A mathematical model that expresses total trihalomethane (TTHM) concentration in terms of initial chlorine concentration, total organic carbon, bromide ion concentration, contact time, and pH is developed for Zai water treatment plant which supplies water to Jabal Amman. Laboratory studies of THMs formation upon chlorination and bromide ion addition at different points of Zai treatment plant were performed.Results showed an increase in THMs concentration upon increasing contact time and chlorine dose. TTHM in the effluent water from Zai treatment plant ranged from 22 ppb to 63 ppb; these...