|Ph.D Student||Shulman Arina|
|Subject||Investigation of Pre-Disinfection by Chlorine Dioxide in|
Water Containing Natural Organic Matter and
|Department||Department of Civil and Environmental Engineering||Supervisor||Professor Emeritus Nava Narkis|
Before the problem of Trihalomethanes arose, it was customary to carry out pre-disinfection with chlorine in order to reduce the load of bacterial pollution in the course of contaminated water treatment. After realizing that pre-disinfection with chlorine, created a large amount of haloorganic compounds hazardous to human health, the chlorine pre-disinfection was prohibited.
The main objective of this research was to explore the possibility of reinstating the pre-disinfection with chlorine dioxide, ClO2, as an alternative disinfectant to chlorine.
From the research results, reliable and effective method of treating problematic water polluted by natural organic matter and microorganisms, a method that includes both disinfection and physico-chemical treatment stages is recommended. It can be suggested to reinstate the pre-disinfection with ClO2, at a large dose of over 3.0 mg/L ClO2. Then, the removal of the residues of ClO2 and chlorite ions by adding Fe+2 ions which will be oxidized to Fe+3 and act as flocculant, will economize the FeCl3 dose, which is used for removing the humic compounds by flocculation. This is followed by adsorption on GAC in order to remove a significant part of the soluble organic substances and the few haloacetic acids created during the pre-disinfection with the ClO2. At the end of the treatment, the second disinfectant should be added, i.e. ClO2 or chlorine at the final disinfection stage, which will prevent the re-growth of microorganisms in the water supply system, and enable to make the utmost of the treatment and produce healthy and safe drinking water.