Scale Seawater Reverse Osmosis Research Articles

Demonstration of a piston type integrated high pressure pump-energy recovery device for reverse osmosis desalination system

Energy recovery device (ERD) plays a vital role in reducing the energy consumption of seawater reverse osmosis (SWRO) desalination process. Numerous investigations have been conducted for large scale ERDs, yet few studies for small scale ERDs (capacity less than 50 m3/d) have been reported. In this paper, a newly invented piston type integrated high pressure pump-energy recovery device (HPP-ERD), which synchronously pressurizes the raw seawater and recovers hydraulic energy from the concentrated brine, is introduced. The structure and working principle of the HPP-ERD is offered. Three versions of HPP-ERD prototypes are tested in a laboratory emulate platform and the test results can manifest the energy-saving feasibility of the HPP-ERD. A practical small scale SWRO project with a capacity of 50 m3/d using the HPP-ERD is surveyed. A performance analysis of the proposed project is implemented for one-month operating duration, which reveals the acceptable energy-saving capability and durability of the HPP-ERD under actual working circumstances. An economic analysis is finally performed and the analysis consequence indicates that the utilization of the HPP-ERD instead of a single high pressure pump can diminish both the payback period and the desalinated water cost of the proposed project remarkably.

Design of photovoltaic system powered a small-scale SWRO desalination plant

This paper illustrates a proposed design to the Center for Solar Energy Research and Studies (CSERS) - Tajura, for the erection and testing of a stand-alone photovoltaic (PV) system for the powering of a small scale seawater reverse-osmosis (SWRO) desalination plant. The plant promises to deliver up to 0.25 m3/hour of potable water from seawater with a salinity of about 38,000 ppm and the osmotic pressure of 26.4bar.In the current paper, ROSA Software by Dow chemical company was used to establish suitable membrane unit at this capacity. A unit of 4 inch of SW30-4040, with a feed pressure of 48 bar, and a salt recovery (R) of 20% with total dissolved solids (TDS) of 190ppm was selected.Also results showed that, the electrical consumption of the SWRO plant was 2500 W, and the specific energy consumption was 10 kWh/m3. The size of the selected stand-alone photovoltaic (PV) system to power a SWRO plant with a mean production capacity of 1.5m³/day (6 hours operating per day), is 48V nominal voltage, 72 PV modules (shell SQ85-P), and 16 batteries with the capacity of 383Amp-Hour each.

Design of photovoltaic system powered a small-scale SWRO desalination plant

This paper illustrates a proposed design to the Center for Solar Energy Research and Studies (CSERS) - Tajura, for the erection and testing of a stand-alone photovoltaic (PV) system for the powering of a small scale seawater reverse-osmosis (SWRO) desalinationplant. The plant promises to deliver up to 0.25 m3/hour of potable water from seawater with a salinity of about 38,000 ppm and osmotic pressure of 26.4bar.In the current paper, ROSA Software by Dow chemical company was used to establish a suitable membrane unit at this capacity. A unit of 4 inch of SW30-4040, with a feed pressure of 48 bar, and a salt recovery (R) of 20% with total dissolved solids (TDS) of 190ppm was selected.Also, results showed that the electrical consumption of the SWRO plant was 2500 W, and the specific energy consumption was 10 kWh/m3. The size of the selected stand-alone photovoltaic (PV) system to power a SWRO plant with a mean production capacity of1.5m³/day (6 hours operating per day), is 48V nominal voltage, 72 PV modules (shell SQ85-P), and 16 batteries with the capacity of 383Amp-Hour each.

Role of pressure-retarded osmosis (PRO) in the mega-ton water project

AbstractReverse osmosis (RO) membranes have been widely applied to seawater desalination and wastewater reclamation, and many large RO plants (>100,000 m3/d) have been constructed since 2000. Energy efficiency is indispensable for large plants, especially for future mega-ton scale seawater reverse osmosis (SWRO) plant (1,000,000 m3/d). In order to reduce energy demand in RO operation, high-efficient low-pressure RO membrane, energy recovery device (ERD), and pressure-retarded osmosis (PRO) which would recover power from salinity gradient between freshwater and concentrated brine were studied in the “Mega-ton Water System” project. A PRO hollow fiber membrane module was newly developed, and a practical continuous operation has been examined at a prototype plant for one year. The maximum 13.5 W/m2 of membrane power density using 10-inch module was established at our prototype PRO plant. As the results of the plant cost estimation and the financial impacts on the energy saving operation at the mega-ton scale...

Energy recovery by PRO in sea water desalination plant

Sea water reverse osmosis (SWRO) would face some problems like energy saving and management of concentrated brine. To solve these problems at the same time, the energy recovery by Pressure Retarded Osmosis (PRO) was proposed in the Mega-ton Water System project. Prototype plant test was conducted using concentrated brine from SWRO plant and fresh water from regional waste water treatment facility. Hollow-fiber membrane module were examined in the prototype plant and the test operation was carried out for more than one year. We have reached the maximum membrane power density, 13.5W/m2, using 10-in. module. Followings were still existing obstacles for further effective PRO. It was also challenging how to get clean fresh water from waste or river water without additional cost. Innovative new technologies were also required to address these concerns. We have also estimated plant cost and surveyed financial impacts on the energy saving of SWRO operation, based on the situation of currently operated SWRO plants worldwide, especially about the Mega-ton scale ones. Those studies indicated that potential market of PRO was 1–2GW, and 10% energy saving was possible on the Megaton scale SWRO plants. Those results indicate that the commercialization plant would be available very near future.

Evaluation of potential particulate/colloidal TEP foulants on a pilot scale SWRO desalination study

This pilot study investigated the variation of potential foulants and different fractions of transparent exopolymer particles (TEP), along the treatment scheme under different conditions. The objectives are to provide a comprehensive understanding on which fraction of TEP is more problematic in seawater reverse osmosis (SWRO) fouling, and which pretreatment can better reduce the concentration of TEP. Results showed that TEP deposited on the RO membranes, and the extent of RO fouling increased with the increase of TEP concentration in RO feed water. More TEP was produced in water after chlorination, probably because of the breakdown of bacterial cells and thus the release of internal exopolymers. Moreover, the cartridge filters could behave as an incubator for the regrowth of bacteria deactivated by chlorination and a spot for potential foulant (bacterial TEP) production, and thus enhance the RO membranes fouling. The presence of residual iron and addition of phosphate based antiscalant may also contribute to the higher biofouling of RO membranes. This pilot study provided an opportunity to identify the TEP related issues under different operational conditions in RO desalination of Red Sea water.

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.

Experimental investigation of the performance of a reverse osmosis desalination unit under full- and part-load operation

Sea water reverse osmosis (SWRO) desalination constitutes a successful technology for covering the potable water needs of islands and coastal regions. SWRO units can be combined with renewable energy technologies such as photovoltaic and wind generators. Conventional small scale SWRO units are not often combined with energy recovery devices; however, these devices can decrease drastically the energy consumption of the SWRO units. Furthermore, in the literature there are references which prove that the operation of a desalination unit in part-load conditions can result in lower specific energy consumption compared to full-load operation. This paper presents the simulation and the experimental investigation under full- and part-load conditions of an existing SWRO desalination unit (50 mS/cm feed water) in order for the desalination unit to be optimally utilized in a polygeneration microgrid topology which uses advanced energy management algorithms. The experimental operation of the SWRO Unit in part-load conditions is achieved by varying the speed of the motor—pump assembly, the pressure and the flow rate of the feed water. During the evaluation of the measurements result, an optimum operating window in the range of 40–57 bar was drawn regarding the operation of the SWRO desalination unit in part- and full-load conditions. More specifically, in this pressure range the average value of fresh water production was 60 L/h with an acceptable fresh water electrical conductivity of 550 μS/cm, and with a specific energy consumption range from 6.1 to 7.7 kWh/m3. With these results the operational parameters of the polygeneration microgrid energy management system can be optimized.

Modular pumps bring efficiencies

Positive displacement, water lubricated axial piston (AP) pump technology can be used in a modular arrangement to replace less efficient, centrifugal (CF) pumps that are currently the dominant solution for high pressure pumping used in large scale seawater reverse osmosis (SWRO) systems. A preliminary review of the modular positive displacement axial piston pump system reveals this new concept is not only a cost effective alternative to traditional centrifugal pump systems, but may have other advantages during the SWRO facility operating period.

SWRO pre-treatment design and operation using Enflo-DAF™ technology

The purpose of this paper is to present an overview of the design for both the full scale and pilot scale seawater reverse osmosis (SWRO) pre-treatment plant comprising Enflo-DAF™ dissolved air flotation (DAF) technology and dual media filtration (DMF) proposed and operating respectively at Ras Al Khair site in Saudi Arabia. The application of both DAF and DMF in the municipal water industry is regarded as well established; however the application of DAF to the treatment of seawater particularly at elevated temperatures and which is also prone to Red Tide or severe algae events is relatively new and there is a limited amount of experience in this area.

Technical review and evaluation of the economics of water desalination: Current and future challenges for better water supply sustainability

Desalination capacity has rapidly increased in the last decade because of the increase in water demand and a significant reduction in desalination cost as a result of significant technological advances, especially in the reverse osmosis process. The cost of desalinated seawater has fallen below US$0.50/m3 for a large scale seawater reverse osmosis plant at a specific location and conditions while in other locations the cost is 50% higher (US$1.00/m3) for a similar facility. In addition to capital and operating costs, other parameters such as local incentives or subsidies may also contribute to the large difference in desalted water cost between regions and facilities. Plant suppliers and consultants have their own cost calculation methodologies, but they are confidential and provide water costs with different accuracies. The few existing costing methodologies and software packages such as WTCost© and DEEP provide an estimated cost with different accuracies and their applications are limited to specific conditions. Most of the available cost estimation tools are of the black box type, which provide few details concerning the parameters and methodologies applied for local conditions. Many desalination plants built recently have greater desalinated water delivery costs caused by special circumstances, such as plant remediation or upgrades, local variation in energy costs, and site-specific issues in raw materials costs (e.g., tariffs and transportation). Therefore, the availability of a more transparent and unique methodology for estimating the cost will help in selecting an appropriate desalination technology suitable for specific locations with consideration of all the parameters influencing the cost. A techno-economic evaluation and review of the costing aspects and the main parameters influencing the total water cost produced by different desalination technologies are herein presented in detail. Some recent developments, such as the increase of unit capacity, improvements in process design and materials, and the use of hybrid systems have contributed to cost reduction as well as reduction in energy consumption. The development of new and emerging low-energy desalination technologies, such as adsorption desalination, will have an impact on cost variation estimation in the future.

Removal of boron from geothermal water by RO System-III-Utilization of SWRO system

In this study, desalination performance of a mini-pilot scale seawater reverse osmosis (SWRO) system installed at geothermal field was investigated. The system was analyzed in terms of product water quality and quantity using two types of FilmTech SWRO membranes (SW30-2540 and a novel high rejection SWRO membrane abbreviated as XUS SW30XHR-2540). To determine the effect of applied pressure on desalination performance of the SWRO system, the process was operated at different pressures. The boron rejection of SWRO membranes was higher than that of BWRO membranes. An average boron rejection of 88% and a salt rejection of 99% were obtained at 20bar of operating pressure by a high rejection XUS SW30XHR-2540 membrane. The average permeate recovery by XUS SW30XHR-2540 membrane was about 16% and it increased to 34% at 40bar of operating pressure. The respective average boron rejection value obtained by SW30-2540 membrane was 84% at 20bar. The average permeate recovery of SW30-2540 membrane was 20% at 20bar while it increased to 37% at 40bar. The quality of product water obtained by both membranes was good according to water standards.

The Development of an Axial Piston Pump Prototype for Seawater Desalination and its Application

High pressure pump is one of the key components in Sea Water Reverse Osmosis (SWRO) desalination project. This paper introduced the development of an axial piston pump prototype which used as a high-pressure pump in SWRO desalination system. After the structure and technique data of the pump were illustrated, the main manufacturing processes of the prototype were introduced. The performance test of the prototype was carried out on an integrated water hydraulics test rig. After this, the prototype was used as a high-pressure pump on a SWRO experimental system. The test and application results prove that the pump is more efficient and quiet than other types, and is suitable for being used as high pressure pump in small and medium scale SWRO desalination project.

Modified operation of a small scale energy recovery device for seawater reverse osmosis

The Clark pump reciprocating pressure intensifier is a well established mechanism for highly efficient brine stream energy recovery in small scale seawater reverse osmosis (SWRO) desalination systems. This article describes operation of a modified Clark pump in which the roles of the two pairs of chambers are reversed and the general arrangement of the complete RO system is substantially altered. In particular, the low-pressure motorised pump that feeds into the standard Clark pump is replaced by a high-pressure motorised pump that sits in parallel with it. A conceptual comparison of the original and modified arrangements is presented, followed by a discussion of the practical modifications made to a standard Clark pump in order to test the concept. The initial tests were successful and results indicating specific energies in the range 3.5–4.5 kWh/m3 are presented.