Characterisation of DBP formation for water quality management – Stage 1

Source waters are disinfected to remove harmful pathogens, but chlorine reacts with organic matter and bromides to form disinfection by-products (DBPs) which can affect health. Water treatment reduces DBPs to safe levels by using alum to remove organic matter before disinfection but some water sources, particularly those with high bromine levels, are still difficult to treat. This research aimed to compile the best protocols for alum coagulation and disinfection when source waters contain different levels of organic matter and bromides, and to relate these to health risks. When organic matter was removed with 125 mg/L alum, and this treated source water was disinfected twice, and the first dose was calculated to generate chlorine levels of 0.5 mg / L for two days before administering the second dose, then DBP levels in drinking water were minimised. Neither alum-treated nor disinfected water caused toxicity in two laboratory tests used to examine risks to health.