Reverse Osmosis Desalination Plant Research Articles

Evaluation of the detrimental effects in osmotic power assisted reverse osmosis (RO) desalination

This study aims to systematically evaluate the detrimental effects, namely concentration polarization (CP) and reverse solute permeation (RSP), and search for the optimum performance of a scale-up osmotic power assisted reverse osmosis (RO) desalination plant. The simulation clearly shows the performance reductions of the hybrid RO-PRO plant due to the CP and RSP effects. However, in both the co-current and counter-current PRO configurations, when the overall dimensionless flow rate decreases, these performance reductions become less significant. In addition, the counter-current PRO has high effectiveness because of the low theoretical net specific energy consumption (SEC) of RO-PRO. It is observed that more severe reduction due to the CP and RSP effects at high overall dimensionless flow rate shrinks the advantageous performance. Furthermore, PRO feed solutions with different concentrations are studied to evaluate the overall performance of the hybrid system. The results indicate that the advantageous performance can be achieved in a range of the concentration of the PRO feed. And with the increase on the PRO feed concentration, the osmotic energy generation reduces but the un-extracted energy due to the detrimental effects is also reduced.

Modified PID control with H∞ loop shaping synthesis for RO desalination plants

This paper deals with the PID control synthesis with robust (H∞) loop shaping framework to manage MIMO reverse osmosis (RO) desalination plants. This new method takes advantage of the robust controller which has a fixed low order of conventional PID scheme guaranteeing robust stability and performance under large parametric uncertainties, external disturbances, and sensor noises. The coprime factor uncertainty description in H∞ loop shaping methodology can cover a wide variety of uncertainties over all frequencies for the RO plants. The test results demonstrate that the achieved controller has high stability margin, showing disturbance and noise attenuation abilities. Furthermore, most interactions between control channels have been decoupled in the complete control system. The presented control approach can help reduce membrane cleaning, save energy, and reduce product water costs for the RO plants. Note that weather changes increase unstableness in RO plants but the water treatment facilities are only dimensioned for PID control. In addition, this study addresses control robustness as well as performance of a RO system against uncertainties, disturbances, and noises. Finally, the present control method can be utilized for efficiently controlling water quality (including quantity) and managing water facility of the RO desalination plants.

Exact free vibration analysis of Timoshenko stepped shaft carrying elastically supported eccentric masses with application on SWRO mechanical system

The aim of the study is to investigate the exact natural frequencies and their associated modal shapes for an axially loaded Timoshenko stepped multi-span shaft or beam system. Each span is carrying an elastically supported eccentric mass and resting on Pasternak elastic foundation. The end and intermediate conditions governing the lateral deflections and slope due to bending of the system have been formulated. Application models have been chosen to verify the reliability of the generalized system frequency equation. Some results of previous works are validated using the present analysis. Real application example of a combined shaft assembly for high pressure boosting device for sea water reverse osmosis (SWRO) desalination plant is investigated. Experimental tests for extended real shaft are carried out. The comparison between the analytical results and the experimental ones, for the first two modes of vibration, shows good agreement with minimal errors. These errors do not exceed 5%. In addition, the results of the proposed shaft model can be easily obtained for any number of spans and attachments. The present model and analysis is important for industrial applications, such as mechanical, civil, naval and for wider range of sea water desalination machinery.

Thermoeconomic analysis of combined power cycle integrated with MSF/SWRO desalination plant

AbstractA comprehensive thermo-economic study based on the exergy accounting method is conducted to evaluate the performance of a combined gas/steam power generation system integrated with a hybrid multistage flash (MSF)/sea water reverse osmosis (SWRO) desalination plants. The plant consists of five combined power generation cycles. Each cycle incorporates, two gas turbines (GT), two heat recovery steam generators, and one steam turbine. The total power generated is 2,645.5 MW. The combined power generation cycles are integrated with a hybrid MSF/SWRO desalination plant with a total water production of 1,000,000 m3/d, of which 70% is produced by MSF and 30% by SWRO. The exergy accounting study revealed that the heat rate of the combined gas/steam power cycle is 6,388.94 kJ/kWh, corresponding to an overall thermal efficiency of 56.34%. On the other hand, the water specific fuel energy consumption of the hybrid SWRO/MSF plant is 33.74 kWh/m3. The suggested exergy cost accounting method shows the water unit...

Energy-exergy analysis of seawater reverse osmosis plants

In this paper, a seawater reverse osmosis desalination plant with various energy recovery systems is studied using exergy analysis. These energy recovery devices include turbines and pressure exchangers as well as infinite area based single and two-stage pressure retarded osmosis units. The appropriate exergetic efficiency definition for such systems is mentioned. The effect of pump and turbine efficiency, salinity, temperature and mass ratio is studied using a validated program. In this regard, modified Van't Hoff constants for a large range of seawater surface temperatures are also determined. The best efficiency was obtained using the pressure exchanger for all systems investigated. Use of pressure retarded osmosis units as energy recovery devices provided efficiencies nearly equal to or less than the hydro-turbine. Thus, for the range investigated, it does not seem to be a viable energy recovery method for reverse osmosis units with seawater feed since constraints such as concentration polarization and finite area would further decrease performance.

Environmental implications of Tajoura reverse osmosis desalination plant

Water resources in North Africa are limited and do not meet the future water demand. The water shortage is very severe in Libya which is located in a semi-desert region. The available water resources in Libya are mainly the groundwater which is not enough to meet its people needs due to many reasons, among them is seawater intrusion. Desalination of seawater is one of the main alternatives for the substitution of water shortage in Libya and other North African countries. Despite the fact that desalination technology is an important option for providing potable/industrial water, it has some negative impacts on environment. High concentrated brine discharges from desalination plant is the main cause of negative impacts. Noise, visual impact, air pollution, impact on the aquifer, and disturbance of recreation areas are other environmental impacts on a more local scale. The aim of this study was to highlight the environmental impacts of Tajoura reverse osmosis desalination plant on the local environment. The findings of this study reveal that the most concerning issues identified from the existing Tajoura RO desalination plant are brine concentrate, noise pollution, and chemical hazards.

Start-up of brackish water desalination for agricultural irrigation in the Canary Islands (Spain)

The Canary Islands are an arid region. Therefore, water resources are scarce and several islands depend strongly on the sea and brackish water desalination. Water desalination, in the water policy of the Canary Islands, has been deeply rooted in the last 40 years, allowing solving and overcoming the shortage. This article concerns the beginning of the brackish water desalination for agricultural purposes in the Canary Islands (Spain). It provides the data and experience acquired during the early years in the region; one of the authors of this paper was working in the department of desalination of the first companies in the Canary Islands like Riegocan, AM García Glez. and Temkon. These companies worked with membrane manufacturers like Fluid System, Filmtec and Desalination Systems and pressure pipe manufacturer—Advanced Structures. Fifteen brackish water reverse osmosis desalination plants were built in the Canary Islands to provide water for agricultural irrigation between 1979 and 1983. These plants had a significant impact on agriculture.

Cost assessment in SWRO desalination plants with a production of 600 m3/d in Canary Islands

Water resources available in the island of Fuerteventura come mostly from small-scale capacity seawater desalination plants. Desalted water demand in the island has grown considerably in the last decade forcing managers to adapt desalinated water supply constantly. Additionally, the operating cost of the plants is relevant. The staff, chemical consumption, cartridge filter, and membrane replacement cost are essential in order to establish more efficient operation conditions of a reverse osmosis desalination plant. This article aims to study and compare the mentioned cost of six different seawater reverse osmosis desalination plants with the same production of 600 m3/d in the island of Fuerteventura. The results show for each of the six cases how costs can be reduced and the essential role of automation dealing with the staff cost with the particular capacity of 600 m3/d.

Economics of Renewable Energy for Water Desalination in Developing Countries

Freshwater shortage in many areas around the world presents a constraint to sustainable development. Desalination of saline water, especially seawater which accounts for more than 97% of the total water quantity on earth, represents a feasible option in many cases. The need for sustainable sources of energy to operate high energy - consumption desalination systems is mandatory. Future, in remote coastal and arid areas, the use of renewable energy for powering desalination plants could be a feasible option in view of several technical, economic and environmental considerations. In this paper, the issue of integration of desalination technologies and renewable energy from specified sources is addressed. The features of Photovoltaic (PV) system combined with reverse osmosis desalination technology, which represents the most commonly applied integration between renewable energy and desalination technology, are analyzed. Further, a case study for conceptual seawater reverse osmosis (SW-RO) desalination plant with 1000 m3/d capacity is presented, based on PV and conventional generators powered with fossil fuel to be installed in a remote coastal area in Egypt, as a typical developing country. The estimated water cost for desalination with PV/ SW-RO system is about $1.21 m3, while ranging between $1.18-1.56 for SW-RO powered with conventional generator powered with fossil fuel. Analysis of the economical, technical and environmental factors depicts the merits of using large scale integrated PV/RO system as an economically feasible water supply with an autonomous power supply.

Improvement of PV/T Based Reverse Osmosis Desalination Plant Performances Using Fuzzy Logic Controller

Photovoltaic based reverse osmosis desalination systems (PV/RO) present an effective method of water desalination especially in remote areas. The increase of the feed water temperature leads to an amelioration of the plant performances. Photovoltaic Thermal Collector (PV/T) represents an ideal power source as it provides both electric and thermal energies for the reverse osmosis process. Nevertheless, PV/T based RO plants should be controlled in order to solve operation problems related to electrical efficiency, reverse osmosis membrane, produced water and the rejected salts. This paper suggests a fuzzy logic controller for the flow rate of the circulating fluid into the PV/T collectors so as to ameliorate the system performances. The designed controller has improved the PV/T field electrical efficiency and preserved the reverse osmosis membrane which upgrades the system productivity. LABVIEW software is used to simulate the controlled system and validate the effectiveness of the controller.

Silica scale formation and effect of sodium and aluminium ions -29Si NMR study

Silica scale formation on reverse osmosis (RO) membrane surface is a significant problem for operation of high recovery RO desalination plant.

The integration of desalination plants and mineral production

A noticeable increase in the number of seawater reverse osmosis (SWRO) desalination plants has been observed during the last decade. This is due to the low energy consumed by reverse osmosis technology and the high freshwater recovery when compared to other desalination technologies. The desalination of seawater is the main source of freshwater in Kuwait. However, SWRO desalination plants generate huge volumes of concentrated brine, which is considered a potential source of mineral content. Some of these minerals are expensive and scarce on earth. The recovery of these minerals from brine can help in increasing the freshwater recovery, reducing the overall cost of desalinated water, offering a new source of raw materials, and decreasing the environmental impact from discharging brine to the sea. This study gives an overview of the different technologies used for the treatment of SWRO brine and explores the benefit to recover and reuse valuable potential minerals in brine. The study is motivated by the strong need to establish a local industry in Kuwait based on the extraction of potential valuable minerals from SWRO brine. Such industries can be combined with desalination plants to form a complex cogeneration of plants that accommodate desalination and power plants.

Energy consumption assessment of 4,000 m3/d SWRO desalination plants

The Canary Islands has been pioneer on desalination in Europe since the 1960s and has continued to use intensively the desalination technologies in order to provide water resources. However, one of the most important problems related to the operating efficient of seawater reverse osmosis (SWRO) desalination plants is dealing with the high-energy consumption. The present article aims to study, define, and compare the energy consumption cost of five SWRO desalination plants with the same production of 4,000 m3/d in the island of Fuerteventura (Canary Islands). The methodology for carrying out the work is based on analyzing the energy consumption data that directly affect to the operating cost. A comparison between different energy recovery systems was carried out using the data collected over 5 years of operation. The article presents an assessment of different ways to get more efficient operating conditions in order to reduce the operating cost.

Characterization of microbial communities in water and biofilms along a large scale SWRO desalination facility: Site-specific prerequisite for biofouling treatments

Biofouling impacts seawater reverse osmosis (SWRO) desalination plants by hindering module performance, increasing energetic demands, and incurring further costs. Here we investigated the spatial–temporal dynamics of microbial communities along the feedwater, pretreatment, and reverse osmosis stages of a large-scale SWRO desalination facility. While the composition of water-based microbial communities varied seasonally, the composition of biofilm microbial communities clustered by locations. Proteobacteria dominated throughout the water and biofilm communities while other dominant phyla varied seasonally and spatially. The microbial community composition significantly differed along the pathway locations of feedwater, rapid sand filtration (RSF), cartridge filters (CF), and the reverse osmosis (RO) membranes. Biofilms on the RSF and CF were composed of more diverse microbial populations than RO biofilms as determined by the effective number of species. Biofilms that developed along the treatment pathway (CF) served as inocula enhancing biofouling downstream on the RO membranes. Subsequently, we believe that prior to the development of advanced antibiofouling treatments for the desalination industries, the site-specific microbial community of feedwater, pretreatment and RO biofouling should be characterized. Site specific identification of these communities will enable optimization of pretreatment and cleaning procedures and can ultimately reduce chemical usage and incurred costs.

Comparative analysis of technical and economic parameters of different schemes of the electric power supply of autonomous desalination plants

This article reviews possible schemes of the power supply of an autonomous reverse osmosis desalination plant that uses a photoelectric converter as primary energy sources. Using the climate data of several regions that have a shortage of fresh water for drinking and technical purposes, a technical and economic evaluation of the use of solar energy for obtaining fresh water in regions with high levels of solar radiation was performed. The prospects of the partial or complete substitution of diesel fuel by energy derived from photoelectric converters in such systems for regions with a high level of insolation and cost of diesel fuel are shown.

Design of a small mobile PV-driven RO water desalination plant to be deployed at the northwest coast of Egypt

Water desalination projects based on reverse osmosis (RO) technology are being introduced in Egypt to combat drinking water shortage in remote areas. RO desalination is a pressure-driven process. This paper focuses on the design of an integrated brackish water and seawater RO desalination and solar photovoltaic (PV) technology. A small Mobile PV-driven RO desalination plant prototype without batteries is designed and tested. Solar-driven RO desalination can potentially break the dependence of conventional desalination on fossil fuels, reduce operational costs, and improve environmental sustainability. Moreover, the innovative features incorporated in the newly designed PV–RO plant prototype are focusing on improving the cost effectiveness of producing drinkable water in remote areas. This is achieved by maximizing energy yield through an integrated automatic single axis PV tracking system with programmed tilting angle adjustment. An autonomous cleaning system for PV modules is adopted for maximizing energy generation efficiency. RO plant components are selected so as to produce 4–5 m3/d of potable water. A basic criterion in the design of this PV-RO prototype is to produce a minimum amount of fresh water by running the plant during peak sun hours. Mobility of the system will provide potable water to isolated villages and population as well as ability to provide good drinking water to different number of people from any source that is not drinkable.

80,000 h operational experience and performance analysis of a brackish water reverse osmosis desalination plant. Assessment of membrane replacement cost

The brackish water reverse osmosis (BWRO) desalination plant has operated successfully for around 80,000h from 2004. Reverse osmosis membrane technology has improved allowing higher salt rejection, permeate water productivity and durability. But when the membranes should be replaced taking into account the energy consumption increase. The aim of this paper is to assess the operating information available and energy consumption to evaluate when it would be appropriate to replace the membranes taking especially into account the long life elements involved. The graphical evolution of feedwater conductivity, permeate conductivity, feed pressure, pressure drop, specific energy consumption (SEC) and the standardization of the permeate flow, salt rejection and SEC are shown. A comparison between specific energy consumption increase due to membrane performance decay, the regularity of chemical cleaning and membrane replacement in terms of costs has been carried out. The results show that the most effective choice for this BWRO desalination plant is not to replace the membranes in the first ten years of operation taking into account the membranes performance and the cost of electricity at the time.

Exergy Analysis of a Two-Pass Reverse Osmosis (RO) Desalination Unit with and without an Energy Recovery Turbine (ERT) and Pressure Exchanger (PX)

This paper presents an exergy analysis of an actual two-pass (RO) desalination system with the seawater solution treated as a real mixture and not an ideal mixture. The actual 127 ton/h two pass RO desalination plant was modeled using IPSEpro software and validated against operating data. The results show that using the (ERT) and (PX) reduced the total power consumption of the SWRO desalination by about 30% and 50% respectively, whereas, the specific power consumption for the SWRO per m3 water decreased from 7.2 kW/m3 to 5.0 kW/m3 with (ERT) and 3.6 kW/m3 with (PX). In addition, the exergy efficiency of the RO desalination improved by 49% with ERT and 77% with PX and exergy destruction was reduced by 40% for (ERT) and 53% for (PX). The results also showed that, when the (ERT) and (PX) were not in use, accounted for 42% of the total exergy destruction. Whereas, when (ERT) and (PX) are in use, the rejected seawater account maximum is 0.64%. Moreover, the (PX) involved the smallest area and highest minimum separation work.

Artificial neural network approach for predicting reverse osmosis desalination plants performance in the Gaza Strip

A rapidly growing technique for producing new water is desalination of seawater and brackish water. In the Gaza Strip the maximum amount of the drinking water is produced through small private desalination facilities. The present paper is concerned with using artificial neural network (ANN) technique to forecast reverse osmosis desalination plant's performance in the Gaza Strip through predicting the next week values of total dissolved solids (TDS) and permeate flowrate of the product water. Multilayer perceptron (MLP) and radial basis function (RBF) neural networks were trained and developed with reference to feed water parameters including: pressure, pH and conductivity to predict permeate flowrate next week values. MLP and RBF neural networks were used for predicting the next week TDS concentrations. Both networks are trained and developed with reference to product water quality variables including: water temperature, pH, conductivity and pressure. The prediction results showed that both types of neural networks are highly satisfactory for predicting TDS level in the product water quality and satisfactory for predicting permeate flowrate. Results of both developed networks were compared with the statistical model and found that ANN predictions are better than the conventional methods.

Evaluation of multivariate statistical analyses for monitoring and prediction of processes in an seawater reverse osmosis desalination plant

Our aim was to analyze, monitor, and predict the outcomes of processes in a full-scale seawater reverse osmosis (SWRO) desalination plant using multivariate statistical techniques. Multivariate analysis of variance (MANOVA) was used to investigate the performance and efficiencies of two SWRO processes, namely, pore controllable fiber filter-reverse osmosis (PCF-SWRO) and sand filtration-ultra filtration-reverse osmosis (SF-UF-SWRO). Principal component analysis (PCA) was applied to monitor the two SWRO processes. PCA monitoring revealed that the SF-UF-SWRO process could be analyzed reliably with a low number of outliers and disturbances. Partial least squares (PLS) analysis was then conducted to predict which of the seven input parameters of feed flow rate, PCF/SF-UF filtrate flow rate, temperature of feed water, turbidity feed, pH, reverse osmosis (RO)flow rate, and pressure had a significant effect on the outcome variables of permeate flow rate and concentration. Root mean squared errors (RMSEs) of the PLS models for permeate flow rates were 31.5 and 28.6 for the PCF-SWRO process and SF-UF-SWRO process, respectively, while RMSEs of permeate concentrations were 350.44 and 289.4, respectively. These results indicate that the SF-UF-SWRO process can be modeled more accurately than the PCF-SWRO process, because the RMSE values of permeate flowrate and concentration obtained using a PLS regression model of the SF-UF-SWRO process were lower than those obtained for the PCF-SWRO process.