Determination of Levels of Regulated and EmergingudTrihalomethanes (THMs) Disinfection By-Products (DBPs) in audCommunity Drinking Water Supply

摘要

Ahmadu Bello University (ABU) drinking water treatment plant (ABUDWTP) uses calcium hypochlorite toudsupply chlorine in disinfecting drinking water supply to the university community. Between 2008 and 2010, 252udwater samples were taken in duplicates along the treatment and distribution systems of ABUDWTP withudammonium chloride as de-chlorinating agent in accordance with United States Environmental Protection Agencyud(USEPA) Method 551.1. This was aimed at determining the concentrations of trihalomethanes (THMs)uddisinfection by-products (THM-DBPs) and the degree of wholesomeness of the drinking water supplied. TheudTHM concentrations in the samples were analysed using Agilent Gas Chromatograph after preliminaryudextraction with methyl tert-butyl ether (MTBE). Samples’ analyses identified six THMs - two additional to theudregulated four. These are Dichlorobromomethane and 1,2-Dibromomethane here classified as emerging THMuddisinfection by-products (EmerTHM-DBPs). Measured total mean concentration of the regulated THMsud(TRegTHM-DBPs) at house level was 1.0601E-02±1.6625E-05 mg/L as against 9.9704E-02±6.4706E-05 mg/Ludfor total mean emerging THM-DBPs (TEmergTHM-DBPs). This TRegTHMs concentration indicates houseudlevel water is within acceptable limits of international standards despite being above the national permissibleudlimit of 0.001 mg/L. Though not considered under exiting drinking water quality index TEmergTHM-DBPsudwere found to account for over 90% of gross THM-DBPs (GTTHM-DBPs) at each sampling stage. TheseudTEmergTHM-DBPs could create health complications on consumers as they are either suspected carcinogens orudrecognised to increase the risk of carcinogenicity and mutagenicity in humans. Both are irritants of several bodyudtissues and are implicated in several health abnormalities including reproductive and fertility disorders as well asudliver and kidney damage. In view of these likely supplementary health burdens, this paper advocates additionaludstricter monitoring and control of these emerging THM-DBPs as they will most probably compound and increaseudthe frontline of health challenges from chlorine disinfected ABU drinking water supply to its consumers