Brackish Water Reverse Osmosis Plant Research Articles

Comparative analysis of integrating standalone renewable energy sources with brackish water reverse osmosis plants: Technical and economic perspectives

This paper tries to simulate and discuss the possible solutions that improve the economic and technical performances of a battery-less renewable energy-powered BWRO system according to the real climate conditions. The systems are considered in two capacities (50 and 100 m3/day) and are powered using photovoltaic panels, wind turbines, or both. Four scenarios are considered to couple the RO unit with renewable energy (RE) sources: simple; elevated brackish water tank; variable frequency drive; and a combination of the latter two. First, the simple approach is optimized for the lowest levelized cost of water, and then the other three scenarios are analyzed based on the optimized results of the first scenario. Results indicate that the hybrid system can provide more water (13,500 and 24,900 m3/year). However, due to its homogenous nature and fewer fluctuations, the PV-based system shows better results from several viewpoints, such as specific energy consumption (1.08 kWh/m3 for both capacities) and unused energy ratio (0.32 and 0.28 for 50 and 100 m3/day devices). Also, the suggested scenarios improve the economic performance of the systems. With the modifications of scenario 4, the PV-based system enhances more and shows the lowest value of levelized cost of water (1.09 $/m3).

Thermodynamic performance assessment of a community-scale brackish water reverse osmosis plant using exergy analysis

Abstract This study investigated the thermodynamic performance of a community-scale membrane-based brackish water reverse osmosis (BWRO) plant at various operating pressures from 13.79 to 27.58 bar and feed salinity levels from 2,000 to 20,000 mg/L. We aimed to identify the components responsible for the exergy losses and to suggest improvements. The results showed that the exergetic efficiency of some individual components had a significant impact on the performance of the desalination plant, where the high-pressure (HP) pump assembly and pressure control valve were identified as the major contributors to exergy losses (57.83–70.59 and 15.75–27.62%, respectively). The inefficiency of the feed pump assembly contributed to 11–12% of the total destruction of exergy under different operating conditions. The analysis further revealed that the exergetic efficiency of the plant was maximum (0.51%) at the feed salinity of 10,000 mg/L and operating pressure of 27.58 bar. It was minimum (0.01%) for the highest salinity (20,000 mg/L) and the lowest operating pressure (13.79 bar), due to the low requirement of work of separation and higher fixed losses. The exergetic efficiency was also correlated to the energetic performance of the BWRO plant at different operating conditions.

A theoretical analysis on upgrading desalination plants with low-salt-rejection reverse osmosis

Brackish water/seawater reverse osmosis (RO) desalination is a key solution to global freshwater scarcity. However, the water recovery (Rw) in conventional RO desalination plants is limited by the operating pressure (∆P). As a novel staged RO technology, low-salt-rejection RO (LSRRO) can potentially enhance the Rw in the desalination plants. In this study, we perform process modeling and techno-economic analysis to evaluate the viability of upgrading current RO desalination plants with LSRRO. Based on the results from process modeling, in typical brackish water RO (BWRO) and seawater RO (SWRO) desalination plants, adding an LSRRO stage can effectively enhance the Rw by 21 and 53 %, respectively, and the energy efficiencies are not compromised with the enhanced Rw. From techno-economic analysis, upgrading RO desalination plant with LSRRO is highly viable. Specifically, after adding an LSRRO stage in a BWRO plant, the Rw can be enhanced from 71 to 81 % without notably increasing the levelized cost of water (LCOW), and adding an LSRRO stage in the SWRO plant with zero brine discharge can reduce the LCOW by 30 %. The findings in our study highlight the vast potential of adopting LSRRO in brackish water/seawater desalination plants, and shed lights on the design of future desalination plants.

Techno-Economic Analysis of Selected PV-BWRO Desalination Plants in the Context of the Water–Energy Nexus for Low–Medium-Income Countries

Jordan was late in adopting seawater and brackish water desalination as a source until the late 1990s and early 2000s. However, ongoing studies are still discussing the technical, economic, and socio-political aspects of brackish water reverse osmosis (BWRO) desalination plants. In this study, the water–energy nexus was considered, in order to highlight the main challenges facing BWRO desalination. We discuss the use of photovoltaic (PV) technology, together with BWRO desalination, as an approach to compensate for ecological, financial, and social challenges in Jordan. For this purpose, the performance of nine existing BWRO desalination plants in the agricultural, domestic, and industrial sectors is assessed. The water performance is assessed based on water consumption, safe yield extraction, plant recovery rate (R, %), and compliance to local and international water quality standards; the Specific Energy Consumption (SEC, kWh/m3) is taken as the main evaluation criterion to assess the energy performance of the BWRO desalination plants; and economic performance is assessed based on the overall cost of water produced per cubic meter (USD/m3). The main environmental component is the brine disposal management practice utilized by each plant. Based on this assessment, the main challenges in BWRO desalination are the unsustainable patterns of water production, mismanaged energy performance, low recovery rates, and improper brine disposal. The challenges in domestic and industrial BWRO desalination, which are completely dependent on the electricity grid, are associated with critical energy and costs losses, as reflected by the high SEC values (in the range of 2.7–5.6 kWh/m3) and high water costs per cubic meter (0.60–1.18 USD/m3). As such, the use of PV solar panels is suggested, in order to reduce the electricity consumption of the assessed BWRO plants. The installation of PV panels resulted in significantly reduced energy costs (by 69–74%) and total costs (by 50–54%), compared with energy costs from the electricity grid, over the lifetime of the assessed BWRO desalination plants.

Changes in Pumping-Induced Groundwater Quality Used to Supply a Large-Capacity Brackish-Water Desalination Facility, Collier County, Florida: A New Aquifer Conceptual Model

Brackish-water reverse osmosis (BWRO) desalination facilities are designed to treat feedwater within a fixed range in salinity. If the salinity and ion concentrations of the feedwater rises above the maximum design concentrations, then the plant may ultimately fail. BWRO plants typically use groundwater as a feedwater source. Prior to the process design, a detailed groundwater assessment is made to characterize the source aquifer system and to develop a solute-transport model that is used to project the changes in water quality over the expected useful life of the facility. Solute transport-modeling performed for the Collier County (Florida) South BWRO facility, which was designed to produce 30,303 m3/d with an expansion to 75,758 m3/d, used an aquifer system conceptual model that assumed upwards migration over time of brackish waters with higher salinities into the production zones. This conceptual model is typical of how most BWRO systems developed in the United States operate. The original solute transport model predicted a range of increases in dissolved chloride concentrations over a 20-year period from a low of 5 mg/L/yr, a mid-range of 35 mg/L/yr, and a high range of 85 mg/L/yr. Actual data collected over a 11- to 13.5-year period showed that the dissolved chloride concentration average of the feed water decreased by 16 mg/L/yr. The original conceptual model was found to be inaccurate in that it suggested an upwards recharging system, whereas downward leakage (or perhaps lateral migration) of fresher water appears to be occurring in the system. This is an example of a long-term solute-transport model audit, which is rarely performed, in which a new conceptual model was found to be applicable to an aquifer system used to feed a BWRO facility.

Conceptual arrangement and basic design of drinking water reverse osmosis desalination plants

To propose a conceptual arrangement of reverse osmosis desalination plants, four comprehensive decision algorithms and a software are developed. Typically, commercial software predict the performance of the reverse osmosis membranes based on their pre-determined configuration; however, the developed decision algorithms and the developed software in this study have the capability of introducing the conceptual arrangement of pretreatment units, reverse osmosis membranes, and energy recovery devices for both seawater and brackish water reverse osmosis plants. To perform a comprehensive study, alongside the developed software and the decision algorithms, both design considerations of the required equipment in pretreatment units and mathematical modeling of reverse osmosis membranes are included. Finally, to validate the accuracy of the developed decision algorithms and the software, four installed reverse osmosis desalination plants for producing drinking water from seawater and brackish water feeds are investigated. The algorithmic proposed plants for all four cases were in close agreement with the implemented industrial cases and World Health Organization standards.

An Air Operated Domestic Brackish Water Reverse Osmosis Plant: Economically Sustainable Solution for Safe Drinking Water Supply for Chronic Kidney Disease of Unknown Etiology Affected Areas in Sri Lanka

Chronic Kidney Disease with unknown etiology (CKDu) is one of the crucial health issues in North Central, Uva, North Western, North, Central, and Eastern Provinces of Sri Lanka and incapacitates the kidney function. The main source for the CKDu has not yet been identified, though many scientists believed that the number of certain drinking water quality parameters is changed due to the contamination of water sources by agricultural activities. Hence, the government of Sri Lanka introduces electrically driven Brackish Water Reverse Osmosis (BWRO) plants with a capacity of 10 tones/day to supply safe drinking water for the impacted community though it is an energy-intensive process. Concurrently, a smaller version of an electrically driven BWRO plant was introduced to the rural farming community for their domestic use. However, it was not practically worked out due to various reasons such as high cost, unavailability of electrical power supply for those villages. In this study, an economical air operated domestic use BWRO plant with zero-emission was designed. This anticipated system significantly reduces the government expenditures to subsidize the water purification cost by 50% of the existing expenses. Besides, simple payback time was found to be 2.5 years, and the benefit-cost ratio to be more than 1. Evaluating the performance with the conventional values, it comprehends with more sustainable and economically viable system compared to the existing method of water purification.

Minimum energy requirements for desalination of brackish groundwater in the United States with comparison to international datasets

This paper uses chemical and physical data from a large 2017 U.S. Geological Survey groundwater dataset with wells in the U.S. and three smaller international groundwater datasets with wells primarily in Australia and Spain to carry out a comprehensive investigation of brackish groundwater composition in relation to minimum desalination energy costs. First, we compute the site-specific least work required for groundwater desalination. Least work of separation represents a baseline for specific energy consumption of desalination systems. We develop simplified equations based on the U.S. data for least work as a function of water recovery ratio and a proxy variable for composition, either total dissolved solids, specific conductance, molality or ionic strength. We show that the U.S. correlations for total dissolved solids and molality may be applied to the international datasets. We find that total molality can be used to calculate the least work of dilute solutions with very high accuracy. Then, we examine the effects of groundwater solute composition on minimum energy requirements, showing that separation requirements increase from calcium to sodium for cations and from sulfate to bicarbonate to chloride for anions, for any given TDS concentration. We study the geographic distribution of least work, total dissolved solids, and major ions concentration across the U.S. We determine areas with both low least work and high water stress in order to highlight regions holding potential for desalination to decrease the disparity between high water demand and low water supply. Finally, we discuss the implications of the USGS results on water resource planning, by comparing least work to the specific energy consumption of brackish water reverse osmosis plants and showing the scaling propensity of major electrolytes and silica in the U.S. groundwater samples.

Desalination for irrigation use: chemical pre-treatment study of Reverse osmosis plant

Desalinated brackish water is becoming an important water source for agricultural irrigation. In Brackish water desalination, pretreatment of reverse osmosis is the key step in designing the plants to avoid membrane fouling and scaling. It is enormously important to carry out a study designed at ensuring the optimization of the pretreatment system for brackish desalination plant in order to optimize the quality of the water fed through the reverse osmosis membranes, to guarantee the highest performance and to minimize the number of shutdowns for chemical cleaning. In this paper, performance evaluation carried out for a brackish water reverse osmosis plant for agricultural application, located in Dokkala Region in Morocco.

Induction time measurements in two brackish water reverse osmosis plants for calcium carbonate precipitation

AbstractIn this research work, the induction time of two brackish water reverse osmosis (BWRO) plants was measured with and without antiscalant (AS) operation with focus on calcium carbonate precipitation. This study focused on two BWRO plants in the Netherlands. The scaling potential of RO concentrate in the plant at recovery of 80% was calculated using the PHREEQC program. Induction times in RO concentrates were measured by collecting RO concentrates directly from the plants, with and without an AS dose in an air-tight glass reactor. The solution was continuously stirred for homogenization and maintained at room temperature using a thermostat. The change in pH of the solution over time was monitored. The time required to change the nucleation phase to just the start of the crystal growth was noted from the pH versus time graph, which was defined as induction time. At the end of the experiments, precipitate with RO concentrate with and without AS dose (plant B) were collected and an X-ray powder diffract...

3-Step approach towards evaluation and elimination of acid use in pre-treatment for a brackish water reverse osmosis process

To control carbonate scale formation on reverse osmosis (RO) membrane surfaces, it is common practice to add acid as a pre-treatment chemical. However, advancements in the formulation of proprietary scale inhibitors have resulted in a re-evaluation of the need to suppress the pH of RO feedwater. In this study, a 3-step approach was taken to eliminate sulfuric acid pre-treatment at a 4.5 MGD (17,000 m3/day) brackish water RO plant operating for over 7 years without previous membrane replacement. The 3-Step approach adopted in this study to evaluate and eliminate use of acid in pre-treatment process involved first pilot testing the plan to reduce the dependence on acid. Secondly, implementing the plan on the full-scale system with conservative pH increments and thirdly continuously screening for scale formation potential using a “canary” monitoring device. This 3-step approach resulted in the successful elimination of sulfuric acid pre-treatment at the brackish water RO plant, with an estimated $105,000 minimum annual cost savings.

Performances Analysis of the Reverse Osmosis Desalination Plant of Brackish Water Used for Irrigation: Case Study

Desalinated brackish water is becoming an important water source for agricultural irrigation. In Brackish water desalination, pretreatment of reverse osmosis is the key step in designing the plants to avoid membrane fouling and scaling. It is enormously important to carry out a study designed at ensuring the optimization of the pretreatment system for brackish desalination plant in order to optimize the quality of the water fed through the reverse osmosis membranes, to guarantee the highest performance and to minimize the number of shutdowns for chemical cleaning. In this paper, performance evaluation carried out for a brackish water reverse osmosis plant for agricultural application, located in Dokkala Region in Morocco. This plant showed poor performances after few months of operating and frequent shutdown. The operating pressure increased significantly and the permeate conductivity decreased surprisingly. To identify the causes for the poor performance, different investigations were carried out. Thus, the pretreatment scheme was thoroughly reviewed to find out the causes of anomalies. The problem was resolved by removing chlorination and sodium bisulfate steps from the pretreatment.

Solve the Water Shortage in a Tourism-Dependent Island: A Proactive Operation Strategy of Pumping Allocation for a BWRO Plant

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.

Comparison of Configurations for High-Recovery Inland Desalination Systems

Desalination of brackish groundwater (BW) is an effective approach to augment water supply, especially for inland regions that are far from seawater resources. Brackish water reverse osmosis (BWRO) desalination is still subject to intensive energy consumption compared to the theoretical minimum energy demand. Here, we review some of the BWRO plants with various system arrangements. We look at how to minimize energy demands, as these contribute considerably to the cost of desalinated water. Different configurations of BWRO system have been compared from the view point of normalized specific energy consumption (SEC). Analysis is made at theoretical limits. The SEC reduction of BWRO can be achieved by (i) increasing number of stages, (ii) using an energy recovery device (ERD), or (iii) operating the BWRO in batch mode or closed circuit mode. Application of more stages not only reduces SEC but also improves water recovery. However, this improvement is less pronounced when the number of stages exceeds four. Alternatively and more favourably, the BWRO system can be operated in Closed Circuit Desalination (CCD) mode and gives a comparative SEC to that of the 3-stage system with a recovery ratio of 80%. A further reduction of about 30% in SEC can be achieved through batch-RO operation. Moreover, the costly ERDs and booster pumps are avoided with both CCD and batch-RO, thus furthering the effectiveness of lowering the costs of these innovative approaches.

Optimal plant operation of brackish water reverse osmosis (BWRO) desalination

Optimal plant operation of brackish water reverse osmosis (BWRO) desalination is studied in this work to reduce specific energy consumption (SEC). A comprehensive first-principles based mathematical model, which explicitly accounts for membrane area and hydraulic permeability, pump characteristic curves, and pressure drops along the RO train, is developed and validated by plant data. A constrained nonlinear optimization is formulated and solved for two RO trains with different service times. It is shown that a 16% reduction in SEC is possible by optimizing operating conditions within the normal operating range of the pump while maintaining the same permeate rate. Results are discussed using dimensionless parameters derived in the author's previous work. Suggestions are made to further reduce SEC in BWRO plant operation.

Environmental life cycle assessment of brackish water reverse osmosis desalination for different electricity production models

The main purpose of this work is to evaluate the importance of electricity production models based on the environmental impacts from a brackish water reverse osmosis (BWRO) plant. Life cycle assessment (LCA) is used to compare the environmental burdens of a BWRO plant with three different electricity production models in the United States, Singapore, and Spain. Input and output flows of BWRO plants are based on a study done by Munoz; life cycle inventories (LCIs) for the United States and Spain are adopted from Ecoinvent Database, while LCI for the Singapore electricity supply scheme is developed for the first time. The results highlight Singapore, the country with unique fuel mixes for electricity generation, achieves relatively better environmental savings in most impact categories at the current stage due to a high percentage of natural gas in the fossil fuel matrix. Results from uncertainty analysis further recognize the significance of this advantage. Furthermore, the results indicate the antiscalant application, power plant efficiency, and fuel exploration and production are also highly associated with the environmental performance of BWRO plant in certain categories. This work provides the first reference to conduct LCA of BWRO plant in Southeast Asia. It also provides a good reference for potential strategies to relieve environmental impacts of the RO desalination process.

Brackish water reverse osmosis (BWRO) operation in feed flow reversal mode using an ex situ scale observation detector (EXSOD)

The feasibility of operating brackish water reverse osmosis (BWRO) desalination in a feed flow reversal (FFR) mode so as to mitigate mineral scaling was evaluated with feed solutions containing calcium, sodium, sulfate and chloride ions. The premise of the FFR approach is to enable dissolution of surface mineral crystals, that form first at the BWRO plant tail elements, by periodic exposure to the undersaturated feed solution. Automatic triggering of FFR was accomplished by integrating an Ex-situ scale observation detector (EXSOD) with the BWRO plant controller. The EXSOD system consisted of a small high pressure plate-and-frame RO cell, with its membrane surface digitally imaged in real-time, to monitor the onset and development of membrane mineral scaling. During normal feed flow (NFF) operation, the EXSOD monitored a concentrate side-stream from the BWRO plant tail element, signaling the BWRO plant controller to initiate FFR when the specified scaling threshold was reached. Once the plant feed flow was reversed, the EXSOD feed stream was switched from the BWRO plant concentrate to the plant's permeate in order to dissolve mineral crystals formed on the EXSOD membrane during NFF operation. Successful operation of automated FFR, whereby scale formation was prevented, required adjustment of the EXSOD operating conditions such that the saturation index in the EXSOD RO cell was at a level that would not result in scale detection significantly before or after scaling would occur in the RO plant. Although the onset of mineral scaling was detected at the level of appearance of the first observable mineral crystal, the results suggest that it would be more practical to trigger FFR based on a threshold that considers both the mineral crystal number density and fractional surface scale coverage. Current work is continuing to demonstrate the broad applicability of FFR mode of RO mineral scale-free operation (with reduced or no antiscalant addition) over a wide range of solution compositions and operating conditions.

RO membrane failure: Investigation of failure during preservation

When membranes were experiencing poor performance in a brackish water reverse osmosis plant, an investigation was carried out to find out why, and what could be done to make them more effective.

Simulation and analysis of an industrial water desalination plant

In this paper, an industrial medium-scale brackish water reverse osmosis plant based on Dow/FilmTec BW30-400 spiral-wound membrane modules was simulated and its performance investigated. Actual operating data is used to validate the computer package. The semi-rigorous model was found to represent the plant with good accuracy; the relative errors in the overall water recovery and salt rejection were 0.37 and 1.33%, respectively. The effects of the arrangement of membrane modules, the operating pressure and the feed flow rate on the performance of the plant were investigated. The single-stage configuration in which all pressure vessels are arranged in parallel was found to yield the best results in terms of the production rate, product quality and overall pressure drop across the feed channel. At low to moderate operating pressures and feed rates, increasing both operating variables will result in higher water production rates and salt rejection. However, high operating pressures lead to a deterioration of the quality of the product whereas high flow feed rates, contrary to one's expectation, result in a reduction in the production rate.

Complete elimination of acid injection in reverse osmosis plants

Antiscalants with broad activity spectra are available today. When properly chosen, a single antiscalant can efficiently and simultaneously control calcium carbonate, calcium sulfate, strontium sulfate, barium sulfate and calcium fluoride scales as well as inorganic foulants resulting from iron, aluminum and reactive silica present in any given water or wastewater. The effectiveness of many antiscalants towards controlling calcium carbonate scaling in reverse osmosis (RO) plants has allowed us, in the past five years, to successfully help eliminate the continuous injection of acid in all RO systems operating with polyamide membranes. A minority of systems with cellulose acetate membranes however still require acidification due to hydrolytic sensitivity of cellulose acetate towards feedwater pH higher than 6. The chemistry behind the main reason for acidification — the prevention of scaling by calcium carbonate — is reviewed. The mechanisms of calcium carbonate scaling and its avoidance by acidification or with antiscalants are discussed. Major seawater and brackish water RO plants around the world are designed and operated with the continuous injection of concentrated sulfuric or hydrochloric acid for scale control, sometimes simultaneously with an antiscalant. We present a case study in southeastern USA of a 5 million gallons permeate per day plant as a typical example among many for the conversion of major municipal RO plants. By suitable selection of an antiscalant, acid elimination was successfully attained with a simultaneous reduction in the antiscalant dosage, in this case to 2–3 mg/1 in the feedwater. While process optimization continues in the plant, current chemical cost savings due to the deletion of 93% sulfuric acid and the associated caustic soda neutralizer alone amounts to 67% of the annual cost of all chemicals used. This does not include savings through benefits accrued in equipment, operation, maintenance and safety in the plant.