Investigating the Treatment of Paper Industry Effluent Using Ozonation Process

Abstract

In this research, the ozonation process has been used as a supplementary stage of purification to reduce the amount of chemical oxygen demand and remove bacteria, especially E. Coli, from the effluent of the paper industry. Box-Behnken Design statistical method is used to optimize the treatment conditions. In this method, the effect of three variables governing the ozonation process, including the initial pH of the effluent, the amount of input ozone (mg/min) O3 and the duration of ozonation (min) t, was investigated. The results showed that the amount of input ozone and pH had the greatest impact on reducing COD (up to about 80%). Also, the maximum efficiency of the ozonation process for the complete removal of E. Coli was seen in acidic conditions with high amounts of ozone and increasing the duration of ozonation. According to the results, it was found that ozone in molecular form and by direct attack in acidic environments played a role in the destruction of pollutants. Design Expert software was used to determine the optimal conditions, minimize residual COD and maximize the efficiency of the ozonation process. The values of pH=5.2, ozone amount (131mg/min) and duration (23 min) are predicted to reach the lowest residual COD value (48 mg/L) and the highest efficiency (100% removal of E. Coli). According to the investigations carried out in this research, it can be concluded that the use of ozonation process to reduce COD and effectively remove E. Coli from the waste water of paper industry is a promising complementary method.

Keywords

• ozonation
• waste water treatment
• experimental design
• paper industry