Filed Tests on Chlorination of Poliovirus in Sewage

Full-scale field tests on the chlorination of poliovirus in sewage were conducted using the effluent at a small trickling filter plant. A vaccine strain of poliovirus was taken as a model and used to seed the flow to the chlorination basin. Measurements of chlorine residual and of oxidation-reduction potential were compared with reductions in virus concentration. Coliform group bacteria counts were made during each test run. High chlorine residuals were found to significantly reduce virus concentration. With a 10-min contact time, a 99% reduction required a final residual of 21 mg per 1. However, on the basis of the work of other investigators and this field study it appears desirable to use measurements of oxidation-reduction potential instead of chlorine residual for control of sewage chlorination. The number of surviving coliform bacteria was not a reliable indication of effectiveness of virus disinfection.