Flux Optimization in Reverse Osmosis via the Solution-Diffusion Model

This paper suggests a new method of predicting flux values at Reverse Osmosis (RO) desalination plants. The solution-diffusion model is utilized to determine the osmotic pressure drops for seawater sources. The same technique was applied to the groundwater source at the Abqaiq plant (500 RO plant) to calculate the osmotic pressure. The calculated osmotic pressures were utilized to determine the appropriate flux rates and membrane resistances of different BWRO Toray membranes and a performance comparison between various membranes has been established. The model results confirm an inverse relationship between membrane thickness and water flux rate. Also, a proportional linear relation between the overall water flux and the applied pressure is identified. Higher flux rates and lower salinity indicate lower membrane resistance yielding higher production. The modeled data predict that BWRO Toray TM720D-440 with an 8" membrane is the optimal choice for treating waters from the three water sources at the Abqaiq plant.

Reverse osmosis (RO) spiral wound membrane generation reached 93.5% in 2020, resulting in 14,000 tons of used RO membranes being discarded annually into landfills, which is unprecedented. The current study aims to chemically convert the end-of-life RO membrane, followed by its performance evaluation and microbial removal efficiency on three different sources of water, i.e., tap water (TW), integrated constructed wetland permeate (ICW-P), and membrane bio-rector permeate (MBR-P), respectively. This was accomplished by selecting 6 years of spent Filmtech (LC-LE-4040) thin film composite type brackish water reverse osmosis (BWRO) membrane, followed by alkaline and acidic cleaning for 2 h. Finally, the conversion was carried out by 6% sodium hypochlorite (NaOCl) with 300,000 ppm/h exposure by active system (AS) using the clean in place CIP pump at 2 bars for 10 h duration. The membrane demonstrated 67% water recovery and 1% saltwater rejection, which means RO membrane now converted into recycled RO (R-RO) or (UF) by removal of the polyamide (PA) layer. Water recovery was 67% for TW, 68% for ICW-P, and 74% for MBR-P, respectively, with the consistent saltwater rejection rate of 1% being observed, while R-RO exhibited an effective COD removal of 65.79%, 62.96%, and 67.72% in TW, ICW-P, and MBR-P, respectively. The highest turbidity removal of 96% in the ICW-P was also recorded for R-RO. For morphological properties, SEM analysis of the R-RO membrane revealed a likewise appearance as a UF membrane, while pore size is also comparable with the UF membrane. The most probable number (MPN) also showed complete removal of total coliforms after passing through the R-RO membrane. These features made the R-RO membrane an excellent choice for drinking water treatment and wastewater treatment polishing steps. This solution can help developing nations to be efficient in resource recovery and contribute to the circular economy.

Implication of zeta potential at different salinities on boron removal by RO membranes

Reverse osmosis desalination: Water sources, technology, and today's challenges

Naturally occurring brackish water, normally containing 500–10,000 mg/L of total dissolved solids, is not safe for direct consumption due to its salinity. The salinity level needs to be reduced to a level below 500 mg/L to make it drinkable as per recommendations of the World Health Organization (WHO). Reverse osmosis (RO) process for water desalination purposes is currently considered to be the most effective, economical, efficient, and optimized method dominating the water purification market. An extensive research has been carried out in the field of membrane-based brackish water reverse osmosis (BWRO) process to improve its desalting performance. Various aspects of a BWRO process system such as nature and type of membrane material, module design parameters, process configuration, energy recovery devices, operating parameters, economical aspects are reviewed in this chapter. Theoretical background of a BWRO process, transport mechanism through BWRO membranes, and desalination performance of BWRO membranes are considered here. An updated review of different commercially available BWRO membranes, membrane modules, and process configurations is also provided. In addition, major components of a typical BWRO plant such as pretreatment unit, pumping system, membrane module section, and post-treatment unit are also described in this review. General process considerations, economic aspects, energy recovery options, and process optimization of a BWRO system are discussed here. High-performance BWRO membranes prepared from polymeric and thin-film composite materials are inserted in commercial spiral wound modules to make the desalting process economically efficient. Concentrated brine rejected from a BWRO plant can be economically treated by installing solar stills at sunlit places. A double-stage membrane process can enhance water recovery of BWRO plants from the usual range of 85–90% to about 95–98%. Brackish water can be purified by BWRO process at reduced cost by using high rejection membranes, installing larger pressure vessels, and adopting hybrid membrane design.

In this study, the applicability of nanofiltration (NF) membranes as a pretreatment prior to reverse osmosis (RO) in seawater desalination was investigated. The membranes used wereNF270 and NF90 as the NF membranes, while the brackish water (BW) RO membrane BW30 was used as the RO membrane. In desalination tests, permeates of the NF membraneswere collected and used as the feed to the BW30 membrane. The calculated permeate fluxes were 6.7 L/h.m2, 11.3 L/h.m2, 24.3 L/h.m2, and 36.6 L/h.m2 for single BW30-35 bar,NF270-30 bar + BW30-35 bar, NF90-30 bar + BW30-25 bar and NF90-30 BW30-35 bar, respectively. The calculated water recovery and rejected salt values were 51.6%, 41.4%,24.8%, 15.4% and 98.2%, 98.2%, 96.0%, 91.0% for NF90-30 bar + BW30-35 bar, NF90-30 bar + BW30-25 bar, NF270-30 bar + BW30-35 bar and single BW30-35 bar, respectively.The qualities of the product waters of integrated systems (NF+BWRO) and the single BWRO system were also investigated. Boron rejection was fairly well with average boronrejections of 59.3% and 60.2% by NF90-30 bar + BW30-25 bar and NF90-30 bar + BW30-35 bar combinations, respectively while single BW30-35 bar gave an average rejection of49.6%. The results obtained showed that the quality of product water obtained using single BWRO did not comply with the irrigation standards, while the integrated systems providedtotal compliance to irrigation standards with the exception of boron.

In many islands, especially those small island developing states (SIDS), are extremely depend on tourism for supporting their economy; however, the development of tourism always accompanies the consumption of natural resources, in which fresh water is particularly essential. An expansion of tourism leads to increased demand for water; consequently, a lack of fresh water can restrict the sustainable development of those islands. With the progress of technique, applying reverse osmosis membrane has become a tendency when treating raw water. The conventional pumping strategies always depend on engineers’ judgments when facing multi-source feed water desalination plant; therefore they could not sure whether their operation could conform to the optimality of water resources management. This research aims at the pumping planning of a brackish water reverse osmosis (BWRO) plant, and proposed a nonlinear mathematical programming model, to design the optimal pumping allocation of a BWRO plant with proactive framework. The results shown that the proposed model of the paper not only could provide available information in BWRO feed water management, but could allow engineers gain new insight through the management sciences.

Pioneering demineralized and desalinated water cost reduction with innovative brackish water RO membrane technology

When designing and building an optimal reverse osmosis (RO) desalination plant, it is important that engineers select effective membrane parameters for optimal application performance. The membrane selection can determine the success or failure of the entire desalination operation. The objective of this work is to review available membrane types and design parameters that can be selected for optimal application to yield the highest potential for plant operations. Factors such as osmotic pressure, water flux values, and membrane resistance will all be evaluated as functions of membrane parameters. The optimization of these parameters will be determined through the deployment of the solution-diffusion model devolved from the Maxwell Stephan Equation. When applying the solution-diffusion model to evaluate RO membranes, the Maxwell Stephan Equation provides mathematical analysis through which the steps for mass transfer through a RO membrane may be observed and calculated. A practical study of the use of the solution-diffusion model will be discussed. This study uses the diffusion-solution model to evaluate the effectiveness of a variety of Toray RO membranes. This practical application confirms two principal hypotheses when using the diffusion-solution model for membrane evaluation. First, there is an inverse relationship between membrane and water flux rate. Second, there is a proportional linear relationship between overall water flux rate and the applied pressure across a membrane.

Capital cost estimation of RO plants: GCC countries versus southern Europe

Performance analysis of a medium-sized industrial reverse osmosis brackish water desalination plant

Exploring mass transfer mechanisms in reverse osmosis membranes: A comparative study of SDM and DSPM-DE models

Tandom reverse osmosis process for zero-liquid discharge

Rejection of selected N -nitrosamines, a group of probable human carcinogens, and their precursors by nanofiltration (NF) and brackish water reverse osmosis (BWRO) membranes was evaluated using a bench-scale cross-flow filtration apparatus. The tested nitrosamines included N -nitrosodimethylamine, N -nitrosomethylethylamine, N -nitrosopyrrolidine, N -nitrosodiethylamine, N -nitrosodi- n -propylamine, and N -nitrosodi- n -butylamine. The target nitrosamine precursors included secondary amines such as dimethylamine, methylethylamine, diethylamine, and dipropylamine. Rejection of nitrosamines varied greatly depending on the tested membranes (9–75% for NF membranes and 54–97% for BWRO membranes) and the molecular weight of nitrosamines. Experimental data obtained with the BWRO membranes matched well with an irreversible thermodynamic model coupled with film theory. The model further suggested that effective diffusion of nitrosamines through the BWRO membranes is responsible for the relatively low rejections o...

The effect of UV pre-treatment on biofouling of BWRO membranes: A field study