Research On Ultraviolet Disinfection In Wastewater Treatment

Compared with other sterilization techniques, UV disinfection has a better effect and a much lower cost and produces no disinfection by-products (DBP).It is widely used in practical engineering.In this study, we take samples from water flowing through sand filter of reclaimed water system of Shandong Jianzhu University, to test the UV disinfection system using static and dynamic methods. The germicidal effects of UV; influence factor (turbidity;initial concentration of microorganism); photoreactive; dynamics and UV combined disinfection results are carefully analyzed. It is of great value in building practical engineering UV disinfection plant.The study shows that UV disinfection inactivates Bacillus and Fecal coliforms highly. The number of Fecal coliforms reduced to reach national standard (GB18918-2002) through experiments; turbidity, initial concentration of microorganism, water thickness layer do affect the disinfectant effectiveness of UV; UV irradiation makes little difference to pH and turbidity of water, while makes small increasing to COD.Microorganism can photoreactive after UV disinfection. Longer UV time is effective on fecal coliforms inactivation and can decrease the photoreactivity of fecal coliforms. Study shows that keeping water samples in dark for24hours after UV irradiation doesn’t have photoreactivation, and keeping water samples under light have photoreactivation, but the numbers of fecal coliforms of all water samples reach national standard (GB18918-2002).In the test of UV combined with H2O2disinfection, the disinfectant effect of fecal coliforms is better than UV disinfection, and grows with increasing of H2O2dosage. However, H2O2easily decompose when exposed under light, that decreases the disinfectant effect. Therefore in the test of UV combined with H2O2disinfection one should use higher density H2O2and closer UV disinfection system.In the test of UV combined with sodium hypochlorite (NaCIO) disinfection, the best strategy is to radiate15sec. under UV first, and then deliver sodium hypochlorite lmg/L. This program reduces the time of UV disinfection and the dosage of sodium hypochlorite (NaClO). Sodium hypochlorite (NaClO) has effectively suppressed photoreactivity of fecal coliforms to solve the problem of no lasting disinfection of UV disinfection.