Influencing Factors Of Virus Inactivation In Drinking Water By Ozone And Chlorine Disinfection

With the development of science and technology, source water has been polluted in different levels. Free chlorine disinfection is the common virus inactivation methods in drinking water plant. It is widely used in disinfection process due to its inactivation ability, easy using and cheaply cost. However, during chlorine disinfection, some disinfection byproducts are generated from the creation of organic matter such as human acid and fulvic acid and chlorine. In order to reduce byproducts generation, ozone and combination processes are emerged as requied. Furthermore, most researches about virus inactivation focused on the fields of hygiene or hospital disinfection, the results of which could offer little guidance to drinking water disinfection processes. As a result, researches about virus disinfection for drinking water are in urgent need.This study researched influence factors of free chlorine and ozone disinfection with MS2coliphage as indicators, such as temperature, pH, organic matter, inorganic particles and ions, compared virus inactivation effect in continous drinking water treatment and measured the virus doses in drinking water plant.The results of ozone inactivating MS2phages in the short-term batch showed that, in deionized water, when the initial dosage of ozone was0.25mg/L, the titer of viruses decreased by4log (99.99%inactivation), which achieved USEPA standards. The CT value was0.32mg·min/L. In purified water, lmg/L ozone was needed to decrease4log titer of viruses and the CT value was5mg·min/L. In all factors, pH, organic matter and Br-, I-ions had great effect on ozone inactivation MS2, temperature and particulate matter had a little effect while ammonia nitrogen and Cl-had no effect on ozone inactivation. As for the kinetic models, Chick model or Chick-Watson model were suitable for describing the survival curves with high ozone dose or low influence factors which were linear and first-order. Hom model can describe the curves which were biphasic or upward concave, but the STDEV of parameter were too high. Jason model were regarded as the most suitable model to describe ozone inactivation MS2.The results of free chlorine inactivating MS2phages in the short-term batch showed that, in deionized water, when the initial dosage of free chlorine was1mg/L, the titer of viruses decreased by4log (99.99%inactivation), which achieved USEPA standards. The CT value was0.8mg·min/L. In purified water,2mg/L ozone was needed to decrease4log titer of viruses and the CT value was180mg·min/L. In all factors, pH, temperature, ammonia nitrogen and organic matter had certain effect on ozone inactivation MS2, Br-,I-and Cl-ions had no effect on ozone inactivation. As for the kinetic models, Chick model or Chick-Watson model were suitable for describing the survival curves with high ozone dose or low influence factors which were linear and first-order. Hom model can describe the curves which were biphasic or upward concave, but the STDEV of parameter were too high. Jason model were regarded as the most suitable model to describe ozone inactivation MS2.In the continuity testing,1mg/L ozone or2mg/L free chlorine were needed to achieved4log reduced of virus. In the combination processes, ozone and free chlorine had synergistic effect.0.5mg/L ozone and0.25mg/L free chlorine could inactivated41og MS2phage. As for the treatment processes, coagulative precipitation and sand filtration processes inactivated lots of MS2, for example coagulative precipitation could reduce3log MS2, while filtration could reduce llog. However, biological activated carbon process increased0.08-1.31og MS2.The result of investigation of virus occurrence in outflow of various process units in drinking water plants showed that, the concentrations of MS2phages were approximately103-104PFU/100L. It had highest dose in summer, then in spring and autumn, and winter had lowest dose of MS2. Coagulative precipitation could reduce3log MS2, and no MS2were detected in filtrated water. There were not MS2nor detected in disinfection outflow and final effluent of both drinking water plants.