| In the past, one of the greatest concerns for the water consumers with the increasing respect to the quality of drinking water is contamination with pathogenic microorganisms. Recently, fungi have received increased focus as drinking water contaminants. The water treatment technological process is only using free chlorine for disinfecting water in underground plant. The disinfection effect of fungi in drinking water is limited. However, the growth of fungi in water distribution systems changes not only the water taste and odour for the worse but also may cause technological and operational difficulties. Recently, the fungi in the underground water will explode, which lead to a large number of visible floc particle in drinking water and seriously affect the quality of water.In this paper, we studied the effects of chlorine, ozone, UV and combined process(ozone/chlorine and UV/chlorine) on the inactivation of fungi, and obtained the optimal conditions of the process. The inactivation dynamics was analysed for the disinfection alone. Meanwhile, we explored how the water quality(pH, temperature, ammonia nitrogen, turbidity, organic matter, alkalinity) influence the inactivation effect. The different effects of chlorine inactivation on three kinds fungi spores were studied. The mechanism of chlorine inactivation was studied by scanning electron microscope(SEM) and hydrophobicity. The main results and conclusions of this paper are as following:(1)The optimal dosage of disinfectant is 2.0 mg/L chlorine with 30 min cantact time by using chlorine alone. The revised of Hom model which the inactivation rate constant was expressed as a function of pH and temperature was expressed as following: ln(Nt/N0)=-0.67(0.63)pH(1.07)TC1.47t0.65, the disinfection kinetic model would accurately simulate the disinfection process. The quality of raw water has a significant effect on the inactivation efficiency and it effects mainly by changing the physical and chemical properties of free chlorine, particulate matter protection, consumption of free chlorine. With the same condition, the effect sequence of inactivation efficiency on the four fungi spores: trichoderma spp., penicillium spp., cladosporium spp.. As the cellualar organell were not found on the SEM picture, we inferred that the main reactive part of chlorine inactivation may be the cell wall and cell membrane.(2)The optimal dosage of disinfectant is 1.0 mg/L ozone with 15 min cantact time by using ozone alone. The ozone disinfection process followed first-order kinetics with the rate constant k of 0.073~0.129 L/mg·s. The sequential disinfection of ozone and chlorine in inactivating fungi is a kind of synergistic effect, which is enhanced with the increase of ozone concentration and contact time. The optimal dosage of combined process is inactivated by 3 min action of 1.0 mg/L ozone pretreatment followed by 15 min action of 2.0 mg/L chlorine.(3) Under the same UV dose(I·t), UV intensity(I) has some influences on the inactivation and higher UV intensity can get good inactivation effect by using UV alone. 97.5% of fungi could be inactivated with the UV dose 100 mJ/cm2 and it could not be completely inactivated by using UV alone. The optimal dosage of disinfectant is using the combination of UV and chemical reagents. The sequential inactivation of UV and chlorine in inactivating fungi is a kind of synergistic effect. The UV disinfection process followed first-order kinetics with the rate constant k of 0.044~0.077 cm2/mW·s. The inactivation effect of higher UV dose and lower chlorine concentration could be equal to that of lower UV dose and higher chlorine concentration under UV-chlorine combination process. The optimal dosage of combined process is inactivated by 30 mJ/cm2 UV pretreatment followed by 30 min action of 1.0 mg/L chlorine. |
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