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1.
Water Sci Technol ; 84(5): 1245-1256, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34534120

RESUMO

In this study, electrochemical oxidation of combed fabric dyeing wastewater was investigated using graphite electrodes. The response surface methodology (RSM) was used to design the experiments via the central composite design (CCD). The planned experiments were done to track color changes and chemical oxygen demand (COD) removal. The experimental results were used to develop optimization models using RSM and the artificial neural network (ANN) and they were compared. The developed models by the two methods were in good agreement with the experimental results. The optimum conditions were found at 150 A/m2, pH 5, and 120 min. The removal efficiencies for color and COD reached 96.6% and 77.69%, respectively. The operating cost at the optimum conditions was also estimated. The energy and the cost of 1 m3 of wastewater required 34.9 kWh and 2.58 US$, respectively. The graphite electrodes can be successfully utilized for treatment of combed fabric dyeing wastewater with reasonable cost.


Assuntos
Grafite , Águas Residuárias , Eletrodos , Redes Neurais de Computação , Têxteis
2.
Water Sci Technol ; 84(3): 752-762, 2021 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-34388132

RESUMO

In this study, an electro-oxidation (EO) process using graphite electrodes as electrode pairs was used for the removal of chemical oxygen demand (COD), ammoniacal nitrogen (NH4+-N), and color from real textile printing wastewater. The effects of solution pH, sodium chloride (NaCl) dosage, sodium hypochlorite (NaOCl), which is the oldest and still most important chlorine-based bleach, dosage, and oxidation time were investigated on the removal efficiencies. Operating conditions for the EO reactor were applied to current density 1 mA/cm2, distance between the electrodes: 2 cm, 150 min operation time, and stirring speed of 500 rpm. At optimum conditions: pH 9.5, applied current density 1 mA/cm2, NaCl dosage of 8 g/L, NaOCl dosage of 44.4 mg/L and 150 min electro-oxidation time, the obtained removal efficiencies were 86.5% and 91.1% for chemical oxygen demand (COD) and ammoniacal nitrogen, respectively. Efficiency was increased to 91.1% for ammoniacal nitrogen from 21.7% after applying EO combined with NaOCl addition compared to individual NaOCl addition.


Assuntos
Águas Residuárias , Poluentes Químicos da Água , Análise da Demanda Biológica de Oxigênio , Eletrodos , Nitrogênio , Oxirredução , Impressão Tridimensional , Cloreto de Sódio , Têxteis , Eliminação de Resíduos Líquidos , Poluentes Químicos da Água/análise
3.
Water Sci Technol ; 81(12): 2488-2500, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32857737

RESUMO

This paper offers a feasible solution for the treatment of membrane concentrate produced from the textile industry, using the Fenton, Advanced Fenton (AF), ozonation and hydrodynamic cavitation (HC) and combination of these processes. The study investigated the optimum oxidant and catalyst concentrations, optimum operational conditions and comparison of these processes. The potential formation of chlorinated organic compounds after oxidation of membrane concentrate was also investigated by analyzing total organic halogen (TOX) and polychlorinated biphenyl (PCBs). Also, toxicity analysis was performed with Vibrio fischeri photobacteria to identify the production possibility of oxidation intermediates that are more toxic and difficult to treat than the targeted contaminants. Maximum removal efficiencies in chemical oxygen demand (COD) and color were 18.8% and 60.7% respectively using HC alone at a cavitation number (CN) of 0.1. Maximum COD, total organic carbon (TOC), and color removal efficiency at molar concentrations of 175 mM H2O2 and 35 mM Fe2+ and pH 3 after 30 min was 87.1, 80.8 and 99%. Combined HC with Fenton showed the highest removal efficiency in terms of COD, TOC, and color. It was also stated that the use of high oxidant concentrations masks the synergistic effect of HC on Fenton processes due to the scavenging effect.


Assuntos
Peróxido de Hidrogênio , Poluentes Químicos da Água , Análise da Demanda Biológica de Oxigênio , Oxirredução , Indústria Têxtil
4.
Water Sci Technol ; 81(10): 2127-2139, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32701491

RESUMO

Membrane fouling mechanisms of the filtration of a mixed-culture microalgal biomass grown in real wastewater were investigated using crossflow filtration experiments. The results of flux measurements, scanning electron microscopy (SEM) and atomic force microscopy (AFM) analyses for three membranes, two microfiltration (PES01 and PES003) and one ultrafiltration (UC030), showed that the UC030 membrane may be more appropriate for microalgae harvesting due to its higher steady flux rate and lower flux reduction during filtration compared to the initial flux (44% for UC030, compared to 86% for PES01 and 79% for PES003). It was also observed that the membrane resistance due to concentration polarization was the dominant membrane resistance in this study for all three membranes, constituting about 67%, 61% and 51% for PES01, PES003, and UC030, respectively. The next largest membrane resistance was provided by pore blocking, while the resistance provided by cake formation was found to be very small for all membranes (3%, 15% and 18% for PES01, PES003 and UC030, respectively), which were also supported by SEM and AFM analyses.


Assuntos
Microalgas , Biomassa , Filtração , Membranas Artificiais , Ultrafiltração , Águas Residuárias
5.
Environ Technol ; 41(4): 440-449, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-30010517

RESUMO

A lab-scale electrodialysis (ED) which consisted of 11 pieces of cation-exchange membranes and 10 pieces of anion-exchange membranes was used to treat concentrated brine of Reverse osmosis (RO) membrane. The effect of operating parameters such as applied voltage, flowrate, and operating mode was investigated to measure the performance of a lab-scale ED. Three different voltages (5, 10, and 15 V) and flowrates (20, 30, and 40 L/h) were applied in order to optimize the operating conditions of the ED system. The maximum TDS removal efficiencies were 85%, 97%, and 98% for 5, 10, and 15 V, respectively. It was concluded that the desalination efficiencies were almost the same at flowrates values of 20, 30 and 40 L/h. The TDS concentration of the treated brine in the concentrate compartment rises to the highest value of 25,400 mg/L with desalination rate of 92.5% after five cycle operation. Moreover, the desalinated brine can be used as fresh water.


Assuntos
Purificação da Água , Ânions , Filtração , Membranas Artificiais , Osmose
6.
Water Sci Technol ; 77(7-8): 1899-1908, 2018 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-29676747

RESUMO

In this study, an integrated aerobic membrane bioreactor (MBR)-nanofiltration (NF) system has been applied for advanced treatment of Opium processing wastewaters to comply with strict discharge limits. Aerobic MBR treatment was successfully applied to high strength industrial wastewater. In aerobic MBR treatment, a non-fouling unique slot aeration system was designed using computational fluid dynamics techniques. The MBR was used to separate treated effluent from dispersed and non-settleable biomass. Respirometric modeling using MBR sludge indicated that the biomass exhibited similar kinetic parameters to that of municipal activated sludge systems. Aerobic MBR/NF treatment reduced chemical oxygen demand (COD) from 32,000 down to 2,500 and 130 mg/L, respectively. The MBR system provided complete removal of total inorganic nitrogen; however, nearly 50 mgN/L organic nitrogen remained in the permeate. Post NF treatment after MBR permeate reduced nitrogen below 20 mgN/L, providing nearly total color removal. In addition, a 90% removal in the conductivity parameter was reached with an integrated MBR/NF system. Finally, post NF application to MBR permeate was found not to be practical at higher pH due to low flux (3-4 L/m2/hour) with low recovery rates (30-40%). As the permeate pH lowered to 5.5, 75% of NF recovery was achieved at a flux of 15 L/m2/hour.


Assuntos
Alcaloides/química , Reatores Biológicos , Filtração/instrumentação , Resíduos Industriais/análise , Eliminação de Resíduos Líquidos/métodos , Aerobiose , Análise da Demanda Biológica de Oxigênio , Membranas Artificiais , Nitrogênio/análise , Ópio/química , Eliminação de Resíduos Líquidos/instrumentação , Águas Residuárias/análise
7.
Environ Technol ; 38(21): 2668-2676, 2017 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-27967603

RESUMO

It has been recognized by the whole world that textile industry which produce large amounts of wastewater with strong color and toxic organic compounds is a major problematical industry requiring effective treatment solutions. In this study, reverse osmosis (RO) membranes were tested on biologically treated real dye bath wastewater with and without pretreatment by nanofiltration (NF) membrane to recovery. Also membrane fouling and reuse potential of membranes were investigated by multiple filtrations. Obtained results showed that only NF is not suitable to produce enough quality to reuse the wastewater in a textile industry as process water while RO provide successfully enough permeate quality. The results recommend that integrated NF/RO membrane process is able to reduce membrane fouling and allow long-term operation for real dye bath wastewater.


Assuntos
Corantes , Eliminação de Resíduos Líquidos , Purificação da Água , Membranas Artificiais , Osmose , Águas Residuárias , Água
8.
Water Sci Technol ; 74(3): 766-76, 2016.
Artigo em Inglês | MEDLINE | ID: mdl-27508382

RESUMO

The objective of this study was to investigate the influences of electroosmosis (EO) and electrophoresis (EP) on the permeate flux in submerged membrane bioreactors. When a polymeric membrane is placed in between an anode and a cathode, both EO and EP occur simultaneously, causing enhancement in flux. Results showed that after 150 min of filtration, the permeate fluxes were 60, 115, 175 and 260 L/m(2)/h at 0, 30, 40 and 50 V, respectively. It was shown that the EO was linearly changing with increasing voltage, reaching up to 54 L/m(2)/h at 50 V. EP was found to be a significant process in removing soluble microbial products from the membrane surface, resulting in an increase in permeate flux as the filtration progressed. About 20-fold of smaller protein and carbohydrate concentrations were found in the cake layer when the electrical field (EF) was applied. However, the EF application promoted pore fouling, because of the calcium and magnesium scaling.


Assuntos
Eletro-Osmose/instrumentação , Eletroforese/instrumentação , Polímeros/química , Águas Residuárias/química , Purificação da Água/instrumentação , Reatores Biológicos , Filtração/instrumentação , Filtração/métodos , Membranas Artificiais , Purificação da Água/métodos
9.
Water Sci Technol ; 67(3): 604-11, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23202566

RESUMO

The objective of this study was to investigate the influence of sludge retention time (SRT) on membrane bio-fouling. An activated sludge reactor was operated at three different SRTs (10, 30, and 50 days). Submerged membrane experiments were performed when the mixed liquor suspended solids (MLSS) concentration reached the steady state conditions. MLSS concentrations reached the steady state at 3,109 ± 194, 6,209 ± 123 and 6,609 ± 280 mg/L for SRTs of 10, 30 and 50 days, respectively. The total soluble microbial products (SMP) were 20.1 ± 3.7, 16.2 ± 7.2 and 28.2 ± 8.4 mg/L at SRTs of 10, 30, and 50 days, respectively. The carbohydrate concentration in the supernatant was about two times more for SRT of 10 days than that for 50 days. The total amount of extracellular polymeric substances (EPS) extracted from the flocs were approximately 74.9 ± 11.9, 67.8 ± 15.0 and 67.5 ± 17.4 mg/g MLSS at three SRTs (10, 30, and 50 days) under the same organic loading rate. The viscosity of the biomass increased with the increasing SRT. The results of flux stepping tests showed that the membrane fouling at SRT 10 days was always higher than that of 30 and 50 days. Four different microfiltration membranes (cellulose acetate, polyethersulfone, mixed ester, and polycarbonate) with three different pore sizes (0.45, 0.22, 0.10 µm) were tested. Filtration resistances were determined for each membrane. Cake resistance was observed to be the most significant fouling mechanism for all membranes.


Assuntos
Incrustação Biológica , Reatores Biológicos , Membranas Artificiais , Esgotos , Carboidratos/análise , Filtração , Interações Hidrofóbicas e Hidrofílicas , Proteínas/análise , Fatores de Tempo , Viscosidade
10.
Bioresour Technol ; 102(13): 6843-9, 2011 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-21536431

RESUMO

The effects of membrane fouling reducers (MFRs) (the cationic polyelectrolyte (CPE) and FeCI(3)) on membrane fouling were studied in a lab-scale jet loop submerged membrane bioreactor (JL-SMBR) system. The optimum dosages of MFRs (CPE dosage=20 mg g(-1)MLSS, FeCI(3) dosage=14 mg g(-1)MLSS) were continuously fed to JL-SMBR system. The soluble and bound EPS concentrations as well as MLSS concentration in the mixed liquor of JL-SMBR were not changed substantially by the addition of MFRs. However, significant differences were observed in particle size and relative hydrophobicity. Filtration tests were performed by using different membrane types (polycarbonate (PC) and nitrocellulose mixed ester (ME)) and various pore sizes (0.45-0.22-0.1 µm). The steady state fluxes (J(ss)) of membranes increased at all membranes after MFRs addition to JL-SMBR. The filtration results showed that MFRs addition was an effective approach in terms of improvement in filtration performance for both membrane types.


Assuntos
Incrustação Biológica/prevenção & controle , Reatores Biológicos , Filtração/instrumentação , Membranas Artificiais , Reatores Biológicos/microbiologia , Polissacarídeos/análise , Eliminação de Resíduos Líquidos
11.
Sci Total Environ ; 385(1-3): 1-11, 2007 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-17706747

RESUMO

Electrokinetic remediation has been investigated extensively as one of the noble technologies in remediation of metal contaminated soils. However, its applications in remediation of organic contaminants have been limited due to low solubilities of organics in water. In addition, most organic contaminants are non-ionic and therefore, they are not mobile under electrical field. The use of surfactants may increase the remediation efficiency by increasing the solubility of organics. Significant fraction of organics associated with soil, can be transferred to micellar phase, which then can be transported toward either cathode or anode, depending on the ionic group of surfactants. In this study, the removal of hydrophobic organic contaminants from a soil using electrokinetic method was investigated in the presence of surfactants. A nonionic surfactant, Tween 80, and an anionic surfactant, SDBS, were used in the experiments. DDT was chosen as the model organic contaminant. Phase distribution studies and column experiments were conducted. It was found that both Tween 80 and SDBS had similar solubilization potentials for DDT. It was also shown that the aqueous DDT mass could reach from 0.01 to 13% of the total mass in the presence of 7500 mg/L of SDBS. No significant movement of DDT was observed when Tween 80 was used in the column experiments. This was attributed to low rates of electroosmotic flows and strong interaction of Tween 80 with the soil. The amount of surfactant was not enough to mobilize DDT significantly in the column studies. On the other hand, electrokinetic transport with SDBS yielded much better results. DDT transport toward the anode within the negatively charged micelles overcame the opposite electrosmotic flow. This was attributed to the lower degree of interaction between the soil and SDBS, and the electrokinetic transport of negatively charged micelles.


Assuntos
DDT/análise , Eletro-Osmose , Recuperação e Remediação Ambiental/métodos , Poluentes do Solo/análise , Tensoativos/química , Cinética , Modelos Teóricos
12.
Bioresour Technol ; 94(3): 245-9, 2004 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-15182830

RESUMO

The removal of chromate anions (CrO(4)(2-)) from aqueous solution by a cationic surfactant-modified yeast was studied in a batch system. Cetyl trimethyl ammonium bromide (CTAB) was used for biomass modification; it substantially improved the biosorption efficiency. The influences of solution pH, CrO(4)(2-) anion concentrations and biomass concentration on the biosorption efficiency were investigated. The biosorption of chromate anions by modified yeast was strongly affected by pH. The optimum pH for biosorption of CrO(4)(2-) by modified yeast was 4.5-5.5. Zeta potential values of modified and unmodified yeast were determined at various pH values. Concentrations ranging from 5.2 to 208 mg/l Cr(VI) were tested and the biosorptive removal efficiency of the metal ions from aqueous solution was more than 99.5%. Freundlich and Langmuir isotherms were used to evaluate the data and the regression constants were determined.


Assuntos
Cromatos/metabolismo , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Leveduras/metabolismo , Adsorção , Biomassa , Cetrimônio , Compostos de Cetrimônio , Concentração de Íons de Hidrogênio , Análise de Regressão
13.
Water Res ; 38(8): 2117-24, 2004 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-15087193

RESUMO

Direct and indirect releases of large quantities of surfactants to the environment may result in serious health and environmental problems. Therefore, surfactants should be removed from water before release to the environment or delivery for public use. Using powdered activated carbon (PAC) as adsorbent and separating particles with a membrane may be an effective technique to remove surfactants. In this study, the removal of surfactants by microfiltration and PAC was investigated and the influences of the operating parameters on the effectiveness on microfiltration were determined. An anionic (LABS) and a cationic surfactant (CTAB) were selected for the experiments. A series of batch experiments were performed to determine the sorption isotherms of surfactants to PAC. Then microfiltration experiments were carried out. The results showed that formation of secondary membrane on the surface and, within the pores of the membrane, increased the retention of surfactants significantly. Increase in transmembrane pressure and pore size of the membrane decreased the rejection rates, but increase in cross-flow velocity increased the rejection rate. Temperature had no apparent affect on the efficiency of surfactant removal. Presence of electrolyte had different effects on CTAB and LABS. The rejection rates of CTAB significantly increased when the concentration of NaCl increased; however, a slight decrease was observed in the rejection rate of LABS at the same conditions.


Assuntos
Carbono/química , Carvão Vegetal/química , Tensoativos/química , Ultrafiltração/métodos , Purificação da Água/métodos , Adsorção , Eletrólitos/química , Membranas Artificiais , Porosidade , Cloreto de Sódio/química , Temperatura , Ultrafiltração/instrumentação , Purificação da Água/instrumentação
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