Bachelor of Science

Disinfection of water by chlorination is known to produce a class of disinfection byproducts known as trihalomethanes (THMs) which are known or suspected carcinogens in our drinking water. The occurrence of THMs in drinking water has been shown to arise from reaction of chlorine disinfectant with organic compounds so-called humic acids which are found in varying quantities in natural waters.

This study shows that both chloroform and carbon tetrachloride were significant chlorine byproducts whereby the former is a major THM species. The concentrations of the halogenated compounds were determined by Purge-and-Trap/Gas Chromatography/Electron Capture Detector. In this study, the critical factors influencing the rate of chloroform production are pH, contact reaction time, light intensity and the presence of photocatalyst. It also shows that the role of the photocatalyst (ferric ions) is more crucial in speeding up the organic degradation process rather than chlorine byproduct formation. Chloroform precursors that were speculated include organic compounds such as acetone as well as various types of freshwater algae which are known to be contributors of humic acid materials. Examples of these algae are the bluegreen algae, green algae, diatoms and the dinoflagellates. Lastly, a TOC (Total Organic Carbon) analysis of the water samples before and after chlorination also confirms the formation of chlorine byproducts during the chlorine disinfection of water.