A Novel RO/FO Hybrid Seawater Desalination System and Its Software Implementation

Mass balance for a novel RO/FO hybrid system in seawater desalination

The desalination industry is undergoing significant expansion and modernization to develop more efficient, larger-scale desalination plants that aim to reduce production costs, corrosion, and CO2 emissions. Currently, non-metallic materials are extensively utilized in the low-pressure components of Sea Water Reverse Osmosis (SWRO) desalination technology. However, ongoing efforts are focused on extending their application to high-pressure components (above 50 bar). This paper highlights the experiences of the desalination plants of Saudi water Authority (SWA) with non-metallic materials in both SWRO and Thermal desalination plants. It also explores future opportunities where the adoption of non-metals in SWRO technology could drive a sustainable transformation by enabling cost-effective and environmentally friendly desalinated water production. Additionally, paper showcases the initiatives and accomplishments of the Water Technologies Innovation Institute and Research Advancement (WTIIRA) in advancing non-metal innovations for the SWRO plants of the Saudi Water Authority (SWA).

Seawater reverse osmosis (SWRO) desalination technology is an important technology for providing potable water for industries and human daily life due to its lower-energy consumption compared to thermal based desalination technology. However, membrane fouling is still a persistent problem in SWRO desalination plants. Organic fouling and biofouling, in particular the interplay between them, are the challenges that require attention. In the first part of my study, the focus was on organic fouling in SWRO desalination process. Classifying organics in seawater will provide an in-depth understanding of the important fraction on SWRO organic fouling. The dissolved organic matter (DOM) in seawater was fractionated and concentrated by a membrane-based technique into three major fractions according to their molecular weight (MW) as defined in the liquid chromatography with organic carbon detection (LC-OCD) method, namely the fraction of biopolymer (F.BP, MW > 1000 Da), fraction of humic substance with building block (F.HS&BB, MW 350 – 1000 Da), and fraction of low molecular weight compounds (F.LMW, MW < 350 Da). An overall recovery of >80% of the organics in seawater was attained. Compared with model foulants such as sodium alginate (SA), bovine serum albumin (BSA), and humic acid (HA), all isolated organic fractions showed lower fluorescence intensities, and had lower fouling potentials than common model foulants used in SWRO fouling studies, thus the model foulants were not good representatives of the natural organics in seawater. In addition, results from atomic force microscopy (AFM) and extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory showed that initial fouling (i.e., foulant-membrane interaction) was the main driver in SWRO organic fouling with F.BP as the major contributor followed by F.LMW. In addition, divalent ions were found to enhance the RO fouling by increasing the adhesion and cohesion forces between foulant-membrane and foulant-foulant. In second part of my study, the focus was on biofouling and the interplay between organic fouling and biofouling in SWRO desalination process by using the isolated dissolved organic fractions. From the assimilable organic carbon (AOC) results, the AOC/DOC ratio was in the order of F.LMW (~35%) > F.BP (~19%) > F.HS&BB (~8%); AOC/DOC of seawater was ~20%; organic compositions of seawater were BP ~6%, HS&BB ~52% and LMW ~42%; thus LMW accounted for >70% of AOC in seawater. Their impact on SWRO biofouling in term of flux decline rate was in the order of F.LMW (~30%) > F.BP (~20%) > F.HS&BB (<10%). Despite being the major organic compound in seawater, HS&BB showed marginal effect on biofouling. The role of indigenous BP was less critical owing to its relatively low concentration. LMW, which was the major AOC contributor, played a significant role in biofouling by promoting microbial growth that contributed to the build-up of soluble microbial products and exopolymeric substances (i.e., in particular BP). Therefore, seawater pretreatment shall focus on the removal of AOC (i.e., LMW) rather than the removal of biopolymer. In third part of my study, the focus was on the LMW removal by using low-pressure NF pretreatment process and the subsequent impact on SWRO fouling. Three different membranes were evaluated: NF270 was a commercial membrane based on polyamide thin film composite with negatively charged surface, NF1 and NF2 were glutaraldehyde cross-linked layer-by-layer polyelectrolyte membranes with positively charged surface (i.e., NF2 contained more polyelectrolyte layers than NF1). The organic/inorganic rejection of NF membranes followed the order of NF2 > NF1 > NF270 while pure water permeability (PWP) was in the order of NF1 > NF270 > NF2. Meanwhile the degree of RO fouling in term of flux decline and foulant amount was in the order of NF270 > NF1 > NF2. In addition, the results suggested that NF membrane can be optimized to achieve excellent removal of LMW, but a balance between permeability, rejection and fouling shall be considered when selecting the membrane for seawater pretreatment. For instance, NF2 membrane with the lowest permeability (~1.9 LMH/bar) was less competitive even though it showed the lowest SWRO fouling (i.e., flux decline ~3%) as compared to NF 1 (permeability of 4.0 LMH/bar, flux decline ~10%).

Energy and environmental issues of seawater reverse osmosis desalination considering boron rejection: A comprehensive review and a case study of exergy analysis

Institute of African research and studies, Cairo University

IMS SWRO Kindasa — Two years of operational experience

Application of World Ocean Atlas data for estimating the relative performance of a new construction of SWRO desalination plant

SeaHERO core technology and its research scope for a seawater reverse osmosis desalination system

Fresh water production by desalination of seawater is an expensive affair. During the last few years, seawater reverse osmosis (SWRO) desalination technology has gone through a remarkable transformation and gained widespread acceptance, which is evident from the increased share of SWRO. Typical SWRO desalination consists of four major components: an intake; a pre-treatment system; a high-pressure pumping system; and a membrane module. The performance of the entire system is dependent upon the proper design and operation of each component and assessed by its ability to produce required quantity of water with acceptable quality at lowest possible cost. Recent advances in seawater reverse osmosis (RO) that has allowed a drastic reduction in the cost of desalinated water include the application of highly efficient energy recovery devices (ERDs) and the utilization of advanced RO membranes. However, fouling and membrane degradation are some of the major challenges faced by the RO systems, which need to be carefully addressed. The chapter discusses various parameters, which are typically used to assess RO desalination plant performance. It will also cover the challenges faced by SWRO plants and measures adopted to address these challenges to maintain the best plant performance.

Life cycle cost of dilution desalination in off-grid locations: A study of water reuse integrated with seawater desalination technology

Water is one of the basic needs for human life, including for people living on the coast. It is difficult to get clean water for consumption because most coastal areas are affected by sea conditions that have high salinity. In order to be consumed, the saline water must be desalinated. Desalination is a process to convert saline water into fresh water. One such desalination technology is using reverse osmosis (RO). The purpose of this study was to determine the process of desalination of seawater into freshwater using the seawater reverse osmosis (SWRO) method. The method used in this research is observation, which is to see directly the stages of the desalination process of seawater into fresh water. The data was obtained in the form of primary data from observations and secondary data from the literature to support primary data. Analysis of the data used in the form of descriptive analysis by describing each stage carried out in the SWRO process. The results showed that the seawater desalination process using SWRO technology had 14 stages. These stages include; intake, raw water pump, raw water reservoir, UF feed pump, Automatic screen, ultrafiltration, UF water reservoir, RO feed pump, HPP &amp; booster, RO membrane, RO water reservoir, permeate pump, chlorine analyzer, product water. In developed and developing countries, SWRO units have been widely used, because by processing seawater into freshwater, there are many benefits for the life cycle and it is environmentally friendly. It also maintains underground fresh water so that it can provide plant life, and trees that provide us with clean oxygen for our lives.

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.

The operation of seawater reverse osmosis (SWRO) desalination facilities has become challenged by the increasing frequency and severity of harmful algal blooms (HABs). The efficiency of algal toxins removal during SWRO and pretreatment processes has critical human health implications. Therefore, a probabilistic materials flow analysis (pMFA) was developed to predict the removal of algal toxins in source water by various pretreatment configurations and operations during SWRO desalination. The results demonstrated that an appreciable quantity of toxins exists in the SWRO permeate (ng/L–µg/L levels), the backwash of pretreatment, and final brine rejects (µg/L–mg/L levels). Varying the pretreatment train configuration resulted in statistically significant differences in toxin removals, where higher removal efficiencies were evidenced in systems employing microfiltration/ultrafiltration (MF/UF) over granular media filtration (GMF). However, this performance depended on operational practices including coagulant addition and transmembrane pressures of MF/UF systems. Acute human health risks during lifetime exposure to algal toxins from ingestion of desalinated water were benign, with margins of safety ranging from 100 to 4000. This study highlights the importance of pretreatment steps during SWRO operation in the removal of algal toxins for managing marine HABs.

Hybrid membrane system for desalination and wastewater treatment : Integrating forward osmosis and low pressure reverse osmosis

Pilot study of emerging low-energy seawater reverse osmosis desalination technologies for high-salinity, high-temperature, and high-turbidity seawater