Title

Applying Green Chemistry To Resolve Membrane Backwash Recycle Stream Interferences With Conventional Coagulation Processes And The Replacement Of Traditional Membrane Cleaning Solutions

Abstract

Ultrafiltration is a membrane process that separates suspended solids from water streams, similar to conventional media filters; however, unlike media filtration, UF membrane filtration is capable of removing colloidal, microbiological and other particles much smaller than what conventional filters can remove. UF technology has gained acceptance within the drinking water community for use in treating surface water supplies in the production of drinking water. UF has, in many instances, replaced media and/or sand filters in conventional coagulation, flocculation, sedimentation and filtration facilities. However, an unintended consequence of this decision is the introduction of cleaning systems for UF that would not have been present for conventional filtration facilities, which may result in non-compliance with the EPA's filter backwash-recycle rule (FBRR) if such chemicals enter the backwash or supernatant streams common to conventional treatment facilities and disrupt the coagulation process. 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. Further testing is ongoing to confirm findings presented herein. © 2012 American Water Works Association.

Publication Date

12-31-2012

Publication Title

AWWA/AMTA Membrane Technology Conference and Exposition 2012

Number of Pages

732-742

Document Type

Article; Proceedings Paper

Personal Identifier

scopus

Socpus ID

84871563184 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/84871563184

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