An experiment with spiral wound reverse osmosis membranes for the Desalination of seawater

Desalination of seawater: an experiment with RO membranes

In the present work, the performance of a small reverse osmosis RO (house scale) desalination unit is experimentally investigated. The influence of test parameters such as salinity of the feed water (2000–3000 ppm), feed water temperature (29–41 °C), and feed flow rate (1.25–1.75 L/min) is considered. The results illustrate that the increase in feed water salinity by about 50% leads to an increase of permeate salinity by about 50%, while permeate flow rate and recovery ratio percent decreases by about 25 and 30%, respectively. Furthermore, for feed salinity less than 2500 ppm, as feed flow rate increases from 1.25 to 1.75 L/min, the salt rejection ratio and permeate flow rate increase from 5 to 7%, respectively, while feed pressure decreased by 16% and recovery ratio percent decreased by 37%. The results demonstrate that increase in feed temperature from 29 to 41 °C leads to an increase in the permeate salinity, while feed pressure and salt rejection ratio percent decrease by about 4 and 6%, respectively. Finally, empirical correlations for permeate salinity, permeate flow rate, feed pressure, recovery ratio percent, and salt rejection ratio percent as functions of feed water flow rate, feed temperature, and feed concentration are obtained.

The main problem with existing desalination technologies is that they consume high input energy to generate fresh water. Secondly, this energy demand is usually met by conventional sources of energy such as fossil fuels. With limited conventional energy reserves predicted for the future, the focus is on the utilization of renewable sources of energy such as solar, wind, and geothermal energy for powering desalination systems. Such a transformation would make the desalination systems more energy efficient, sustainable, and economical. In this paper, a novel concentrated solar powered (CSP) flash desalination system with direct heating and pressure modulation is presented. A lab-scale prototype was designed, manufactured, and tested for feed water collected from the Arabian Sea and in climatic conditions of Al-Khobar city in Saudi Arabia. The effect of three process parameters, namely, feed water temperature (30–40 °C), feed water flow rate (0.003–0.006 kg/s), and vacuum pressure (0.1–0.3 bar) on distillate production, was investigated. System modelling and optimization were done using Design Expert software and Response Surface Methodology (RSM). The central composite design technique was employed for the optimization of process parameters. The adequacy of the developed distillate production model was verified by ANOVA. The optimum values of feed water temperature, flow rate, and vacuum pressure are reported to be 40 °C, 0.005 kg/s, and 0.1 bar, respectively, resulting in distillate production of 0.001 kg/s.

Requirement of reverse osmosis (RO) process at places facing energy and water quality problem makes its assessment and optimization vital while considering recovery, rejection as well as specific energy consumption. In the present paper, three thin film composite (TFC) RO membranes (make: CSM, Dow and Vontron) in spiral wound (SW) configuration have been chosen to study their relative performance. Comparative study of RO membranes was conducted using experimental observations supported by mem- brane characterization. Optimization experiments were performed using central composite design (CCD) of response surface metho- dology (RSM). Four input variables viz. feed water pH, temperature, pressure and concentration were optimized and interaction be- tween them was observed, while, recovery, rejection and specific energy consumption (SEC) were taken as response attributes. The experiments conducted employing the optimized input values validated the developed RSM model. Predictive model using multiple response optimization revealed the optimal efficiency of CSM RO membrane at 6.53 pH, 1500 mg/L concentration, 0.78 MPa pressure and 31.94oC temperature producing 19.25% water recovery, 89.21% salt rejection and 17.60 kWh/m3 SEC, respectively. Membrane surface characterization was carried out by FE-SEM, AFM, contact angle measurement and FTIR. The lesser contact angle and smoother surface apparently contributed to the better performance of CSM RO membrane. This paper may demonstrate a simple method for optimizing the commercially available small scale RO membranes.

A brackish water reverse osmosis desalination plant based on exergy analysis was simulated and its performance was investigated. The computational model base on diffusion and convection transport mechanisms and concentration polarization concept was developed to predict the performance of RO membrane using different feed water concentration, feed flow rate, feed water pressure, membrane specification and feed water properties. The mathematical model has had good accuracy with reference data. The influence of operating parameters such as feed water pressure and temperature on the performance of the system was studied. Exergetic efficiency and destruction of streams exergy were calculated. Finally, multi-objective optimization for highest exergetic efficiency and permeate flow rate was done.

Applicability and limitation of the industrial reverse osmosis system simulators

Optimizing energy efficiency in brackish water reverse osmosis (BWRO): A comprehensive study on prioritizing critical operating parameters for specific energy consumption minimization

Experimental RO facility to study the heating effect of raw water on the varying main parameters

To control the quality of reverse osmosis (RO) product water and reduce operational costs and environmental impacts by increasing the system’s energy efficiency, it is necessary to identify the influence of process parameters on energy consumption and permeate water quality. This paper introduces a case study focused on the application of Design of Experiments (DOE) method in an industrial-scale RO desalination plant. In this study, energy consumption and permeate water salinity are formulated in terms of system design (the number of membranes and system recovery rate) and flow parameters (feed water flow rate, alkalinity, thermal effects, and salinity). Findings indicate that energy consumption decreases by increasing feed water temperature and the number of membranes. Moreover, increasing feed water flow rate and alkalinity leads to higher quality permeate water (lower salinity), whereas, increasing the number of membranes and system recovery rate and higher feed water temperature and salinity, increases the salinity of permeate water. The findings provide insight into the RO process features and can help designers and operators achieve a higher energy efficiency and better performance in the design and operation of RO units and the presented solution can be built into systems for comprehensive techno-economic evaluation of RO-based processes to consider changes in effective parameters.

A holistic framework for improving the prediction of reverse osmosis membrane performance using machine learning

Performance evaluation of two RO membrane configurations in a MSF/RO hybrid system

Boron removal in new generation reverse osmosis (RO) membranes using two-pass RO without pH adjustment

Energy, exergy and exergoeconomic (3E) analysis and multi-objective optimization of a closed-circuit desalination system with side-conduit

The application of the Bacterial Regrowth Potential method and Flow Cytometry for biofouling detection at the Penneshaw Desalination Plant in South Australia

Due to water scarcity in the Arabic gulf region, water desalination technologies are considered extremely important. The present work represents a fundamental study on the effect of basic operating and design variables on the flux of an air gap membrane distillation (AGMD) unit for water desalination. The flat sheet, channeled air gap membrane distillation module was designed and manufactured locally. The effect of feed flow rate, feed temperature, coolant water temperature, the air gap width, and the water salinity on the module flux are investigated. Analytical model for heat and mass transfer is used to predict the flux and the model results are compared to the experimental ones. Results showed that the technique has good potential to be used for water desalination. The permeate flux is increased by increasing feed flow rate, feed temperature, decreasing the air gap width, decreasing coolant temperature, and decreasing salinity of feed water. For a given feed flow rate, the width of the air gap and the feed water temperature are found to be the most effective parameters in increasing the distillate flux. Predicting the permeate flux with analytical models for heat and mass transfer showed good agreement with experimental results.