Demonstrating ultra-filtration and reverse osmosis performance using size exclusion chromatography

Area of Science:

• Environmental Science
• Water Treatment Technologies
• Analytical Chemistry

Background:

• Advanced water treatment plants utilize ultrafiltration (UF) and reverse osmosis (RO) for high-quality recycled water.
• Assessing the performance of these membrane processes is crucial for ensuring water quality and suitability for purpose.

Purpose of the Study:

• To quantify and characterize the removal of dissolved organic carbon (DOC) throughout a UF/3-stage RO pilot plant.
• To evaluate the effectiveness of UF and RO stages in removing different fractions of organic matter.
• To understand changes in DOC character and their implications for process performance assessment.

Main Methods:

• Utilized size exclusion chromatography (SEC) with organic carbon, organic nitrogen, and UV(254) detection.
• Analyzed DOC concentration and character changes across a UF/3-stage RO pilot plant.
• Quantified removal efficiencies for different organic matter fractions.

Main Results:

• Achieved an average removal of 97% of influent DOC, producing water with less than 0.5 mg L(-1) of carbon.
• UF removed over half of the biopolymer fraction (4.5% DOC removal).
• RO removed most DOC, with minor exceptions of low molecular weight humics, acids, and neutral fractions, indicating altered rejection mechanisms.

Conclusions:

• Total organic carbon (TOC) monitoring is important, but analyzing DOC character offers superior insight into advanced water treatment performance.
• Understanding the specific organic fractions removed and their molecular weights enhances process assessment.
• The study highlights the complementary roles of UF and RO in DOC removal and character modification.