טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentShulman Arina
SubjectInvestigation of Pre-Disinfection by Chlorine Dioxide in
Water Containing Natural Organic Matter and
Bromides
DepartmentDepartment of Civil and Environmental Engineering
Supervisor Professor Emeritus Nava Narkis


Abstract

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.