Removal of hardness from groundwater using two nanofiltration membranes: experimental study and modeling

Abstract

a b s t r a c tWater hardness causes potentially costly nuisance problems in homes and in industry, such as disabling washing, formation of tartar carbonate and magnesium hydroxide in the pipe network of hot water. In this work, the ability of two commercial nanofiltration membranes (NF90, NF270) to remove hardness from the Maâmora groundwater (North of Morocco) was studied. Experiments were carried out in the pressure range of 5-40 bar and for different total hardness (TH) of the feed water. The effects of the trans-membrane pressure on the permeate flux and retention rate were investigated for each membrane. The results show that the nanofiltration membranes are capable of retaining the total hardness present in groundwater. Experiment results were correlated and analysed using Spiegler-Kedem model. Model parameters (the reflection coefficients and the solute permeability) have been determined for the two membranes using an adequate mathematical optimization procedure (Levenberg-Marquardt´s algorithm: LMA). Model predictions of Ca 2+ and Mg 2+ rejection were used to calculate rejection for Total Hardness. The modeling results were in good agreement with the experimental data for both NF90 and NF270 membrane. The correlation coefficient was greater than 0.9 in all cases. Also, statistical analysis of residual errors based on the root mean square error (RMSE), the normalized root mean square error (NRMSE) and the Nash-sutcliffe efficiency (NSE) coefficient demonstrates the good performance of the model and the optimization procedure. Results of this study are of great importance for local managers since waters of Maâmora groundwater are locally used in many areas and are part of several water management plans.

Runge–Kutta Numerical Method Followed by Richardson’s Extrapolation for Efficient Ion Rejection Reassessment of a Novel Defect-Free Synthesized Nanofiltration Membrane

“…where is the Stokes radius and is the effective pore radius (membrane) of ion i. Equations (20) and (21) were finally obtained through a substitution of Equations (11), (15), (16), (17), and (18) into Equations (5) and (9…”

“…A nanofiltration (NF) membrane is a pressure-driven process exhibiting properties that lie betwixt ultrafiltration (UF) and reverse osmosis (RO) [ 5 ]. NF membranes have proven their effectiveness in several sectors such as water reclamation [ 6 ] and dye separation [ 7 ], heavy metals [ 8 , 9 ], pesticides [ 10 ], viruses and bacteria [ 11 , 12 ], beverages [ 13 ], natural organic matter [ 14 ], food [ 15 ], dairy processing [ 16 ], hardness removing [ 17 ], taste and odors [ 18 ], and even water softening [ 19 ]. Since there are several applications for NF membranes, there is, therefore, a compelling need to understand its separation behavior and how to improve the solute particles’ transport mechanisms through its active selective layer, especially in water desalination.…”