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- Nanofibrillated cationic cellulose derivatives as flocculants for domestic wastewater treatmentPublication . Ribau Teixeira, Margarida; Ismail, Abdullah; Medronho, Bruno; Alves, Luís; Pedrosa, Jorge F.S.; Ferreira, Paulo J.T.; Serrão Sousa, Vânia; Rosa Da Costa, AnaNatural-based coagulants have emerged as a reliable option to implement more sustainable operations and management of wastewater treatment plants. This work aims at evaluating the use of cationic nanofibrillated celluloses (cNFC) as novel bio-based flocculants to treat domestic wastewaters by the most widely employed treatment process – coagulation/flocculation. Two cNFC samples were prepared with different charge densities and tested as coagulant/flocculants using different water characteristics. The effect of cNFCs was studied by measuring the residual turbidity and dissolved organic carbon. The aggregation mechanism and kinetics of flocculation were also evaluated. Results show that cNFC can be used as an efficient flocculant to treat medium and high DOC waters since they considerably reduce turbidity (turbidity removals varied between 66.0 % and 85.7 % for the waters and cNFCs tested) without increasing dissolved organic carbon. Instead, cNFC removed dissolved organic carbon from domestic wastewaters (between 22.1 % and 65.5 % of DOC removals for the waters and cNFCs tested), which is a novel remarkable finding and a step forward in this knowledge area. High density charged cNFC revealed superior removal capacity at lower doses than the commercial coagulant FeCl3.
- Natural organic matter and disinfection by-products formation potential in conventional and advanced water treatmentsPublication . Rosa, Sónia M.; Serrão Sousa, Vânia; Ribau Teixeira, MargaridaThe performance of a conventional sequence (pre-ozonation, coagulation/flocculation/sedimentation, filtration, disinfection) and two advance sequences (pre-ozonation, nanofiltration; pre-ozonation, coagulation/flocculation/sedimentation, nanofiltration) on the removal of natural organic matter (NOM) and disinfection by-products (DBPs) formation potential was evaluated. Raw and treated waters were characterized in terms of molecular weight, which includes the amount of NOM removed and the qualitative changes in the NOM characteristics (molecular weight and hydrophobicity) since they could be directly related with the DBPs formation. The results demonstrate that, for the type of raw water analysed (hydrophilic with low dissolved organic carbon content), both treatment sequences remove larger molecular weight compounds. However, the sequences with nanofiltration have a higher percentage of low molecular weight compounds removed, when compared with conventional sequence, thus the water from nanofiltration sequences will have lower DBPs formation potential.
- Nanofiltration ability to remove copper oxide and silver nanoparticles: The role of surface charge and sizePublication . Serrão Sousa, Vânia; Santos, C.; Ribau Teixeira, Margarida; Marsh, N.This work pretends to study the performance of nanofiltration (NF) membranes in the removal of copper oxide and silver nanoparticles (NPs) and evaluate the role of surface charge and size of the NPs on this performance. Results demonstrate that positive charged CuO NPs are adsorbed onto negatively charged NF membrane, whereas for the negatively charged Ag NPs the adsorption on the membrane surface is much lower. For CuO NPs, NF270 is very efficient and the main mechanism of removal seems to be adsorption. For Ag NPs, removals are low due to the hydrodynamic diameter of the NPs at this pH compared to the membrane cut-off (similar to 170 Da).
- Immunocytotoxicity, cytogenotoxicity and genotoxicity of cadmium-based quantum dots in the marine mussel Mytilus galloprovincialisPublication . Lopes Rocha, Thiago; Gomes, Tânia; Cardoso, Cátia; Letendre, Julie; Pinheiro, José Paulo; Serrão Sousa, Vânia; Ribau Teixeira, Margarida; Bebianno, MariaThere is an increased use of Quantum Dot (QDs) in biological and biomedical applications, but little is known about their marine ecotoxicology. So, the aim of this study was to investigate the possible immunocytotoxic, cytogenotoxic and genotoxic effects of cadmium telluride QDs (CdTe QDs) on the marine mussel Mytilus galloprovincialis. Mussels were exposed to 10 μg L(-1) of CdTe QDs or to soluble Cd [Cd(NO3)2] for 14 days and Cd accumulation, immunocytotoxicity [hemocyte density, cell viability, lysosomal membrane stability (LMS), differential cell counts (DCC)], cytogenotoxicity (micronucleus test and nuclear abnormalities assay) and genotoxicity (comet assay) were analyzed. Results show that in vivo exposure to QDs, Cd is accumulated in mussel soft tissues and hemolymph and induce immunotoxic effects mediated by a decrease in LMS, changes in DCC, as well as genotoxicity (DNA damage). However, QDs do not induce significant changes in hemocytes density, cell viability and cytogenetic parameters in opposition to Cd(2+). Soluble Cd is the most cytotoxic and cytogenotoxic form on Mytilus hemocytes due to a higher accumulation of Cd in tissues. Results indicate that immunotoxicity and genotoxicity of CdTe QDs and Cd(2+) are mediated by different modes of action and show that Mytilus hemocytes are important targets for in vivo QDs toxicity.
- Desempenho da flotação por ar dissolvido na remoção de cianobactérias de diferentes morfologiasPublication . Serrão Sousa, Vânia; Teixeira, Margarida RibauA presença de cianobactérias em reservatórios utilizados para produção de água para consumo humano representa um elevado risco para a saúde pública. Estes organismos contribuem para a redução da qualidade da água e têm a capacidade de produzir cianotoxinas que podem afectar a saúde humana e animal. Existem casos em todo o mundo de intoxicação letal de diversos animais por consumo de água de lagos contaminados com cianobactérias, e mesmo casos de morte de humanos, atribuídas à exposição de cianotoxinas. De modo a fazer face a este crescente problema é necessário desenvolver e implementar tecnologias de tratamento de água nas ETA que permitam fazer face a uma florescência de cianobactérias num reservatório de água destinado ao abastecimento humano. Neste trabalho avaliou-se a capacidade do processo C/F/DAF na remoção cianobactérias de diferentes morfologias, células e colónias de M. aeruginosa e filamentos de P. rubescens, em águas sintéticas hidrofóbicas e hidrofílicas, com concentração de DOC moderada e moderada/elevada. Assim como da sequência C/F/DAF→NF na remoção de células e de toxinas de cianobactérias. A remoção de NOM e o seu efeito na remoção de cianobactérias foram também avaliados. Concluiu-se que o processo C/F/DAF é eficiente na remoção de cianobactérias de diferentes morfologias, com remoções entre 78 e 100% de MC intra. No entanto, a morfologia que apresentou remoções mais elevadas foram os filamentos, enquanto as colónias apresentaram valores mais baixos. Globalmente, verificou-se que o aumento da concentração de NOM facilita a remoção de cianobactérias, sendo que as águas hidrofóbicas apresentaram-se mais fáceis de tratar por C/F/DAF. Por sua vez, o tratamento C/F/DAF→NF, é uma opção eficiente para fazer face a um eventual bloom de cianobactérias em ETA, uma vez que a remoção de cianobactérias (em MC intra e chl_a) foi de 100% e a remoção de microcistina extracelular de 95%, aproximadamente.
- Conventional water treatment improvement through enhanced conventional and hybrid membrane processes to remove Ag, CuO and TiO2 nanoparticles mixture in surface watersPublication . Serrão Sousa, Vânia; Ribau Teixeira, MargaridaThis study proposes, for the first time, to improve the most used process in water treatment, conventional coagulation (coagulation/flocculation/sedimentation, C/F/S), to maximally remove a mixture of engineered nanoparticles (ENPs) from surface waters. Thus, conventional coagulation enhanced with powdered activated carbon (C/F/S + PAC) and hybrid membrane treatment, integrating conventional C/F/S with ultrafiltration (C/F/S. UF), were optimised to maximise the removal of a mixture of ENPs (TiO2, CuO and Ag, 1:1:1) from surface waters. Results demonstrated that both optimized C/F/S + PAC and C/F/S. UF improved the removal of the metal-based ENPs in mixture, compared to conventional C/F/S, from hydrophilic natural waters with low and medium turbidity. In C/F/S + PAC treatment, Ag, Cu and Ti removal efficiencies were higher than 99%, and only ca. 3.0-2.9 mu g Ag/L and 2.0-2.5 mu g Cu/L were found in waters, while Ti concentrations were below the detection limit, representing a significant improvement to C/F/S performance, where in same situations the residual concentrations reached the 16 mu g/L. In this treatment, PAC acted as an adsorbent and also enhanced the settleability of the aggregates (ENPs-natural organic matter (NOM)) formed during C/F. In the C/F/S. UF, at 90% of water recovery rate, Ti and Cu removal efficiencies were approximately 100%, but ca. 5.0-7.0 mu g/L of Ag were found in the permeate water. After C/F/S, the Ti/Cu-NOM aggregates were removed by UF membranes, due to the size exclusion mechanism but, because of some Ag dissolution, the ionic Ag passed through the membrane pores. Overall, the processes optimisation to the ENPs removal did not affect their ability to remove other target compounds (turbidity, dissolved organic carbon, specific UV absorbance and aluminium).
- Green technologies for cyanobacteria and natural organic matter water treatment using natural based productsPublication . Ribau Teixeira, Margarida; Camacho, Franciele Pereira; Serrão Sousa, Vânia; Bergamasco, RosangelaGreen technologies are environmentally friendly operations that limit the negative impacts of traditional industrial activities and can contribute to solving the challenge of sustainable water management. This work aims to develop a green water treatment sequence using a natural coagulant (Moringa oleifera) and a natural activated carbon (vegetable coconut palm) to remove Microcystis aeruginosa and natural organic matter in an integrated process. The proposed sequence, coagulation/flocculation/dissolved air flotation and activated carbon, is an eco-friendly and innovative option for water treatment managers, since it includes environmentally friendly products for the contaminant removal from water, replacing the traditional inorganic/synthetic coagulants and adsorbents. Results demonstrated that waters with concentrations as high as 150-200 mu g/I. of chlorophyll a and natural organic matter between 5 and 16 mg C/L presented removals higher than 80% for turbidity and chlorophyll a, 70-80% for dissolved organic matter and 80-90% for UV254nm. Moringa oleifera natural coagulant removed almost 80% of Microcystis aeruginosa cells in coagulation/flocculation/dissolved air flotation processes. The coconut palm activated carbon showed a high capacity to adsorb DOC from water with a maximum adsorbed capacity of 51.8 mg/g at equilibrium. The values obtained in treated water for the parameters measured are very encouraging, so this innovative integrated sequence may be used for improving water quality, benefiting human health and wellbeing. (C) 2017 Elsevier Ltd. All rights reserved.
- Removal of a mixture of metal nanoparticles from natural surface waters using traditional coagulation processPublication . Serrão Sousa, Vânia; Ribau Teixeira, MargaridaEngineered nanoparticles (ENPs) present in natural water systems and wastewater treatment plants, due to their wide use in industrial products and consumer goods, represent a hazard to human health, especially if occur in surface waters used for human consumption. Different nanoparticles may co-exist in the natural waters and until now no works have been developed on the impact of the co-existing nanoparticles on water treatment processes. Thus, this work evaluates the removal of different co-existing metal-based ENPs (TiO2, Ag and CuO) from natural surface waters applying the most used water treatment process, coagulation/flocculation/sedimentation (C/F/ S). Results showed that C/F/S is effective in the removal of the co-existing ENPs from the studied hydrophilic natural waters (low/medium turbidity and moderate/moderate-high natural organic matter content) with efficiencies above 93% for TiO2, Ag and CuO nanoparticles. The formation of destabilised nanoparticle-organic matter aggregates in C/F promoted their precipitation. For the lowest turbidity and organic content water, Ti presented the lowest concentration, followed by Ag and Cu, because of titanium properties. For the highest turbidity and organic content water, the residual Cu concentration was the lowest and Ag the highest, due to the natural water characteristics. Water characteristics played an important role on the coagulant demand and removal of ENPs mixture by C/F/S. Results also demonstrated that ENPs mixture did not hampered the treated water quality for turbidity and natural organic matter. For the lowest turbidity and natural organic matter water, ENPs appear to contribute to a higher removal of these parameters.
- The effect of TiO2 nanoparticles removal on drinking water quality produced by conventional treatment C/F/SPublication . Serrão Sousa, Vânia; Corniciuc, Claudia; Ribau Teixeira, MargaridaNanoparticles, namely titanium dioxide (TiO2), are emerging contaminants widely used to commercial and industrial applications, are a potential hazard and can cause damage to environment and human health due to their toxicity. Therefore, their removal from the water is urgent to minimize or eliminate the adverse environmental and human effects. This work, investigates the efficiency of conventional coagulation/flocculation/sedimentation (C/F/S) from drinking water treatment to remove TiO2 nano particles (NPs) from surface waters, and pretends to understand if the removal of TiO2 NPs affects the ability of C/F/S to remove natural organic matter (NOM) and turbidity, and consequently affects the quality of the treated water. Results show that TiO2 NPs removal is high (>90%) for all the waters studied (hydrophobic and hydrophilic waters) and the treated water quality is not compromised (turbidity, Ti and Al concentrations, pH and conductivity are below the national and international guidelines). In addition, TiO2 initial concentrations, ranging between 0.2 and 10 mg/L, have not a significant impact on NPs removal by C/F/S. Therefore, the widely used polyaluminium based coagulants are effective in the removal of TiO2 NPs by conventional C/F/S treatment, but removal is strongly influenced by the water characteristics. Hydrophobic waters need a higher coagulant dose than hydrophilic waters to achieve the same TiO2 NPs removals, as well as water with higher UV254nm values. The principal mechanism involved in TiO2 NPs removal is charge neutralisation. (C) 2016 Elsevier Ltd. All rights reserved.
- Metal-based engineered nanoparticles in the drinking water treatment systems: a critical reviewPublication . Serrão Sousa, Vânia; Ribau Teixeira, MargaridaThe emergence of nanotechnologically-enabled materials, compounds or products inevitably leads to engineered nanoparticles (ENPs) released into surface waters. ENPs have already been detected in wastewater streams, drinking water sources and even in tap water at concentrations in the ng/L and mu g/L range, making the latter a potential route for humans. The presence of ENPs in raw waters raises concerns over the possibility that ENPs might pose a hazard to the quality and security of drinking water and whether drinking water treatment plants (DWTPs) are prepared to handle this problem. Therefore, it is essential to critically evaluate if ENPs can be effectively removed through water treatment processes to control environmental and human health risks associated with their release. This review includes a summary of the available information on production, presence, potential hazards to human health and environment, and release and behaviour of metal-based ENPs in surface waters and drinking water. In addition, the most extensively studied water treatment processes to remove metal-based ENPs, specifically conventional and advanced processes, are discussed and highlighted in detail. Furthermore, this work identifies the research gaps regarding ENPs removal in DWTPs and discusses future aspects of ENPs in water treatment.
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