The Effect of Physicochemical Parameters on the Process of Water Disinfection Using Chitosan

Abstract

Increasing demands to the quality of drinking water necessitate the search for environmentally friendly and effective methods of its disinfection and purification. The purpose of this work was to study the disinfecting activity of chitosan (ChTS) obtained from natural polymer chitine in relation to E. coli and C. albicans depending on the physicochemical parameters of medium. It has been established that the degree of inactivation of E. coli culture does not depend on the type of ChTS used in this study: high-molecular ChTS₁ (molecular weight (Mw) = 100–300 kDa) and low-molecular ChTS₂ (Mw = 50–60 kDa) with the deacetylation degree of 95 and 75–85%, respectively. In the case of C. albicans, high-molecular weight ChTS with deacetylation degree of 95% is a more effective disinfecting agent. The highest degree of C. albicans inactivation by using ChTS₁ is achieved in a weak acid medium (pH 5.0), while at pH 8.5 the disinfecting effect is negligible. For the first time, a significant contribution of the process of flocculation of microorganisms by chitosan to the total effect of water disinfection has been shown that is especially pronounced at relatively short contact periods (< 1 h) of the culture with chitosan. It is shown that the presence of impurities of an organic and inorganic nature in water reduces both the disinfecting and flocculating effects of polysaccharide in relation to the microbiological objects. It is, probably, associated with the competing activity of these impurities on the interaction of ChTS molecules with microorganisms. The attained results confirm that C. albicans is a more reliable test object of disinfection processes as compared to E. coli that is of practical importance.