RO Desalination Plants Research Articles

A Multi Objective Optimization Approach for Ro-Desalination Plant Using Integrated Energy Sources

A Multi Objective Optimization Approach for Ro-Desalination Plant Using Integrated Energy Sources

Flow conditions affecting the induction period of CaSO4 scaling on RO membranes

The extent of the induction period preceding the inception of scale formation is of major interest in the design and operation of RO desalination plants. The objective of present work was to investigate induction time phenomena related to CaSO4 scale precipitation from supersaturated solutions without or with the presence of a polycarboxylic acid based anti-scalant (AS). Membrane tests were carried out at different CaSO4 supersaturation levels (0.75–4.20) and crossflow velocities (0.1–2.5m/s) using both tubular and spiral wound membranes. Stirred beakers tests were also conducted.Membrane induction times in the flow systems increased linearly with the increase of flow Reynolds (Re) number from 80 to 6800 both without and with AS. The induction period in the presence of the AS was higher than that observed in AS free solutions. However, the extension of the induction period induced by the AS increased markedly with the Re number. Comparison of induction times measured in membranes and stirred beaker systems revealed a critical Re number below which induction time was shorter in the membrane system and above which the induction time was longer in the membrane system compared to the beaker test.

Investigating the integration of desalination units into cogeneration systems utilizing R-curve tool

In this study, the integration of different desalination systems into cogeneration systems has been examined. Based on the operating conditions of the cogeneration system, this integration can result in either the improvement or impairment of the cogeneration efficiency. The R-curve is a powerful tool to investigate the effect of this integration on the cogeneration system performance. Several scenarios for integration of RO and MED systems at different operating points are investigated. Some case studies are examined using the presented concept to verify the proposed methodology. There is a significant variation in the economics of the systems in the presented integration scenarios. The R-curve has been utilized for the integration of MED and RO desalination technologies with cogeneration systems to identify effective ways to decrease the operating cost. As an illustration, based on the operating conditions, the integration of a 24MW RO desalination plant can either provide a 12.123MW fuel saving or cause 23.502MW excess fuel consumption due to different cogeneration performances in the same cogeneration system (case study 1). Also, the integration of 17.8MW(t) MED unit can either cause 47.835MW excess fuel consumption or provide 28.974MW fuel saving (case study 2).

Water Storage Instead of Energy Storage for Desalination Powered by Renewable Energy—King Island Case Study

In this paper, we scrutinized the energy storage options used in mitigation of the intermittent nature of renewable energy resources for desalination process. In off-grid islands and remote areas, renewable energy is often combined with appropriate energy storage technologies (ESTs) to provide a consistent and reliable electric power source. We demonstrated that in developing a renewable energy scheme for desalination purposes, product (water) storage is a more reliable and techno-economic solution. For a King Island (Southeast Australia) case-study, electric power production from renewable energy sources was sized under transient conditions to meet the dynamic demand of freshwater throughout the year. Among four proposed scenarios, we found the most economic option by sizing a 13 MW solar photovoltaic (PV) field to instantly run a proportional RO desalination plant and generate immediate freshwater in diurnal times without the need for energy storage. The excess generated water was stored in 4 × 50 ML (mega liter) storage tanks to meet the load in those solar deficit times. It was also demonstrated that integrating well-sized solar PV with wind power production shows more consistent energy/water profiles that harmonize the transient nature of energy sources with the water consumption dynamics, but that would have trivial economic penalties caused by larger desalination and water storage capacities.

The key to efficient RO desalination

Europe, like other parts of the world, could see more RO desalination plants as changing weather puts more stress on conventional water supplies. But plant longevity and operational costs depend on a marriage of engineering disciplines and careful design says Peter Brewer, general manager of ACWA Services.

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.

Exergetic efficiency of NF, RO and EDR desalination plants

Exergetic analysis of a 2250gpm brackish water desalination plant in California was performed using its operational data. The plant contains nanofiltration, reverse osmosis and electrodialysis reversal units subject to the same source water. The correct definition of exergetic efficiency for such systems was discussed. The effect of feed salinity was also used for further illustrating the difference in the second-law efficiency definitions. The preferred definition can be used to determine the specific energy consumption and makes thermodynamic sense. The nanofiltration, reverse osmosis and electrodialysis reversal units had efficiencies of 0.087%, 0.066% and 0.078%, respectively, which are very low. Various energy recovery devices including a pressure retarded osmosis unit (having infinite area) were applied to the system to see relative increase in second-law efficiency. For the preferred definition, it was seen that the nanofiltration unit had the best efficiency. In terms of alternative designs using energy recovery devices, the pressure retarded osmosis option had efficiencies approximately equal to the hydro-turbine while the highest efficiency occurred through the use of a pressure exchanger at the plant inlet salinity. Therefore, it does not seem to be a practical energy recovery method for the investigated desalination systems.

CoorsTek forms membrane sciences group - combining hydrogen and oxygen transport membrane technologies

Detrimental biofilms on RO membranes remain a crucial challenge for seawater desalination. Comparative analysis of 16S rRNA gene amplicon sequencing data revealed differences and commonalities of biofilm communities associated with unit operations in the two largest seawater desalination facilities in the U.S., the Claude "Bud" Lewis Carlsbad Desalination Plant and the Tampa Bay Seater Desalination facility. At both plants, feedwater collected at a single time point was a poor indicator of the RO membrane communities, which showed far greater taxa diversity. The analysis of prefilter cartridges from the Carlsbad plant revealed similarly high taxon diversity as the RO module biofilms, with relevant differences. Algal sequences were enriched on the prefilter cartridges as were sequences representing Bdellovibrionota, which are predatory bacteria. Sequences representing opportunistic Gammaproteobacteria (i.e., Shewanella, Woesia) were present in significantly higher relative abundance on the RO membranes than in the prefilter cartridges, suggesting growth of certain taxa in the RO modules. Untargeted metabolomics distinguished intra- and inter-desalination plant biofilm samples, highlighting the potential value of this tool for biofilm monitoring. These findings underscore the value of omics tools for effective microbial monitoring, to understand biofouling dynamics within RO desalination plants, and to provide insight for the development of ecologically-informed biofilm control measures.

Cost-effective sustainable operation policy of Jeddah RO desalination plant under production pumps failure using mathematical programming

Seawater desalination is one of the most important means of securing water for domestic needs in arid geographical regions such as Saudi Arabia. Water production of Jeddah desalination plant is critical in meeting the city’s increasing water demands. The plant uses reverse osmosis technique with a production system consisting mainly of a permeate tank and production pumps. Failure or shutdown of any operating pump causes serious issues in demand and loss of production. The objective of this study is to develop a cost-effective operation policy that ensures the plant’s continuous production rate throughout the failure of any production pump. Mathematical optimization technique is used to explore possible and optimal solutions for the plant’s operation policies. The case was formulated as mixed-integer programming to minimize an objective function. POM-QM for Windows package was used to solve the problem using branch and bound method. This mathematical programming proved to be a powerful technique not only in solving for an optimal solution of a minimization problem, but also in generating a nearly optimal feasible solution of best operation policy in a given setting of water production system. The technique is capable of solving the optimal operation policy at minimal cost for any given scenario in the solution space under the shutdown condition of any operating pump. In addition to saving operational and maintenance costs, the obtained solutions can be adopted to prevent huge quantities of water production from being wasted into the sea. Hence, these solutions exhibit best practice and management of water resources.

The use of phosphorus-free antiscalants in BWRO desalination plants and brine disposal pipelines

Today, most RO desalination plants are using phosphorus-based antiscalants for preventing salt precipitation (scaling) and to achieve high membrane performance, as measured by reduced trans-membrane pressure, salt passage and increased permeate flow. However, phosphorus antiscalants in brine disposal can be an environmental issue that should be considered and studied when installing a desalination plant. The purpose of this research is to examine different types of phosphorus-free antiscalants and to find combinations of good membrane performance (varied recovery rates) and environmental antiscalants. Together, the Granot and Lahat BWRO desalination plants will produce approximately 30 Mm3 in 2014. They are part of a large project: “The Aquifer Rehabilitation,” which aims to protect the Israeli costal aquifer from saline infiltration. The concentrate from these inland BWRO desalination plants is sent along a unique 30-km-long brine disposal pipeline to the Mediterranean Sea (“Granot-Ashkelon” pipeline). Obviously, the preferred phosphorus-free antiscalant should prevent salt precipitation (scaling) in both the RO membranes and the lengthy brine disposal pipeline. The use of phosphorus-free antiscalant should achieve stable membrane performance. To date, five different antiscalants (four of them, phosphorus free) were tested at a pilot plant at the Granot site. This BWRO pilot plant contains two systems: (i) the desalination branch, which has similar alignment and pre-treatment as the Granot desalination plant, and (ii) a brine flow system that simulates true brine flow conditions. This system was used to validate the possibility of salt precipitation in the long brine pipeline. Experiment results carried out on four phosphorus-free antiscalants show that stable membrane performance did not occur. This research continues in pursuit of compounds that can satisfy the increasingly stringent environmental requirements in this field. According to the experiments schedule, additional phosphorus-free antiscalant will be tested in Granot BWRO pilot plant.

Statistical regression and modeliing analysis for reverse osmosis desalination process

Experiment is conducted, across different units of a typical desalination plant, to build correlations between inputs/outputs. Steady-state statistical models of reverse osmosis (RO) are developed using stream characteristic data (flow rate, concentration and pH) over a period of time. Data-driven models are useful for deciding real time operational control strategies of desalination plant. The statistical analysis of correlations obtained indicates that permeate characteristics depend on feed stream flow rate by a second degree polynomial. Significance of regression was evaluated based on multivariate ANOVA analysis, on visual standardized residuals distribution and their means for confidence levels of 95% and 99%, clearly validating these models. Sensitivity of parameters is found from interaction and co-relation studies. These models will help in safe operation and control of RO-desalination plant.

水不足に挑戦するRO海水淡水化プラント(<メカライフ特集>合のものづくり)

水不足に挑戦するRO海水淡水化プラント(<メカライフ特集>合のものづくり)

Performance evaluation of five years operation experience of WMZM RO desalination plant

The main two supply of potable water to Amman city are Zai water treatment plant (represent 60%) and Wadi Ma’in, Zara, and Mujib (WMZM) water treatment plant (represent 30%). WMZM receives raw water from three main sources originally flowing to the Dead Sea, now collected and conveyed to a raw water reservoir at the treatment plant to produce about 110,000 m3/day. WMZM was commissioned in 2006 and still operating at the original design capacity. WMZM water treatment plant and its conveyance system are presently operated by Jordan Water Company—Miyahuna. This paper covers the plant description, original design parameters, and RO membrane performance after more than five years of operation.

Potential of osmotic power generation by pressure retarded osmosis using seawater as feed solution: Analysis and experiments

The most commonly explored salinity-gradient scheme in the pressure retarded osmosis (PRO) process is based on the pairing of seawater and river water as a salinity gradient resource. However, due to the lack of a high-performance PRO membrane, a sufficient osmotic pressure differential across the membrane active layer to produce high power density cannot be attained with this seawater–river water pair. While high-performance PRO membranes have to be developed, there are other approaches to increase power density that combine several salinity gradient resources more efficiently. This study analyzes scenarios of osmotic power generation by PRO based on a variety of salinity gradient resources. Brine from RO (or future FO) desalination plants and municipal wastewater effluent (or brackish water) may be used as a high-salinity draw solution and low-salinity feed solution, respectively. The use of high salinity brines (as draw solution) from future FO desalination plants paired with seawater (as feed solution) may be an especially viable approach for a hybrid process of FO desalination and PRO power generation. In this approach, seawater is the only input resource, and there is no need to have separate intake and pre-treatment for the feed and draw solutions as in the conventional seawater–river water PRO scheme. From the analysis of these scenarios, we performed experiments with seawater (0.5M NaCl) as feed solution to investigate the feasibility of the PRO process with the various proposed schemes. For the 2M draw/0.5M feed solution scheme at a solution temperature of 30°C, a water flux of 13.9Lm−2h−1 and corresponding projected power density of 4.7W/m2 were obtained at a hydraulic pressure difference of 12.5bar using a commercial cellulose triacetate FO membrane. This study demonstrates that osmotic power generation by pressure retarded osmosis using seawater as a feed solution is potentially viable through the introduction of a hybrid process of FO desalination and PRO osmotic power generation.

Techno-economic analysis of combined concentrating solar power and desalination plant configurations in Israel and Jordan

Combined concentrating solar power (CSP) and desalination plants represent a realistic future option for the production of electricity and fresh water for countries of the world’s sunbelt. In this paper, parabolic trough power plants for electricity production have been analysed in combination with multi-effect distillation (MED) and ultrafiltration/reverse osmosis (RO) desalination plants for two sites in Israel (Ashdod) and Jordan (Aqaba). Both RO and MED desalination plants were designed for a fresh water production capacity of 24,000 m3/d. The power block of the CSP plant was selected to meet the steam consumption of the MED plant at the design point, which led to a gross electrical power generation capacity of the power block of 42 MWel. Due to the low availability and generally high cost of coastal land, the CSP + RO plant consists of two separate units. It was assumed that the CSP plant is located at an inland location where there is land available. The RO plant is located at the sea, while the MED plant is located at the CSP site. The pumping of the seawater and the water transmission system add about 0.2 $/m3 to the levelized water costs of the CSP + MED plant compared with a plant located at the sea. Three different sizes of high temperature heat storages (0 h, 6 h and 12 h of additional full load operation of the steam turbine) were applied to find the most economic setup. At current prices for heat storage units, systems with huge heat storage capacities become economic only at high feed-in tariffs for electricity and thus high revenues. The price of the electricity generated by the CSP plant was varied to show the influence of the feed-in tariff on the water generating costs. The levelized costs of water (LCOW) strongly depend on the electricity price. Water costs in Ashdod are higher than those in Aqaba due to the lower solar irradiance. For Aqaba, LCOW of about 1 $/m3 can be realized if a feed-in tariff of about 0.24 $/kWh for electricity from renewable energy sources is established.

A novel approach for SWRO desalination plants operation, comprising single pass boron removal and reuse of CO2 in the post treatment step

A different approach is presented for the operation of seawater RO desalination plants in which the boron concentration in the product water should not exceed 0.3mgB/l. The approach is based on strong acid (either H2SO4 or HCl) dosage to the feed water to attain pH∼4.3, followed by CO2 stripping and subsequently strong base addition to pH 9.00–9.25. At this high pH range, a high B removal efficiency is attained, and since the water is practically devoid of carbonate species, no CaCO3(s) scaling takes place, and pH elevation is limited by Mg(OH)2(s) precipitation, expected only at pH>9.45. The approach enables operation in the absence of antiscalants. Furthermore, CO2 stripping is effected in stripping towers in two steps: the high CO2(aq) concentration is first stripped by vacuum-operated stripping towers and the CO2-rich air is used for dissolution of calcite in the post treatment stage. The remaining CO2 mass is stripped to the atmosphere using blower-assisted stripping towers. This paper aims at introducing the new concept and providing “proof of concept”. The paper addresses experimental and theoretical aspects of the proposed process, as well as engineering and economic evaluation. The proposed approach is shown to be both technically feasible and cost effective, as compared with conventional boron removal alternatives.

Study of Membrane Fouling and Trihalomethane Formation in Reverse Osmosis Desalination Pilot Unit

The objective of this research is to study the combined effect of natural organic matter of benisaf sea water (west of Algeria) on the trihalomethane formation and reverse osmosis membrane fouling. The chlorination method for disinfection of sea water in the pre-treatment step is widely used on several RO desalination plants, which present a disadvantage such as the trihalomethane produced caused by the reactivity of natural organic matter with chlorine. The THM formation on pretreated feed sea water and permeate will be also evaluated by monitoring using several parameters such as Total organic carbon (TOC), Specific ultraviolet visible absorption (SUVA), Ultraviolet absorption at 254 nm (UV254) . Reverse osmosis pilot plant unit has been chosen to determine the membrane fouling will be determined using ATR-FTIR spectra of clean and fouled membrane and atomic force microscopy (AFM) to assess the membrane fouling.

Prediction of the behaviour of the Silt Density Index (SDI) in the Caribbean Seawater and its impact on RO desalination plants

The environmental characteristics of the seawater and its impacts on planning and operating RO desalination plants were always the concern of several scientists around the world. In this article, a study has been performed to investigate the seasonal characteristic of seawater in the Caribbean. The Radial Basis Function Networks (RBFN) was the methodology used in this paper where the redistribution of centres and the input training data possess significant effects in the model. The proposed method is based on clustering of input space vectors and computing weights of Euclidian distances and histogram equalization within each cluster for determining the centre and width of each receptive field. The model allows predicting the behaviour of the SDI using field data (turbidity and salinity) taking into account the tides (the Gulf of Paria) and seasonal changes (hurricane or dry seasons). The results indicated that during the hurricane season, the parameters can change up to 32% between seasons along year due to the change of direction of the inshore currents. Also values higher than 6 in the SDI indicated a very high potential for fouling. This article offers to the project engineers a new door in the application of precautionary principles in the design of desalination plants.

Thermo-economic analysis of a combined solar organic Rankine cycle-reverse osmosis desalination process with different energy recovery configurations

Thermo-economy is a useful and powerful tool that combines thermodynamics and economics. It can evaluate how irreversibility and costs of any process affect the exergoeconomic cost of the product. In this work, a number of comparisons for solar thermal-powered different recovery units for reverse osmosis desalination system are performed using thermo-economic analysis. Three different configurations are used for this comparison (Basic, Pelton Wheel Turbine, and the Pressure Exchanger) with Sharm El-Shiekh RO desalination plant for a total productivity about 145.8 m 3/h (40.5 kg/s). As a result of this analysis, the unit product cost of Pelton Wheel Turbine (PWT) and Pressure Exchanger (PEX) configurations are 24% and 24.2% respectively less than that of the basic configuration. Thermo-economic analysis shows that the minimum investment and operating & maintenance costs are obtained by PEX configuration. Also, it achieves minimum exergy destruction against the two other configurations (Pelton Wheel and Basic systems). Therefore, the final conclusion of this work is that the PEX configuration is more economical than either stand alone or PWT configurations.

Phosboucraa desalination plant for the phosphate industry — optimization of process unit and RO performance

The phosphate industry is a big consumer of water. In Morocco, water consumption by the phosphate industry located in the southern region represents approximately 14% of the national industrial consumption. To solve the problem of water shortage in that region, the Cherifian Office of Phosphates have been using desalinated water. After a brief presentation of the genesis of desalination at the Phosboucraa site, the paper reports on the new RO desalination plant. The performance of the plant and the results of the optimisation operations are described. The advantages of desalination by reverse osmosis compared with multi-stage-flash or thermal compression are presented.