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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]

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]

Membrane-based desalting processes including reverse osmosis (RO), forward osmosis (FO), and membrane distillation (MD) were systematically evaluated for concentrating RO brine. Basic characteristics of membrane processes were first examined. Commercial polyamide RO exhibited higher water and lower salt permeability coefficients than cellulose FO membrane. However, salt rejection by FO seemed to be higher than RO primarily due to the hindrance of reverse draw solute flux. The water flux of MD comparable to RO was obtained when temperature gradient was more than 20–30°C. The applicability of RO, FO, and MD was further tested with real brine obtained from full-scale RO plant processing brackish water. Results demonstrated that water flux was not significantly reduced in MD, while severe flux decline was observed in both RO and FO at high recovery. To elucidate major causes of different flux behaviors, the fouled membrane surfaces were analyzed by scanning electron microscopy with energy dispersive X-ray spectroscopy and X-ray diffraction. Foulant analysis suggested that CaCO3scaling occurred particularly at high water recovery, which was in good agreement with water quality simulation. CaCO3scaling, however, had only small impact on flux behavior in MD. From these findings, MD could be suggested as the best option for concentrating industrial RO brine if low-grade heat (below 50–70°C) is available. [ABSTRACT FROM PUBLISHER]

Generally, rainwater harvesting has been less acceptable as a stable water resource for the countries with large disparities in seasonal rainfall including Korea. In this study, rainwater harvesting system suitable for South Korea was investigated systematically. The simulation method utilizing daily rainfall data collected for the last 10 years was developed to determine the critical size of rainwater tank which could supply harvested rainwater continuously. The estimation of rainwater tank size was further simplified by developing a correlation of volume to area fractions. Extensive simulation was performed to evaluate the feasibility of rainwater harvesting for seven major cities in South Korea. The resulting rainwater tank was too large to be economically feasible, compared to daily harvested rainwater used. Thus, rainwater harvesting system was integrated with alternative water resources such as wastewater reclamation by membrane bioreactor (MBR) to enhance the applicability of rainwater harvesting without compromising continuous water supply. [ABSTRACT FROM AUTHOR]

Bacterial biofilm communities formed on different membrane surfaces were investigated based on 16S rRNA gene sequence analysis. The biofilm communities were distinct from those of mixed-liquor and consisted mainly of Beta- and Gammaproteobacteria. Sequences of Xathomonas and Aquabacterium were mostly retrieved from the biofilm samples rather than from the mixed liquor. Furthermore, statistical analyses demonstrated the importance of a physico-chemical property of membrane, surface roughness, in structuring the bacterial biofilm communities. [ABSTRACT FROM AUTHOR]

With the world's population growing rapidly, pressure is increasing on the limited fresh water resources. Membrane technology could play a vital role in solving the water scarcity issues through alternative sources such as saline water sources and wastewater reclamation. The current generation of membrane technologies, particularly reverse osmosis (RO), has significantly improved in performance. However, RO desalination is still energy intensive and any effort to improve energy efficiency increases total cost of the product water. Since energy, environment and climate change issues are all inter-related, desalination for large-scale irrigation requires new novel technologies that address the energy issues. Forward osmosis (FO) is an emerging membrane technology. However, FO desalination for potable water is still a challenge because, recovery and regeneration of draw solutes require additional processes and energy. This article focuses on the application of FO desalination for non-potable irrigation where maximum water is required. In this concept of fertiliser drawn FO (FDFO) desalination, fertilisers are used as draw solutions (DS). The diluted draw solution after desalination can be directly applied for fertigation without the need for recovery and regeneration of DS. FDFO desalination can make irrigation water available at comparatively lower energy than the current desalination technologies. As a low energy technology, FDFO can be easily powered by renewable energy sources and therefore suitable for inland and remote applications. This article outlines the concept of FDFO desalination and critically evaluates the scope and limitations of this technology for fertigation, including suggestions on options to overcome some of these limitations. [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 ≈ 0.01 × total dissolved solids in mg/L) and had to be determined specifically for the particular feed water being processed. [ABSTRACT FROM AUTHOR]

Chloroform was treated with ultrasound at 35 and 283 kHz in a compound parabolic concentrators (CPCs) system to assess the applicability of ultrasound as a supporting process of solar-photocatalysis and verify the enhancement of ultrasound combined solar-photocatalysis. Chloroform was degraded by 22.5% in the Solar/TiO2 process over a 200 min period. At an ultrasound frequency of 283 kHz, chloroform was degraded by 52.6% (Sono), 47.0% (Sono/TiO2) and 64.4% (Sono/Solar/TiO2). On the other hand, at 35 kHz, chloroform was degraded by 49.0% (Sono), 46.1% (Sono/TiO2) and 80.0% (Sono/Solar/TiO2). Ultrasound at 35 kHz was more effective for degrading chloroform in the Sono/Solar/TiO2 process than 283 kHz. The rate of hydrogen peroxide formation, particle size and specific surface area of TiO2 were measured to determine why 35 kHz is more effective than 283 kHz. [ABSTRACT FROM AUTHOR]