Photoinactivation of Escherichia coli and Enterococcus hirae in aqueous solution

Abstract

Water is essential to sustain all human related activity. However, water pollution due to different type of contamination limits its use. Among the different contaminating agents that may be present in water, coliforms poses a serious threat to the quality of water as it can lead to several diseases including cholera, dysentery, diarrhoea etc. therefore removal of these microorganisms from water prior to its use is usually carried out by a process commonly referred to as disinfection.Disinfection is often a chemical unit operation which commonly uses chlorine, hypochlorite, chloramines, chlorine dioxide, bromine and ozone. Among these, chlorine is the most widely used disinfectant for both drinking water and tertiary treatment of wastewaters. Its popularity is due to a high oxidizing potential that provides a minimum level of residual chlorine throughout the distribution system and protects against microbial recontamination. However, it has now been realized that the disinfection by-products due to the chlorination process has both carcinogenic and mutagenic effects on mammals, and therefore, its validity has become questionable. Due to this concern, recent research is focussed towards novel disinfection methods. Compared to the existing chemical methods for disinfection, photosensitization method using photoactive compounds appears more promising due to its easy implementation and low cost. It involves the combination of three non-toxic substance, i.e. a photosensitizer, light and molecular oxygen to achieve the purpose. Although, this technique has been found successful for medical applications, it is not well studied for wastewater applications.