Investigating chlorine consumption through semi-mechanistic modeling and its implications for trihalomethane formation: A comparison of diverse drinking water

In many regions, drinking water disinfection is crucial for the inactivation of microorganisms. However, chemical reactions between chlorine and natural organic matter and inorganic compounds can result in unwanted formation of disinfection by-products (DBPs). 25 non-chlorinated tap water samples from different regions of Germany were chlorinated to evaluate the chlorine consumption and formation of DBPs. Most of the water samples quickly consumed the initially dosed chlorine (NaOCl as 1 mg/L Cl₂), leaving less than 10% residual chlorine after 2 h. A strong correlation between ultra-violet absorption at a wavelength of 254 nm (UV₂₅₄) and chlorine consumption was observed. A mathematical model using this correlation could well predict chlorine consumption over time. The model can be used to design chlorine booster stations in water distribution networks. The formation of trihalomethanes (THM) including trichloromethane (chloroform), tribromomethane (bromoform), bromodichloromethane, and dibromochloromethane was analyzed. The results revealed varying levels of THM. While the highest total THM concentrations reached 93.8 μg/L, the lowest concentration was 10.7 μg/L.