ZhengXingyu,MaMingliang,YuanRui,et al.Residual Chlorine Variation and Disinfection Byproducts Formation during Emergency Disinfection with NaClO in Wastewater Treatment Plants[J].China Water & Wastewater,2026,42(15):21-29.
Residual Chlorine Variation and Disinfection Byproducts Formation during Emergency Disinfection with NaClO in Wastewater Treatment Plants
China Water & Wastewater[ISSN:1000-4062/CN:12-1073/TU]
volume:
第42卷
Number:
第15期
Page:
21-29
Column:
Date of publication:
2026-08-01
- Keywords:
- emergency disinfection; chlorine dioxide (ClO2); sodium hypochlorite (NaClO); available chlorine consumption pattern; disinfection byproducts (DBPs)
- Abstract:
- ANaClO is commonly used as an emergency disinfectant in wastewater treatment plants （WWTPs）that employ ClO2 as the primary disinfection process. However, the decay patterns of residual chlorine, the formation characteristics of disinfection byproducts (DBPs), and the effectiveness of NaClO in responding to typical high chlorine-consuming pollutants during emergency disinfection remain unclear, which limits the reliability and safety in practical applications. To address this, this study systematically investigated the variations in residual chlorine and the generation patterns of DBPs during emergency NaClO disinfection, as well as its response efficacy to high chlorine-consuming pollutants, using influent from the contact tanks of ten WWTPs in Chongqing that adopt ClO2 as the primary disinfectant. The results showed that as the NaClO dosage increased, the effective chlorine consumption gradually stabilized within 45 minutes (the designed hydraulic retention time of the contact tank). The theoretical maximum chlorine demand for WWTPs in Chongqing ranged from 4.3 mg/L to 9.3 mg/L. Meanwhile, the residual ClO2 concentration in the disinfected effluent increased with higher NaClO dosages. Regarding DBPs, the formation of trichloromethane (TCM) tended to stabilize with increasing NaClO dosage, whereas the formation of trichloroacetic acid (TCAA) continued to rise, indicating that TCAA was a key byproduct requiring focused control during emergency disinfection. Compared to phenolic and amine organic pollutants,NO2- and Fe2+ exerted a more significant impact on the ClO2 disinfection system. Pilot-scale experiments further confirmed that an emergency NaClO dosage of 10-15 mg/L could effectively offset the influence of 10 mg/L NO2-/Fe2+ on the total effective residual chlorine in the effluent.
Last Update:
2026-08-01