污水厂出水经紫外线(UV)消毒后在排放过程中会出现微生物的复活现象,为此考察了采用UV—氯和UV—过氧乙酸(PAA)控制光复活的效果。经研究发现:在UV照射剂量为5.4mJ/cm2、投氯量为2.5 mg/L、反应时间为10 m in和UV照射剂量为5.4 mJ/cm2...污水厂出水经紫外线(UV)消毒后在排放过程中会出现微生物的复活现象,为此考察了采用UV—氯和UV—过氧乙酸(PAA)控制光复活的效果。经研究发现:在UV照射剂量为5.4mJ/cm2、投氯量为2.5 mg/L、反应时间为10 m in和UV照射剂量为5.4 mJ/cm2、过氧乙酸投量为10 mg/L、反应时间为10 m in的条件下,对大肠菌群的灭活率均可达4个对数级以上,并能控制光复活现象。从消毒稳定性、经济适用性、安全毒副性等方面考虑,可采用UV—PAA作为污水厂出水消毒及抑制光复活的技术。展开更多
Several disinfection processes of ultraviolet （UV）, chlorine or UV followed by chlorine were investigated in municipal wastewater according to the inactivation of Escherichia coli, Shigella dysenteriae and toxicity ...Several disinfection processes of ultraviolet （UV）, chlorine or UV followed by chlorine were investigated in municipal wastewater according to the inactivation of Escherichia coli, Shigella dysenteriae and toxicity formation. The UV inactivation of the tested pathogenic bacteria was not affected by the quality of water. It was found that the inactivated bacteria were obviously reactivated after one day in dark. Fluorescent light irradiation increased the bacteria repair. The increase of UV dosage could cause more damage to bacteria to inhibit bacteria self-repair. No photoreactivation was detected when the UV dose was up to 80 mJ/cm2 for E. coli DH5ct, and 23 mJ/cm2 for S. dysenteriae. Nevertheless, sequential use of 8 mJ/cm2 of UV and low concentration of chlorine （1.5 mg/L） could effectively inhibit the photoreactivation and inactivate E. coli below the detection limits within seven days. Compared to chlorination alone, the sequential disinfection decreased the genotoxicity of treated wastewater, especially for the sample with high NH3-N concentration.展开更多
The history of the repair of damaged DNA can be traced to the mid-1930s. Since then multiple DNA repair mechanisms, as well as other biological responses to DNA damage, have been discovered and their regulation has be...The history of the repair of damaged DNA can be traced to the mid-1930s. Since then multiple DNA repair mechanisms, as well as other biological responses to DNA damage, have been discovered and their regulation has been studied. This article briefly recounts the early history of this field.展开更多
The combination of low-dose ozone with ultraviolet （UV） irradiation should be an option to give benefit to disinfection and reduce drawbacks of UV and ozone disinfection. However, less is known about the disinfectio...The combination of low-dose ozone with ultraviolet （UV） irradiation should be an option to give benefit to disinfection and reduce drawbacks of UV and ozone disinfection. However, less is known about the disinfection performance of UV and ozone （UV/ozone） coexposure and sequential UV-followed-by-ozone （UV- ozone） and ozone-followed-by-UV （ozone-UV） expo- sures. In this study, inactivation of E. coli and bacterioph- age MS2 by UV, ozone, UV/ozone coexposure, and sequential UV-ozone and ozone-UV exposures was investigated and compared. Synergistic effects of 0.5-0.9 log kill on E. coli inactivation, including increases in the rate and efficiency, were observed after the UV/ozone coexposure at ozone concentrations as low as 0.05 mg-L-1 in ultrapure water. The coexposure with 0.02-mg.L-1 ozone did not enhance the inactivation but repressed E. coli photoreactivation. Little enhancement on E. coli inactivation was found after the sequential UV-ozone or ozone-UV exposures. The synergistic effect on MS2 inactivation was less significant after the UV/ozone coexposure, and more significant after the sequential ozone-UV and UV-ozone exposures, which was 0.2 log kill for the former and 0.8 log kill for the latter two processes, at ozone dose of 0.1 mg. t-1 and UV dose of 8.55 mJ. cm 2 in ultrapure water. The synergistic effects on disinfection were also observed in tap water. These results show that the combination of UV and low-dose ozone is a promising technology for securing microbiological quality of water.展开更多
文摘污水厂出水经紫外线(UV)消毒后在排放过程中会出现微生物的复活现象,为此考察了采用UV—氯和UV—过氧乙酸(PAA)控制光复活的效果。经研究发现:在UV照射剂量为5.4mJ/cm2、投氯量为2.5 mg/L、反应时间为10 m in和UV照射剂量为5.4 mJ/cm2、过氧乙酸投量为10 mg/L、反应时间为10 m in的条件下,对大肠菌群的灭活率均可达4个对数级以上,并能控制光复活现象。从消毒稳定性、经济适用性、安全毒副性等方面考虑,可采用UV—PAA作为污水厂出水消毒及抑制光复活的技术。
基金supported by the National Major Project of Science & Technology Ministry of China (No. 2008ZX07314-003,2009ZX07424-003)the National HiTech Research and Development Program (863) of China (No. 2008AA062501,2008AA06A414)
文摘Several disinfection processes of ultraviolet （UV）, chlorine or UV followed by chlorine were investigated in municipal wastewater according to the inactivation of Escherichia coli, Shigella dysenteriae and toxicity formation. The UV inactivation of the tested pathogenic bacteria was not affected by the quality of water. It was found that the inactivated bacteria were obviously reactivated after one day in dark. Fluorescent light irradiation increased the bacteria repair. The increase of UV dosage could cause more damage to bacteria to inhibit bacteria self-repair. No photoreactivation was detected when the UV dose was up to 80 mJ/cm2 for E. coli DH5ct, and 23 mJ/cm2 for S. dysenteriae. Nevertheless, sequential use of 8 mJ/cm2 of UV and low concentration of chlorine （1.5 mg/L） could effectively inhibit the photoreactivation and inactivate E. coli below the detection limits within seven days. Compared to chlorination alone, the sequential disinfection decreased the genotoxicity of treated wastewater, especially for the sample with high NH3-N concentration.
文摘The history of the repair of damaged DNA can be traced to the mid-1930s. Since then multiple DNA repair mechanisms, as well as other biological responses to DNA damage, have been discovered and their regulation has been studied. This article briefly recounts the early history of this field.
基金We acknowledge the financial support from the National Natural Science Foundation of China （Grant No. 51108117） and the Hong Kong Innovation and Technology Fund （No. ITS/336/09）.
文摘The combination of low-dose ozone with ultraviolet （UV） irradiation should be an option to give benefit to disinfection and reduce drawbacks of UV and ozone disinfection. However, less is known about the disinfection performance of UV and ozone （UV/ozone） coexposure and sequential UV-followed-by-ozone （UV- ozone） and ozone-followed-by-UV （ozone-UV） expo- sures. In this study, inactivation of E. coli and bacterioph- age MS2 by UV, ozone, UV/ozone coexposure, and sequential UV-ozone and ozone-UV exposures was investigated and compared. Synergistic effects of 0.5-0.9 log kill on E. coli inactivation, including increases in the rate and efficiency, were observed after the UV/ozone coexposure at ozone concentrations as low as 0.05 mg-L-1 in ultrapure water. The coexposure with 0.02-mg.L-1 ozone did not enhance the inactivation but repressed E. coli photoreactivation. Little enhancement on E. coli inactivation was found after the sequential UV-ozone or ozone-UV exposures. The synergistic effect on MS2 inactivation was less significant after the UV/ozone coexposure, and more significant after the sequential ozone-UV and UV-ozone exposures, which was 0.2 log kill for the former and 0.8 log kill for the latter two processes, at ozone dose of 0.1 mg. t-1 and UV dose of 8.55 mJ. cm 2 in ultrapure water. The synergistic effects on disinfection were also observed in tap water. These results show that the combination of UV and low-dose ozone is a promising technology for securing microbiological quality of water.
