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Semi-batch reverse osmosis (SBRO) is an innovative membrane process renowned for its compact system and high recovery in desalination and water reuse. While academic research provides valuable insights, aligning it with real-world implementation is crucial. The study aims to understand the current progress in SBRO for brackish water desalination by identifying performance disparities between academic research and practical applications, evaluating practical performances under realistic parameters, and proposing future research directions. Through gathering and comparing data from SBRO research and practices, performance disparities between theoretical projections and real-world applications were identified. The analysis revealed that specific energy consumption (SEC) in academic research had been underestimated by applying impractical pump efficiencies, and permeate quality was often neglected. To assess the practical SEC and permeate quality of SBRO, engineering design calculations were performed with realistic parameters. Based on the evaluation, the importance of maintaining suitable recovery and incorporating a permeate tank was emphasized to avoid a significant increase in SEC and to stabilize water quality, respectively. Given the challenges of the SBRO system, the discussion further outlined research directions addressing issues in energy efficiency, permeate quality, membrane fouling/scaling, and practical design/operation. It recommended considering these practical aspects for the broader applications of SBRO. [Display omitted] • Current progress in SBRO was identified with theoretical and industrial perspectives. • Process modeling with engineering designs was applied to evaluate SBRO performance. • Data from SBRO research and practices were collected and critically compared. • SEC and permeate quality of SBRO were estimated by considering practical conditions. • Future research directions were outlined for the expansion of SBRO technology. [ABSTRACT FROM AUTHOR]

The increasing impact of climate change has worsened drought conditions, leading to a surge in the demand for seawater desalination. However, current seawater reverse osmosis (SWRO) desalination technologies are not energy-efficient for handling the high-salinity, high-temperature, and high-turbidity seawater found in the Arabian Gulf. Therefore, a pilot-scale SWRO desalination plant was established to evaluate the new desalination technologies. The pilot plant tested high-performance SWRO membranes, meshed tube filtration (MTF) as a low-energy pretreatment for the high turbidity induced by algal blooms, and membrane capacitive deionization (MCDI) to improve permeate quality. The high-performance SWRO membrane demonstrated exceptional salt rejection and produced permeate quality in the range of 250–455 mg/L from the feed with salinities of 47,500–53,500 mg/L. MTF was effective in controlling turbidity, and the energy consumption was reduced by 77 % compared to the existing pretreatment process. Furthermore, MCDI exhibited similar levels of energy efficiency as brackish water reverse osmosis and may have the potential for future deployment by enhancing process development. Based on the pilot plant results, it is expected that a 100,000–200,000 m3/d SWRO desalination plant will have a specific energy consumption of 3.11–3.13 kWh/m3 for final product water quality at or below 200 mg/L. [Display omitted] • A pilot-scale SWRO desalination plant was used to investigate low-energy technologies. • Developed SWRO membranes significantly decreased feed TDS under normal pressure. • MTF reduced feed turbidity effectively and consumed lower energy compared to DAF. • MCDI demonstrated potential as a substitute for BWRO in two-pass RO systems. • The SEC of SWRO desalination plants was evaluated as 3.11 kWh/m3 through scale-up. [ABSTRACT FROM AUTHOR]

While single-stage is the general configuration for seawater reverse osmosis (SWRO), the two-stage design can increase the overall recovery of an SWRO system. Due to its high-recovery operation, the specific energy consumption (SEC) of two-stage SWRO is higher than that of single-stage. Thus, the two-stage configuration has not been extensively applied in the current desalination market. In contrast, recent studies have reported that the two-stage design can lower the SEC of SWRO compared to that of single-stage. However, the analyses were biased towards SEC, and the practical design aspects (e.g., permeate quality, water flux, and design ratios) were not systemically considered. Thus, this study examines the applicability of a two-stage SWRO system with a capacity of 100,000 m3/d that employs 1200 pressure vessels (PVs). Two-stage SWRO actually consumed a greater amount of energy than that of single-stage for typical SWRO recovery with the same number of PVs. In contrast, single- and two-stage SWRO produced permeate similar in quality, while the two-stage exhibited superior water-flux distribution along the PVs. Additionally, optimal ratios of permeate flow rate and number of PVs were determined by energy recovery devices type, where the ratio of 1:2 was selected for the reverse osmosis system with a pressure exchanger and 2:1 for that with a Pelton turbine. Considering SEC and other operational aspects, the use of two-stage SWRO was feasible at a 50–70% recovery rate. Image 1 • Two-stage SWRO is fundamentally analyzed and optimized for seawater desalination. • SEC of two-stage SWRO is higher than that of single-stage in typical recovery. • Water quality of single- and two-stage SWRO is similar at the same average flux. • Optimal ratios of permeate flow rate and number of PVs vary depending on ERD types. • Two-stage SWRO is more energy-efficient at a high recovery rate (e.g., 50–70%). [ABSTRACT FROM AUTHOR]