Application of chlorine dioxide for secondary effluent polishing

January 05, 2023

F. Vaezi, K. Naddafi, F. Karimi and M. Alimohammadi Department of Environmental Health Engineering, School of Public Health and Institute of Health Research Center, Tehran University of Medical Sciences, Tehran, Iran

Abstract

There are still many difficulties for developing the projects of using treated effluents. In this study, the efficiency of chlorine deoxide in the process of preparing the effluent of Sahebgharanieh Plant of Tehran for reuse purposes has been determind.

Major results are as follows: Total COD reductions resulted from effluent treatment by ClO2 solutions having concentrations equal to 1/4, 1/2 and 1/1 of COD samples at one hour contact time have been about 42%, 49% and 59% respectively. Total suspended solids were also reduced by treatment with ClO2 solutions having the certain concentrations mentioned, and the reductions were about 37% ,47% and 58% respectively. Besides total and fecal coliforms results indicated that ClO2 apllied was quite efficient in effluent disinfection. The conclusion is that reasonable reductions would be expected in the amounts of remained major pollutants and so reuse applications for some non-potable purposes may become possible.

The acidification of chlorite has been used for ClO2 generation as it is better suited to small treatment systems.

Results

Figure 2 shows the results of secondary effluent treatment in total COD reduction by ClO2 in different contact times.

In Figure 3, the efficiencies of COD removal by ClO2 in different pHs could be considered in one hour contact time and results of total and dissolved COD reduction by various amounts of ClO2 solution can be seen in Figure 4. Although the disinfection effect of ClO2 is a well known phenomena, the efficiency of the treatment in reduction of both total and fecal coliforms was determined.

The results of this treatment in 60minutes contact time with various concentrations of ClO2 solutions are in Table 1. Finaly, Figure 5 shows the results of TSS removal by various amounts of ClO2 solutions in one hour contact time.