ENHANCED COAGULATION: DETERMINATION OF CONTROLLING CRITERIA AND AN EFFECT ON TURBIDITY REMOVAL

doi:2005.10.3.105

Environmental Engineering Research 2005;10(3): 105-111. DOI: https://doi.org/10.4491/eer.2005.10.3.105

Department of Civil Engineering, Kyungnam University, Masan, Korea

Received: November 9, 2004; Accepted: April 9, 2005.

ABSTRACT

The applicability of the USEPA's (United States Environmental Protection Agency) three criteria of enhanced coagulation (criterion I-TOC level less than 2 mg/L before chlorination; criterion II-% requirement of TOC removal; criterion Ill-point of diminishing return) for Korean waters was evaluated in this study. This study also investigated an effect of enhanced coagulation on turbidity removal, and attempted to identify the best coagulant for enhanced coagulation. Three different waters were used in this study: one river water and two lake waters. Five different coagulants were used: alum, liquid alum, PAC1, ferric chloride with and without water. Results of this study showed that all three criteria were achievable for the tested waters. For these waters, controlling criterion was found to be different depending upon raw water characteristics. When initial TOC level was low (< 4 mg/T), criterion I (< 2 mg/L) could be the controlling criterion. As TOC level increased, criterion II (% TOC removal) became the controlling criteria. It was possible to achieve different goals of turbidity and TOC removals. Although the optimum region of TOC removal was more acidic than that of turbidity removal, there was no conflict between these two removals. The best coagulant was found to be different depending upon the evaluation tool: maximum and optimum removal. Ferric chloride was more effective than alum in terms of the maximum TOC removal, while Al-based coagulant such as alum or PAC1 was the best coagulant in terms of the optimum TOC removal.

Keywords: enhanced coagulation | controlling criteria | turbidity removal | best coagulant | optimum TOC removal