Studying Of Inactivation Of Bacillus Subtilis By Chlorine Combined With UVC-LED In Water

If pathogenic microorganisms are present in drinking water sources,not only will it cause a large-scale outbreak of water-borne infectious diseases,but it will also threaten life safety and jeopardize the safety and stability of the society.Although the traditional chlorine disinfection process has many advantages,but with the discovery and in-depth study of new pathogenic microorganisms,it has found that most of which have resistance to chlorine,and the chlorine disinfection process will generate many the disinfection byproducts which have the potential harms of carcinogenicity,teratogenicity and mutation,so the conventional chlorine disinfection process will not meet people’s needs for safe water quality.Water plants have applied ultraviolet radiation to the disinfection process,it has the advantages of not producing disinfection byproducts and easy operation,however,there are problems such as failure to provide continuous disinfection capabilities.So this test combines chlorine with UV,not only it can reduce the dosage of chlorine,the production of disinfection byproducts,and provide continuous disinfection capabilities,but also the free radicals which is generated by the reaction can improve the inactivation efficiency.and Bacillus subtilis was selected as the representative microorganism that is hard to be inactivated,to explore the influence of changes in common water quality factors on inactivation effect,and conduct mechanism research.the following conclusions were obtained:（1）In the inactivation of bacillus subtilis by chlorine alone The inactivation efficiency increased with the increase of the chlorine concentration.When the concentration was 10mg/L and the inactivation reached 100min,the log inactivation rate reached 5.6,which is 1.8 times that of 2mg/L;Inactivation ability is stronger under acidic conditions,At p H6,the log inactivation rate was 5.7 at 100 min reaction,which was 19times that of p H9;Increasing the temperature within a certain range,the inactivation effect increases first and then decreases.When the temperature was 25℃,the inactivation rate is 5 at 100min reaction time,which is 1.3 higher than 5℃and 0.21 higher than 30℃;Manganese ion had an inhibitory effect on inactivation.When the concentration was 10mg/L,the log inactivation rate was 4.19,which is 0.81 less than 0 mg/L.（2）In the inactivation of bacillus subtilis by UVC-LED alone Increasing the temperature within a certain range,the inactivation effect increases first and then decreases,When the UV radiation dose was 100m J·cm^-2,the log inactivation rate at 40℃was 3.96,which was 1.33 higher than 5℃and 0.18 higher than 50℃;As the organic matter concentration increased,the inactivation effect decrease d to a certain extent.When the dose of UV radiation was 100m J·cm^-2,the log inactivation rate of 0mg/L was 3.82,and when it is increased to 10mg/L,it decreased by 0.51;The presence of manganese ions had inhibitory effect on inactivation.When the dose of ultraviolet radiation reached 100m J·cm^-2,the log inactivation rate of 0 mg/L was 3.82,and when it was increased to 10mg/L,it decreases by 0.56.（3）In the inactivation of bacillus subtilis by chlorine combine with UVC-LED After the chlorine concentration was saturated,hypochlorous acid wound scavenge with free radicals.After that,even if the concentration continued to increase,the inactivation effect wound not be greatly improved.When the dose of UV radiation was 100m J·cm^-2,the log inactivation rate of 10mg/L was 6.13,which is 1.48 more than 2mg/L,and 0.13less than 30mg/L;With the increased of p H value,the concentration of hypochlorous acid decreased,some hydroxyl radicals were annihilated,and the inactivat ion effect was significantly reduced.When the dose of UV radiation was 100m J·cm^-2,the logarithmic inactivation rate of p H6 was 6.59,which was 2.67 higher than that of p H9;Manganese ions could absorb ultraviolet rays and react with hypochlorous acid,it has inhibitory effect on inactivation.When the dose of UV radiation was 100m J·cm^-2,the log inactivation rate of 0mg/L was 5.9,which is an increase of 0.8 compared with 10mg/L.（4）In the study of inactivation mechanism Free radicals generated by chlorine combined with UVC-LED could effectively destroy the spore structure,it wound allows highly oxidizing substances such as hypochlorous acid to enter cells,causing damage to nucleic acids and enzymes.This prevented important activities such as replication and transcription,which ultimately led to cell death.