Applying Green Chemistry to Resolve Membrane Backwash Recycle Stream Interferences with Conventional Coagulation Processes and the Replacement of Traditional Membrane Cleaning Solutions

In this work (partial results) a series of jar testing experiments were conducted to identify the impacts of tricarboxylic citric acid on the effectiveness of aluminum sulfate and ferric chloride coagulants. Acetic acid, a monocarboxylic acid, was also evaluated for the purposes of comparison with citric acid. Citric acid was found to adversely affect coagulation at lower acid to coagulant molar ratios than acetic acid, and coagulation interference thresholds for three different surface waters were identified for both acids based on settled water turbidity goals recommended by the U.S.EPA. Preliminary studies were conducted at the pilot scale where acetic acid was used in chemically enhanced backwashes (CEB). Initial data indicates that acetic acid serves as an effective substitute for citric acid CEB under the conditions tested.