Targeting bulk and trace organics during advanced membrane treatment leading to indirect potable reuse

摘要

The objective of this study was to develop an approach to address removal of bulk organic carbon and selected trace organics present in reclaimed water during advanced membrane treatment. The study was conducted using a pilot-scale membrane facility at the Yuma Water Quality Improvement Center in Arizona. In addition, studies at full-scale were performed at the Scottsdale Water Campus employing tertiary treatment followed by microfiltration and reverse osmosis prior to direct injection. To investigate the fate of bulk organics (effluent organic matter), total organic carbon (TOC) and UV absorbance (UVA) were measured followed by advanced characterization technologies such as solid-state carbon-13 nuclear magnetic resonance spectroscopy and size exclusion chromatography with online TOC and UVA detection. Lessons learned from this study are that membranes can efficiently reject high-molecular weight organic matter (characterized as fulvic acids) depending on the molecular weight cut-off of the membrane. However, approximately 40 to 50 percent of the remaining TOC in permeates consists of low molecular weight acids and neutrals representing a molecular weight range of ～500 Dalton and less. Several emerging contaminants were detected in tertiary effluent used for advanced membrane treatment. However, EDTA, NTA, APECs, anti-inflammatory drugs, anti-epileptics, blood lipid regulators, and diagnostic contrast agents were not detected in nanofiltration or reverse osmosis permeates. These findings indicate that high-pressure membrane can serve as a reliable barrier for compounds of concern.