Inactivation Efficiency And Mechanism Of Fungi With UV And UV Based AOPs In Drinking Groundwater Supply System

Pathogenic microorganisms in drinking water have received increasing attentions in the last decades.The outbreak of fungi in drinking groundwater sources can prod uce taste and odor problems,cause toxicity and form lots of visible flocs.Some species can be potentially pathogenic,allergenic,and toxigenic species,it can be associated with health related effects such as skin lesions,allergy reactions and systemic infections especially towards insusceptible individuals.However,only Swedish water authority has a regulation to restrict the quantity of fungi?lower than 100 CFU/100 m L?in drinking water supply system.The primary goals of this study are to explore the inactivation efficiency of UV,UV based advanced oxidation processes?AOPs??UV-PMS/PS/H₂O₂?and sequential inactivation?UV/Cl₂?towards Trichoderma sp.,Penicillium sp.,Acremonium sp.,Cladosporium sp.Also,this study evaluated the enhancement of UV-AOPs towards fungi inactivation in phosphate buffer saline?PBS?and actual groundwater background.Furthermore,the factors that affecting inactivation by UV alone and UV/PMS were investigated.In addition,this study also discussed the difference of sequential inactivation?UV/Cl₂?towards fungi inactivation.Last but not least,the inactivation mechanisms were discussed by monitoring the release of intracellular matters?DNA,protein and ATP?and the morphology's change using scanning electron microscope?SEM?.The result of research shows that:?1?The inactivation of fungal spores is consistent with first-order kinetics.The resistance to UV is in order: Cladosporium sp.>Penicillium sp.>Acremonium sp.>Trichoderma sp.,which is far outweighing E·coli due to the bigger cell size,different composition of cell wall and structurally more complex.UV-PMS/PS/H₂O₂ showed enhanced effect towards fungi spores inactivation,PMS shows the best enhancement towards UV inactivation,and then PS,the last is H₂O₂.Inactivation efficiency of UV/Cl₂ : Cl₂-UV sequential disinfection>UV-C l2 sequential disinfection>UV/Cl₂ concurrent disinfection.C l2-UV sequential disinfection is recommended while Cladosporium sp.and Penicillium sp.are dominant genera in source water,on the other side,UV-Cl₂ sequential disinfection showed best enhancement while Cladosporium sp.is the dominant genus.?2?With the increase of PMS dosage from 0.05 to 0.3 mM,the inactivation efficiency of fungal spores can increase significantly.High dosage oxidizing agent?UV dosage: 40 m J/cm2,PMS dosage: 0.3 m M?could inactivate all the fungi spores in a short hydraulic retention time.The actual groundwater showed greater influence towards Trichoderma sp.,Cladosporium sp.and Penicillium sp.inactivation,and the major influencing parameters are DOC,iron and manganese.Besides,the inactivation efficiency of UV/PMS was influenced slightly by actual groundwater than UV alone.?3?Extracellular DNA and protein level maintain low and stable while UV disinfection,whereas DNA and protein increase with the disinfection time while chlorine or UV/PMS disinfection.With the increase of DNA and protein level in order: Cladosporium sp.>Penicillium sp.>Acremonium sp.>Trichoderma sp.,which is in accordance with the order of spore's size.For all the four genera of fungal spores,the total ATP does not change anymore.During UV irradiation,no intracellular ATP is released for all the four genera of fungal spores.However,chlorine or UV/PMS increases the level of extracellular ATP significantly.The intracellular ATP increase is in accordance to the cell size.The results showed that VBNC spores exist,which are in a dormant state.Before inactivation,the surface of spores is smooth,and the shape of spores look full and barely wrinkled.After UV inactivation,the spores look integrity as well but just shrinks a little.However,after the inactivation by chlorine or UV/PMS,the shape of spores changes a lot,some of them crack and some surface become sunken.