Formation of ineffective chlorine during humic Biotin-HPDP chlorination were conducted in 45-mL glass screw-cap amber vials with PTFE-lined septa under headspace-free condition at room temperature (25 ± 1 °C) and pH 7.0 (5 mM phosphate buffer). The applied free chlorine dose was 5 mg/L as Cl2. The dissolved organic carbon (DOC) concentrations of humic acid were varied from 0 to 15 mg-C/L. After 30 min reaction, the total chlorine, free chlorine, NH2Cl and ineffective chlorine were determined.
To investigate the aldosterone composition of residual chlorine including ineffective chlorine in finished and tap waters, the total chlorine, free chlorine, NH2Cl and ineffective chlorine in four collected water samples (DWTP1, TW, DWTP2 and DWTP3) were examined. DWTP1 sample was stored in dark at room temperature (25 ± 1 °C) to study the ineffective chlorine change over time. The total chlorine, free chlorine, NH2Cl and ineffective chlorine were measured at 4 h, 24 h and 48 h, respectively.