Studies On Risk And Controlling Of Opportunistic Pathogenic Bacteria In Tap Water In Drinking Water Distrubtion System

The water quality of drinking water,which was affected by many factors,is vital important to people's safe life.In this study,the control of Opportunistic Pathogens(OPs)in different water treatment processes of drinking water treatment plants(DWTPs)were investigated.Moreover,the effects of UV-ultrafiltration on the control of OPs in tap water were studied.Meanwhile,and the influence of ultraviolet(UV)on the microbial community structure in ultrafiltration and filtered water were analyzed.Based on the results of this study,it would be prudent,to provide insight into factors that may facilitate in controlling OPs growth in drinking water.(1)Effects of different drinking water treatment processes on OPs controlWater samples collected from four different drinking water distribution systems in eastern China were investigated according to quantitative PCR(Q-PCR),which is a fast,reliable,safe and culture-independent method,and the health risks of OPs in drinking water were also evaluated by Quantitative Microbial Risk Assessment(QMRA).The results are as follows:(a).turbidity and CODMn removal by coagulation/sedimentation decreases the availability of attachment and growth sites for OPs.O3-BAC(66%-98%)was more effective in removing OPs than BAC(20%-78%).(b)Using canonical correspondence analysis(CCA),it was found that residual chlorine in water was negatively correlated with OPs,HPC and total bacteria(16S r RNA),and disinfection was the most critical process for OPs removal(50%-99%).(c)QMRA analysis suggests annual infection risks of Mycobacterium avium were all between 10-3-10-4,exceeding the U.S.EPA level and the WHO benchmark risk level.(2)Controlling of OPs in tap water using UV-ultrafiltration treatmentThe results indicated that self-made UV treatment equipment can decrease the regrowth of OPs in tap water effectively.(a)OPs removal in the effluent of ultrafiltration membrane were10%-100%,the EPS is reduced by 9%,and the ATP is reduced by 39%.(b)UV treatment also reduces the growth of microorganisms on the surface of the ultrafiltration membrane.ATP and EPS on the ultrafiltration membrane are reduced by 39% and 3%,and the removal rate of OPs is5% to 11%.(c)Hydroxyl radicals and superoxide radicals generated after UV treatment increase the membrane flux of the ultrafiltration membrane,which improves the disinfection effect,resulting in a significant decrease in the OPs content of the ultrafiltration membrane effluent,and the content of microbes on the membrane and the secretion of extracellular polymeric substances reduced apparently.(3)Effect of UV on microbial community structure by ultrafiltrationThe results of high-throughput sequencing technology showed that the UV treatment reduced the diversity and richness of ultrafiltration membranes and microbial colonies in the effluent and in the membrane as well.Besides,the microbial community,especially bacterial composition was remarkably affffected by ultraviolet.