years are presented. Open surface waterflow of the Kupa River is used by the water supply system. In the first study period (1995-1997), the physicochemical treatment of natural surface water input included only gaseous chlorine in pretreatment and in disinfection and did not include ozone. In the second period from 1998 on, pretreatment with ozone was introduced and gaseous chlorine was used as a secondary disinfectant. In the third period from 2004 on, gaseous chlorine was substituted by chlorine dioxide for disinfection and re-chlorination. The study results showed that the formation of trihalomethanes (THMs) was significant only when gaseous chlorine was used in pretreatment and as the final disinfectant. Chlorine dioxide produced little THMs, and chlorite concentration detected was below guideline values. Preozonation generally decreased THMs formation from postchlorination, either chlorine or chlorine dioxide was used as secondary disinfectant.

drinking water; ozone; chlorine; chlorine dioxide; disinfection byproducts

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