Effects of O-3/Cl-2 disinfection on corrosion and opportunistic pathogens growth in drinking water distribution systems

The effects of O-3/Cl-2 disinfection on corrosion and the growth of opportunistic pathogens in drinking water distribution systems were studied using annular reactors (ARs). The corrosion process and most probable number (MPN) analysis indicated that the higher content of iron-oxidizing bacteria and iron-reducing bacteria in biofilms of the AR treated with O-3/Cl-2 induced higher Fe3O4 formation in corrosion scales. These corrosion scales became more stable than the ones that formed in the AR treated with Cl-2 alone. O-3/Cl(2 )disinfection inhibited corrosion and iron release efficiently by changing the content of corrosion-related bacteria. Moreover, ozone disinfection inactivated or damaged the opportunistic pathogens due to its strong oxidizing properties. The damaged bacteria resulting from initial ozone treatment were inactivated by the subsequent chlorine disinfection. Compared with the AR treated with Cl-2 alone, the opportunistic pathogens M. avium and L. pneumophila were not detectable in effluents of the AR treated with O-3/Cl-2, and decreased to (4.60 +/- 0.14) and (3.09 +/- 0.12) log(10) (gene copies/g corrosion scales) in biofilms, respectively. The amoeba counts were also lower in the AR treated with O-3/Cl-2. Therefore, O-3/Cl-2 disinfection can effectively control opportunistic pathogens in effluents and biofilms of an AR used as a model for a drinking water distribution system. (C) 2018 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.