Evaluation of trihalomethanes risk in water system: A case study

摘要

The main objective of this study was to undertake the multipathway exposure assessment for different water borne disinfection byproduct Trihalomethanes (THM) species contained in the chlorinated drinking water samples collected from different district areas of Kaohsiung City,Taiwan.Tap water samples from 10 locations were collect and analyzed quarterly during a two-year investigation period.Results show that the lifetime cancer risks for Bromodichloromethane (BDCM) contributed the highest percentage (55％) to the total risks,followed by chloroform (9％),and Chlorodibromomethane (CDBM) (36％).The lifetime cancer risks of total THMs in all administration districts were lower than 10-5.Results show that the District 7 had the highest cancer risk mainly due to the exposure to chloroform and BDCM through multipath ways.Intermediate chlorination station located inside District 7 caused high concentrations of free residual chlorine in drinking water,which resulted in the formation of THMs.Compared to other THMs,chloroform posed a higher cancer risk to city residents through dermalexposure.This was due to the fact that tap water would be further treated (e.g.,boiling) by city residents before it was used for drinking.Thus,oral ingestion was not the main exposure route.Results from this study would be helpful in developing a drinking water treatment and management plan for the city water treatment system.