Reverse Osmosis Design Research Articles

Boosting sustainable water production by upstream integration of desalination with saltworks in the Mediterranean region

SEArcularMINE is an EU project that is focused on mineral extraction from saltwork bitterns, adopting a circular approach. Within this context, this work shows the possibility of completing the circular scheme with an upwind integration of seawater desalination that can provide freshwater to the local community but also use the brine reject to feed the saltwork in order to increase its productivity. In this study, a specific case of a natural saltwork in Trapani (Italy) is presented, assuming to place a desalination plant very close to the saltworks, so that the brine can be sent there without an additional energy input. After choosing the best desalination technology, demonstrating that Reverse Osmosis (RO) is more suitable than thermal processes from both economic and environmental point of view, the details of the RO design are presented. Then, preliminary calculations using a simple model for the saltwork ponds have been performed, showing that the brine feed can either increase the salt productivity by more than 50% or that the ponds surface can be reduced by more than 40%. Finally, evaporation experiments on desalination brines have been performed to demonstrate that no changes in salt quality occur compared to the standard seawater feed.

High recovery reverse osmosis design to minimize wastewater of ultra-pure water production process

High recovery reverse osmosis design to minimize wastewater of ultra-pure water production process

Superstructure based optimization of reverse osmosis desalination systems fed by decarbonated high-pH seawater under boron restrictions

This paper presents a superstructure based optimization of reverse osmosis (RO) system fed by decarbonated seawater (DS) at high pH value under boron restrictions. Each RO stage/pass could be operated with high boron rejection. The permeate split (PS) design allows permeates with different quality collecting from both sides of pressure vessel (PV). The pH variations are fitted by experiment and simulated results from the literature. The accuracy of the RO model is also validated. Results showed that about 3.48%−18.31% water cost and 3.04%−14.61% energy consumption savings are achieved by permeate split with decarbonated seawater (PSDS) design. Water cost is less influenced by pH values for PSDS design, which might be a robust solution for pH control. A two-stage stochastic model is performed to obtain robust and flexible designs considering uncertainties of the RO design problem. Both operational conditions and process flow are adjusted to save water cost and energy consumption.

Thin Film Composite Polyamide Reverse Osmosis Membrane Technology towards a Circular Economy.

It is estimated that Reverse Osmosis (RO) desalination will produce, by 2025, more than 2,000,000 end-of-life membranes annually worldwide. This review examines the implementation of circular economy principles in RO technology through a comprehensive analysis of the RO membrane life cycle (manufacturing, usage, and end-of-life management). Future RO design should incorporate a biobased composition (biopolymers, recycled materials, and green solvents), improve the durability of the membranes (fouling and chlorine resistance), and facilitate the recyclability of the modules. Moreover, proper membrane maintenance at the usage phase, attained through the implementation of feed pre-treatment, early fouling detection, and membrane cleaning methods can help extend the service time of RO elements. Currently, end-of-life membranes are dumped in landfills, which is contrary to the waste hierarchy. This review analyses up to now developed alternative valorisation routes of end-of-life RO membranes, including reuse, direct and indirect recycling, and energy recovery, placing a special focus on emerging indirect recycling strategies. Lastly, Life Cycle Assessment is presented as a holistic methodology to evaluate the environmental and economic burdens of membrane recycling strategies. According to the European Commission’s objectives set through the Green Deal, future perspectives indicate that end-of-life membrane valorisation strategies will keep gaining increasing interest in the upcoming years.

Trends and errors in reverse osmosis membrane performance calculations stemming from test pressure and simplifying assumptions about concentration polarization and solute rejection

A primary goal in the design of reverse osmosis (RO) membranes is to improve water-solute selectivity and water permeance. These transport properties are commonly calculated in the literature using the solution-diffusion model with selectivity (A/B, bar−1) defined as the ratio between water permeance (A, L.m−2.h−1.bar−1) and solute permeance (B, L.m−2.h−1). In calculating transport properties, researchers often use simplifying assumptions about concentration polarization (CP; i.e., assuming negligible CP or a certain extent of CP) and solute rejection (i.e., assuming solute rejection is approximately 1 to enable the explicit use of the CP modulus in solute permeance calculations). Although using these assumptions to calculate transport properties is common practice, we could not find a study that evaluated the errors associated with using them. The uncertainty in these errors could impede unequivocally identifying manufacturing approaches that break through the commonly plotted trade-off frontier between selectivity and water permeance (A/B vs. A); however, we did not find in the literature a study that quantified such errors. Accordingly, we aimed to: (1) quantify the error in transport properties (A, B, and A/B) calculated using common simplifying assumptions about CP and rejection; and (2) determine if using simplifying assumptions affects conclusions drawn about membrane performance or trends concerning the trade-off frontier. Results show that compared with the case where no simplifying assumptions were made, simplified calculations were least accurate at low pressures for water permeance (up to 78% overestimation) and high pressures for solute permeance (up to 188% overestimation). Accordingly, the corresponding selectivities were least accurate at low pressure (up to 111% overestimation) and high pressure (up to 66% underestimation), and conclusions drawn about membrane performance and trade-off trends were pressure-dependent. Importantly, even in the absence of simplifying assumptions, selectivity results were pressure-dependent, indicating the importance of standardizing test conditions for the continued use of current performance metrics (i.e., A/B and A). We propose a two-pressure approach—collecting data for A and B at a high and a low pressure, respectively—combined with simplifying assumptions for more accurate simplified estimations of selectivity (< 10% absolute error). Our work contributes to a better understanding of the effects of operating pressure and key simplifying assumptions commonly used in calculating RO membrane performance metrics and interpretation of corresponding results.

Numerical Simulations of Calcium Sulphate Scaling in Full-Scale Brackish Water Reverse Osmosis Pressure Vessels Using Computational Fluid Dynamics.

Coal mine waters often have high salinity, hardness and alkalinity. The treatment of coal mine water requires careful management of multi-stage reverse osmosis (RO) systems to achieve effective recovery of water for domestic reuse, as well as zero liquid discharge to minimise the impact to the local environment. Design of RO systems for coal mine water treatment has been limited to the use of commercial design packages provided by membrane manufacturers, which do not provide insights into the impact of operating parameters such as feedwater salinity, concentrations of sparingly soluble salts, feed pressure and their interactions with different RO modules on the fouling/scaling potential of RO membranes. This also restricts the use of novel RO products and the delivery of an optimum design based on real needs. In this work, a mathematical model was developed to simulate a standard brackish water RO pressure vessel consisting six full-size RO membrane elements, using computational fluid dynamics (CFD). The model can be used to predict the permeate flowrate, water recovery levels, as well as the spatial information of the accumulation and scaling potential of sparingly soluble salts on the membrane surface. The results obtained from the model showed good agreement with the results obtained from the commercial RO design software WAVE. The CFD model was then used to predict the scaling threshold on various positions of a full-scale RO element, at different operating conditions, using parametric simulations based on Central Composite Designs. Outputs from this work not only provide insights into the microscopic flow characteristics of multiple full-scale elements in the RO pressure vessel, but also predicts the position where scaling would occur, at different feed conditions, for any RO products.

Does Pressure-Retarded Osmosis Help Reverse Osmosis in Desalination?

In a recent study [Parra, A. Ind. Eng. Chem. Res. 2019, 588 3060−3071], the design of reverse osmosis (RO) systems for desalination of water at different concentrations was studied and optimal solu...

Design of Reverse Osmosis Desalination Plant at Remote Coastal Area

During the long dry season hit most parts of East Java in 2019, there were 566 villages in 180 sub-districts that are categorized as dry areas with critical clean water supply, 236 villages in 93 sub-districts as rare dry areas, and 20 villages in 14 sub-districts experienced limited dryness. In big cities in Indonesia, clean water service coverage has only reached 64.3%, while in rural areas still at 69.4%. This proves that most of the regions in Indonesia still experiencing a clean water crisis. Therefore, alternative clean water processing technology is needed to help supply clean water in these areas. Desalination as one of the technologies is essential for coastal areas that are remote from freshwater resources. In this paper, authors propose a design of photovoltaic reverse osmosis (PVRO) desalination plant at remote coastal area to supply clean water. A 100 m3/day design of PVRO, which is compact and energy efficient including the ultrafiltration method is introduced.

Design, modelling and optimisation of a batch reverse osmosis (RO) desalination system using a free piston for brackish water treatment

Batch RO is a concept for achieving the minimum possible energy consumption in desalination, even at high recoveries. We present a batch RO design that operates cyclically in two alternating phases. The system uses a free piston, housed in a pressure vessel, to transfer pressure from the feed fluid to the recirculating fluid. No complete design procedure for this configuration currently exists. To fill this gap, we present a systematic model based on justified assumptions. The specific energy consumption (SEC) is broken down into contributions from the feed pump, recirculating pump, and auxiliary loads. The calculation of feed pump SEC includes three non-ideal correction factors: concentration polarisation, longitudinal concentration gradient, and salt retention. The model requires only the solution of explicit algebraic equations, without need of specialised numerical techniques, and is implemented in a simple 3-step procedure. The model is applied to an example involving desalination of brackish water using an 8-inch spiral-wound RO module. The design parameters are explored and optimised in a sensitivity analysis. The results show that the optimised batch RO at 80% recovery can produce fresh water with low-energy consumption, achieving 2nd law efficiency of 33.2% compared to 10–15% for conventional brackish water RO.

MINLP Model for Reverse Osmosis Network Design under Time-Variant Operation Constraints

Reverse osmosis (RO) is a very well-established technology for water desalination. Commercial RO systems are composed of several numbers of RO passes with auxiliary equipment such as high-pressure pumps and pressure-exchanger units to facilitate the separation, and to deliver clean water. Available design models for the RO network represent mixed integer nonlinear programming (MINLP) formulations. In addition, the existing RO design MINLP models are static in nature. These models are not suitable for RO network design under time-variant constraints. In this study, a multiperiod MINLP model is detailed for the RO network design. High-level design decision variables are related to the RO network configuration and equipment sizing, which are independent of time. These decisions are modeled by discrete and continuous variables. Low-level time-variant decision variables are related to the RO network operation and modeled by continuous variables. The operation decision variables are constrained by the design variables through different time periods to satisfy water-demand constraints. In addition, several correlations are considered in this study to estimate water and RO transport properties during the separation process. Case studies are analyzed to show the application of the mathematical programming model.

Super-twisting sliding mode control and robust loop shaping design of RO desalination process powered by PV generator

Reverse osmosis (RO) desalination technique is the most widely used technology for supplying fresh water since it offers many advantages. Developing an accurate control strategy is one of the most challenging jobs in RO desalination plant especially under uncertainties and disturbances conditions to avoid all possible system failures and damages for safe operations. This paper presents an overall architecture of reverse osmosis desalination process supplied by a stand-alone photovoltaic (PV) system. A dynamic modeling of various components of this architecture is developed. A control strategy of the whole system is addressed with a controller for each part. Furthermore, special attention is given here to the robust control design of reverse osmosis (RO) membrane to address large set point changes and capability to reject external disturbances and to cope with parametric uncertainties as variations in feed water salinity. The control block is divided into two loops the first one using the loop shaping design method and the super-twisting sliding mode control is applied for the second loop. Simulation results investigating different scenarios show the efficiency of the proposed scheme.

Reverse Osmosis Network Rigorous Design Optimization

In this work, we propose a methodology to solve a nonlinear mathematical model for the optimal design of reverse osmosis (RO) networks, which ameliorates the shortcomings of the computational performance and sometimes convergence failures of commercial software to solve the rigorous mixed integer nonlinear programming (MINLP) models. Our strategy consists of the use of a genetic algorithm to obtain initial values for a full nonlinear MINLP model. In addition, because the genetic algorithm based on the rigorous model equations is insurmountably slow, we use metamodels to reduce the mathematical complexity and considerably speed up the run. We explore the effects of the feed flow, seawater concentration, number of reverse osmosis stages, and the maximum number of membrane modules in each pressure vessel on the total annualized cost of the plant.

Assessing the feasibility of applying Reverse Osmosis technology at MN Port

This paper aims to assess the feasibility of applying Reverse Osmosis (RO) technology at MN Port. Hydro-oceanography analysis was performed to understand sea conditions in the proximity of MN Port and to determine water intake point. Furthermore, design analysis was also conducted to determine the most suitable RO design to be applied. Based on the hydro-oceanography analysis, the study area is generally shallow water areas with the depth ranges from 2-10 meters, and the type of tide is diurnal tide. The speed and direction of ocean currents range from 0.01-0.06 m/s with the dominant direction trending northeast and north. Based on the port development plan and hydro-oceanography analysis, it is recommended that the water intake point is at the north of the port. The results obtained from several analyses show that RO technology can be applied at MN Port.

Effective design of reverse osmosis based desalination process considering wide range of salinity and seawater temperature

The design of reverse osmosis (RO) network for desalination for a wide range of salinity and seawater temperature is considered here. We start with a flexible superstructure that contains all possible alternatives of a potential RO network and refine the network during the synthesis using model based optimization technique. The synthesis problem is posed to find out an optimal RO network which will minimize the total annualized cost consisting of capital costs (costs of sea water pre-treatment, pump, turbine and membrane modules) and operating costs (pumping energy, chemicals, maintenance and membrane replacement) while fulfilling a given fresh water demand and quality. The problem results in a mixed-integer non-linear programming (MINLP) problem due to the presence of both integer and non-integer decision variables. Outer approximation algorithm within gPROMS software is used to solve the optimization problem. The results revealed that the feed salinity and temperature have significant impact on the RO network design and operation.

Optimal design of reverse osmosis‐based water treatment systems

AbstractWe address the problem of optimal design of reverse osmosis (RO)‐based water treatment systems. A superstructure optimization method is proposed to solve the problem, where the superstructure for a RO system is structurally enhanced with additional features. We formulate the problem as mixed‐integer nonlinear program which is solved to yield optimal results. A case study on desalination is considered in this work, and the numerical results obtained using our approach are validated using a commercial simulation tool. We further extend the problem by considering the effects of degradation of membrane performance over time and solve it by representing the problem as a two‐stage stochastic program. This new approach is highly useful for identifying minimum cost robust designs for membrane‐based water purification systems, which are especially important in desalination applications. © 2012 American Institute of Chemical Engineers AIChE J, 2012

Application of membrane processes in drinking water treatment–state of art

Membrane technology is widely accepted as a means of producing various qualities of water from surface water, well water, brackish water and seawater. In the treatment of water for drinking purposes first of all pressure-driven membrane techniques are used. The choice of the suitable membrane process depends on the size of the removed contaminants and admixtures from the water. Desalination of seawater and brackish groundwater is often the way to obtaining drinking water. Significant improvements in technology and design of reverse osmosis, the availability of alternative energy sources, the possibility of pretreatment and applied materials have caused the process to become environmentally-friendly source of fresh water in many regions of the world, particularly in those where their sources are limited. Nanofiltration and to some extent the reverse osmosis are the methods of water softening, as well as to remove disinfection by-products precursors and micropollutants. To remove inorganic micro-pollutants ...

Split partial second pass design for SWRO plants

All over the world, the reverse osmosis (RO) desalination plants are providing populations and industries with high quality freshwater. There are various requirements on water quality produced by RO desalination plants depending on final purpose of water usage. In recent years, the requirement for low Boron concentrations in RO permeate was the main parameter to be considered in designing many seawater RO systems. Beside the development of new RO membranes with improved Boron rejection, there are also other design options which can help to achieve required product quality. One of such options is also Split Partial Second Pass (SPSP) RO design. The principle of a SPSP design is based on the fact, that front elements in RO pressure vessel are always producing better permeate quality than elements at the back of the pressure vessel. In order to take advantage of better permeate quality at the front of the vessel in SPSP design, permeate is collected from both sides of the pressure vessel. Low TDS front permeate is than sent directly to final product line, while higher TDS back permeate is treated by partial second pass RO plant. At the end of the process, both permeate streams are blended together to create the final product of required quality. The SPSP design allows to select the right ratio between front and back permeate in order to obtain final product of required quality in terms of Boron, TDS and other quality parameters. The SPSP design provides cost effective option by minimizing the size of the second pass RO, which allows substantial savings on capital investments aswell as in operating cost of the plant. This paper will present in more details the SPSP design option and requirements, the important parameters influencing SPSP design and different ways of the control, and finally it will discuss benefits and savings resulting from this RO design option. It will also present actual operating data from seawater RO plant using this design option.

Evaluation of an innovative polyvinyl chloride (PVC) ultrafiltration membrane for wastewater treatment

The use of ultrafiltration (UF) employing a polyvinyl chloride (PVC) membrane (LH3-1060-V) as pretreatment for a reverse osmosis (RO) system treating secondary water effluent at the Scottsdale Water Campus was investigated. Membrane fouling tendency was evaluated, foulants were characterized, and chemical cleaning was optimized. Feed and permeate water qualities were indexed to address the effect of UF as a pretreatment on the RO process, in view of RO design and scale calculations. The results showed that the pilot plant operated stably for 102 days with a chemical cleaning interval of 69 days. The transmembrane pressure (TMP) ranged from 35.44 to 71.15 kPa, and the normalized flux was 72 L/(m 2 h) at 20 °C. The majority of the foulants were organic compounds (tannins, fulvic acids, humic acids, amino sugars, etc.) along with a few inorganic ones (iron, calcium, etc.). SEM–EDX mapping showed that most of the foulants deposited on the inner surface of the fiber. The best cleaning sequence for the fouled membrane was found to be 2% sodium hydroxide–0.5% citric acid, as 97% of the initial membrane flux was restored. The PVC-UF membrane efficiently removed turbidity, suspended solids and color, with removal efficiencies of 96.41%, 88.33%, and 50.00%, respectively. The UF pretreatment was found to enhance the RO average permeate flux and recovery by 34% and 21%, respectively, compared to the simulated conventional pretreatment system.

Comparison of multiple port and end port connections for pressure vessels

The design of reverse osmosis and nano filtration plants is essentially influenced not only by the module arrangement, but also by the arrangement of the pressure vessel connections. Multifarious design possibilities can be considered as a result of many improvements introduced over the last few years. The key attributes is the three purposes port arrangement, feed-, concentrate- and permeate connection while comparing multiple port versus end port design. The following paper discusses the main factors for future plant design: • Cost savings by reducing the complexity of stainless steel piping in multiple port design. • The impact of the more compact design on total foot print required for the membrane plant, • How can technical risks, especially corrosion, be considerably reduced, and • The impact of the hydraulic design of the entire piping system and its influence on energy costs.

Multi-objective optimization of RO desalination plants

A process optimization method has been developed for the design of reverse osmosis (RO) processes. RO process configurations are systematically generated using a flexible superstructure and evaluated by economical (investment and operating costs), technical (energy requirement, water recovery rate) and environmental performance indicators (Life Cycle Assessment). The simultaneous optimization of the RO process layout and operating conditions constitutes a mixed-integer nonlinear programming (MINLP) problem, which is solved using a multi-objective optimization (MOO) approach. The MOO identifies the best technological alternatives for the set of selected objectives. In a given context, it allows to define a set of optimal solutions representing the trade-off between conflicting objectives such as economical costs and environmental impacts. As a case study, the methodology is applied on a brackish water reverse osmosis (BWRO) desalination project, for which the optimal design is characterized depending on the economical conditions.