Abstract

Experiments for the characterization of inactivation were performed in a series of batch processes with the total coliform used as a general indicator organism based on the chlorine residuals as a disinfectant. The water samples were taken from the outlet of a settling basin in a conventional surface water treatment system that is provided with the raw water drawn from the mid-stream of the Han River. The inactivation of total coliform was experimentally analyzed for the dose of disinfectant, contact time, filtration and mixing intensity. The curves obtained from a series of batch processes were shaped with a general tailing-off and biphasic mode of inactivation, i.e. a sharp loss of bacterial viability within 15 min followed by an extended phase. In order to observe the effect of carry-over suspended solids on chlorine consumption and disinfection efficiency, the water samples were filtered, prior to inoculation with coliforms, with membranes of both 2.5 um and 11.0 um pore size, and with a sand filter of 1.0 mm in effective size and of 1.4 in uniformity coefficient. As far as the disinfection efficiency is concerned, there were no significant differences. The parameters estimated by the models of Chick-Watson, Hom and Selleck from our experimental data obtained within 120 min are: log(N/N_0 )=-0.16CT with n=1, log(N/N_0 )=-0.71C^0.87 T with n=/1 for the Chick-Watson model, log (N/N_0 )=-1.87C^0.47 T^ 0.36 for the Hom model, log (N/N_0 )=-2.13log (1+CT/0.11) for the Selleck model. It is notable that among the models reviewed with regard to the experimental data obtained, the Selleck model appeared to most closely resemble the total coliform survival curve.

• Keywords: disinfection; total coliform; chlorine; model; parameters