Suspended particle effects on ClO2/ultraviolet light combined disinfection of effluent

The concentration of suspended solids of effluent often varies in a wide range, therefore the dose of ultraviolet light (UV) in disinfection process needs to be adjusted to meet the disinfection criterion at a high frequency, and the desired disinfection effect is difficult to be ensured. The particles size and particle-associated fecal coliform (F.C.) contribution, and their influence on UV disinfection were investigated when ClO2 and UV combined disinfection process was used. The results showed that suspended solids content had a major impact on UV disinfection efficiency, especially the large particle size fraction. Particles (D>10 microm) associated F. C. were difficult to be disinfected and were the main part of the tailings of F.C. inactivation curve. Pre-ClO2 oxidation could reduce the number of particles in effluent, and make large particles decrease to small ones. Therefore, the influence of particles on UV disinfection could be reduced after pre-ClO2 oxidation, and the resistance ability to particle loadings of combined process was enhanced. Moreover, the combined process has a lot of advantages, such as low toxicity, low operational/maintenance costs; it is also convenient to be established in the existing wastewater plant or the new planned one.