Understanding the organic micropollutants transport mechanisms in the fertilizer-drawn forward osmosis process

© 2019 Elsevier Ltd We systematically investigated the transport mechanisms of organic micropollutants (OMPs) in a fertilizer-drawn forward osmosis (FDFO) membrane process. Four representative OMPs, i.e., atenolol, atrazine, primidone, and caffeine, were chosen for their different molecular weights and structural characteristics. All the FDFO experiments were conducted with the membrane active layer on the feed solution (FS) side using three different fertilizer draw solutions (DS): potassium chloride (KCl), monoammonium phosphate (MAP), and diammonium phosphate (DAP) due to their different properties (i.e., osmotic pressure, diffusivity, viscosity and solution pH). Using KCl as the DS resulted in both the highest water flux and the highest reverse solute flux (RSF), while MAP and DAP resulted in similar water fluxes with varying RSF. The pH of the FS increased with DAP as the DS due to the reverse diffusion of NH4+ ions from the DS toward the FS, while for MAP and DAP DS, the pH of the FS was not impacted. The OMPs transport behavior (OMPs flux) was evaluated and compared with a simulated OMPs flux obtained via the pore-hindrance transport model to identify the effects of the OMPs structural properties. When MAP was used as DS, the OMPs flux was dominantly influenced by the physicochemical properties (i.e., hydrophobicity and surface charge). Those OMPs with positive charge and more hydrophobic, exhibited higher forward OMP fluxes. With DAP as the DS, the more hydrated FO membrane (caused by increased pH) as well as the enhanced RSF hindered OMPs transport through the FO membrane. With KCl as DS, the structural properties of the OMPs were dominant factors in the OMPs flux, however the higher RSF of the KCl draw solute may likely hamper the OMPs transport through the membrane especially those with higher MW (e.g., atenolol). The pore-hindrance model can be instrumental in understanding the effects of the hydrodynamic properties and the surface properties on the OMPs transport behaviors

Investigation of pilot-scale 8040 FO membrane module under different operating conditions for brackish water desalination 2 3

Abstract 8 Two spiral wound forward osmosis (SWFO) membrane modules with different spacer design (CS; 9 corrugated spacer and MS; medium spacer) were investigated for the fertilizer drawn forward osmosis 10 desalination of brackish groundwater (BGW) at a pilot-scale level. This study mainly focused on 11 examining the influence of various operating conditions such as feed flow rate, total dissolved solids 12 (TDS) concentration of the BGW feed, and draw solution (DS) concentrations using ammonium 13 sulphate ((NH 4 ) 2 SO 4 , SOA) on the performance of two membrane modules. The feed flow rate played 14 a positive role in the average water flux of the pilot-scale FO membrane module due to enhanced 15 mass transfer coefficient across the membrane surface. Feed TDS and DS concentrations also played a 16 significant role in both FO membrane modules because they are directly related to the osmotic driving 17 force and membrane fouling tendency. CS module performed slightly better than MS module during 18 all experiments due to probably enhanced mass transfer and lower fouling propensity associated with 19 the corrugated spacer. Besides, CS spacer provides larger channel space that can accommodate larger 20 volume of DS and hence could maintain higher DS concentration. However, the extent of dilution for 21 the CS module is slightly lower. 22 2

Boron transport through polyamide-based thin film composite forward osmosis membranes

The boron transport in forward osmosis (FO) process using thin film composite (TFC) membranes has been investigated. Two common fertilizers were used as draw solutes and a model seawater as the feed. The influence of several physical and chemical operating conditions on boron solute flux and boron rejection rates was investigated. The examined factors include draw solution types, membrane orientation, feed and draw solution concentrations, boron feed concentration, crossflow rate, and feed solution pH. The key mechanisms that govern boron transports are reverse draw solute flux and internal concentration polarization experienced by the membrane during the FO process. Results show that the use of draw solute with small hydrated radius could improve boron rejection hindered by the higher reverse diffusion of draw solutes. The osmotic process operated in the pressure retarded osmosis (PRO) mode results in lower boron rejection. However, the most effective boron removal was achieved by operating the feed solution at high pH (pH = 11) because boron in the solution contains larger-size borate species, and thus increases boron rejection rate up to 94% by electrostatic repulsion. This study mainly focused on the performance of TFC membrane in boron removal. (C) 2014 Elsevier B.V. All rights reservedclose3

Simultaneous phosphorous and nitrogen recovery from source-separated urine: A novel application for fertiliser drawn forward osmosis

Re-thinking our approach to dealing with waste is one of the major challenges in achieving a more sustainable society. However, it could also generate numerous opportunities. Specifically, in the context of wastewater, nutrients, energy and water could be mined from it. Because of its exceptionally high nitrogen (N) and phosphorous (P) concentration, human urine is particularly suitable to be processed for fertiliser production. In the present study, forward osmosis (FO) was employed to mine the P and N from human urine. Two Mg2+-fertilisers, i.e. MgSO4 and Mg(NO3)(2) were selected as draw solution (DS) to dewater synthetic non-hydrolysed urine. In this process, the Mg2+ reverse salt flux (RSF) were used to recover P as struvite. Simultaneously, the urea was recovered in the DS as it is poorly rejected by the FO membrane. The results showed that, after concentrating the urine by 60%, about 40% of the P and 50% of the N were recovered. XRD and SEM EDX analysis confirmed that P was precipitated as mineral struvite. If successfully tested on real urine, this process could be applied to treat the urine collected in urban areas e.g., high-rise building. After the filtration, the solid struvite could be sold for inland applications whereas the diluted fertiliser used for direct fertigation of green walls, parks or for urban farming. Finally, reduction in the load of N, P to the downstream wastewater treatment plant would also ensure a more sustainable urban water cycle

Removal of organic micro-pollutants by conventional membrane bioreactors and high-retention membrane bioreactors

The ubiquitous presence of organic micropollutants (OMPs) in the environment as a result of continuous discharge from wastewater treatment plants (WWTPs) into water matrices—even at trace concentrations (ng/L)—is of great concern, both in the public and environmental health domains. This fact essentially warrants developing and implementing energy-efficient, economical, sustainable and easy to handle technologies to meet stringent legislative requirements. Membrane-based processes—both stand-alone or integration of membrane processes—are an attractive option for the removal of OMPs because of their high reliability compared with conventional process, least chemical consumption and smaller footprint. This review summarizes recent research (mainly 2015–present) on the application of conventional aerobic and anaerobic membrane bioreactors used for the removal of organic micropollutants (OMP) from wastewater. Integration and hybridization of membrane processes with other physicochemical processes are becoming promising options for OMP removal. Recent studies on high retention membrane bioreactors (HRMBRs) such as osmotic membrane bioreactor (OMBRs) and membrane distillation bioreactors (MDBRs) are discussed. Future prospects of membrane bioreactors (MBRs) and HRMBRs for improving OMP removal from wastewater are also proposed

Control of the antagonistic effects of heat-assisted chlorine oxidative degradation on pressure retarded osmosis thin film composite membrane surface

During pressure retarded osmosis (PRO) operation, thin film composite (TFC) membranes are continuously exposed to chemicals present in the stream that can deteriorate the membrane's selective layer with exposure time. Following this observation, TFC membranes are placed in controlled oxidative degradation conditions using aqueous NaOCl solutions. Active chlorine, along with heat, can thin out the dense layer and, when controlled and optimized, can tune the membrane surface properties and separation efficiency as desirable for specific applications. The chlorine oxidative degradation is optimized in terms of chlorine exposure (a factor of both exposure time and chemical dosage), solution pH, and the subsequent heating time. After the chemical modification process, the membrane surface properties were characterized and the PRO performance as well as the osmotic energy harvesting capability were determined. The modified membranes exhibited different levels of polyamide degradation and increase in water permeability, which came along with decrease in selectivity. Optimization of the chlorine oxidative degradation using response surface methodology was performed to maximize the water permeability and extractable osmotic power while keeping salt rejection satisfactory. After performing chlorine oxidation at the following optimized conditions: 3025 ppm Cl2·h, pH 10.72, and 3 min heating time, initial non-pressure retarded water flux of 73.2 L m−2 h−1, specific reverse solute flux of 1.17 g L−1, and power density of 18.71 W m−2 (corresponding to water flux of 56.1 L m-2 h-1) at 12 bar were obtained using 0.6 M NaCl as draw and deionized water as feed.- Qatar National Research Fund (QNRF) grant #NPRP 10-1231-160069. - Australian Research Council (ARC) grant #IH170100009