Objective: To compare the effects of disinfection of chlorine dioxide (ClO2), sodium hypochlorite(NaClO) and their combination (ClO + NaClO) on simulative water samples.
Method: The simulative water samples containing 5.0 x 10(4) - 5.0 x 10(5) cfu/100ml Escherichia coli were prepared in laboratory and disinfected by different doses of chlorine dioxide, sodium hypochlorite and their combination for 60, 60, 30 + 60 min respectively. The kill ratio for Escherichia coli, and the residual chlorine dioxide, and the product of chlorite ion (ClO2-) and total residual chlorine were detected and compared by the membrane filter(MF) technique and electrometric titration.
Result: The minimum effective dosage (MED) for disinfect of simulative water samples were 0.4 mg/L of chlorine dioxide, 0.5 mg/L of sodium hypochlorite, and the 0.1 mg/L + 0.3 mg/L or 0.2 mg/L + 0.2 mg/L of their combination. By comparision with disinfection of ClO2 and NaClO alone, the residual chlorine dioxide increased 13.43% - 166.67% in simulative water sample under disinfection by the combination of ClO2 + NaClO, While chlorite ion decreased 13.11% - 19.97% and total residual chlorine increased 9.34% - 40.15%.
Conclusion: The combination of chlorine dioxide and sodium hypochlorite for disinfection of drinking water could achieve better effect of disinfection and decrease disinfection by-products as well.