Rejection Efficiency of Water Quality Parameters by Reverse Osmosis and Nanofiltration Membranes

Abstract

The objective of this study was to evaluate the effectiveness of reserve osmosis (RO) and nanofiltration (NF) membranes, under various solution chemistries, on water quality. The effects of organic carbon, divalent and monovalent cations, bacteria, and permeate drag on the rejection efficiencies of three different membranes were investigated through a series of laboratory bench-scale experiments. Quantitative models were successfully developed to predict the rejection of turbidity, divalent and monovalent cations, ultraviolet absorbance at 253.7 nm (UV254), and dissolved organic carbon (DOC) by membrane filtration. It was found that mechanical sieving (measured as molecular weight cutoff, MWCO) and electrostatic interactions were the most significant parameters since they were found to be important in nearly all models developed. For negatively charged membranes, under high ionic strength solution environments that repress electrostatic interaction between charged compounds and membranes, passage of compounds was mainly a function of size exclusion (i.e. MWCO). Further, of the feedwater parameters tested, bacteria concentration was observed to be the most significant influence on UV254, divalent cation and monovalent cation rejections. The developed models revealed that interactions between feedwater composition and membrane properties impacted the rejection efficiency of membranes as significantly as water composition and membrane properties individually.

Hyperbranched Polyethyleneimine Induced Cross-Linking of Polyamide−imide Nanofiltration Hollow Fiber Membranes for Effective Removal of Ciprofloxacin

“…Because these two membranes share a similar MWCO (1278 Da), their rejections become quite similar. 11 Their permeate fluxes also drop gradually, due to fouling induced by the adsorption of positively charged ciprofloxacin on the negatively charged surface.…”

Study of the hydrophilic‐enhanced ultrafiltration membrane

“…It is widely accepted that natural organic matter is considered a major promoter of abiotic fouling in filtration processes using membranes [7][8][9][10]. Based on hydrophobic interactions between the membrane surface and natural organic matter and/or microorganisms, it would be expected that use of hydrophilic membranes would decrease fouling.…”

“…Based on hydrophobic interactions between the membrane surface and natural organic matter and/or microorganisms, it would be expected that use of hydrophilic membranes would decrease fouling. However, hydrophilic membranes experience lower fouling but suffer from limitations such as susceptibility to surfactants and lack of mechanical strength, [7,25] and can be fouled by surfactants. Based on the above observations an ideal membrane would be one with the low fouling properties of hydrophilic membranes along with the high chemical resistance of hydrophobic membranes.…”

Membrane potential across reverse osmosis membranes under pressure gradient

“…Reverse osmosis (RO) membranes are utilized in a wide range of applications such as drinking water treatment, waste water reclamation, and production of ultrapure water [1][2][3]. Composite RO membrane composed of a dense active layer and a porous support layer is commonly utilized due to its high flux and high mechanical strength.…”