Trihalomethane formation during swimming pool water disinfection using hypobromous and hypochlorous acids

The formation of trihalomethanes (THMs) in a model swimming pool using hypobromous and hypochlorous acids as disinfectants has been studied. Factorial design was used to generate and process data from systematically-conducted experiments on a series of 11 samples of swimming pool simulant. The variables considered were organic loading (urine and humic acid concentration), disinfectant type and concentration, incubation time and degree of agitation. A disinfectant concentration of 6 mg l−1 was used throughout. The variables affecting bromoform formation were urine and humic acid concentration and disinfectant type. Interactions were observed between humic acid and urine and also between urine and disinfectant. The effect of urine was to suppress bromoform formation. Levels of chlorine-containing THMs were unaffected by humic acid at the concentrations used; only the urine concentration and disinfectant type had a significant effect on these THMs. No interactions between any three or more variables were observed for any THM.