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A photoelectrochemical (PEC) oxidation and flow-electrode capacitive deionization (FCDI) dual system was explored for the effective treatment of brackish water. Two anodic electrodes with electrochemically self-doped TiO2 arrays (blue-mesh/ blue-plate TiO2 nanotube arrays (BM-TNA & BP-TNA)) were fabricated by annealing at 600 °C, and applied for the treatment of a water system. Specifically, the BM-TNA confirmed lower electrical resistance and superior performance under multiple light source (UV-A, -B, and -C). Furthermore, the system generated powerful oxidizing reactive oxygen species (ROS), which were assessed via degradation of eight organic pollutants: bisphenol-A, 4-chlorophenol, cimetidine, sulfamethoxazole, benzoic acid, phenol, nitrobenzene, and acetaminophen. Decomposition efficiency was stable throughout a wide range of pH, and durability of the BM-TNA electrode was demonstrated through long-term operation. Concurrently, optimization of the FCDI process via key operational parameters (electrode mass loading, and applied voltage) achieved superior desalination performance, and specific energy consumption (SEC). In particular, increased mass loading enhanced charge transportation through the formation of stable charge-percolation pathways, leading to improved solution conductance. Finally, the feasibility of the dual system (PEC-FCDI) was verified through complete degradation of the organic substrates and successful desalination of the brackish water. [ABSTRACT FROM AUTHOR]

Performance of a two-stage full-scale reverse osmosis (RO) process for a desalination plant in Florida was simulated with a mathematical model based on the principles of membrane transport and mass conservation. In this model, water flux at any point along the filtration channel is calculated locally according to the basic transport theory of RO membranes. The changes in cross-flow velocity and salt concentration along the filtration channel were determined using mass balance principles of water and salt. Simulations of the plant performance were compared with the in-plant observation data over a period of more than 300 days. The results showed that the model could adequately describe the performance of the full-scale RO process based on a few module and operating parameters. The study also revealed that salt rejection of a RO membrane changed with feed salt concentration. The osmotic pressure coefficient that fits best with performance of this plant was substantially lower than the value determined with the 'rule of thumb' (i.e., osmotic pressure in psi [approximately equal to] 0.01 x total dissolved solids in mg/L) and had to be determined specifically for the particular feed water being processed. CE Database keywords: Membranes; Desalination; Water treatment; Simulation.

Fouling indices have been extensively investigated in membrane applications, for evaluating the feed-water fouling potential and providing guidelines for the pretreatment process. For the past few decades, the silt density index (SDI) has been adopted as the most mature fouling index in many seawater reverse osmosis desalination plants. Recently, a modified fouling index (MFI) has gained attention since it compensates for the defects of the SDI. Its publication by ASTM Standard promoted more settlements in practical applications. To gain insight into the use of a membrane-fouling index, this paper reviewed SDI and MFI applications in laboratory-, pilot-, and plant-scale verifications, under conditions likely to be encountered in seawater desalination. The main focus was on the historical development of the fouling indices from theoretical basis to full-scale applications and the identification of future opportunities to expand their reliability in real applications. In particular, the practical implications associated with plant operation were documented to support an in-depth understanding of the MFI values. [ABSTRACT FROM AUTHOR]

Abstract Internally staged design (ISD) was introduced as a method to lower front reverse osmosis (RO) element fluxes, yielding operational benefits. Systematic selection of the best ISD combinations has not been conducted as it is dependent on operating conditions (i.e., RO recovery and average flux). This study aimed to optimize seawater reverse osmosis (SWRO) operations using ISD for better product water quality and energy efficiency. A total of 36 ISD combinations were configured with three commercial SWRO membranes and systematically examined under varying operating conditions which were simulations of typical SWRO operation. A Pareto-optimal front, a non-dominated feasible solution set, was created to understand the tradeoff relationship between permeate quality and specific energy consumption while considering all parameters. The Pareto-optimal front was classified into five phases, and an analysis of phase changes provided optimal parameter settings for SWRO operation. However, the occurrence of colloidal fouling altered optimal ISD combinations on the Pareto-optimal front. Particularly, when SWRO membranes were fouled at high-recovery and -flux conditions, ISD combinations employing three different membrane types exhibited superior performance in terms of energy efficiency. With these results, the best SWRO operation was suggested depending on its performance requirements, and the advantages of ISD were further delineated. Graphical abstract fx1 Highlights • SWRO with ISD was optimized to achieve better water quality and energy efficiency. • Efficient SWRO performance control was examined by Pareto-optimal front analysis. • Colloidal fouling changes the best ISD combinations on the Pareto-optimal front. • ISD with three SWRO membrane types is feasible at high-recovery and -flux operations. • The optimal SWRO operation mode is proposed based on its performance requirements. [ABSTRACT FROM AUTHOR]

The effects of discharged brine from desalination plants, particularly brine containing algal toxins during harmful agal bloom (HAB) occurrence, are a major concern for marine life and, as a result, human health. Therefore, removing algal toxins from desalination brine is critical for safeguarding both human health and the marine environment. The present work examined the mineralization of domoic acid (DA), an algal toxin, in highly concentrated seawater for the first time using an ultraviolet light activated peroxymonosulfate (UV/PMS) system. Mineralization efficiencies, effects of various anion concentrations, and reaction by-products were investigated. The presence of anions such as chloride, bromide, and bicarbonate reduces the mineralization efficiency of the UV/PMS system, with bromide being the most detrimental. Although DA can be effectively degraded in synthetic seawater (35,000 ppm), total mineralization is not possible within 180 min of reaction time, with only 38.4 %, 44.8 %, and 41 % TOC removal in pH 3, 5, and 7, respectively, when 1 mM of PMS was used. Analyses of treated hypersaline seawater using ultra-high-resolution liquid chromatography coupled with quadrupole time-of-flight mass spectrometry and ion chromatography revealed that DA was completely degraded in synthetic seawater and that, in the presence of algal organic matter, no toxic by-product was generated during the detoxification process. Overall, the UV/PMS system has the potential to be an effective treatment strategy for algal toxins in seawater during HAB events in the SWRO desalination process. [Display omitted] • Domoic acid (DA) mineralization efficiency by UV/PMS system was investigated. • DA can be effectively removed in deionized water and synthetic seawater. • Anions affected the mineralization efficiency with the most detrimental being Br −> Cl −>HCO 3 −. • No halogenation byproducts, chlorates, or bromates were detected after treating DA in hypersaline seawater. [ABSTRACT FROM AUTHOR]