The increasing demand for drinking water has led to the adoption of unconventional water sources, like water reuse. Reverse osmosis (RO) and Nanofiltration (NF) membranes are effective barriers against trace organic contaminants for potable water reuse applications. However, the use of RO is being challenged by NF, primarily due to NF’s potential to achieve similar contaminant passage rates as RO but with higher productivity and lower energy requirements. NF can be more efficient implementation for organic pollutants removal. As the RO generally achieves ≥95% rejection of NaCl, NF membranes have relatively loose structure allowing more water permeation and producing low-saline concentrate which results in lower energy consumption. This study compares NF with RO membranes on contaminant passages and energy consumption for potable water reuse applications.

Aim

Ultra-filtered treated reclaimed wastewater was used to study the transport of contaminants through NF and RO membranes for potable water reuse applications with focus to assess NF as a sustainable alternative to RO. This study compares the permeate water quality of NF and RO membranes to evaluate their water permeability and solute rejection passage in bench-scale systems. Additionally, this study provides details on the organic compounds permeating through the membranes in terms of molecular weight, hydrophobicity, and TOrCs rejection. Subsequently, engineering-scale experiments employing NF were used to evaluate the rejection rates of contaminants and estimate the energy consumption.

Method

Reverse osmosis and nanofiltration membranes were tested in bench-scale and pilot scale systems using UF-filtered reclaimed wastewater. Ion chromatography (IC) and inductively coupled plasma mass spectrometry (ICP-MS) were used to measure anions and cations concentration. For organics, Total Organic Carbon analyzer (TOC) was used to measure TOC concentration, size-exclusion chromatography (SEC) for molecular weight, and UHPLC-MS/MS for quantification of trace organics.

Results

RO and dense (NF90) and loose (NF270) NF membranes were tested in both bench-scale and pilot scale systems utilizing UF-filtered reclaimed wastewater. The highest solute passage was observed ....