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Villacorte L.O.,UNESCO-IHE Institute for Water Education | Villacorte L.O.,Center of Excellence for Sustainable Water Technology | Tabatabai S.A.A.,UNESCO-IHE Institute for Water Education | Tabatabai S.A.A.,Water Desalination and Reuse Center | And 7 more authors.
Desalination | Year: 2015

This article reviews the occurrence of HABs in seawater, their effects on the operation of seawater reverse osmosis (SWRO) plants, the indicators for quantifying/predicting these effects, and the pretreatment strategies for mitigating operational issues during algal blooms. The potential issues in SWRO plants during HABs are particulate/organic fouling of pretreatment systems and biological fouling of RO membranes, mainly due to accumulation of algal organic matter (AOM). The presence of HAB toxins in desalinated water is also a potential concern but only at very low concentrations. Monitoring algal cell density, AOM concentrations and membrane fouling indices is a promising approach to assess the quality of SWRO feedwater and performance of the pretreatment system. When geological condition is favourable, subsurface intake can be a robust pretreatment for SWRO during HABs. Existing SWRO plants with open intake and are fitted with granular media filtration can improve performance in terms of capacity and product water quality, if preceded by dissolved air flotation or sedimentation. However, the application of advanced pretreatment using ultrafiltration membrane with in-line coagulation is often a better option as it is capable of maintaining stable operation and better RO feed water quality during algal bloom periods with significantly lower chemical consumption. © 2015 Elsevier B.V.

Ghebremichael K.,UNESCO IHE | Muchelemba E.,UNESCO IHE | Petrusevski B.,UNESCO IHE | Amy G.,Water Desalination and Reuse Center
Journal of Water Supply: Research and Technology - AQUA | Year: 2011

Electrochemically activated (ECA) water is being extensively studied and considered as an alternative to chlorine for disinfection. Some researchers claim that ECA is by and large a chlorine solution, while others claim the presence of reactive oxygen species such as ozone and hydroxyl radicals in addition to chlorine. This study compares sodium hypochlorite (NaOCl) and ECA in terms of disinfection efficacy, trihalomethanes (THMs) formation, stability and composition. The studies were carried out under different process conditions (pH 5,7 and 9, disinfectant concentrations of 2-5 mg/L and dissolved organic carbon (DOC) concentration of 2-4 mg/L). The results indicated that in the presence of low DOC (<2 mg/L) ECA showed better disinfection efficacy for Escherichia coli inactivation, formed lower THM and had better stability compared with NaOCl at both pH 5 and 7. Stability studies of stock solutions showed that over a period of 30 days, ECA decayed by only 5% while NaOCl decayed by 37.5% at temperatures of 4 °C. In a fresh ECA of 200 mg/L chlorine, about 5.3 mg/L ozone and 36.9 mg/L ClO2 were detected. The study demonstrates that ECA could be a suitable alternative to NaOCl where decentralized production and use are required. © IWA Publishing 2011.

Le Roux J.,Water Desalination and Reuse Center | Le Roux J.,University Paris Est Creteil | Nihemaiti M.,Water Desalination and Reuse Center | Nihemaiti M.,Curtin University Australia | And 2 more authors.
Water Research | Year: 2016

Water treatment utilities are diversifying their water sources and often rely on waters enriched in nitrogen-containing compounds (e.g., ammonia, organic nitrogen such as amino acids). The disinfection of waters exhibiting high levels of nitrogen has been associated with the formation of nitrogenous disinfection byproducts (N-DBPs) such as haloacetonitriles (HANs) and haloacetamides (HAcAms). While the potential precursors of HANs have been extensively studied, only few investigations are available regarding the nature of HAcAm precursors. Previous research has suggested that HAcAms are hydrolysis products of HANs. Nevertheless, it has been recently suggested that HAcAms can be formed independently, especially during chloramination of humic substances. When used as a disinfectant, monochloramine can also be a source of nitrogen for N-DBPs. This study investigated the role of aromatic organic matter in the formation of N-DBPs (HAcAms and HANs) upon chloramination. Formation kinetics were performed from various fractions of organic matter isolated from surface waters or treated wastewater effluents. Experiments were conducted with 15N-labeled monochloramine (15NH2Cl) to trace the origin of nitrogen. N-DBP formation showed a two-step profile: (1) a rapid formation following second-order reaction kinetics and incorporating nitrogen atom originating from the organic matrix (e.g., amine groups); and (2) a slower and linear increase correlated with exposure to chloramines, incorporating inorganic nitrogen (15N) from 15NH2Cl into aromatic moieties. Organic matter isolates showing high aromatic character (i.e., high SUVA) exhibited high reactivity characterized by a major incorporation of 15N in N-DBPs. A significantly lower incorporation was observed for low-aromatic-content organic matter. 15N-DCAcAm and 15N-DCAN formations exhibited a linear correlation, suggesting a similar behavior of 15N incorporation as SUVA increases. Chloramination of aromatic model compounds (i.e., phenol and resorcinol) showed higher HAcAm and HAN formation potentials than nitrogenous precursors (i.e., amino acids) usually considered as main precursors of these N-DBPs. These results demonstrate the importance of aromatic organic compounds in the formation of N-DBPs, which is of significant importance for water treatment facilities using chloramines as final disinfectant. © 2015 Elsevier Ltd.

PubMed | Imaging and Characterization Core Laboratory, Water Desalination and Reuse Center and King Abdullah University of Science and Technology
Type: Journal Article | Journal: ACS applied materials & interfaces | Year: 2016

Engineering and scaling-up new materials for better water desalination are imperative to find alternative fresh water sources to meet future demands. Herein, the fabrication of hydrophobic poly(ether imide) composite nanofiber membranes doped with novel ethylene-pentafluorophenylene-based periodic mesoporous organosilica nanoparticles is reported for enhanced and fouling resistant membrane distillation. Novel organosilica nanoparticles were homogeneously incorporated into electrospun nanofiber membranes depicting a proportional increase of hydrophobicity to the particle contents. Direct contact membrane distillation experiments on the organosilica-doped membrane with only 5% doping showed an increase of flux of 140% compared to commercial membranes. The high porosity of organosilica nanoparticles was further utilized to load the eugenol antimicrobial agent which produced a dramatic enhancement of the antibiofouling properties of the membrane of 70% after 24 h.

Le Roux J.,Water Desalination and Reuse Center | Nada N.,NOMAC | Khan M.T.,Water Desalination and Reuse Center | Croue J.-P.,Water Desalination and Reuse Center
Desalination | Year: 2015

The aim of this study was to assess the formation and the behavior of halogenated byproducts (regulated THMs and HAAs, as well as nitrogenous, brominated and iodinated DBPs including the emerging iodo-THMs) along the treatment train of full-scale desalination plants. One thermal multi-stage flash distillation (MSF) plant and two reverse osmosis (RO) plants located on the Red Sea coast of Saudi Arabia. DBPs formed during the prechlorination step were efficiently removed along the treatment processes (MSF or RO). Desalination plants fed with good seawater quality and using intermittent chlorine injection did not show high DBP formation and discharge. One RO plant with a lower raw water quality and using continuous chlorination at the intake formed more DBPs. In this plant, some non-regulated DBPs (e.g., dibromoacetonitrile and iodo-THMs) reached the product water in low concentrations (< 1.5 μg/L). Regulated THMs and HAAs were far below their maximum contamination levels set by the US Environmental Protection Agency. Substantial amounts of DBPs are disposed to the sea; low concentrations of DBPs were indeed detected in the water on shore of the desalination plants. © 2014 Elsevier B.V.

Zhang Z.,Water Desalination and Reuse Center | Yang X.,Water Desalination and Reuse Center | Hedhili M.N.,King Abdullah University of Science and Technology | Ahmed E.,Water Desalination and Reuse Center | And 2 more authors.
ACS Applied Materials and Interfaces | Year: 2014

In this article, we report that the combination of microwave heating and ethylene glycol, a mild reducing agent, can induce Ti3+ self-doping in TiO2. A hierarchical TiO2 nanotube array with the top layer serving as TiO2 photonic crystals (TiO2 NTPCs) was selected as the base photoelectrode. The self-doped TiO2 NTPCs demonstrated a 10-fold increase in visible-light photocurrent density compared to the nondoped one, and the optimized saturation photocurrent density under simulated AM 1.5G illumination was identified to be 2.5 mA cm-2 at 1.23 V versus reversible hydrogen electrode, which is comparable to the highest values ever reported for TiO2-based photoelectrodes. The significant enhancement of photoelectrochemical performance can be ascribed to the rational coupling of morphological and electronic features of the self-doped TiO 2 NTPCs: (1) the periodically morphological structure of the photonic crystal layer traps broadband visible light, (2) the electronic interband state induced from self-doping of Ti3+ can be excited in the visible-light region, and (3) the captured light by the photonic crystal layer is absorbed by the self-doped interbands. © 2013 American Chemical Society.

Karunakaran M.,King Abdullah University of Science and Technology | Nunes S.P.,Water Desalination and Reuse Center | Qiu X.,King Abdullah University of Science and Technology | Yu H.,King Abdullah University of Science and Technology | Peinemann K.-V.,King Abdullah University of Science and Technology
Journal of Membrane Science | Year: 2014

A simple and efficient approach towards the fabrication of a skinned membrane with highly ordered pores in the nanometer range is presented here. We successfully combined the self-assembly of PS-b-PEO block copolymer and water induced phase separation for the preparation of isoporous PS-b-PEO block copolymer membranes. We produced for the first time asymmetric isoporous PS-b-PEO membranes with a 100nm thin isoporous separating layer using water at room temperature as coagulant. This was possible by careful selection of the block lengths and the solvent system. FESEM, AFM and TEM measurements were employed to characterize the nanopores of membranes. The pure water fluxes were measured and the flux of membrane was exceptionally high (around 800Lm-2h-1bar-1). Protein rejection measurements were carried out for this membrane and the membrane had a retention of about 67% of BSA and 99% of γ-globulin. © 2013 Elsevier B.V.

Yu H.,King Abdullah University of Science and Technology | Qiu X.,King Abdullah University of Science and Technology | Nunes S.P.,Water Desalination and Reuse Center | Peinemann K.-V.,King Abdullah University of Science and Technology
Angewandte Chemie - International Edition | Year: 2014

The combination of nonsolvent-induced phase separation and the self-assembly of block copolymers can lead to asymmetric membranes with a thin highly ordered isoporous skin layer. The effective pore size of such membranes is usually larger than 15 nm. We reduced the pore size of these membranes by electroless gold deposition. We demonstrate that the pore sizes can be controlled precisely between 3 and 20 nm leading to a tunable sharp size discrimination in filtration processes. Besides fractionation of nanoparticles and biomaterials, controlled drug delivery is an attractive potential application. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Zhang Z.,Water Desalination and Reuse Center | Zhang L.,Water Desalination and Reuse Center | Hedhili M.N.,King Abdullah University of Science and Technology | Zhang H.,Water Desalination and Reuse Center | Wang P.,Water Desalination and Reuse Center
Nano Letters | Year: 2013

A visible light responsive plasmonic photocatalytic composite material is designed by rationally selecting Au nanocrystals and assembling them with the TiO2-based photonic crystal substrate. The selection of the Au nanocrystals is so that their surface plasmonic resonance (SPR) wavelength matches the photonic band gap of the photonic crystal and thus that the SPR of the Au receives remarkable assistance from the photonic crystal substrate. The design of the composite material is expected to significantly increase the Au SPR intensity and consequently boost the hot electron injection from the Au nanocrystals into the conduction band of TiO2, leading to a considerably enhanced water splitting performance of the material under visible light. A proof-of-concept example is provided by assembling 20 nm Au nanocrystals, with a SPR peak at 556 nm, onto the photonic crystal which is seamlessly connected on TiO2 nanotube array. Under visible light illumination (>420 nm), the designed material produced a photocurrent density of ∼150 μA cm-2, which is the highest value ever reported in any plasmonic Au/TiO2 system under visible light irradiation due to the photonic crystal-assisted SPR. This work contributes to the rational design of the visible light responsive plasmonic photocatalytic composite material based on wide band gap metal oxides for photoelectrochemical applications. © 2012 American Chemical Society.

PubMed | Water Desalination and Reuse Center and King Abdullah University of Science and Technology
Type: | Journal: Scientific reports | Year: 2015

Molecular-based approaches were used to characterize the coastal microbiota and to elucidate the trophic state of Red Sea. Nutrient content and enterococci numbers were monitored, and used to correlate with the abundance of microbial markers. Microbial source tracking revealed the presence of >1 human-associated Bacteroides spp. at some of the near-shore sampling sites and at a heavily frequented beach. Water samples collected from the beaches had occasional exceedances in enterococci numbers, higher total organic carbon (TOC, 1.48-2.18mg/L) and nitrogen (TN, 0.15-0.27mg/L) than that detected in the near-shore waters. Enterococci abundances obtained from next-generation sequencing did not correlate well with the cultured enterococci numbers. The abundance of certain genera, for example Arcobacter, Pseudomonas and unclassified Campylobacterales, was observed to exhibit slight correlation with TOC and TN. Low abundance of functional genes accounting for up to 41copies/L of each Pseudomonas aeruginosa and Campylobacter coli were detected. Arcobacter butzleri was also detected in abundance ranging from 111 to 238copies/L. Operational taxonomic units (OTUs) associated with cyanobacteria, Prochlorococcus, Ostreococcus spp. and Gramella were more prevalent in waters that were likely impacted by urban runoffs and recreational activities. These OTUs could potentially serve as quantifiable markers indicative of the water quality.

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