Chlorine dioxide drinking water pre-oxidation and disinfection: A review of its effectiveness, mechanisms, and disinfection by-products
M. Mzinyathi, V. Muthuraj, E. O. Ajala, Babak Kakavandi, S. Janse van Rensburg, Thabo T.I. Nkambule, Gcina Mamba
Abstract
Effective drinking water disinfection requires robust microbial inactivation with minimal disinfection by-product (DBP) formation. Chlorine dioxide (ClO 2 ), a potential alternative to chlorine (Cl 2 ), has gained significant attention in this context. This review provides a comprehensive analysis of ClO 2 in drinking water pre-oxidation and disinfection, exploring its properties, generation, and mechanisms against diverse microbes, including resistant fungal spores, viruses, and bacteria. Key findings highlight ClO 2 superior efficacy, with some studies showing significantly higher pathogen inactivation rates (e.g., 98 % S. aureus reduction at 1.5 mg/L ClO 2 vs. 2.5 mg/L Cl 2 ) and reduced DBP formation (e.g., 30.3 and 5.4 times less total THMs and HAAs, respectively, compared to Cl 2 disinfection). Also, the review highlights the effectiveness of ClO 2 in pre-oxidation, particularly manganese and iron removal, and taste and odour control, and oxidation of emerging pollutants such as pharmaceuticals. In addition, the formation of DBPs during ClO 2 application, their control, regulatory frameworks, have been discussed. Finally, the review highlights some of the challenges and future direction for ClO 2 disinfection to ensure successful global adoption. This review will be a valuable resource for water treatment utilities and researchers involved in water disinfection research, and also influence the development and modification of current drinking water standards to factor in a more comprehensive monitoring programme for DBPs. • ClO 2 shows versatility and effectiveness towards disinfection and oxidation of EMPs. • Microbial inactivation via oxidation of cell covers and leakage of cell contents. • Lower formation of organic DBPs in ClO 2 disinfection compared to Cl 2 . • Optimised ClO 2 dosing to balance effectiveness and DBP control. • ClO 2 based hybrid processes offer better disinfection and DBP control.