Application of volume-retarded osmosis and low-pressure membrane hybrid process for water reclamation

Real-time fouling monitoring and membrane autopsy analysis in forward osmosis for wastewater reuse

Forward osmosis process in emerging technology which can applicable in wastewater reuse and desalination simultaneously. In this study, the development of fouling on the FO membrane surface was monitored in real-time. The investigation of fouling layer physical and chemical characteristics was assessed by performance evaluation and in-depth analysis of fouling layer. Non-invasive visual monitoring and in-depth autopsy, combined with the performance and image analyses provided a better understanding of fouling phenomena. The relative roughness of the fouling layer was correlated with water flux decrease while the fouling layer thickness decreased rapidly when fouling was stabilized. From 66-day operation using the primary wastewater as the feed, membrane fouling development was classified into 4 phases: virgin performance, initial deposition, stabilization and aggregation. With the growing fouling layer and with aggregation, the removal rate of organic matter was reduced from 99 to 70%. Conversely, the removal rate of inorganic matter was maintained at a level higher than 90%. The fractionation of physical and chemical extraction had the following characteristics: TPI>HPI>HPO and HPI>TPI>HPO respectively. Also, low molecular weight and building blocks like organic matter were observed with a high composition ratio of fouling layer. Through the correlation between the process performance, real-time monitoring of fouling layer formation and deep-layer fouling analysis, it was possible to identify the major membrane contaminants and propose process optimization guidelines.

Low-pressure volume retarded osmosis for removal of per- and polyfluoroalkyl substances

Forward osmosis is an energy efficient process that is capable of recovering high-quality water from secondary wastewater treatment. However, regeneration of the draw solution (DS) is a problem that needs to be addressed. Herein, we developed and optimized a one-step process that does not require additional treatment for the DS. This process, called pressure assisted-volume retarded osmosis (PA-VRO), utilizes naturally occurring pressure with the aid of a small inlet pressure (< 1 bar). Poly(styrenesulfonate) was employed as the DS, for its high solubility in water and large molecular size (∼70,000 Da). Accordingly, real wastewater was employed as the feed solution for 48 h to remove perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) through PA-VRO. The rejection rates for PFOA/PFOS and poly(sodium-4-styrenesulfonate) (PSS) were observed to exceed 98%, after 24 h and 99%, after 48 h. Moreover, there were no traceable amounts of PFOA/PFOS in the DS, and hence the detected concentrations of PFOA and PFOS can be attributed to the residuals from the equipment. Therefore, this well-optimized PA-VRO process can be utilized for potable water production from treated wastewater.

Effects of co-existence of organic matter and microplastics on the rejection of PFCs by forward osmosis membrane

Perfluorinated chemical (PFC)-based materials have been widely applied in industry. In this study, the influence of PFCs on the physicochemical properties of membranes and that of the co-existence of organic matter and microplastics on the removal rate in the process of forward osmosis (FO) was examined. The water flux, reverse salt flux, and rejection of PFCs were evaluated under w and w/o contaminants. The lowest rejection rates of PFCs in FO membranes were observed to be 92.2% and 90.4% for FO-TFC and PA-Aqua FO membranes, respectively. The main rejection mechanism of the FO membrane is the sieving effect (p-value: PA-TFC-0.015, PA-Aqua-0.002) based on molecular volume, which is more dominant than the electrostatic repulsive force and hydrophobic interaction, the major rejection mechanisms of existing trace contaminants. In addition, we observed that the effects of co-existing pollutants in raw water have an insignificant effect on the rejection of PFCs because of the physical and chemical stability of PFCs. According to the results of this study, using the FO membrane, PFCs can effectively control not only their self-existence but also when contaminants co-exist with them in water bodies.

Membrane processes

This literature review provides a review for publications in 2018 and 2019 and includes information membrane processes findings for municipal and industrial applications. This review is a subsection of the annual Water Environment Federation literature review for Treatment Systems section. The following topics are covered in this literature review: industrial wastewater and membrane. Bioreactor (MBR) configuration, membrane fouling, design, reuse, nutrient removal, operation, anaerobic membrane systems, microconstituents removal, membrane technology advances, and modeling. Other sub-sections of the Treatment Systems section that might relate to this literature review include the following: Biological Fixed-Film Systems, Activated Sludge, and Other Aerobic Suspended Culture Processes, Anaerobic Processes, and Water Reclamation and Reuse. This publication might also have related information on membrane processes: Industrial Wastes, Hazardous Wastes, and Fate and Effects of Pollutants.

Application of volume retarded osmosis - Low pressure membrane hybrid process for recovery of heavy metals in acid mine drainage

Recovery of heavy metals in acid mine drainage (AMD) such as Mn, Fe, Cu, Zn, As, Cd and Pb was evaluated using volume retarded osmosis and low-pressure membrane (VRO-LPM) process. In VRO-LPM process, the draw solution (DS) is regenerated by the naturally generated pressure, giving its economic value. Ethylenediaminetetraacetic acid tetrasodium salt (EDTA-4Na) and Poly (sodium-4-styrenesulfonate, PSS-Na) were used and compared to determine more suitable DS in heavy metal recovery from the AMD. Forward osmosis (FO) and nanofiltration (NF) membrane were employed in VRO-LPM process, due to the low EDTA-4Na rejection (about 50%) in ultrafiltration (UF) process. For the FO part in the VRO-LPM process, PSS-Na had flux values of 0.12, 0.11 and 0.05 L m^-2 h^-1 and at osmotic pressure of 8.9, 12 and 13 bar, respectively. Unlike the flux values, the RSF of PSS remained at 0.01 mmol h^-1 at all osmotic pressures. For EDTA-4Na, the flux values were 0.10, 0.06 and 0.04 L m^-2 h^-1, which are relatively higher than those of PSS-Na; and the RSF values were 0.1, 1.2, 2.2 mmol h^-1, which are higher compared to those of PSS-Na. Unlike PSS-Na, RSF for EDTA-4Na increased as the concentration increases. In the NF part of the VRO-LPM process, PSS-Na had higher water flux and rejection than EDTA-4Na, and the flux and rejection both decreased with concentration for both PSS-Na and EDTA-4Na. The overall rejection in VRO-LPM process was over 95% for all heavy metal ions. Therefore, VRO-LPM process has proven its ability to be used in AMD treatment for heavy metal removal.

Application of a volume retarded osmosis-low pressure membrane hybrid process for treatment of acid whey

This study evaluated the treatment of acid whey through a volume-retarded osmosis-low-pressure membrane (VRO-LPM) hybrid process. The VRO-LPM process uses pressure naturally generated inside the closed draw solution (DS) tank to regenerate the DS, making it an economic process. Poly (sodium-4-styrenesulfonate) (PSS) and carboxymethyl cellulose (CMC) were compared to determine which was a more suitable DS for acid whey treatment. Forward osmosis (FO) and ultrafiltration (UF) membranes were used in the VRO-LPM hybrid process because a single UF process showed high water flux and rejection efficiencies above 85% for both PSS and CMC. In both the FO and UF parts of the VRO-LPM process, PSS had a higher water flux than CMC. However, the increasing rate of the feed solution (FS) for CMC was greater than that of PSS, however the overall rejection efficiencies were similar for both DS. Therefore, the VRO-LPM process can be applied to acid whey treatment, and CMC seems to be a better choice of DS than PSS because of its higher concentrating ratio of FS and high overall rejection.