Membrane Technologies: A Double-Edged Sword for Water Treatment?

EPA Grant Number: FP917779
Title: Membrane Technologies: A Double-Edged Sword for Water Treatment?
Investigators: Beciragic, Alma
Institution: University of North Carolina at Chapel Hill
EPA Project Officer: Lee, Sonja
Project Period: September 1, 2015 through August 31, 2018
Project Amount: $132,000
RFA: STAR Graduate Fellowships (2015) RFA Text |  Recipients Lists
Research Category: Academic Fellowships

Objective:

The objectives of this study are three-fold: (1) to understand the chemical formations and organic leaching resulting from interactions between chemical disinfectants (chlorine, chloramine, chlorine dioxide, and ozone) and various high- and low- pressure drinking water treatment membranes, (2) to understand how these disinfectant/membrane interactions are affected by various physio-chemical and system configuration changes (pH, temperature, presence of ions, static versus dynamic systems), and (3) to understand potential health risks that may arise from the byproduct formations.

Approach:

Both static and dynamic systems (ie. as simple as mixing, or complex as a cross-flow system) will be used to study the reactions between the membrane/disinfectant. For preliminary testing, disinfectants will be dosed at a high level and membrane area will be increased to maximize the ability to measure analytes. Using gas chromatography coupled with an electron capture detector, halogenated byproducts can be measured according to US EPA method 551.1. Organic leaching can be assessed using a TOC analyzer, while aggregate halogenated byproducts can be measured using a Total Organic Halide analyzer (TOX). Initially, the disinfectant/membrane contact time for byproduct and leaching analysis will be 7 days; this will be adjusted as necessary to optimize analyte detection. Afterwards, experiments will be repeated at disinfectant doses that are more relevant to water treatment. The impacts of physio-chemical parameters on byproduct formation and leaching will also be explored by testing targeted combinations as determined by the literature. Sample extracts will be concentrated for a) structural analysis on LC-MS, and b) toxicological analysis using targeted assays.

Expected Results:

Preliminary results suggest that there are detectable levels of organic halides formed when high doses of chloramine come into contact with fully aromatic polyamide membranes (ESPA2 and SWC4+, specifically). Evidence from the literature suggests that greater disinfectant contact times, higher pH, and more concentrated ion presence are all associated with greater leaching from membranes. Moreover, the presence of ions in the matrix (ie. chloride or bromide) could affect which byproducts are formed and in what concentration. I hypothesize that similar trends will be seen with the various disinfectant/membrane combinations to be tested in this study.

Supplemental Keywords:

Membranes (Reverse Osmosis, Nanofiltration, Ultrafiltration, Microfiltration), Water Treatment, Disinfection, Disinfection By-products (DBPs), Organic Leaching, Potable Reuse