Effet de la chloration sur la formation de trihalomethanes dans les eaux alimentant la ville de Casablanca au Maroc (Effect of chlorination on trihalomethanes formation in feed water of Casablanca in Morocco)

To maintain the quality of drinking water, from the water treatment plant to consumerʹs tap water, a residual concentration of chlorine has to be maintained throughout the distribution system and protects against microbial recontamination (remnant effect). In Morocco, the pre-oxidation and final disinfection are carried out using chlorine. The injection of chlorine is carried out at different points of the distribution network: i) at the outlet of the water treatment plant; ii) at the inlet of the storage tank; iii) at the outlet of the storage tank, and; vi) during the distribution of water at different points of the network up to consumerʹs tap water. The objective of this work is to follow the effect of chlorination on by-products formation (organochlorinated compounds, trihalomethanes (THMs)). Initially, analytical characterization, monitoring of physicochemical parameters and determination of THMs have been carried out for Bou Regreg water sampled at different points of the distribution network. In a second time, a natural water taken as reference was contaminated with humic acid (used as precursors of THMs) in order to follow the change in THMs concentration while applying the same processes encountered in water treatment plants of Morocco. The results show that, the increase in chlorine concentration greatly affects water contamination by THMs.