Most utilities use some forms of chlorine to safeguard drinking water from bacteria re-growth and biofilm formation during water supply transportation and distribution. It could increase the threats of disinfection by-products (DBPs) formation - mainly trihalomethanes (THMs) - in water. In this paper, a mathematical model that expresses THM concentrations in terms of initial chlorine dose, total organic carbon (TOC), bromide ion concentration, contact time, temperature, algae and pH are developed from experimental bench studies. Another objective of this paper is to characterize the main aspects of water quality deterioration in a distribution system. The effect of residence time on chlorine uptake and the formation and evolution of DBPs in drinking water distribution system are discussed.
Simple regression analysis has been done to explain the significance of correlation between the THM levels and these variables. In these analyses, THM formation showed a high linear significant correlation with contact time (p < 0.0001 & R2 = 0.97), pH (p = 0.0001 & R2 = 0.86), temperature (p = 0.0001 & R2 = 0.88) and chlorine dose (p = 0.0001 & R2 = 0.91). Although algae and TOC were used in the study as THM precursors, there was no significant correlation between their concentration and THM formation. Predictive models were developed in this study to predict the THM formation. The predictive values showed good agreement with the measured THM concentrations from filed study model.
The results of THM formation by reacting disinfectant with deposits showed that the increase in THM concentration was negligible during chloramination, while it was noticeable during chlorination. |
