Effect of operating parameters on the selectivity of nanofiltration phosphates transfer through a Nanomax-50 membrane

Simultaneous phosphate recovery and sodium removal from brackish aquaculture effluent via diafiltration-nanofiltration process

Expansion of the aquaculture industry has been accompanied by environmental impact as the discharged effluent contains excess nutrients such as phosphorus compounds. Recovery of such nutrients is not economically feasible as it presents in trace amounts. Furthermore, brackish aquaculture effluent which contains high sodium chloride (NaCl) content makes the treated solution inappropriate for fertilizer production. Herein, this study proposed a diafiltration-nanofiltration route to perform a simultaneous phosphate concentrating and osmotion (sodium) removal from brackish aquaculture effluent. Effects of operating pressure, phosphate, and sodium content on membrane performance were first determined using Desal-5 DK membrane with three types of solutions namely (i) freshwater without NaCl, (ii) dilute brackish water with 1,500 mg/L NaCl, and (iii) brackish water with 10,000 mg/L NaCl. It was found that at 4 bar operating pressure, it could achieve higher phosphate rejection and sodium permeance. The presence of NaCl negatively influenced both phosphate rejection and concentrating factor (CF) due to the salt screening effect. It was noteworthy that negative sodium rejection (up to -16%, CF <1) could be attained, indicating the concentrating effect for sodium was negligible. The concentrating process was effective to concentrate phosphate by 2-fold but less effective in removing sodium. Diafiltration was then introduced and resulted in about 76% of sodium removal. Diafiltration-nanofiltration (DF-NF) mode was shown to be a more efficient method than nanofiltration-diafiltration (NF-DF) mode as phosphate could be concentrated up to 2 factors with 99 wt% of sodium being removed from the real brackish aquaculture effluent. These findings showed that DF-NF is a feasible approach for concentrating phosphate while removing sodium ions from aquaculture effluent and the recovered nutrient solution has huge potential to be applied as liquid fertilizer for hydroponic plants.

Factors influencing pressure-driven membrane-assisted volatile fatty acids recovery and purification-A review

Volatile fatty acids (VFAs) are building block chemicals that can be produced through bioconversion of organic waste streams via anaerobic digestion as intermediate products. Purified VFAs are applicable in a wide range of industrial applications such as food, textiles, cosmetics, pharmaceuticals etc. production. The present review focuses on VFAs recovery methods and technologies such as adsorption, distillation, extraction, gas stripping, esterification and membrane based techniques etc., while presenting a discussion of their pros and cons. Moreover, a great attention has been given to the recovery of VFAs through membrane filtration as a promising sustainable clarification, fractionation and concentration approach. In this regard, a thorough overview of factors affecting membrane filtration performance for VFAs recovery has been presented. Filtration techniques such as nanofiltration and reverse osmosis have shown to be capable of recovering over 90% of VFAs content from organic effluent steams, proving the direct effect of membrane materials/surface chemistry, pore size and solution pH in recovery success level. Overall, this review presents a new insight into challenges and potentials of membrane filtration for VFAs recovery based on the effects of factors such as operational parameters, membrane properties and effluent characteristics.

Enhanced modelling and experimental validation of ultra-low pressure reverse osmosis membrane system for treatment of synthetic brackish water

Water purification from brackish water sources has been acknowledged as one of the most promising ways to produce drinkable water in water-scarce areas. In this study, an ultra-low pressure reverse osmosis (ULPRO) membrane was numerically and experimentally investigated to produce drinking water by the removal of sodium chloride salt which provides further validation of the model from a practical perspective. An enhanced predictive model based on the Donnan-Steric Pore Model with dielectric exclusion (DSPM-DE) incorporating the osmotic effects was formulated in process simulation. The feed pressure and concentration were optimized as input variables and interaction between them was observed, while salt rejection and water recovery rate were taken as response attributes. The results obtained on the ULPRO membrane showed that the performance depends on the charge, steric, and dielectric effects. Furthermore, the enhanced model was validated with the experimental data attained from a laboratory-scale filtration system with good accuracy in the salt rejection and water recovery results. Comparing the enhanced DSPM-DE with the existing solution diffusion model reveals that the enhanced model predicts the membrane performance better and thereby qualifies itself as a reliable model for desalination of brackish water using ULPRO membrane.

Fabrication and characterization of a novel nanofiltration membrane by the interfacial polymerization of 1,4-diaminocyclohexane (DCH) and trimesoyl chloride (TMC)

A novel thin-film composite polyamide membrane for nanofiltration is prepared, and the addition of sodium N-cyclohexylsulfamate is found to have a significant influence on its performance.