Analysis of the proper bicarbonate concentration for shipboard seawater reverse osmosis remineralization

Salinity Gradient Power (SGP) based on the controlled mixing between two solutions at different salinities is a viable alternative to produce power from renewable sources. Pressure Retarded Osmosis (PRO) is one of the most promising technologies proposed so far for the exploitation of such energy source. Apart from the typical source of salinity gradients, namely river water and seawater, more and more interest has been raised recently towards the use of non-conventional saline solutions. In this work, water originating from a sewage treatment plant is used as the dilute solution (feed solution), while brine exiting from a desalination plant is used as the concentrate (draw solution), thus being efficiently diluted before the discharge into the sea. Aim of this work is to investigate the performance of PRO modules arranged in series via a purposely developed process model based on transport and balance equations. Detrimental effects due non-ideal phenomena as salt diffusion through the membrane, concentration polarization were taken into account. Pumping power was also accounted for. Geometrical data were derived from existing spiral wound membrane modules typically employed in Reverse Osmosis. The effect of solution velocity, number of PRO units and operative hydraulic pressure (applied on the draw solution channel) on the process performance was investigated. Results show that the dependence of the net power on velocity and applied pressure is not monotonic thereby exhibiting a maximum: under optimized conditions, a maximum net power of ~1.5kW corresponding to a net power density of ~6.6 W/m 2 can be obtained with six identical PRO modules. Along with this power production, a simultaneous brine dilution of more than 22% was found at the same conditions. However, despite the potential shown by the model, the main limitation for a real process might be the real performances of the osmotic membranes in terms of mechanical robustness and resistance against fouling phenomena. In this regard, valuable contributions may come from nanotechnologies ad-hoc developed.

Corrosion inhibition of 2-undecyl-N-carboxymethyl-N-hydroxyethyl imidazoline (UH- CI) on carbon steel in an artificial water, which simulated the water produced by seawater reverse osmosis (RO) process, was investigated by mass loss test, electrochemical methods, and X-ray pho- toelectron spectroscopy (XPS). Results show that UHCI could inhibit the corrosion of carbon steel, and the inhibition efficiency increases with the increasing concentration of UHCI. The UHCI acts as an anodic type inhibitor responsible for reducing the anodic current density. XPS results suggest that UHCI was adsorbed on the mild steel surface, which can effectively protect carbon steel from corrosion in the artificial water. Quantum chemical calculation results reveal that carboxymethyl and the ring of UHCI play the important role when UHCI adsorbed on carbon steel surface, which leads to the enhancement in the corrosion resistance of carbon steel and thereby a reduction in the

Desalination of brackish water by nanofiltration and reverse osmosis

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.

Desalination plants in Australia, review and facts

The growth in demand for freshwater is partially satisfied by desalination plants that increasingly use membrane technologies and, among them, reverse osmosis (RO), to produce purified water. Seawater desalination offers a seemingly unlimited, steady supply of high-quality water, without impairing natural freshwater ecosystems. The desalination of brackish groundwater provides another option towards increasing water supplies for inland regions. RO is a membrane technology widely applied in water desalination, the production of potable water, and more recently in tertiary wastewater treatment. There are some seawater RO (SWRO) plants coupled with renewable energies on the Canary Islands (photovoltaic and wind), and islands of Croatia and Norway (wind energy); there are also similar projects in Jordan, the Egyptian desert, Australia, and Saudi Arabia among others. Research on sustainable treatments applicable to RO concentrates has continually grown in recent years. Several review articles about traditional and emerging technologies for RO concentrates have been published recently.

Chronic Kidney Disease of uncertain etiology (CKDu) is a fatal disease which causes death from kidney failure due to the unknown risk factors and has already affected more than 400,000 people in rural agricultural landscape (dry zone) of Sri Lanka. This has become a major health hazard in Sri Lanka. The drinking water is supplied using bowsers and several reverse osmosis (RO) plants have been installed in some areas of Sri Lanka and they are not viable solutions. Therefore, rainwater comes up as an alternative for drinking water. The primary objective of this study is to determine whether rainwater can be used as an alternative safe drinking water source in Girandurukotte area in terms of water quality. The physical, chemical and biological analysis were performed to compare the water quality parameters of 3 water sources (groundwater, surface water and rainwater) in the Girandurukotte area. The sample size of each source is 20 (n=20) and rainwater collected in pre-monsoon and post-monsoon periods. The most common storage tanks (polyethylene (PE) and ferrocement (FC) were subjected to this study to compare the water quality depending on the material of the rainwater tank. The results show that there is a significant difference in rainwater in terms of water quality compared to groundwater and surface water. There is a significant difference (p<0.05) in parameters such as, colour, turbidity, pH, Cd, As, Zn, Pb, Na, K, Mg, free ammonia, fluoride, total hardness, total alkalinity, nitrate and nitrite. In the comparison of storage material, rainwater in FC tank was high in pH while rainwater in PE tank was lower in pH and have a significant difference (p<0.05) for some water quality parameters such as pH, total alkalinity and total dissolved solids. Still water quality of rainwater collected in both tanks (PE and FC) was within portable drinking water standards (Sri Lanka Standards; 614, 2013) and there is no likelihood of Cd, Pb and As contamination in rainwater and fluoride content, hardness is well below safe limits. Keywords: CKDu, Rainwater harvesting, Groundwater, Ferrocement, Polyethylene

Life cycle assessment of hybrid electrodialysis and reverse osmosis seawater desalination systems

Investigation of compounds that degrade biofilm polysaccharides on reverse osmosis membranes from a full scale desalination plant to alleviate biofouling

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

Water scarcity represents one of the most critical environmental and economic challenges worldwide, especially in arid and semi-arid regions lacking access to reliable freshwater sources. In response, seawater desalination has emerged as a strategic solution to ensure a sustainable and secure supply of potable water for various applications. Among desalination technologies, Reverse Osmosis (RO) stands out for its high efficiency and widespread adoption, primarily due to its relatively low specific energy consumption compared to thermal-based methods. However, high operational costs particularly those related to energy consumption remain a barrier, as most conventional desalination plants rely on fossil fuels, contributing significantly to greenhouse gas emissions and environmental degradation. In this context, integrating renewable energy sources, specifically solar photovoltaic (PV) and wind energy, offers a viable pathway to reduce operational expenditures and minimize environmental impact. Several studies have demonstrated that hybrid renewable energy systems can enhance the sustainability and energy autonomy of desalination plants, aligning with Global Sustainable Development Goals (SDGs). This study conducts a techno-economic analysis of a Seawater Reverse Osmosis (SWRO) plant located in Al Wajh, Saudi Arabia. Detailed Capital expenditures (CAPEX) and Operational Expenditures (OPEX) were estimated for both conventional electricity-based operation and for configurations utilizing solar and wind energy in the same location. An energy simulation model was conducted to determine the optimal number of wind turbines required to maximize energy efficiency while minimizing excess power generation. The analysis revealed that the SWRO powered by renewable energy achieved an energy efficiency of 99%, compared to its conventional electricity-powered counterpart, with an energy surplus of no more than 4%. CAPEX and OPEX cost projections were calculated for both scenarios: conventional grid electricity and renewable energy sources. The findings indicated that the unit production cost per cubic meter of the SWRO plant was 0.59–0.76 $/m3 in the case of grid electricity, whereas it was 0.74–1.12 $/m3 under renewable energy integration. This cost disparity is primarily attributed to the higher CAPEX required for the renewable energy-powered SWRO system, which amounted to 0.28–0.36 $/m3, in contrast to a significantly lower CAPEX of only 0.06–0.09 $/m3 for the electricity-based SWRO configuration. Moreover, artificial intelligence (AI) was employed to support the results and forecast future water demand based on regional climate conditions and consumption patterns. The study concludes with a set of recommendations aimed at optimizing the integration of renewable energy technologies into desalination systems to enhance long-term economic and environmental sustainability.

Sliding vane pressure exchanger (SVPE) is expected to be an efficient device which recovers pressure energy from liquid streams in seawater reverse osmosis (SWRO) system. In this work, a matching design of vane number and port location was proposed to eliminate the short circuit flow, reversed flow, liquid decompression and compression. The contact performance between the cylinder and vane was studied by the proposed vane dynamics model. Then, the vane dynamics model in conjunction with the energy loss model were used to evaluate the work transfer efficiency of SVPE. The critical condition of contact performance and the work transfer efficiency of SVPE were simulated. Finally, the influences of device parameters on the work transfer efficiency were discussed. The results suggest a careful selection of device parameters, such as rotational speed, vane thickness and vane length, is critical in order to improve the work transfer efficiency of SVPE.

Based on the thermal and membrane desalination technology, this study presents an analysis of an integrated single stage TVC-RO system. The hybrid system produces fresh water with an adjustable salinity in parallel operation. A steam ejector and a pressure exchanger are applied as the energy recovery devices. For comparison, a coupling system without energy recovery process is also modeled in the steady-state condition. System performance is evaluated by specific energy consumption and production ratio. The effects of several design parameters on system performance are investigated including boiling temperature, compression ratio, motive steam pressure, and target recovery rate. Results of the analysis indicate that the product salinity is adjustable in the TVC-RO system, and the system performance is largely dominated by system configurations and design parameters. To improve the system performance, the use of energy recovery device is necessary, and the membrane operation is recommended if the process is less demanding on product purity. A better performance can be obtained by increasing the target recovery rate of the RO membrane and decreasing compression ratio and motive steam pressure of the ejector. As the boiling temperature increases, one can expect that the production rate increases at a cost of a higher specific energy consumption.

The Most Advanced Membrane Analysis and the Save-Energy Type Membrane-Low-Pressure Seawater Reverse Osmosis Membrane Developed by “Mega-ton Water System” Project

Al Dur SWRO plant: a double challenge for pre- and post-treatments