Disinfectant efficacy of chlorite and chlorine dioxide in drinking water biofilms

• Published in: Water research (Oxford) 2005-05, Vol.39 (9), p.1809-1817
• Main Authors: Gagnon, G.A., Rand, J.L., O’Leary, K.C., Rygel, A.C., Chauret, C., Andrews, R.C.
• Format: Article
• Language: English
• Subjects: antimicrobial agents; Applied sciences; Bacteria - drug effects; Bacteria - growth & development; Biofilm; Biofilms - drug effects; Biofilms - growth & development; Biological and medical sciences; Bioreactors; Biotechnology; Chlorides - pharmacology; Chlorine Compounds - pharmacology; Chlorine dioxide; Chlorite; chlorite (mineral); Colony Count, Microbial; disinfectants; Disinfectants - pharmacology; Disinfection; Distribution system; drinking water; Environment and pollution; Exact sciences and technology; Fundamental and applied biological sciences. Psychology; Heterotrophic bacteria; Industrial applications and implications. Economical aspects; Iron; Other industrial wastes. Sewage sludge; Oxides - pharmacology; Pollution; Polycarboxylate Cement; Wastes; Water Microbiology; Water Purification - methods; Water Supply; water treatment; Water treatment and pollution
• ISSN: 0043-1354; 1879-2448
• DOI: 10.1016/j.watres.2005.02.004

The drinking water industry is closely examining options to maintain disinfection in distribution systems. In particular this research compared the relative efficiency of the chlorite ion (ClO 2 −) to chlorine dioxide (ClO 2) for biofilm control. Chlorite levels were selected for monitoring since they are typically observed in the distribution system as a by-product whenever chlorine dioxide is applied for primary or secondary disinfection. Previous research has reported the chlorite ion to be effective in mitigating nitrification in distribution systems. Annular reactors (ARs) containing polycarbonate and cast iron coupons were used to simulate water quality conditions in a distribution system. Following a 4 week acclimation period, individual ARs operated in parallel were dosed with high (0.25 mg/l) and low (0.1 mg/l) chlorite concentrations and with high (0.5 mg/l) and low (0.25 mg/l) chlorine dioxide concentrations, as measured in the effluent of the AR. Another set of ARs that contained cast iron and polycarbonate coupons served as controls and did not receive any disinfection. The data presented herein show that the presence of chlorite at low concentration levels was not effective at reducing heterotrophic bacteria. Log reductions of attached heterotrophic bacteria for low and high chlorite ranged between 0.20 and 0.34. Chlorine dioxide had greater log reductions for attached heterotrophic bacteria ranging from 0.52 to 1.36 at the higher dose. The greatest log reduction in suspended heterotrophic bacteria was for high dose of ClO 2 on either cast iron or polycarbonate coupons (1.77 and 1.55). These data indicate that it would be necessary to maintain a chlorine dioxide residual concentration in distribution systems for control of microbiological regrowth.