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1.
Ecotoxicol Environ Saf ; 208: 111419, 2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-33075585

RESUMO

Although domestic wastewater and its reclaimed water are alternative water resources in arid region, investigation of their negative effect must be done to prevent environmental pollution. In this paper, a short-term column experiment was conducted to simulate the infiltration process of wastewater in desert soil. Alfalfa was planted and irrigated with fresh water for control (CK), tertiary treated domestic wastewater (TTW), secondary treated domestic wastewater (STW) and raw domestic wastewater untreated (RW). The effect of wastewater application on desert soil, drainage and plant properties was evaluated. Experimental results demonstrated that the tested desert soil has no soil structure, organic matter, nor microbial community while possess high infiltration rate. The use of wastewater significantly improved plant growth, and the biomass of TTW, RW, STW were 5.5, 4.3, 2.9 times of CK. The infiltration rate of water in bare soil was high (high to low: TTW, CK, RW, STW), while plant growth reduced infiltration rate (ca. 40% with TTW and RW). Wastewater irrigation and plant growth decreased soil zeta potential, while increased formation of aggregates and bacterial abundance and diversity in soil. Top soil (0-30 cm) accumulation of nitrogen (N), phosphorus (P), organic matter and E. coli was evidenced and all could go down to deep soil and drainage with constant wastewater use. It was concluded that domestic wastewater had big potential in desert soil vegetation recovering and function restoration. Nevertheless, the N, salt, P and organic matter and E. coli in wastewater could give rise to desert soil and groundwater contamination if improper treatment was used.


Assuntos
Irrigação Agrícola/métodos , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/análise , Bactérias , Escherichia coli , Água Doce , Microbiota , Plantas , Areia , Solo/química , Microbiologia do Solo
2.
Ecotoxicol Environ Saf ; 208: 111522, 2021 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-33120272

RESUMO

Nanofiltration concentration leachate is a high concentration organic wastewater with low biodegradability and high toxicity. To explore the feasibility of a combined Heat/UV activated persulfate process on nanofiltration concentrated leachate, the effects of persulfate concentration, initial solution pH before reaction, UV-lamp power and reaction temperature on the removal of organic pollutant were systematically investigated. Results indicated that the maximum rate of chemical oxygen demand (COD), ammonia-nitrogen (NH3-N) and absorbance of organic matter under UV light at 254 nm (UV254) removal from the leachate were 65.4%, 51.4% and 98.1%, respectively, at a persulfate concentration of 18 g L-1, initial solution pH before reaction of 9.0, UV-lamp power of 60 W and temperature of 80 °C. The results of three-dimensional fluorescence and UV254 showed that the removal rates of humic substances contained in the nanofiltration concentrated leachate were over 98%. In addition, the results of free radical scavenging showed that hydroxyl radicals were dominant under alkaline conditions. The results of this study demonstrated that coupling heat and ultraviolet activated persulfate oxidation is a promising technique for the treatment of nanofiltration concentrated leachate.


Assuntos
Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/análise , Amônia , Biodegradação Ambiental , Análise da Demanda Biológica de Oxigênio , Filtração , Temperatura Alta , Substâncias Húmicas/análise , Nitrogênio , Oxirredução , Temperatura , Raios Ultravioleta , Águas Residuárias
3.
Chemosphere ; 262: 127698, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32791365

RESUMO

The influence of electromagnetic fields on bacterial denitrification has been tested on synthetic media with sludges from wastewater treatment stations, in batch mode. The effects of the intensity of the magnetic induction ratio B (mT), reaction volume and initial biomass concentration on the kinetics of the denitrification process were studied. Magnetic field had both an optimal stimulating effect on the activity of the denitrifying flora for B (mT)/mgx values of the order of 0.212, and an inhibitory effect for the values beyond the latter.Sludges underwent multiple exposure cycles to magnetic fields. It was shown that, after three exposure cycles, denitrification kinetics went from 6.5 to 12.7 mg N-NO-3.L-1.h-1 which corresponds to a 2.7 fold improvement. The improved performance persists even after the cessation of the magnetic field. Observation of the sludge by the environmentalelectron microscope shows that the microbial population forming the starting sludge; changed following exposure to the magnetic field. The action of the; electromagnetic field on the microbial populations in denitrification resulted in the modification of the diversity of the flora that is initially present, favoring the development of Proteo bacteria, particularly the Betaproteo bacteria subclass, which results in improved denitrification.


Assuntos
Eliminação de Resíduos Líquidos/métodos , Bactérias , Biomassa , Reatores Biológicos/microbiologia , Desnitrificação , Campos Eletromagnéticos , Campos Magnéticos , Nitrogênio/análise , Esgotos/microbiologia , Águas Residuárias
4.
Ecotoxicol Environ Saf ; 207: 111258, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-32971319

RESUMO

This study investigated whether bioaugmentation improves sulfamethoxazole (SMX) degradation and nitrogen removal in the Moving Bed Biofilm Reactor (MBBR) system. The effects of the C/N ratio on SMX degradation and nitrogen removal were also evaluated. Using MBBR system operation experiments, the bioaugmented reactor was found to perform more effectively than the non-bioaugmentation reactor, with the highest SMX, nitrate-N, and ammonia-N removal efficiencies of 80.49, 94.70, and 96.09%, respectively. The changes in the sulfonamide resistance genes and bacterial communities were detected at various operating conditions. The results indicate that the diversity of the bacterial communities and the abundance of resistance genes were markedly influenced by bioaugmentation and the C/N ratio, with Achromobacter among the dominant genera in the MBBR system. The bio-toxicity of samples, calculated as the inhibition percentage (IP) toward Escherichia coli, was found to decrease to non-toxic ranges after treatment.


Assuntos
Aquicultura , Sulfametoxazol/metabolismo , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/metabolismo , Achromobacter/metabolismo , Amônia , Biofilmes , Reatores Biológicos/microbiologia , Nitratos , Nitrogênio , Águas Residuárias/microbiologia
5.
Ecotoxicol Environ Saf ; 207: 111253, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-32911183

RESUMO

Phytoremediation of polyester resin wastewater containing 1,4-dioxane and heavy metals using Lemna gibba (L.gibba) was enhanced by incorporation of perforated polyethylene carrier materials (PCM) onto the duckweed pond (DWP) system. The DWP module was operated at a hydraulic retention times (HRTs) of 2, 4 and 6 days and as well as 1,4-dioxane loading rate of 16, 25 and 48 g/m3.d. The maximum removal efficiency of 54 ± 2.5% was achieved for 1,4-dioxane at an HRT of 6 days and loading rate of 16 g1,4-dioxane/m3.d. Similarly, the DWP system provided removal efficiencies of 28.3 ± 2.1, 93.2 ± 7.6, 95.7 ± 8.9 and 93.6 ± 4.9% for Cd2+, Cu2+, Zn2+ and Ni2+ at influent concentration of 0.037 ± 0.01, 1.2 ± 0.9, 27.2 ± 4.7 and 4.6 ± 1.2 mg/L respectively. The structural analysis by Fourier-transform infrared spectroscopy (FTIR) clearly displayed a reduction of 1,4- dioxane in the treated effluent. A strong peak was detected for L. gibba plants at frequency of 3417.71 cm-1 due to N-H stretching, which confirm the proposed mechanism of partially conversion of 1,4-dioxane into amino acids. Glycine, serine, aspartic, threonine and alanine content were increased in L. gibba by values of 35 ± 2.2, 40 ± 3.2, 48 ± 3.7, 31 ± 2.8, and 56 ± 4.1%, respectively. The contribution of DWP unit as a greenhouse gases (GHG) emissions were relatively low (1.65 gCO2/Kg BODremoved.d., and 18.3 gCO2/Kg biomass.d) due to photosynthesis process, low excess sludge production and consumption of CO2 for nitrification process (1.4 gCO2/kgN removed.d). Based on these results, it is recommended to apply such a technology for treatment of polyester resin wastewater containing 1,4-dioxane and heavy metals at a HRT not exceeding 6 days.


Assuntos
Dioxanos/análise , Gases de Efeito Estufa/análise , Metais Pesados/análise , Eliminação de Resíduos Líquidos/métodos , Araceae , Biodegradação Ambiental , Biomassa , Nitrificação , Poliésteres , Tanques/análise , Esgotos/análise , Águas Residuárias/análise
6.
Chemosphere ; 262: 128357, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33182098

RESUMO

The cost-effective recovery of phosphate is of great significance to the mitigation of phosphorus resource depletion crisis. The electrochemical-decomposition of dolomite was developed to recover phosphate and ammonium from aqueous solution. The dolomite ore is mainly composed of CaMg(CO3)2 (53.73%), CaCO3 (28.93%) and SiO2 (16.59%). The continuous release of Mg2+ and Ca2+ were achieved by electrochemically decomposing dolomite ore, accompanied by the generation of base solution (9.0-10.5). The main factors affecting the recovery performance of phosphate (PO4-P) and ammonium (NH4-N) are current, initial concentration of PO4-P and NH4-N, initial pH of feed solution and feed rate. For a 30-d operation, the recovery rate of PO4-P was maintained at 90-97% and that of NH4-N at 50-60% under optimized operating conditions. The recovered product had low water solubility but high citric-acid-soluble, and was proposed as a slow-release fertilizer for crops. The proposed process as a simple, effective and green route may serve as a new strategy for recovering PO4-P and NH4-N from wastewaters.


Assuntos
Compostos de Amônio/química , Carbonato de Cálcio/química , Técnicas Eletroquímicas/métodos , Magnésio/química , Fosfatos/química , Eliminação de Resíduos Líquidos/métodos , Compostos de Amônio/isolamento & purificação , Cálcio/química , Eletrodos , Fertilizantes , Concentração de Íons de Hidrogênio , Fosfatos/isolamento & purificação , Fósforo/química , Dióxido de Silício , Soluções , Águas Residuárias/química , Poluentes Químicos da Água/química
7.
Chemosphere ; 262: 128358, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33182147

RESUMO

Discharge of heavy metals from various sources of industrial wastewater poses significant environmental and health concerns. Thus, efficient recovery of precious metals from wastewater employing sustainable, rapid, and cost-effective treatment methods is highly desirable. In this work, palladium nanoparticles (Pd NPs) were successfully recovered from industrial wastewater using a pulsed laser process in the absence of additives or reducing agents. Notably, the developed approach is faster and more environmentally friendly than other conventional recovery methods. The recovered Pd NPs were characterized by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and inductively coupled plasma optical emission spectroscopy (ICP-OES). Various pulsed laser parameters (i.e., laser wavelength, power, and irradiation time) were optimized to obtain ideal conditions for the pulsed laser ablation process. Effective recovery of the Pd metal from industrial wastewater was achieved at a laser wavelength of 355 nm, power of 40 mJ/pulse, and irradiation time of 30 min. The Pd NPs exhibited excellent catalytic activity toward the reduction of 4-nitrophenol. Thus, the recovered materials showed remarkable potential for application in degradation of toxic aromatic nitro compounds in the environment.


Assuntos
Nanopartículas Metálicas/química , Nitrofenóis/química , Paládio/química , Eliminação de Resíduos Líquidos/métodos , Catálise , Lasers , Microscopia Eletrônica de Varredura , Microscopia Eletrônica de Transmissão , Oxirredução , Paládio/isolamento & purificação , Águas Residuárias/química , Poluentes Químicos da Água/química , Poluentes Químicos da Água/isolamento & purificação , Difração de Raios X
8.
Chemosphere ; 263: 127949, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32822933

RESUMO

This work develops a halophilic biocarriers-MBR for saline pharmaceutical wastewater treatment. The system has effectively treated the ampicillin-containing saline wastewater for 32 days, when the ampicillin concentration is lower than 20 mg/L. The system can tolerate the saline organic wastewater with a reasonable biodegradability (removals of COD over 75%) when the ampicillin concentration is 50 mg/L. The system has a bad performance in biodegradation (COD removals around 60-70%) and fouled within 16 days at a high ampicillin concentration of 100 mg/L. At high transmembrane pressures over 30 KPa, some ampicillin molecules may permeate through the membrane causing decreases in the ampicillin removal. The concentrations of protein and carbohydrate in EPS and SMP have increased over time and with increasing the ampicillin concentration. The method of biofouling control in MBR for the ampicillin situations has been proposed based on monitoring the concentrations of EPS and SMP. The drying-assisted monitoring of membrane biofoulants has showed a better efficiency than the monitoring of transmembrane pressure for membrane anti-biofouling in the treatment of pharmaceutical saline wastewaters where a spectroscopic detection can be hardly applied. This work may benefit relative research works for the control of biodegradation performance and membrane biofouling to better treat saline pharmaceutical wastewaters.


Assuntos
Preparações Farmacêuticas/análise , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/química , Ampicilina , Biodegradação Ambiental , Incrustação Biológica , Reatores Biológicos , Membranas Artificiais , Purificação da Água/métodos
9.
Chemosphere ; 263: 127889, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32828053

RESUMO

Fe2O3 and its composites have been extensively investigated and employed for the remediation of contaminated water with the characteristics of low cost, outstanding chemical stability, high efficiency of visible light utilization, excellent magnetic ability and abundant active sites for adsorption and degradation. In this review, the potentials of Fe2O3 in water remediation were discussed and summarized in detail. Firstly, various synthesis methods of Fe2O3 and its composites were reviewed and compared. Based on the structures and characteristics of the obtained materials, their applications and related mechanisms in pollutants removal were surveyed and discussed. Furthermore, several strategies for optimizing the remediation processes, including dispersion, immobilization, nano/micromotor construction and simultaneous decontamination, were also highlighted and discussed. Finally, recommendations for further work in the development of novel Fe2O3-related materials and its practical applications were proposed.


Assuntos
Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/química , Adsorção , Compostos Férricos/química , Águas Residuárias/química , Água , Poluentes Químicos da Água/análise , Purificação da Água/métodos
10.
Chemosphere ; 263: 127934, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32828055

RESUMO

A high ammonia concentration and chemical oxygen demand (COD) in piggery wastewater force it to be diluted before conventional microalgal treatment to reduce ammonia toxicity. Incomplete treatment of ammonia and COD in piggery wastewater may cause eutrophication, resulting in algal blooms. This study tried to treat raw piggery wastewater without dilution, using three strains of microalgae (Chlorella sorokiniana, Coelastrella sp. and Acutodesmus nygaardii) that outcompeted other algae under heterotrophic, mixotrophic, and autotrophic conditions, respectively, through adaptive evolution at high ammonia concentration. The three stepwise processes were designed to remove (1) small particles, COD, and phosphorus in the 1st heterotrophic C. sorokiniana cultivation, (2) ammonia and COD in the 2nd mixotrophic Coelastrella sp. cultivation, and (3) the remaining ammonia in the 3rd photoautotrophic A. nygaardii cultivation. To enhance ammonia uptake rate, each algal species were inoculated after 2-day nitrogen starvation. When the N-starved three species were inoculated at each step sequentially at 7 g/L for 2 days, the final phosphorus, COD, and ammonia removal efficiencies were 100% (16.4-0 mg/L), 92% (6820-545 mg/L), 90% (850-81 mg/L) and turbidity (99%) after total 6 days.


Assuntos
Adaptação Fisiológica/fisiologia , Amônia/metabolismo , Biodegradação Ambiental , Microalgas/fisiologia , Eliminação de Resíduos Líquidos/métodos , Animais , Processos Autotróficos , Análise da Demanda Biológica de Oxigênio , Biomassa , Chlorella , Processos Heterotróficos , Nitrogênio , Fósforo , Suínos , Águas Residuárias
11.
Chemosphere ; 263: 127907, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32835972

RESUMO

Electrocoagulation (EC) process is found as effective water and wastewater treatment method, as it can able to remove a variety of pollutants, treat various industrial wastewater, and able to handle fluctuations in pollutant quality and quantity. The performance of EC process can be improved significantly in combination with degradation processes. Different combinations of EC process with Fenton, electro-Fenton, photo-Fenton, photocatalysis, sonochemical treatment, ozonation, indirect electrochemical oxidation, anodic oxidation and sulfate radical based advanced oxidation process are found very effective for the treatment of water and wastewater. Enhanced performance of EC process in combination with degradation process was reported in most of the articles.


Assuntos
Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/química , Poluentes Químicos da Água/análise , Eletrocoagulação , Eletrodos , Peróxido de Hidrogênio , Oxirredução , Sulfatos , Água
12.
Chemosphere ; 263: 127987, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32835980

RESUMO

The high value-added use of tannery solid waste and elimination of tannery liquid waste in the leather-making industry have attracted widespread attention. In this study, a MgO-doped biochar (MgO/BC) adsorbent was successfully prepared by utilizing tannery solid waste (i.e., non-tanned hide wastes) as the biomass material for dye removal from tannery wastewater. Characterization results indicated that MgO was uniformly embedded into the porous BC structure. The adsorption capacity of acid orange II by MgO/BC reached up to 448.4 mg g-1, which drastically exceeded the pure BC and other reported adsorbents. The adsorption behavior of acid orange II by MgO/BC matched nicely with Langmuir isotherm and pseudo-second-order kinetic model. This satisfactory adsorption capacity of MgO/BC for acid orange II was mainly due to the large specific surface area and the enhanced electrostatic interaction. According to the BET, zeta potential and XPS analysis, the possible mechanism towards acid orange II removal was attributed to the pore filling, surface complexation, electrostatic attraction and π-π interaction. In addition, MgO/BC showed the efficient removal towards anionic dyes from actual tannery wastewater. This work could provide guidance for the value-added utilization of tannery solid waste and a practical way to remove dyes from tannery wastewater.


Assuntos
Corantes/análise , Curtume , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/análise , Adsorção , Compostos Azo , Carvão Vegetal , Cinética , Naftalenos , Resíduos Sólidos , Águas Residuárias/química
13.
Chemosphere ; 263: 127944, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32854006

RESUMO

Pharmaceutically active compounds (PhACs) have been frequently detected in aquatic environment and raised concerns because of their environmental persistence and potential ecological risk, especially carbamazepine (CBZ), erythromycin (ERY), atenolol (ATL) and clofibric acid (CA). The UV/H2O2 advanced oxidation process was considered as an effective process to remove pharmaceuticals in wastewater. Because of the diverse structure of pharmaceuticals and the various wastewater matrices, this study established two models to predict the degradation of 4 PhACs in wastewater by UV/H2O2. Besides, the degradation pathway and toxicity of 4 PhACs by UV/H2O2 were explored. The degradation of 4 PhACs by UV/H2O2 followed the pseudo first-order kinetics pattern. The degradation rate of pharmaceuticals decreased as CBZ > ATL > CA > ERY. A kinetic model combining the steady state concentrations of HO∙ successfully predicted the degradation process of pharmaceuticals in 14 secondary municipal wastewater effluents. Also, a water matrix prediction model by response surface methodology (RSM) was established to estimate the degradation of pharmaceuticals well. A detailed and systematic comparison of two models in the objectives of models, predicting target contaminants, types of wastewater and parameters of models was made. In addition, the tentative transformation pathways of 4 PhACs by UV/H2O2 were proposed. 4 PhACs after UV/H2O2 treatment enhanced the toxicity, and prolongation of treatment time can reduce the toxicity on the luminescence.


Assuntos
Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/química , Carbamazepina/análise , Eritromicina , Peróxido de Hidrogênio , Cinética , Modelos Químicos , Oxirredução , Raios Ultravioleta , Águas Residuárias/química , Água , Poluentes Químicos da Água/análise , Purificação da Água/métodos
14.
Chemosphere ; 263: 127945, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-32854007

RESUMO

To reduce undesired iron leaching in Fenton reaction and to realize reusability of catalyst, chitosan-coated activated carbon cloth support loaded with nano zero-valent iron (ACC-CH-nZVI) was applied as a heterogeneous Fenton catalyst to treat melanoidin wastewater. Chitosan coating on ACC by chemical crosslinking results in 6% chitosan on ACC subsequently loading 3.5% iron. At optimum conditions, ACC-CH-nZVI leads to 88.4% and 76.2% of color and chemical oxygen demand (COD) removal, respectively, upon treating synthetic melanoidin wastewater of 8000 mg/l COD. The corresponding weight ratio of consumed H2O2 to COD is 1.02, far below the stoichiometric ratio 2.125, indicating the economic value of this catalyst. Reusability of ACC-CH-nZVI is demonstrated for five cycles of treatment with minimal iron leaching (<2%). The high removal efficiency and very low levels of iron leaching suggests that ACC-CH-nZVI is a highly efficient and cost-effective catalyst for Fenton-like oxidation of non-biodegradable organic wastes in water.


Assuntos
Polímeros/análise , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/química , Análise da Demanda Biológica de Oxigênio , Catálise , Carvão Vegetal , Peróxido de Hidrogênio , Ferro , Oxirredução , Águas Residuárias , Poluentes Químicos da Água/análise
15.
Artigo em Inglês | MEDLINE | ID: mdl-33142999

RESUMO

A single-stage anaerobic ammonium oxidation (ANAMMOX) process with an integrated biofilm-activated sludge system was carried out in a laboratory-scale flow-through reactor (volume = 57.6 L) to treat pharmaceutical wastewater containing chlortetracycline. Partial nitrification was successfully achieved after 48 days of treatment with a nitrite accumulation of 70%. The activity of ammonia oxidizing bacteria (AOB) decreased when the chemical oxygen demand (COD) concentration of the influent was 3000 mg/L. When switching to the single-stage ANAMMOX operation, (T = 32-34 °C, DO = 0.4-0.8 mg/L, pH = 8.0-8.5), the total nitrogen (TN) removal loading rate and efficiency were 1.0 kg/m3/d and 75.2%, respectively, when the ammonium concentration of the influent was 287 ± 146 mg/L for 73 days. The findings of this study imply that single-stage ANAMMOX can achieve high nitrogen removal rates and effectively treat pharmaceutical wastewater with high concentrations of COD (1000 mg/L) and ammonium.


Assuntos
Compostos de Amônio/farmacologia , Desnitrificação , Nitrogênio/isolamento & purificação , Esgotos , Eliminação de Resíduos Líquidos/métodos , Anaerobiose , Reatores Biológicos/microbiologia , Humanos , Nitrogênio/metabolismo , Oxirredução , Águas Residuárias , Purificação da Água/métodos
16.
Artigo em Inglês | MEDLINE | ID: mdl-33023188

RESUMO

This article deals with the possibility of using a biosorbent in the form of a mixture of cones from coniferous trees to remove the residual concentration of hazardous metals contained in hazardous waste, which is disposed of in a neutralization station. The efficiency of the tested biosorbent in removing Ni, Zn, Cu, and Fe was monitored here. Laboratory research was carried out before the actual testing of the biosorbent directly in the operation of the neutralization station. With regard to the planned use of the biosorbent in the operational test, the laboratory experiments were performed in a batch mode and for the most problematic metals (Ni and Zn). The laboratory tests with real wastewater have shown that the biosorbent can be used to remove hazardous metals. Under the given conditions, 96% of Ni and 19% of Zn were removed after 20 min when using NaOH activated biosorbent with the concentration of 0.1 mol L-1. The inactivated biosorbent removed 93% of Ni and 31% of Zn. The tested biosorbent was also successful during the operational tests. The inactivated biosorbent was applied due to the financial costs. It was used for the pre-treatment of hazardous waste in a preparation tank, where a significant reduction in the concentration of hazardous metals occurred, but the values of Ni, Cu, and Zn still failed to meet the emission limits. After 72 h, we measured 10 mg L-1 from the original 4,056 mg L-1 of Ni, 1 mg L-1 from the original 2,252 mg L-1 of Cu, 1 mg L-1 from the original 4,020 mg L-1 of Zn, and 7 mg L-1 from the original 1,853 mg L-1 of Fe. However, even after neutralization, the treated water did not meet the emission limits for discharging into the sewer system. The biosorbent was, therefore, used in the filtration unit as well, which was placed in front of the Parshall flume. After passing through the filtration unit, the concentrations of all the monitored parameters were reduced to a minimum, and the values met the prescribed emission limits. The biosorbent was further used to thicken the residual sludge in the waste pre-treatment tank, which contributed to a significant reduction in the overall cost of disposing of residual hazardous waste. This waste was converted from liquid to solid-state.


Assuntos
Metais Pesados/análise , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/análise , Adsorção , República Tcheca , Metais , Águas Residuárias , Zinco/análise
17.
Chemosphere ; 261: 128179, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33113649

RESUMO

Understanding how wastewater treatment plants (WWTPs) process microplastics (MPs) will help informing management practices to reduce MP emissions to the environment. We show that composite 24 h samples taken at three replications from the outflow of the grit chamber, primary settling tank and clarifier of the WWTP of Sari City, on the southern coast of the Caspian Sea, contained 12667 ± 668, 3514 ± 543 and 423 ± 44.9 MP/m3, respectively. Fibers accounted for 94.9%, 89.9% and 77.5% of the total number of MPs, respectively. The MP removal efficiency was 96.7%. MP shape (fiber, particle), size and structure were the most important factors determining their removal in different steps of the wastewater treatment process. The structure of microfibers (polyester, acrylic and nylon) and the consequent higher density than water explained their high removal (72.3%) in the primary settling tank. However, size was more important in microparticle removal with particles ≥500 µm being removed in the primary settling tank and <500 µm in the clarifier unit. The smallest particles (37-300 µm) showed the lowest removal efficiency. The predominant types of fibers and particles were polyester and polyethylene, respectively, which are likely to originate from the washing of synthetic textiles and from microbeads in toothpaste and cosmetics. Despite the efficiency of the Sari WWTP in removing MPs, it remains a major emission source of MPs to the Caspian Sea due to its high daily discharge load.


Assuntos
Microplásticos/isolamento & purificação , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água/isolamento & purificação , Mar Cáspio , Cidades , Irã (Geográfico) , Microplásticos/química , Nylons/química , Nylons/isolamento & purificação , Poliésteres/química , Poliésteres/isolamento & purificação , Polietileno/química , Polietileno/isolamento & purificação , Têxteis , Águas Residuárias/química , Poluentes Químicos da Água/química
18.
Chemosphere ; 261: 128172, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33113654

RESUMO

Nitritation is currently known as a bottleneck for mainstream nitrite shunt or partial nitritation/anammox (PN/A). Here we propose a new approach to selectively eliminate nitrite oxidizing bacteria (NOB) for mainstream nitritation by low-dose ultraviolet-A (UVA) irradiation. The results showed that mainstream nitritation was rapidly achieved within 10 days with UVA irradiation at the dose of 0.87 µE L-1 s-1, and nitrite accumulation ratio (NO2--N/(NO2--N + NO3--N) ×100%) stabilized over 80%. Microbial community analysis revealed that two typical NOB populations (Nitrospira and Ca. Nitrotoga) detected in the control reactor were suppressed efficiently in UVA irradiation reactor, whereas the Nitrosomonas genus of ammonium oxidizing bacteria (AOB) remained at similar level. Intracellular reactive oxygen species (ROS) analysis indicated that NOB-dominant sludge tends to generate more intracellular ROS compared with AOB-dominant sludge in the presence of UVA, leading to the inactivation and elimination of NOB. Additionally, amounts of microalgae found in UVA irradiation reactor could help to suppress NOB by generating ROS during photosynthesis. Briefly, the UVA irradiation approach proposed in this study was shown to be promising in NOB suppression for reliable mainstream nitritation.


Assuntos
Bactérias/efeitos da radiação , Reatores Biológicos/microbiologia , Nitritos/metabolismo , Raios Ultravioleta , Eliminação de Resíduos Líquidos/métodos , Compostos de Amônio/metabolismo , Microbiota , Nitrogênio/metabolismo , Nitrosomonas/efeitos da radiação , Oxirredução , Espécies Reativas de Oxigênio/metabolismo , Esgotos/microbiologia , Eliminação de Resíduos Líquidos/instrumentação
19.
Chemosphere ; 261: 127929, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33113658

RESUMO

To elucidate the effects of extracellular polymeric substance (EPS) on the sludge dewaterability, this study comparatively investigated the changes in EPS composition and spatial distribution, together with the sludge dewaterability after lysozyme (LZM) conditioning. The protein concentration in the tightly bound EPS (TB-EPS) increased from 3.47 mg g-1 DS to 4.99 mg g-1 DS within the first 2 min, then gradually decreased, which could be described by a piecewise linear function. Unlike TB-EPS, the protein content variation trend in both soluble EPS (S-EPS) and loosely bound EPS (LB-EPS) followed the typical first-order kinetics. Additionally, the extended DLVO theory was employed in combination with viscoelastic acoustic response analysis to further explore the impact of EPS composition on water adhesion and microbial cell. After the extraction of S-EPS from the conditioned sludge, the adsorption free energy (ΔGadh) of EPS ascended to -61.05 mJ m-2, indicating the weakened microbial hydrophobicity. By contrast, the ΔGadh value declined after the subsequent extraction of LB-EPS and TB-EPS. Meanwhile, the adsorption potential energy between S-EPS and microbial cells showed an increasing trend, whereas the repulsion potential energy between TB-EPS and microbial cells fell to 1.40 × 104 kT, signifying a weakened adsorption capacity to water. Accordingly, the viscosity and shear modulus of each EPS layer were reduced after conditioning, which contributed to the transformation of bound water into free water. These changes reasonably explained the results that the water content in the dewatered sludge after conditioning was reduced to 58.54%, and the bound water content decreased by 15.06%.


Assuntos
Matriz Extracelular de Substâncias Poliméricas/química , Muramidase/química , Proteínas/análise , Esgotos/química , Eliminação de Resíduos Líquidos/métodos , Água/análise , Acústica , Adsorção , Cinética , Esgotos/análise , Viscosidade
20.
Chemosphere ; 261: 128201, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-33113663

RESUMO

In this work, Ti/SnO2-RuO2 dimensionally stable anode has been successfully fabricated via thermal decomposition method and further used for highly efficient electrocatalytic degradation of alizarin cyanin green (ACG) dye wastewater. The morphology, crystal structure and composition of Ti/SnO2-RuO2 electrode are characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray fluorescence spectroscopy (XRF), respectively. The result of accelerated life test suggests that as-prepared Ti/SnO2-RuO2 anode exhibits excellent electrochemical stability. Some parameters, such as reaction temperature, initial pH, electrode spacing and current density, have been investigated in detail to optimize the degradation condition of ACG. The results show that the decolorization efficiency and chemical oxygen demand removal efficiency of ACG reach up to 80.4% and 51.3% after only 40 min, respectively, under the optimal condition (reaction temperature 25 °C, pH 5, electrode spacing 1.0 cm and current density 3 mA cm-2). Furthermore, the kinetics analysis reveals that the process of electrocatalytic degradation of ACG follows the law of quasi-first-order kinetics. The excellent electrochemical activity demonstrates that the Ti/SnO2-RuO2 electrode presents a favorable application prospect in the electrochemical treatment of anthraquinone dye wastewater.


Assuntos
Antraquinonas/química , Carbocianinas/química , Eletrodos , Eliminação de Resíduos Líquidos/instrumentação , Análise da Demanda Biológica de Oxigênio , Corantes/química , Concentração de Íons de Hidrogênio , Microscopia Eletrônica de Varredura , Oxirredução , Compostos de Rutênio/química , Espectrometria por Raios X , Temperatura , Compostos de Estanho/química , Titânio/química , Eliminação de Resíduos Líquidos/métodos , Águas Residuárias/química , Poluentes Químicos da Água/química , Difração de Raios X
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