Effect of Copper(II) on Natural Organic Matter Removal During Drinking Water Coagulation Using Aluminum‐Based Coagulants: Fid-Bau Portal

Effect of Copper(II) on Natural Organic Matter Removal During Drinking Water Coagulation Using Aluminum‐Based Coagulants

Liu, Guojing / Zhang, Xiangru / Talley, Jeffrey W.

Abstract

Coagulation has been proposed as a best available technology for controlling natural organic matter (NOM) during drinking water treatment. The presence of heavy metals such as copper(II) in source water, which may form copper–NOM complexes and/or interact with a coagulant, may pose a potential challenge on the coagulation of NOM. In this work, the effect of copper(II) on NOM removal by coagulation using alum or PAX‐18 (a commercial polymerized aluminum chloride from Kemiron Inc., Bartow, Florida) was examined. The results show that the presence of 1 to 10 mg/L of copper(II) in the simulated waters improved the total organic carbon (TOC) removal by up to 25% for alum coagulation and by up to 22% for PAX‐18 coagulation. The increased NOM removal with the presence of copper(II) in the waters can most likely be ascribed to the formation copper–NOM complexes that may be more adsorbable on aluminum precipitates and to the formation of copper(II) co‐precipitates that may also adsorb NOM. The presence of 1 to 5 mg/L of copper(II) in the waters containing 3 mg/L NOM as carbon was reduced below the maximum contaminant level goal (1.3 mg/L as copper) using either coagulant. The results suggest that the presence of copper(II) in source water may not adversely affect the NOM removal by coagulation. A good linear correlation was observed between the TOC removal efficiency and the log‐total moles of the precipitated metals, which include the metal ion from a coagulant and the divalent metal ion(s) in source water.