Experimental investigation on the combined use of C1O2 and NaC1O for drinking water treatment

In Italy, most of the plants producing water for human consumption, use Chlorine Dioxide (C1O2) and Sodium Hypochlorite (NaC1O) for the oxidation and disinfection treatments. These chemical disinfectants, which are very effective as regards the oxidation power, the disinfection capability and the bacteriostatic action, produce by-products harmful for human health: Chlorite and Trihalomethanes (THMs) respectively. The Italian Regulations (D.Lgs. 31/2001) sets very restrictive limits for the maximum concentration of these by-products in drinking water. Moreover, from December 2006, the limit for chlorite will be even more restrictive and, with present treatment process, the compliance with the regulation will be very difficult. Therefore the experimentation of alternative treatment techniques and products is of great interest. This article presents an experimental investigation on the combined use of C1O2 and NaC1O in the treatment of final water from two different plants producing drinking water in Florence. The main objective of this investigation was to evaluate the use of these two products in combination so as to keep the advantages (disinfection efficiency and stability in water) and to minimize the disadvantages (by-products formation) present when using this products separately. Positive results achieved in the experimental phase were used to evaluate the possible applications on real drinking water treatment conditions