Efficiency of the UV/H₂O₂ process for the disinfection of humic surface waters

Abstract

The efficiency of the UV/H₂O₂ process for the disinfection of total coliforms and the prevention of bacterial regrowth in humic surface waters were investigated. Inactivation of total coliforms was determined in water samples containing various concentrations ranging from 0–10 mg/L dissolved organic carbon (DOC) of fulvic acid, which were exposed to various doses (68–681 mWs/cm²) of UV radiation in the presence of 0.125 mg/L and 3.000 mg/L of hydrogen peroxide. Disinfection efficiencies of the UV radiation and the UV/H₂O₂ processes were compared. The results of bacterial inactivation experiments showed that the performances of the UV and the UV/H₂O₂ (0.125) were comparable whereas the UV/H₂O₂ (3.000) process showed significant improvement in performance, especially, in highly humic waters. Inactivation coefficient appeared to be almost doubled by the addition of 3.000 mg/L hydrogen peroxide during the treatment of highly humic waters. In contradiction to significant regrowth which occurred in the single UV radiation treatment, residual bacteria following the UV/H₂O₂ (0.125) and the UV/H₂O₂ (3.000) treatments were completely inactivated during dark incubation indicating the elimination of possible bacterial regrowth.

Keywords:

• UV disinfection
• total coliforms
• humic substances
• Hydrogen peroxide
• Fulvic acid
• regrowth
• inactivation
• surface water.

Acknowledgements

The authors would like to acknowledge Research Fund of Uludağ University for their financial support provided for this research Project 2002/77.

Notes

*R Squared = 0.971; UV:UV dose; FA: Fulvic acid concentration; H₂O₂: Hydrogen peroxide concentration.