Evaluation of trihalomethanes in tap water samples of Karachi city [Pakistan]

ABSTRACT

The chlorination of water containing natural organic matter leads to the formation of disinfection by-products. Trihalomethanes [THM[s]] are the major category of disinfection by-product in chlorinated drinking water. This study aimed to investigate the presence of THM[s] in tap water samples collected from different localities of Karachi city. Liquid-liquid extraction and gas chromatography with an electron capture detector was used for the determination of THM[s]. The concentration of THM[s] in tap water samples of Karachi was found below the WHO guideline values. The mean concentration of chloroform, bromodichloromethane and dibromochloromethane were found as 30.40, 1.04 and 0.09 micro g L[-1] respectively. The relative standard deviations for these THM species were 1.15, 1.61 and 1.81 respectively. Bromoform [CHB[r3]] was not detected. On the basis of the results obtained by principal component analysis [PCA], CHCl[3] was found to be the most significant principal component. The effect of free chlorine residual and pH on the concentration of THM[s] were also assessed