Pollution of water sources with emerging contaminants (micropollutants) is a fact known worldwide. Although the risks of micropollutants in sources of water are partly recognized, interpretation of consequences are controversial; thus, the future effects of altered water with micropollutants remains uncertain and may constitute a point of conc

The objective and focus of this study is to fully understand trace organic pollutant transport through NF/RO membranes. An extension of the classical solution-diffusion model had been developed that relates transport through NF/RO membranes directly to membrane structure descriptors (i.e., effective barrier layer pore size, porosity and thickness, etc.). In general, model predictions agreed well with experimental data suggesting the model captures the phenomenological behavior of commercial NF/RO membranes for separations relevant to modern water treatment objectives. The model also provides new mechanistic insights about the "effective structure" of NF/RO composite membranes and how trace organic solutes are rejected. These results suggest it is possible and important to fine-tune the surface energy of membrane and membrane structure (pore size, porosity, thickness) to achieve high membrane selectivity for certain solute. The effects of feed solution ionic strength, pH and divalent cation content on NF/RO membrane structure and performance were elucidated experimentally and fitted with the newly developed model. Generally, water permeabilities of all three membranes decreased with ionic strength and divalent cation content, but increased with pH. For RO membranes, neutral solute rejection decreased with pH and divalent cation content, but increased with ionic strength and the salt rejection remained independent with water chemistry except for very low pH of 3; for a NF membrane, solute rejection was more sensitive to water chemistry and neutral solute rejection decreased with ionic strength, pH, but increased with divalent cation content. Ultimately, these new insights may be useful in selection of already commercial or design of new NF/RO membranes for removal of chemicals of emerging concern in water treatment. Four different organic solute removals by six different commercial NF/RO membranes in laboratory re-created groundwater matrix were experimentally determined. SWRO membranes exhibited excellent removal efficiency (> 90%) for both NDMA and 1,4-dioxane in groundwater, while NF membranes showed inefficient separation. Correlation studies suggested that both size exclusion and thermodynamic partitioning play important roles in trace organics removal and a partition coefficient, which combines both steric effects and solute-membrane interactions, can be employed to predict organic solute rejection by NF/RO membranes.

This monograph delineates the retention mechanisms of emerging trace organic contaminants by several nanofiltration (NF) and reverse osmosis membranes. Retention of neutral trace organics by a tight NF or RO membrane is dominated by steric (size) exclusion, whereas both electrostatic repulsion and steric exclusion govern the retention of negatively charged trace organics by a loose NF membrane. Speciation of trace organics may lead to a dramatic change in retention as a function of pH, with much greater retention observed for ionized, negatively charged trace organics. Retention of the negatively charged trace organics decreases as the solution's ionic strength increases due to charge shielding and double layer compression. For uncharged trace organic species, intrinsic physicochemical properties of the trace organic molecules can substantially affect their retention. This monograph also critically demonstrates the possible complexity of a real membrane filtration system where trace organic contaminants are of concern. Factors such as operating conditions and feed solution composition can influence the filtration of trace organics.

The purpose of this study was to explore whether n

As reuse of municipal water resource recovery facility (WRRF) effluent becomes vital to augment diminishing fresh drinking water resources, concern exists that conventional barriers may prove deficient and the upcycling of contaminants of emerging concern (CECs) could prove harmful to human health and aquatic species if more effective and robust treatment barriers are not in place. There are no federal Safe Drinking Water Act (SDWA) regulations in place specifically for direct potable reuse (DPR) of WRRF effluent. Out of necessity, some states are developing their own DPR reuse regulations. Currently, reverse osmosis (RO) is the default full advanced treatment (FAT) barrier for CEC control. However, the potential exists for tight thin-film composite (TFC) nanofiltration (NF) membranes to provide acceptable CEC rejection efficacies for less capital, operations and maintenance (O&M), energy, and waste generated. Recognizing the inherent complexity of CEC rejection by membranes, this research program was designed to elucidate the vital predictive variables influencing the rejection of 96 CECs found in municipal WRRF effluents. Each of the CECs was cataloged by their intended use and quantitative structure activity relationship (QSAR) properties, and measured in secondary effluent samples from WRRFs in Texas and Oklahoma. These secondary effluent samples were then processed in bench-scale, stirred, dead-end pressure cells with water treatment industry-specified TFC NF and RO membranes. A multi-level, multi-variable model was developed to predict the probable rejection coefficients of CECs with the studied NF membrane. The model was developed from variables selected for their association with known membrane rejection mechanisms, CEC-specific QSAR properties, and characteristics of the actual solute matrix. R statistics software version 3.1.3 was utilized for property collinearity analysis, outlier analysis, and regression modeling. The Pearson correlation method was utilized for selection of the most vital predictor variables for modeling. The resulting Quantitative Molecular Properties Model (QMPM) predicted the NF rejection CECs based on size, ionic charge, and hydrophobicity. Furthermore, the QMPM was verified against a CEC rejection dataset published by an independent study for a similar commercially available TFC NF membrane.

An updated guide to the growing field of nanofiltration including fundamental principles, important industrial applications as well as novel materials With contributions from an international panel of experts, the revised second edition of Nanofiltration contains a comprehensive overview of this growing field. The book covers the basic principles of nanofiltration including the design and characterizations of nanofiltration membranes. The expert contributors highlight the broad ranges of industrial applications including water treatment, food, pulp and paper, and textiles. The book explores photocatalytic nanofiltration reactors, organic solvent nanofiltration, as well as nanofiltration in metal and acid recovery. In addition, information on the most recent developments in the field are examined including nanofiltration retentate treatment and renewable energy-powered nanofiltration. The authors also consider the future of nanofiltration materials such as carbon- as well as polymer-based materials. This important book: Explores the fast growing field of the membrane process of nanofiltration Examines the rapidly expanding industrial sector's use of membranes for water purification Covers the most important industrial applications with a strong focus on water treatment Contains a section on new membrane materials, including carbon-based and polymer-based materials, as well as information on artificial ion and water channels as biomimetic membranes Written for scientists and engineers in the fields of chemistry, environment, food and materials, the second edition of Nanofiltration provides a comprehensive overview of the field, outlines the principles of the technology, explores the industrial applications, and discusses new materials.