Effect of preozonation and prechlorination on total organic carbon removal in surface water treatment in Iran

Abstract

In drinking water treatment, prechlorination and preozonation are often applied in order to control micro-organisms and taste and odour causing materials, which may influence organics removal by pre-oxidation and adsorption. Using commercial and natural water humid substances, the positive effect of prechlorination and preozonation as an aid to coagulation-flocculation of these compounds were confirmed by the removal of total organic carbon (TOC). These experiments were conducted at bench-scale through a series of jar tests using different pH, coagulant dosage and TOC concentration of approx. 4, 8 and 12 mg/l. In addition to TOC removal, the existence of an optimum preozonation dose and an optimum prechlorination dose were also confirmed. Experiments show that prechlorination and preozonation can improve coagulation and flocculation depended on TOC concentration of influent surface raw water. The results demonstrate a differential effect between prechlorination and preozonation on removal of TOC. Preozonation showed a positive effect on a system with low influent TOC and very low molecular weight (noncolloidal) humic substances.