避光处理对污水紫外线消毒后大肠杆菌光复活的影响研究

以大肠杆菌为受试菌种,研究了避光处理对紫外线消毒后三级出水中细菌光复活的影响.将紫外线消毒后的水样避光放置一定时间后再置于光复活条件下,研究了大肠杆菌的复活特性.结果表明,避光放置6h以内,见光后大肠杆菌的光复活能力即刻恢复,并最终达到与非避光处理基本相同的最大复活值;5 mJ/cm2和20mJ/cm2紫外线剂量照射后,最大复活百分比分别为31.1%和0.45%,复活速率分别为1.67×104CFU·(mL·h)-1和125 CFU·(mL·h)-1.延长避光时间至24 h,5 mJ/cm2和20mJ/cm2紫外线剂量照射后的大肠杆菌见光后,最大复活百分比分别减小到10.0%和0.3%,复活速率分别减小到830CFU·(mL·h)-1和20CFU·(mL·h)-1.以上结果表明,延迟消毒后出水见光时间,只能在一定程度上推迟或削弱大肠杆菌的光复活,并不能有效保证复活受到抑制,即紫外线消毒后出水中的微生物仍然存在高的复活风险.

Dark Treatment Effects on Photoreactivation Characteristics of Escherichia coli in a Tertiary Effluent Disinfected by UV

The effect of dark treatment on photoreactivation of Escherichia coli in a tertiary effluent disinfected by UV was studied. The effluent of sand filtration of a sewage treatment plant was disinfected by UV, kept in darkness for a period of time, and then put under photoreactivating light to investigate the photoreactivation. The experimental results indicated that the photoreactivation potential could recover immediately after water samples were kept in darkness for less than 6 h. The percentage photoreactivation of the water samples disinfected by UV with doses of 5 mJ/cm2 and 20 mJ/cm2 were 31.1% and 0.4%, respectively, and the photoreactivation rates were 1.67 x 10(4) CFU x (mL x h)(-1) and 125 CFU x (mL x h)(-1). When dark treatment time was prolonged to 24 h, the percentage photoreactivation and photoreactivation rates were lowered to 10.0% and 0.3%, 830 CFU x (mL x h)(-1) and 20 CFU x (mL x h)(-1), respectively. Those suggested that photoreactivation can only be weakened, but can not be controlled completely even after being kept in darkness for 24 h. So the safety concern on photoreactivation after UV disinfection of wastewater should be taken into account.