The Growth And Outbreak Of Filamentous Fungi In Groundwater And Its Inactivation Using Chlorine Dioxide

Fungi are a kind of heterotrophic eukaryotic microorganisms,including single cell yeasts and multicellular filamentous fungi.Filamentous fungi are widespread in the water resources,it can breed and spread in water.The fungus can enter drinking water distribution system through several pollution ways,including breakthrough of water treatment process,deficiencies in stored water facilities cross-connections,mains breaks and intrusions,and during mains installation and maintenance.Once introduced,the fungus can survive on the inner surface of the pipe and form biofilms within the pipe system,or can be suspended in water.And once there is outbreak of fungi in the water supply system,it can cause serious harm to human health through drinking water and taking a shower.This paper mainly discusses the growth of three dominant genera of filamentous fungi in groundwater and culture medium,influence of environmental conditions(temperature,pH)and nutrients(carbon,nitrogen and phosphorus)on the growth of fungi,formation of fungal biofilm,inactivation efficiency and kinetic of fungi with chlorine dioxide,the influencing factors,inactivation mechanism.The main conclusions are as follows:(1)The growth process of fungi was not divided into adaptive phase,logarithmic phase,stationary phase and decline phase,but was roughly divided into growth demurrage phase,rapidly growing phase,decline phase.The influence of pH and temperature on the fungal growth was important,an alkaline environment was easy for fungi to grow,suitable temperature range for the growth of fungi was 20 ~ 25 ?.Among the three nutrients,carbon had the greatest impact,followed by phosphorus,and finally nitrogen.The effect of iron manganese concentration on the growth of fungi was very small,which could be neglected,but the carbon and nitrogen ratio had a great influence on it,and 10:1 was the most suitable the carbon nitrogen ratio for the growth of fungi.(2)Chlorine dioxide is one kind of disinfectant that can effectively inactivate fungal spores and more effective than free chlorine.The inactivation process of fungal spores chlorine dioxide fitted with Chick – Watson model well,different fungal spores showed different resistance to chlorine dioxide,resistance of three kinds of spore is in order : Cladosporium sp.> Trichoderma sp.> Penicillium sp.,fungi is more resistant to chlorine dioxide than bacteria.Within a certain range,the increase of the concentration of chlorine dioxide and rising temperature will enhance the inactivation efficiency of chlorine dioxide for fungus,and the presence of humic acid can inhibit inactivation of fungal spores with chlorine dioxide,the influence of groundwater matrix is negative.(3)The leakage of intracellular material,the increase of extracellular ATP,the leakage of intracellular DNA and proteins,and changes of the morphology of spores after inactivated with chlorine dioxide showed that chlorine dioxide had strong oxidation,which can destroy the cell wall and cell membrane of fungal spores,resulting in fungal spore inactivation.(4)The inactivation of fungal biofilm is more difficult than fungal spores with chlorine dioxide.When the concentration of chlorine dioxide was 40 mg/L,the contact time was 60 minutes,the highest inactivation efficiency for three kinds of fungal biofilm was about 60%.The results also showed that the resistance of fungal biofilm to chlorine dioxide was much greater than that of fungal spores.