Reduction of organic matter and disinfection by products formation at surface water treatment plants in Egypt

Abstract

Although the removal of colloidal particles continues to be an important reason for using coagulation, currently a newer approach, the removal of organic matter to reduce the formation of disinfection byproducts (DBPs) such as trihalomethanes (THMs) are suspected carcinogens. Inefficient removal of total organic carbon (TOC) leads to the formation of carcinogenic THMs. This motivates the research efforts to find a way to reduce them in potable water. The first objective of this research is monitoring the water quality (raw and produced) for selected three water treatment plants within Giza Governorate to reveal the most polluted site (high TOC in the raw water and THMs in the treated water) in the study areas. The second objective of this study is enhancing coagulation to reduce TOC and THMs from surface water treating. In this study, two different coagulants aluminum sulfate (alum), and ferric chloride were tested under different conditions of pH and coagulant concentration to determine their effectiveness for removal of TOC, THMs and turbidity. Optimum values for the mentioned conditions were used to achieve the maximum reduction for TOC and THMs in Al-Ayat drinking water treatment plant (DWTP) which recorded the highest concentration of TOC and THMs. Ferric chloride as a coagulant achieved the maximum removal percentage % of TOC, THMs and turbidity as 79%, 82% and 94%, respectively, at ferric chloride dose 100 mg/L, while alum as a coagulant recorded the maximum removal percentage % of TOC, THMs and turbidity as 46%, 52% and 91%, respectively, at alum dose 100 mg/L. The results indicated that ferric chloride as a coagulant has the highest efficiency reduction of TOC, THMs and turbidity if compared to alum with the same dose added.

Keywords

• Surface water
• TOC
• THMs
• alum
• ferric chloride