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1.
J Photochem Photobiol B ; 202: 111638, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31733613

RESUMO

The present study investigates the phycoremediation potentials of two microalgal consortia (MAC1 and MAC2) for treating sewage water and producing biomass with high lipid, protein and chlorophyll contents. During the study, the microalgal strains were tested for lipid enhancement, biomass production and contaminant removal from wastewater. The microalgal consortia showed prolific growth in wastewater with 75% dilution and accumulated higher lipid content of 31.33% dry cell weight in MAC1. The maximum biomass (50% diluted wastewater) for both the consortia was 1.53 and 1.04 gL-1. Total chlorophyll (19.17-25.17 µg mL-1) and protein contents (0.12-0.16 mg mL-1) for both the consortia were found to be maximum in 75 WW. MAC1 was capable of removing 86.27% of total organic carbon and 87.6% of chemical oxygen demand. Approximately, 94% of nitrate and phosphate contents were removed from the initial contents of wastewater. Heavy metal removal efficiency was also found to be better and showed 85.06% Cu, 75.2% Cr, 98.2% Pb, and 99.6% Cd removal by the algal consortia. Pyrolytic decomposition of algal consortia was observed using thermogravimetric analysis. The stepwise decomposition of algae indicated distinct losses of functional groups. The gas chromatography-mass spectrometric analysis revealed the majority of saturated fatty acids followed by monounsaturated and polyunsaturated fatty acids. Thus, the present study proved that both the consortia show tremendous potential for the treatment of domestic wastewaters with successive lipid enhancement for biodiesel production.


Assuntos
Biocombustíveis/análise , Ácidos Graxos/metabolismo , Microalgas/crescimento & desenvolvimento , Eliminação de Resíduos Líquidos/métodos , Proteínas de Algas/metabolismo , Biomassa , Clorofila/análise , Ácidos Graxos/análise , Cromatografia Gasosa-Espectrometria de Massas , Metais Pesados/química , Metais Pesados/metabolismo , Microalgas/metabolismo
2.
Chemosphere ; 239: 124743, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31514007

RESUMO

Ethylenediaminetetraacetic acid (EDTA) could form stable complexes with toxic metals such as nickel due to its strong chelation. In this study, with the same doping level of Co and N, MoO2 and ZIF-67 were used as precursors to prepare MoO2@Co/N and FeC@Co/N electrocatalysts for the modified graphite felt cathodes in heterogeneous-electro-Fenton-like reaction (HEFL) system. The X-ray diffraction and X-ray photoelectron spectroscopy results indicated that both of the catalysts are dominated with pyridinic N (2.42% and 2.82%) upon co-doping Co/N, and FeC@Co/N exhibited an obviously higher additional sp-hybridized nitrogen (sp-N) peak. The co-doping of Co/N induced the lattice modifications to produce more lattice defects, where pyridinic N and sp-N, related with the active sites (C-N, Co-Nx), were formed at near-ring defects along sheet edges through the nitrogen replacement of CC groups. FeC@Co/N demonstrated superior oxygen reduction reaction catalytic activity in terms of Cyclic Voltammetry and Rotating Ring-disk Electrode, and exhibited the remarkably higher current density (30 mA) and lower onset potential (-0.208 V) in Linear Sweep Voltammetry analysis. In the FeC@Co/N/CF modified HEFL system, despite the generated H2O2 concentrations (62.5 mg L-1) is not very high, the reducing reaction of ≡Fe(III)/Co(III)-OH could get the electron directly from the cathode, which would greatly reduce the consumption of H2O2, high utilization efficiency of H2O2 (η: 87.63%) could greatly improve the EDTA-Ni removal (97.5%) and TOC (92.6%). This work demonstrates the feasibility of utilizing FeC@Co/N/CF as a cathode for breaking metal-complex in HEFL process.


Assuntos
Cobalto/química , Ácido Edético/química , Técnicas Eletroquímicas/métodos , Nanopartículas Metálicas/química , Níquel/química , Catálise , Descontaminação , Técnicas Eletroquímicas/instrumentação , Eletrodos , Grafite/química , Peróxido de Hidrogênio/química , Ferro/química , Nitrogênio/química , Oxirredução , Piridinas/química , Eliminação de Resíduos Líquidos/instrumentação , Eliminação de Resíduos Líquidos/métodos
3.
Chemosphere ; 240: 124925, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31563715

RESUMO

A study was conducted to understand the impact of reverse osmosis concentrate (ROC) characteristics on the efficacy of biological activated carbon (BAC) based treatments for removing organics and nutrients from two ROC streams (ROCa derived from municipal waste input with high salinity, and ROCb derived from domestic waste plus industrial trade waste with markedly lower salinity). Fluorescence excitation and emission matrix spectra and molecular weight analysis demonstrated that ROCa and ROCb had a significantly different composition of organic compounds due to the petrochemical processing and abattoir waste compounds in ROCb. Although the sequence of coagulation, UV/H2O2 and BAC gave the highest organic removal from the two ROCs (67% DOC for ROCa and 62% for ROCb), UV/H2O2 followed by BAC achieved satisfactory removal (>55%) for both ROC types. Sequential treatment involving coagulation gave better phosphorus removal (>90%) than any single treatment (<65%). Total nitrogen (TN) removal was fairly low (<50%) for all the treatment options and the salinity level had insignificant impact on nitrogen removal. Analysis of bacterial communities suggested that higher phosphorus removal and lower total nitrogen and nitrate removal from ROCb than ROCa was related to the presence of various denitrifying or phosphorus accumulating bacteria in the BAC.


Assuntos
Carvão Vegetal/química , Compostos Orgânicos/análise , Osmose , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Desnitrificação , Filtração/métodos , Peróxido de Hidrogênio/química , Nitrogênio/análise , Fósforo , Salinidade , Águas Residuárias/química
4.
Chemosphere ; 240: 124915, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31563105

RESUMO

In animal livestock heavy metals are widely used as feed additives to control enteric bacterial infections as well as to enhance the integrity of the immune system. As these metals are only partially adsorbed by animals, the content of heavy metals in manure and wastewaters causes soil and ground water contamination, with Zn2+ and Cu2+ being the most critical output from pig livestock. Phytoremediation is considered a valid strategy to improve the purity of wastewaters. This work studied the effect of Zn2+ and Cu2+ on the morphology and protein expression in Thelypteris palustris and Typha latifolia plants, cultured in a wetland pilot system. Despite the absence of macroscopic alterations, remodeling of cell walls and changes in carbohydrate metabolism were observed in the rhizomes of both plants and in leaves of Thelypteris palustris. However, similar modifications seemed to be determined by the alterations of different mechanisms in these plants. These data also suggested that marsh ferns are more sensitive to metals than monocots. Whereas toleration mechanisms seemed to be activated in Typha latifolia, in Thelypteris palustris the observed modifications appeared as slight toxic effects due to metal exposure. This study clearly indicates that both plants could be successfully employed in in situ phytoremediation systems, to remove Cu2+ and Zn2+ at concentrations that are ten times higher than the legal limits, without affecting plant growth.


Assuntos
Biodegradação Ambiental/efeitos dos fármacos , Cobre/toxicidade , Traqueófitas/metabolismo , Typhaceae/metabolismo , Eliminação de Resíduos Líquidos/métodos , Zinco/toxicidade , Animais , Parede Celular/efeitos dos fármacos , Parede Celular/metabolismo , Cobre/farmacocinética , Gado , Esterco , Projetos Piloto , Células Vegetais/efeitos dos fármacos , Células Vegetais/metabolismo , Folhas de Planta/efeitos dos fármacos , Folhas de Planta/metabolismo , Proteínas de Plantas , Especificidade da Espécie , Suínos , Traqueófitas/efeitos dos fármacos , Typhaceae/efeitos dos fármacos , Águas Residuárias/química , Águas Residuárias/toxicidade , Poluentes Químicos da Água/farmacocinética , Poluentes Químicos da Água/toxicidade , Áreas Alagadas , Zinco/farmacocinética
5.
Chemosphere ; 240: 124912, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31574437

RESUMO

In this work, the combination of biological and electrochemical processes to mineralize oxyfluorfen has been studied. First, an acclimatized mixed-culture biological treatment was used to degrade the biodegradable fraction of the pesticide, reaching up to 90% removal. After that, the non-biodegraded fraction was oxidised by electrolysis using boron-doped diamond as the anode. The results showed that the electrochemical technique was able to completely mineralize the residual pollutants. The study of the influence of the supporting electrolyte on the electrochemical process showed that the trace mineral solution used in the biological treatment was enough to completely mineralize the oxyfluorfen, resulting in total organic carbon removal rates that were well-fitted by a first-order model with a kinetic constant of 0.91 h-1. However, the first-order degradation rate increased approximately 20% when Na2SO4 was added as supporting electrolyte, reaching a degradation rate of 1.16 h-1 with a power consumption that was approximately 70% lower.


Assuntos
Eletrólise/métodos , Éteres Difenil Halogenados/química , Éteres Difenil Halogenados/metabolismo , Poluentes Químicos da Água/química , Poluentes Químicos da Água/metabolismo , Reatores Biológicos/microbiologia , Boro , Diamante , Eletrodos , Eletrólise/instrumentação , Cinética , Oxirredução , Praguicidas/química , Praguicidas/metabolismo , Sulfatos/química , Eliminação de Resíduos Líquidos/métodos
6.
Chemosphere ; 240: 124911, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31726614

RESUMO

The reuse of treated municipal wastewater (herein referred to as reclaimed water) in agricultural irrigation (RWAI) as a means to alleviate water scarcity is gaining increasing policy attention, particularly in areas where water demand mitigation measures have proved insufficient. However, reclaimed water reuse in practice is lagging behind policy ambition, with <2.5% of it reused in a European context. A key barrier identified as limiting its full valorisation is concern over its impact on human and environmental health. To address this concern, and to meet further objectives including achieving parity between current reclaimed water reuse guidelines operational in various Member States, the European Commission has proposed a regulation which identifies minimum quality requirements (MQR) for a range of microbiological and physico-chemical parameters but the inclusion of compounds of emerging concern (CECs) in terms of the determination of quality standards (QS) is missing. This paper reviews the existing pertinent EU legislation in terms of identifying the need for CEC QS for RWAI, considering the scope and remit of on-going pan-European chemicals prioritisation schemes. It also evaluates opportunities to link in with the existing EQS derivation methodology under the EU WFD to address all protection targets in the environmental compartments exposed via potential pathways of RWAI. Finally, it identifies the main data gaps and research needs for terrestrial ecosystems, the removal efficiency of CECs by WWTPs and transformation products generated during the wastewater reuse cycle.


Assuntos
Irrigação Agrícola/normas , Eliminação de Resíduos Líquidos/normas , Águas Residuárias/química , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/normas , Irrigação Agrícola/métodos , Ecossistema , Humanos , Eliminação de Resíduos Líquidos/métodos
7.
Sci Total Environ ; 698: 134166, 2020 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-31494421

RESUMO

The development of efficient and regenerable adsorbent coupled with advanced oxidation for enhanced thallium (Tl) removal has been a recent focus on wastewater treatment. In this study, a magnetite-based biochar derived from watermelon rinds was synthesized and used as a sustainable adsorbent and catalyst for hypochlorite oxidation and removal of Tl(I) from wastewater. The addition of hypochlorite substantially enhanced the Tl(I) removal under normal pH range (6-9). Maximum Tl adsorption capacity of 1123 mg/g was achieved, which is 12.3% higher than the highest value previously reported. The magnetic biochar can be regenerated using 0.1 mol/L HNO3 solution for elution in only 5 min, with a Tl desorption efficiency of 78.9%. The Tl removal efficiency was constantly higher than 98.5% during five consecutive recycle tests, indicating the effective reuse performance of the adsorbent. Oxidation, surface precipitation, pore retention and surface complexation were the main mechanisms for Tl(I) removal. The re-dissolution of Tl compounds and ion exchange of Tl cations with proton were the main mechanisms for adsorbent regeneration. Given the fast oxidation rate, high adsorption capacity, steady reusability and facile separability, this magnetic biochar-hypochlorite technique is a promising means for Tl(I) removal from wastewater. The catalytic hypochlorite oxidation induced by the magnetic biochar has also great potential to the effective removal of other pollutants.


Assuntos
Carvão Vegetal/química , Óxido Ferroso-Férrico/química , Tálio/análise , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/análise , Adsorção , Ácido Hipocloroso , Tálio/química , Águas Residuárias , Poluentes Químicos da Água/química
8.
Sci Total Environ ; 699: 134389, 2020 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-31522050

RESUMO

Intracellular polyphosphate (poly-P) plays important roles in Enhanced biological phosphorus removal (EBPR) process, but an effective and reliable protocol for extracting intracellular P and its poly-P in EBPR sludge without hydrolysis of poly-P has not been setup yet. In the study, it was revealed that the severe hydrolysis of intracellular poly-P occurred during the different extraction processes, such as acid (i.e., HClO4, H2SO4 and HCl), basic (i.e., NaOH and KOH) and freezing-grind (under different solid-liquid ratios), but it did not occur during ultrasonic extraction process. The optimal extraction process of the ultrasonic protocol was 10 w/mL of ultrasonic power density and 15 min of ultrasonic time, when the extraction efficiency of intracellular P was 88.24 ±â€¯1.56%. In addition, the extraction efficiency of intracellular P could be furtherly improved by that the 0.75 mol/L LiCl solution was used to resuspend the bacterial cell before ultrasonic extraction (i.e., LiCl-ultrasonic protocol). The ultrasonic protocol was more suitable to extract the intracellular P and its poly-P of EBPR sludge than the other 4 protocols (i.e., PCA-NaOH, EDTA-NaOH, freezing-grind and LiCl-ultrasonic), which had the technical characteristics of (i) with relatively high extraction efficiency of intracellular P, (ii) without hydrolysis of intracellular poly-P, (iii) with weak noise signal in 31P NMR spectrum and (iv) with simple extraction process and short extraction time. It was founded by the ultrasonic protocol that there was the high content (82.88%-89.79% of intracellular P content) of intracellular poly-P with long average chain length (376.4-383.2) in the EBPR sludges. Importantly, it was confirmed that the EBPR process was related to the combined action of extracellular and intracellular poly-P using a new fractionation method of P in EBPR sludge, which included the ultrasonic protocol at high power density for extracting the intracellular P and its poly-P.


Assuntos
Fósforo , Polifosfatos , Eliminação de Resíduos Líquidos/métodos , Bactérias , Biodegradação Ambiental , Reatores Biológicos , Espectroscopia de Ressonância Magnética , Esgotos
9.
Sci Total Environ ; 699: 134365, 2020 Jan 10.
Artigo em Inglês | MEDLINE | ID: mdl-31677459

RESUMO

Methane production from microalgae can be enhanced through anaerobic co-digestion with carbon-rich substrates and thus mitigate the inhibition risk associated with its low C:N ratio. Acclimated microbial communities for microalgae disruption can be used as a source of natural enzymes in bioenergy production. However, co-substrates with a certain microbial diversity such as primary sludge might shift the microbial structure. Substrates were generated in a Water Resource Recovery Facility (WRRF) and combined as follows: Scenedesmus or Chlorella digestion and microalgae co-digestion with primary sludge. The study was performed using two lab-scale Anaerobic Membrane Bioreactors (AnMBR). During three years, different feedstocks scenarios for methane production were evaluated with a special focus on the microbial diversity of the AnMBR. 57% of the population was shared between the different feedstock scenarios, revealing the importance of Anaerolineaceae members besides Smithella and Methanosaeta genera. The addition of primary sludge enhanced the microbial diversity of the system during both Chlorella and Scenedesmus co-digestion and promoted different microbial structures. Aceticlastic methanogen Methanosaeta was dominant in all the feedstock scenarios. A more remarkable role of syntrophic fatty acid degraders (Smithella, Syntrophobacteraceae) was observed during co-digestion when only microalgae were digested. However, no significant changes were observed in the microbial composition during anaerobic microalgae digestion when feeding only Chlorella or Scenedesmus. This is the first work revealing the composition of complex communities for semi-continuous bioenergy production from WRRF streams. The stability and maintenance of a microbial core over-time in semi-continuous AnMBRs is here shown supporting their future application in full-scale systems for raw microalgae digestion or co-digestion.


Assuntos
Microalgas , Eliminação de Resíduos Líquidos/métodos , Biocombustíveis , Reatores Biológicos , Chlorella , Estudos Longitudinais , Microbiota , Scenedesmus
10.
Chemosphere ; 238: 124598, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31446276

RESUMO

Sewage sludge dewatering is an efficient approach to reduce the volume of sludge for the subsequent disposal. In this study, a novel one-step acidification sludge dewatering method was developed with using oxalic acid as a conditioner. In laboratory-scale experiments with the dosage of 200 mg/g dry solid (DS), the normalized capillary suction time and the specific resistance to filtration were respectively decreased by 78.7% and 60.0% after 30 min of oxalic acid conditioning, much more efficient than those conditioned with sulfuric acid and hydrochloric acid at the same pH value. This superior dewatering performance was attributed to two factors. One was that oxalic acid could more efficiently promote the hydrolysis of polysaccharide, especially pectins, to release bound water. The other was that OA could dissolve more Fe3+ and Al3+, as well as form precipitate with Ca2+ in sludge, which may act as flocculants or co-precipitator for the subsequent sludge particles coagulation. In pilot-scale experiments, the water content of oxalic acid conditioned sludge cake was reduced to 60% under the optimum conditions, while the reagent cost was as low as 110.0 USD/t DS. This work provides a cost-effective and easy-operated sewage sludge disposal technique, and also sheds light on the potential of oxalic acid in environmental waste treatment.


Assuntos
Dessecação/métodos , Ácido Oxálico/química , Esgotos/química , Eliminação de Resíduos Líquidos/métodos , Filtração , Floculação , Ácido Clorídrico/química , Concentração de Íons de Hidrogênio , Hidrólise , Polissacarídeos/metabolismo , Ácidos Sulfúricos/química , Água/química
11.
Chemosphere ; 238: 124649, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31466005

RESUMO

Electro-Fenton (EF) with peroxi-coagulation (PC) as an emerging electro-chemical advanced oxidation method has been extensively applied to treat refractory wastewater. However, the studies on the pretreatment of the raw coke plant wastewater by EF process were still lacking. In this study, a lab-scale EF system (Fe as anode and graphite as cathode) achieved the highest COD removal of 69.2% based on the preliminary experiments. The process parameters and corresponding COD removal performance were further optimized using response surface methodology (RSM) combined with Box-Behnken experimental design (BBD). The optimal conditions were obtained as: 3.2 mA cm-2 of current density, 2 h of the reaction time and 2.6 of the initial pH value, with the COD removal reaching 70.0%. Fourier infrared (FTIR), fluorescence excitation-emmission matrix (EEM) and gas chromatography-mass spectrometry (GC-MS) also revealed the degradation behaviors of dissolved organic matters (DOMs) by characterizing their structures and compositions before and after EF pretreatment, thus greatly improving the biodegradability of the wastewater. Moreover, the EF process for COD removal well followed third-order kinetics model. These findings give helpful guidance to design, optimize and control the EF process as a favourable pretreatment for actual refractory coking wastewater in practice.


Assuntos
Coque , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/química , Purificação da Água/métodos , Peróxido de Hidrogênio/química , Cinética , Oxirredução , Eliminação de Resíduos Líquidos/normas , Poluentes Químicos da Água/química
12.
Chemosphere ; 238: 124671, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31473527

RESUMO

In this study, Fe/Cu, Fe/Al/Cu, Fe/Cu/C and Fe/Al/Cu/C internal electrolysis systems (IESs) were constructed and used to treat methylene blue dye (MB) wastewater. The effects of filler mass ratio, filler dosage, solution pH, reaction time and reaction temperature on COD removal were discussed, while the kinetics, thermodynamics and mechanism of COD removal were also investigated. The results showed that when the COD removal rates were basically the same, the reaction times of Fe/Al/Cu, Fe/Cu/C and Fe/Al/Cu/C IESs were shorter, and the filler dosages were lower. For the four systems, the appropriate pH was around 5, while the suitable reaction temperature was in the range of 20-25 °C. The COD removals of these four IESs were generally greater than 90%. The COD removal processes of the four systems could be better described by the improved pseudo-second-kinetic model, and the liquid film diffusion was the rate-controlling step. Moreover, the COD removal was a spontaneous and endothermic process. MB was degraded into inorganic substances in four steps. In addition, the FTIR characterization of the fillers before and after reaction suggests the four IESs have good stability.


Assuntos
Eletrólise/métodos , Azul de Metileno/química , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/química , Adsorção , Eletrólise/normas , Cinética , Termodinâmica , Eliminação de Resíduos Líquidos/normas , Poluentes Químicos da Água/química
13.
Chemosphere ; 239: 124768, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31518917

RESUMO

There is a need for cheap but, efficient methods for the removal of precious metals from wastewaters, which are normally lost during mineral processing. Moreover, the disposal of yeast waste from brewing has been a problem in many parts of the world. In this study, the removal of Pt(IV) from aqueous solutions using the readily available bentonite clay functionalised with spent yeast from brewing was investigated. The maximum adsorption capacity of Pt(IV) with 100 mg yeast-functionalised bentonite at pH 2 within 90 min was 255 µg g-1 (98.5% efficiency) but, decreased as pH increased. The adsorption capacity of Pt(IV) was insignificantly (p > 0.05) affected by the presence of competing ions (Fe(III), Ca(II), Mg(II), K(I), Co(II), Ni(II), Hf(IV), Zn(II) and other platinum group metals (PGMs)). Moreover, most of these metals were significantly adsorbed along with Pt(IV). The indicative cost-benefit analysis showed that 1 kg of the yeast-functionalised bentonite can remove ∼700 g Pt(IV) in which a profit of more than USD20000 can be made. The bentonite functionalised with spent yeast from brewing has a potential to recover lost PGMs in wastewater. Since, this is a cheap process, the mining and other industries can make much profit from such recoveries.


Assuntos
Bentonita/química , Platina/isolamento & purificação , Saccharomyces cerevisiae/química , Poluentes Químicos da Água/isolamento & purificação , Adsorção , Concentração de Íons de Hidrogênio , Resíduos Industriais , Metais/química , Soluções , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias , Água/química
14.
Chemosphere ; 238: 124669, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31524613

RESUMO

Sugar production is a water intensive process that produces a large amount of wastewaters with high concentration of chemical oxygen demand (COD), mostly consists of organic carbon compounds. Conventional treatment methods are limited to provide the necessary treatment of effluent COD to meet the regulatory limits prior to discharge. The treatment performance of electrooxidation (EO) and electrochemical peroxidation (ECP) for organic removal were investigated in a laboratory scale study. The experimental conditions were optimized for both EO and ECP using Box-Behnken Design (BBD) and the models provided highly significant quadratic models for both treatment methods. The effects of pH, H2O2 dosage, current density, and operation time were investigated using BBD. The results showed that EO could remove 75% of organics at optimum conditions of pH 5.3; current density of 48.5 mA cm-2; and operation time of 393 min. The predicted values were in reasonable agreement with measured values. ECP could remove total and soluble COD and total and dissolved organic carbon by 65, 64, 66, and 63%, respectively at optimum conditions of H2O2 dosage of 21 mL L-1; current density of 48 mA cm-2; and operation time of 361 min. The methods were compared based on removal efficiency and energy consumption during operation.


Assuntos
Beta vulgaris/química , Técnicas Eletroquímicas/métodos , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/química , Purificação da Água/métodos , Análise da Demanda Biológica de Oxigênio , Técnicas Eletroquímicas/normas , Peróxido de Hidrogênio , Indústrias , Compostos Orgânicos , Oxirredução , Açúcares , Eliminação de Resíduos Líquidos/normas , Poluentes Químicos da Água/química , Purificação da Água/normas
15.
Chemosphere ; 239: 124763, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31526989

RESUMO

Nonredox metal ions have been widely recognized to be important in a wide range of biological and chemical oxidations as Lewis acids (LA). However, the role of LA in peroxymonosulfate (PMS) activation for wastewater treatment has not been considered until now. This study shows that oxidizing power of PMS can be promoted after binding nonredox metal ions such as Ca2+ as LA, leading to the easier reduction of the oxidant to radicals and substantial enhancement of dye degradation by employing manganese oxides OMS-2 as model catalysts. Increased with Lewis acidity of the metal ion, the rate of PMS decomposition enhanced linearly, while the dye degradation rate first increased and then declined due to the formation of a larger amount of dioxygen. The interactions between Ca2+ and PMS were further investigated by Raman, cyclic voltammetry and XPS; and the detailed mechanism of PMS activation was proposed. The performance of Ca2++OMS-2/PMS system under different conditions was also studied. The findings indicate the importance of LA in PMS activation reaction and their role must be considered in other transition metal oxides/PMS systems. It will be also helpful to design new and highly active catalysts for the reactions.


Assuntos
Ácidos de Lewis/química , Compostos de Manganês/química , Óxidos/química , Peróxidos/química , Poluentes Químicos da Água/química , Cálcio/química , Catálise , Corantes/química , Oxidantes/química , Oxirredução , Soluções , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/química
16.
Chemosphere ; 240: 124804, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31541900

RESUMO

Chemical oxygen demand (COD) is one of the most important water quality parameters that quantifies the amount of oxygen needed to oxidize oxidizable pollutants (mainly organics) in water samples. However, erroneous COD results were commonly observed for bromide-rich industrial wastewater samples using standard COD test. Bromide in water sample is known to seriously interfere with COD test. However, there is no satisfactory approach to effectively eliminate bromide interference thus far. In this study, two strategies, namely masking and correction, were investigated for their effectiveness to suppress bromide interference. For the masking strategy, silver ion was assessed for its effectiveness to neutralize bromide in water samples through precipitation and complex formation reactions. Silver ion offered only partial masking effect on bromide, while the residue bromide can still cause significant interference on COD determination. For the correction strategy, an equivalent redox reaction reflecting bromide interference mechanism was proposed, and a theoretical correction factor of 0.1 g COD/g Br- was found based on stoichiometry. The effectiveness of the proposed correction factor for bromide interference under different wastewater pollutant matrix was evaluated using different types of wastewater samples (synthetic wastewater, domestic wastewater and bromide-rich industrial wastewater) with varying amounts of bromide (from 0 to 2000 mg L-1) added to the samples. The findings showed that with bromide concentration up to 600 mg L-1, the correction factor of 0.1 g COD/g Br- was applicable to all the tested wastewater samples, suggesting that this correction strategy could be practically used to eliminate bromide interference in standard COD test.


Assuntos
Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/análise , Análise da Demanda Biológica de Oxigênio , Brometos , Monitoramento Ambiental , Resíduos Industriais , Indústrias , Oxigênio/química , Águas Residuárias/análise , Qualidade da Água
17.
Sci Total Environ ; 700: 134510, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31629267

RESUMO

Manganese-oxidizing aerobic granular sludge (Mn-AGS) is a novel extension of AGS technology to treat arsenic (As) in organic wastewater. In this study, Mn-AGS was first applied to treat real wastewater (bottom ash leachates) containing high levels of As(III) and Cu(II) in a sequencing batch reactor (SBR) for 91 days. Influent and effluent As(III), As(V), Cu(II), as well as pH and chemical oxygen demand (COD) were monitored daily, and sludge was collected regularly for morphological observation, chemical characterization, and microbial analysis. The results indicated that As(III) and Cu(II) could be efficiently removed from wastewater (∼83% and ∼100%, respectively), but the performance was sensitive to pH variation, especially for As(III). The removed As and Cu were mostly bound to carbonates (60.2 ±â€¯2.0% and 70.0 ±â€¯0.6%, respectively) and Fe/Mn oxides (28.2 ±â€¯1.6% and 14.6 ±â€¯0.5%, respectively) in the final sludge. Influent As(III) was partially oxidized into As(V), and high fractions of As(V) were obtained in the Fe/Mn oxide-bound phase. Unexpectedly, microbial analysis revealed that community richness was only slightly changed when the influent was acidized (pH 4.0) but greatly reduced after the influent pH back to 6.0. It could be explained by that acid-fast bacteria rapidly grew after pH recovery and eliminated non-acid-fast bacteria. This work further supported the practical application of Mn-AGS to treat As(III)-containing organic wastewaters.


Assuntos
Arsênico/metabolismo , Cobre/metabolismo , Manganês/metabolismo , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/metabolismo , Aerobiose , Arsênico/análise , Águas Residuárias/química , Poluentes Químicos da Água/análise
18.
Sci Total Environ ; 700: 134536, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31689651

RESUMO

Heterogeneous electro-Fenton (EF) technology has been wildly applied for the treatment of wastewater containing dyes and other organic pollutants. However, biologically treatment should be further applied after heterogeneous electro-Fenton process in order get better effluent quality. In the present study, a simple electropolymerization method using poly (3,4-ethylenedioxythiophene) (PEDOT) and graphene oxide (GO) was applied for graphite felt (GF) electrode modification as cathode in EF system, and coupling subsequently aerobic granular sludge (AGS) biological treatment for dye wastewater treatment. The modified electrode was characterized by scanning electron microscopy (SEM), Raman spectrum, and cyclic voltammetry (CV). Data implied that much higher H2O2 productivity, current response and coulomb efficiency (CE) were achieved by using GO/PEDOT:NaPSS modified GF. The results could be ascribed to the synergistic effect between PEDOT and GO that accelerated the electron transfer rate. Moreover, the H2O2 production capacity remained over 84.2% after 10-times reuses for GO/PEDOT:NaPSS modified GF, indicating that GO significantly improved the stability and life of electrode. Compared with the single system, the total organic carbon (TOC) and chemical oxygen demand (COD) removal efficiencies of the combined system degradation methylene blue (MB) wastewater were significantly improved. Therefore, this modified GF could be used as a potentially useful cathode in heterogeneous EF technology for actual wastewater treatment and the combined system have a promising engineering application value in MB wastewater degradation field.


Assuntos
Corantes/química , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/química , Análise da Demanda Biológica de Oxigênio , Compostos Bicíclicos Heterocíclicos com Pontes , Eletrodos , Grafite , Peróxido de Hidrogênio , Azul de Metileno , Polímeros , Esgotos , Águas Residuárias/química
19.
Sci Total Environ ; 700: 135079, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31706088

RESUMO

Numerous studies have examined the performance of mineral and biomass-based sorbents for metal removal under laboratory conditions, but few pilot-scale tests have been performed on possible water purification systems in which these sorbents can be used. This study addressed this issue by evaluating the suitability of selected sorbents for use in continuous-flow continuous stirred tank reactors (CSTR) followed by sedimentation in laboratory and in situ pilot-scale experiments. Acid (HCl)-modified peat (M-Peat), a commercially available mineral sorbent containing mainly magnesium (Mg) carbonates, Mg oxides and Mg silicates (Mineral-P) and a calcium-rich ground granular blast furnace slag (by-product of stainless steel production (Slag) were tested for treatment of metallurgical industry wastewater (laboratory, pilot). Overall, higher metal removal was achieved from samples with higher initial metal concentrations. M-Peat achieved good removal of Zn (50-70%) and Ni (30-50%) in laboratory and pilot experiments. However, the poor settling characteristics of M-Peat can restrict its application in systems where sedimentation is the solid-liquid separation process applied. Mineral-P showed good performance in removing 65-85% of Zn present in the water and it performed similarly in laboratory and pilot tests. However, low concentrations of As and Ni leached from Mineral-P in all tests. Slag achieved good performance in treatment of the industrial wastewater, removing 65-80% of Zn and 60-80% of Pb during pilot tests. However, low concentrations of Cr and Cu were leached from Slag in a few tests. As a by-product of the same (metallurgical) industry, ground granular blast furnace slag is an excellent candidate for reducing Zn concentrations from industrial wastewater flows.


Assuntos
Metais Pesados/análise , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/análise , Adsorção , Sedimentos Geológicos , Resíduos Industriais , Metalurgia , Minerais , Águas Residuárias
20.
Sci Total Environ ; 700: 134576, 2020 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-31706092

RESUMO

The treatment of olive mill wastewater (OMW) in Jordan was investigated in this work using ultrasound oxidation (sonolysis) combined with other advanced oxidation processes such as ultraviolet radiation, hydrogen peroxide (H2O2) and titanium oxide (TiO2) catalyst. The efficiency of the combined oxidation process was evaluated based on the changes in the chemical oxygen demand (COD). The results showed that 59% COD removal was achieved within 90 min in the ultrasound /UV/TiO2 system. A more significant synergistic effect was observed on the COD removal efficiency when a combination of US/UV/TiO2 (sonophotocatalytic) processes was used at low ultrasound frequency. The results were then compared with the COD values obtained when each of these processes was used individually. The effects of different operating conditions such as, ultrasound power, initial COD concentration, the concentration of TiO2, frequency of ultrasound, and temperature on the OMW oxidation efficiency were studied and evaluated. The effect of adding a radical scavenger (sodium carbonate) on the OMW oxidation efficiency was investigated. The results showed that the sonophotocatalytic oxidation of OMW was affected by the initial COD, acoustic power, temperature and TiO2 concentration. The sonophotocatalytic oxidation of OMW increased with increasing the ultrasound power, temperature and H2O2 concentration. Sonolysis at frequency of 40 kHz combined with photocatalysis was not observed to have a significant effect on the OMW oxidation compared to sonication at frequency of 20 kHz. It was also found that the OMW oxidation was suppressed by the presence of the radical scavenger. The COD removal efficiency increased slightly with the increase of TiO2 concentration up to certain point due to the formation of oxidizing species. At ultrasound frequency of 20 kHz, considerable COD reduction of OMW was reported, indicating the effectiveness of the combined US/UV/TiO2 process for the OMW treatment.


Assuntos
Resíduos Industriais , Olea , Eliminação de Resíduos Líquidos/métodos , Jordânia , Oxirredução , Sonicação , Águas Residuárias
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