A kinetic model for chlorine consumption in grey water

In view of the present interest on grey water reuse, this paper describes the residual chlorine decay in grey water chlorinated samples. Several theoretical models were compared, resulting in a parallel first-order model with four adjustable parameters, which showed satisfactory adjustment to experimental data. According to this model, the added hypochlorite was divided into three fractions of different reactivity. A first fraction was rapidly reduced to stable compounds, such as chloride, without interest from a disinfectant point of view. Then, the remaining compounds with oxidative and disinfectant properties were differentiated into two other fractions of different reactivity, i.e., a higher reactive fraction which disappears in few hours, and a slower fraction which remains for several days. Kinetic parameters from 45 grey water samples are reported.