Seawater Reverse Osmosis System Research Articles

Optimize and analyze a large-scale grid-tied solar PV-powered SWRO system for sustainable water-energy nexus

The lack of clean water and access to energy are two major obstacles to global sustainable systems. The development of solar photovoltaic (PV) technology gained the attention of water desalination projects due to its cost decline, carbon-free emission, and the on-site energy production. However, studies on in-depth analysis of the performance of these systems remain rare. This study performs a comprehensive a design optimization and seven-factor analysis (energy, exergy, economic, environmental, energoeconomic, exergoeconomic, enviroeconomic - 7E) of a grid-tied PV system powering a large-scale seawater reverse osmosis (SWRO) plant. First, an optimal design model is developed based on real hourly measured data for the SWRO load demand and renewable resources, while considering net energy metering mechanism. The objective function is delineated to diminish the energy cost of the system, concomitant with the imposition of operational constraints. Second, an analytical model is established to perform exergetic calculations for the optimal design. Third, a sensitivity analysis is conducted to show how the model parameters affect the system design and costs. The results show that the optimal system relies on a 4.25 MW solar PV array and a 3.125 MW grid-tied inverter. This configuration reduces the levelized cost of energy by 48.3 % and carbon emissions by 50 % compared to a grid-only system. The implementation of net-metering has also maximized the designed system's revenues to 263,834 $/year. Further, the optimally designed system achieves a lower levelized cost of water (0.2217 $/m3), minimal capacity shortage, and negligible unmet load ratios (0.048 %) despite grid outages. From the exergetic assessment, the proposed system has a high exergy efficiency (9.3 %) which can be achieved despite the high value of the exergy loss. Moreover, the energoeconomic and exergoeconomic indicators have recorded tiny values (3.35E-5 kWh/$ and 0.0311 kWh/$, respectively), which are considered a desired outcome. Notably, a profit of 4285.4$ is achieved through the sale of carbon emissions reduction. The sensitivity analysis revealed an increase in the system's total cost of 4.91 % and 9.36 % and the system's energy cost of 4.91 % and 8.7 % if the energy purchase price raised by 10 % and 20 %, respectively. Also, it indicates that a fall in the electricity sellback rate of 10 % would remarkably raise the system's energy cost by 47.3 %. Finally, reducing the PV-Inverter costs by 15 % would drop the system's net present and energy costs by 51.4 % and 60 %, respectively. Overall, the insights from this study have the potential to expedite the realization of sustainable development goals 6, 7, and 13, particularly in developing nations abundant in solar energy resources.

Effects of the Design of Pressure Vessels on Performance and Hydrodynamic Parameters in Two-Pass Seawater Reverse Osmosis Systems

Effects of the Design of Pressure Vessels on Performance and Hydrodynamic Parameters in Two-Pass Seawater Reverse Osmosis Systems

Performance Analysis of Reverse Osmosis Desalination Plant, Study Case of BBRI Plant

Desalination using seawater resources has been a cornerstone in meeting both human and industrial water demands for several decades. Some well-known methods are thermal desalination and membrane desalination. Among these, membrane desalination stands out, employing reverse osmosis (RO) technology, wherein seawater is pressurized and forced through a semi-permeable membrane to produce purified water. Black Bear Resources Indonesia (BBRI), which operates in the chemical industry relies on RO technology to cater its desalination requirements within the manufacturing facility. Notably, BBRI's desalination plant is equipped with both Seawater Reverse Osmosis (SWRO) and Brackish Water Reverse Osmosis (BWRO) modules. In the SWRO unit, the Hydranautic SWC-6 Max membrane is employed, while the BWRO unit features the Hydranautic ESPA-2 LD membrane. Both modules adopt the spiral wound configuration utilizing polyamide composite material. To determine the reliability of factory operations and dependability, a comprehensive performance analysis of the SWRO and BWRO units is imperative. This analysis encompasses critical parameters such as Recovery Rate, Membrane Flux, Percent Rejection, Concentration Rejection, and Specific Energy Consumption (SEC). Notably, performance degradation in both SWRO and BWRO systems primarily stems from membrane fouling, scaling phenomena, and the natural aging of the membranes.

Techno‐enviro‐economic design of small‐scale membrane‐based seawater desalination systems integrated with hybrid autonomous renewable power systems

AbstractThis article aims to search the technical, environmental, and economic model of an off‐grid hybrid power generation system that supplies electricity to a seawater reverse osmosis (RO) system. Net present cost (NPC) and levelized cost of electricity (LCOE) values were used to determine the optimal system sizing powering a reverse osmosis desalination system for different sites where is located south and west coast of Türkiye. In the proposed power systems, PV panels, wind turbines, diesel generators, lead‐acid batteries, and converters were used. In the instance where the lowest LCOE of 0.301$/kWh is calculated, the optimal system comprises of a 25.7 kW PV array, one wind turbine (rated at 10 kW), 152 kWh LA batteries, and a 6.76 kW converter. The levelized cost of water (LCOW) value for this case was calculated as 1.168 $/m3. The LCOE value was calculated as 0.529 $/kWh for the power system, which is considered as a base case and consists of only a diesel generator, where no renewable energy source is used. For the base case, the carbon footprint of electricity generation is 35,127 kg/year. According to CO2 sequestration analysis result, the number of trees (Pinus Brutia) to be planted was calculated as approximately 164 tree/year over the lifetime of the power system for base case.

Resource recovery from RO concentrate using nanofiltration: Impact of active layer thickness on performance

Modelling the removal of monovalent and divalent ions from seawater via nanofiltration is crucial for pre-treatment in seawater reverse osmosis systems. Effective separation of divalent ions through nanofiltration and allowing the permeate containing only monovalent ions to pass through the reverse osmosis system produces pure NaCl salt from the concentrate. However, the Donnan steric pore model and dielectric exclusion assume a uniformly distributed cylinder pore morphology, which is not representative of the actual membrane structure. This study analyzed the impact of membrane thickness on neutral solute removal and investigated the effect of two different methods for calculating the Peclet number on rejection rates of monovalent and divalent salts. Results show that membrane thickness has a significant effect on rejection rates, particularly for uncharged solutes in the range of 0.5–0.7 solute radius to membrane pore size ratio. Operating pressures above 10 bar favour the use of effective active layer thickness over the membrane pore size to calculate the Peclet number. At low pressures, using the effective active layer can lead to overestimation of monovalent salt rejection and underestimation of divalent salt rejection. This study highlights the importance of appropriate Peclet number calculation methods based on applied pressure when modelling membrane separation performance.

Numerical study on the energy consumption characteristics of a novel integrated pump-motor unit for SWRO desalination system

Energy recovery device (ERD) is a critical component in seawater reverse osmosis (SWRO) desalination systems, which recovers hydraulic energy from the high-pressure brine and effectively reduces system energy consumption. In this thesis, a novel integrated seawater desalination pump-motor energy recovery device (ISPM-ERD) without the slipper/swashplate interface is proposed to further reduce energy consumption and improve system integration, which is able of concomitantly achieving seawater pressurization and energy recovery. A co-simulation multibody dynamic model with rigid-flexible coupling is applied to precisely examine the internal power loss of ISPM-ERD, especially volumetric loss and mechanical loss of the key lubricating interface. Besides, the influence of shaft rotational speed and working pressure on the power loss and overall efficiency of ISPM-ERD are comparatively investigated. In addition, a performance study of the presented ISPM-ERD is carried out based on the co-simulation model, which reveals the energy recovery efficiency and specific energy consumption (SEC) of ISPM-ERD under various operating conditions. The results indicate that the proposed ISPM-ERD is sufficient to meet the needs of the small-scale SWRO systems, whose energy recovery efficiency is more than 90.1 % in the 3.0–7.0 MPa operating pressure range and the SEC of freshwater production is 2.94 kW·h/m3 under rated working conditions.

Feasibility assessment of alternative environmentally friendly disinfection technique for reverse osmosis-based desalination process

In the seawater reverse osmosis (SWRO) process, the chlorine-based disinfection method poses significant incidental problems, such as producing disinfection by-products and damaging the SWRO membrane surface directly. Chlorine dioxide can control the biofouling layer and relatively stable disinfection approach during the operation. Major two perspective views, such as process stability (water flux and salt rejection) and membrane surface functionality, we evaluated chlorine dioxide feasibility as an alternative disinfection. Standard SWRO performance was evaluated at various operation conditions (inlet pressure and flow rate) using a customized SWRO system. For the stability of the chlorine dioxide disinfection approach, the chemical exposure test was conducted within the concentration and time-variant. While full total 30 days of long-term operation with continuous chlorine dioxide (0.5 mg/L) stripping during the SWRO desalination process, water flux and salt rejection rate maintain 26.7 L.min−1 and 99.7 % respectively.

Comparative life cycle assessment of seawater desalination technologies enhanced by graphene membranes

Graphene oxide (GO)-enhanced membranes are being developed to solve major limitations in both reverse osmosis (RO) and membrane distillation (MD) technologies, which include high electricity and thermal energy consumption. This study performed, for the first time, a life cycle assessment to determine the effects of using GO-enhanced membranes on the environmental impacts of seawater desalination via RO and MD. Four scenarios were evaluated and eighteen environmental impacts were quantified according to the ReCiPe impact assessment method. The average impacts for the RO-GO scenarios were lower than those of RO by 3–7 %. The reduction in the climate change impact was 3–8 %, which could avoid the release of 380–850 kt CO2 eq. per year globally if these membranes were used in current seawater RO systems. The MD-GO scenarios had, on average, 27–34 % lower impacts than the MD scenarios. Overall, the RO-GO systems were the most favourable, with lower impacts than MD-GO for most categories. However, using solar-thermal energy instead of natural gas in MD desalination would lead to 43–93 % lower impacts in nine categories than RO powered predominantly by fossil fuels. This includes climate change, which would be 64 % lower; however, freshwater ecotoxicity would be more than four-times higher. The results of this work indicate the potential environmental benefits of GO-enhanced membranes and discuss the future developments needed to improve the performance of RO and MD.

A proposed safe design of the reverse osmosis system

In a seawater reverse osmosis (SWRO) desalination plant, the SWRO system includes the high-pressure pump, the high-pressure piping, the energy recovery equipment, the pressure vessels and the RO membranes. The membranes are the most delicate part of the plant and are subject to continuous operational variations during water production. Designers of plants propose various solutions to protect the RO system through the use of mechanical and control/automation devices. This paper aims to present several design and operational considerations and address them through a proposed technical solution. With the correct combination of instruments, the RO membranes are protected and the overpressure in the system can only happen due to malfunction or failure of the instruments.

Effects of Total Dissolved Solids on Pressure Drop and Net Driving Pressure in Different Designs of Brackish and Seawater Reverse Osmosis Systems

Effects of Total Dissolved Solids on Pressure Drop and Net Driving Pressure in Different Designs of Brackish and Seawater Reverse Osmosis Systems

Optimal design and operation of reverse osmosis seawater desalination system for boron removal with economic, energy, and environmental concerns

This paper introduces a superstructure-based simultaneous optimum design and operation of seawater reverse osmosis (RO) system with boron removal under time-variant constraints. Three operational strategies are utilized to improve operability of the system under boron restrictions, including changing the activated number of pressure vessels, permeates split ratio, and pH values. Moreover, exergo-environmental and exergo-econoenvironmental analysis models are integrated. The economic efficiency, energy utilization, and environmental impact could be optimized in both design and operation phases. The effect of water tank area, membrane type, and boron concentration on water production are investigated with constant feed conditions. Choosing proper water tank volume and type of membrane could not only reduce cost but also better operation conditions, such as improving the efficiency of pumps and reducing feed pH of RO pass 2. When both the eco-costs/value ratio and emergy rate of product are added as a penalty, the annual operation cost (a reduction of 5.50 %), emergy rate (a reduction of 7.02 %) and eco-costs/value ratio (a reduction of 7.48 %) of the product could be reduced with only a small amount of water cost increment (about 2.66 %). Improving the efficiency of pumps would be an effective method to improve overall performance of the RO plant.

Performance model for reverse osmosis

To meet the increasing global demand for freshwater, seawater reverse osmosis (SWRO) has become a widely used technology to produce freshwater from seawater. A SWRO system consists of different components such as pumps, membranes, valves, and energy recovery devices. While it may be simple for process designers to understand the individual performance of each piece of equipment, the performance of an entire SWRO system can be complex and counter-intuitive. Furthermore, SWRO processes are energy-intensive; thus, to minimize the Specific Energy Consumption (SEC) of the process, it is of utmost importance that the performance of the system is monitored in real-time. Due to periodic changes in seawater quality and weather conditions, the operating parameters in a SWRO plant need continuous tweaking to minimize energy consumption and optimize the use of chemicals such that product water quality requirements are met. This calls for the need of a performance monitoring and optimization tool for SWRO. Since the advent of RO in 1950, such a system has never existed. Here, we present the first performance model for reverse osmosis (PMRO) for monitoring and optimizing the performance of SWRO assets;the developed model predicts the SEC of an operating SWRO plant with 93 % accuracy.

Research on the pressure and flow characteristics of seawater axial piston pump considering cavitation for reverse osmosis desalination system

Seawater axial piston pump (SWAPP) has been widely used as the power component in the seawater reverse osmosis (SWRO) desalination systems, whose flow quality could result in significant influences on the performance of RO membranes and SWRO system. This thesis proposed an efficient fully parameterized mathematical approach for the flow and pressure characteristics of SWAPP that is modeled by lumped parameter techniques considering gaseous and vaporous cavitation simultaneously. To address the complex structure of the port plate in SWAPP, especially silencing groove, an innovative model based on the Monte Carlo method was originally proposed, and In-depth comparison with piecewise functions validated the accuracy, efficient and convenient of Monte Carlo approach for calculating the flow area of SWAPP. Particularly, the influence of shaft rotational speed and inlet pressure on the instantaneous discharge flow and pressure of SWAPP was comparatively studied. In addition, a SWRO desalination system was constructed to evaluate the effect of discharge pressure of SWAPP on the RO concentrated brine pressure. The results indicate that the presented model can precisely capture the instantaneous discharge pressure and flow of SWAPP. Besides, increasing the shaft rotational speed and inlet pressure are reliable solutions to enhance the flow performance of SWRO system.

Development and fluid fluctuation analysis of a novel valve-controlled energy recovery device for small-scale reverse osmosis desalination systems

Energy recovery devices (ERD) are vital for improving the energy efficiency of reverse osmosis (RO). Nevertheless, small-scale seawater RO systems are rarely equipped with ERDs, mainly because of the associated high capital and maintenance costs. Herein, we propose a new type of reciprocating switcher (RS)-ERD with dual self-boost hydraulic cylinders that can pre-pressurize the low-pressure hydraulic cylinder during stroke switching. The structure and working process of the pre-pressurization reciprocating switcher (PPRS)-ERD are presented, and mathematical models of the entire system are established. Based on these models, a detailed performance analysis is performed. Compared to the conventional RS-ERD, both the high pressure (HP) check valve cores and hydraulic cylinders move smoothly, which suggests that the vibrations of the check valves and cylinders can be neglected. The maximum pressure fluctuation amplitudes of HP seawater (HPS) at the outlet and HP brine (HPB) at the inlet are 0.015 MPa and 0.016 MPa, which represent decreases of 98.91 % and 98.87 %, respectively. The flow fluctuation amplitudes of HPS and HPB do not exceed 0.17 m3/h and 0.07 m3/h, which represent improvements of 95.34 % and 96.59 %, respectively.

Simulation-based assessment of safe operating windows and optimization in full-scale seawater reverse osmosis systems

Reverse osmosis (RO) is the most widely used desalination technology for both seawater and brackish water. Unfortunately, RO remains an energy intensive technology despite the efforts being made to overcome this drawback. One of the factors that could help to minimize this issue is the optimal design and operation of RO systems. Membrane manufacturers are continuously improving and releasing new spiral wound membrane modules (SWMMs) that nonetheless need to be studied in order to determine how to achieve the best highest possible performance from them. The aim of this study was to evaluate the safe operating windows (SOWs) of 9 commercial SWMMs in pressure vessels (PVs) with 7 of these elements in a single stage seawater reverse osmosis (SWRO) system. The permeability coefficients of the SWMMs were taken from a novel membrane open database. These coefficients and the characteristics of the SWMMs were introduced in a simulation algorithm to estimate the behavior of the SWRO system. SOWs were determined without considering any energy recovery device, although these were considered for the calculation of the minimum energy consumption. The SWMMs were compared and the optimal operating points were identified for each one. The results showed the highest difference was around 0.2 kWhm−3 between SWMMs in their optimal operating point with respect to the minimum specific energy consumption. It was also found that this difference increases slightly with rises in feedwater concentration. For a wide range of PV power inputs, the SWMMs were able to reach quite similar maximum flux recovery rates. Experimental work is needed to obtain more reliable predictions of SWRO systems working in wide operating ranges.

Simulation and optimisation of a SWRO system in Cape Town, South Africa

Seawater reverse osmosis (SWRO) system is popular in most islands and coastal areas around the world with limited fresh water resources. A SWRO system was designed to fulfil 50% of the population water demand in Cape Town, South Africa, which can lead up to 383,353 m3/day in the next 15 years. The total dissolved solid (TDS) within the product (i.e. drinking water) was lowered to 600 ppm by referring to standard guideline stated by the World Health Organization (WHO). Design flowrate was set at 766,704 m3/day and the parameters such as feed, permeate, concentrate flowrate, number of vessels, number of membrane elements, number of stages, seawater chemical composition, temperature, pressure, and system configuration were considered in this study. Reverse Osmosis System Analysis (ROSA) 2017 software was integrated the design with simulation to further understand how different parameters affect one another in SWRO system. The TDS standard value of 600 ppm in the products were 73.76 ppm and 181.13 ppm after further optimisation. The efficiency of the SWRO system recovery rate was 75.87% and specific energy consumption (SEC) was 6.18 kwh/m3, greater than the previous value of 50% and 9.7 kwh/m3 in terms of recovery percentage and SEC respectively. The findings indicate that a lower amount of feed and energy is needed to achieve the desired production value. Hence, it is also resulting in major savings in terms of operating cost for SWRO system.

Simulation-Based Assessment of Safe Operating Windows and Optimization in Seawater Reverse Osmosis Systems

Simulation-Based Assessment of Safe Operating Windows and Optimization in Seawater Reverse Osmosis Systems

A water-heat combined supply system based on waste heat from a coastal nuclear power plant in northern China

• A new water-heat combined supply system based on waste heat is proposed. • The system realizes the simultaneous delivery of water and heat. • The heating and water supply costs are 34.27 ¥/GJ and 4.08 ¥/m 3 , respectively. • The system has a higher exergy efficiency and a better economic benefit. Based on the existing waste heat recovery technology and seawater desalination technology, a water-heat combined supply system based on waste heat from a costal nuclear power plant is proposed. The proposed system can improve the heating capacity of district heating systems and reduce the energy consumption of water-generating seawater reverse osmosis systems by recovering the waste heat from exhaust steam in a nuclear power plant. Through the simultaneous delivery of water and heat, the long-distance conveyance cost is reduced. The thermodynamic characteristics, energy-saving properties, environmental benefits, and economic efficiency of the proposed system are discussed and analysed. The results show that the heating capacity of the proposed system is increased by 55.5% compared to the original extraction steam heating load. The exergy efficiency is 16.07% higher and the heating cost is 12.32 ¥/GJ lower than those of traditional cogeneration district heating systems. The water supply cost of the proposed system is 2.95 ¥/m 3 lower than that of the conventional desalination water supply system. The current results of this study will be helpful in solving problems related to heat and water resource shortages and the high costs of long-distance heat and water conveyance in coastal areas.

Performance evaluation and boron rejection in a SWRO system under variable operating conditions

It is well known that reverse osmosis (RO) is the leading desalination technology. As an energy intensive technology, the exploitation of renewable energy sources (RES) to power RO systems is a attractive option. A strategy to take advantage of all the available energy of an off-grid renewable system is to work with the RO system under variable operating conditions. This implies additional challenges in terms of water production and permeate quality, among others. Boron rejection is one of the main concerns in seawater RO (SWRO) systems. The aim of this work was to evaluate the performance and boron rejection of a single-stage SWRO system with 7 membrane elements per pressure vessel under variable operating conditions. The initial permeability coefficients of two SWRO membranes (TM820L-440 and TM820S-400) were calculated from experimental data of a full-scale SWRO desalination plant. These coefficients and the characteristics of the membranes were introduced in a simulation algorithm to estimate the behavior of the SWRO system. The results show that, compared with the TM820S-400 membrane, the TM820L-440 performed better in terms of boron rejection in the form of boric acid, but worse in terms of water production. When RES-powered SWRO systems are designed to work under variable operating conditions, consideration needs to be given to the safe operation window in terms of boron concentration in the permeate and to variation of the permeability coefficient of the membranes.

Performance evaluation of a Sea water reverse osmosis system at different operating scenarios

Performance evaluation of a Sea water reverse osmosis system at different operating scenarios