Azo Dye Wastewater Treatment Research Articles

Simultaneous optimization of electric production, azo dye, and yeast wastewater treatment in microbial fuel cell: Selection of the most suitable optimal conditions by PROMETHEE

Microbial fuel cell is a clean technology in which waste treatment and energy production continue simultaneously. Process performance depends on the independent variables and their interaction with each other specific to the waste to be treated. In this study, Microbial Fuel Cell (MFC), in which yeast production process wastewater is oxidized in the anolyte, and azo dye is reduced in the catholyte under abiotic conditions, was optimized using the Response Surface Methodology for maximum waste treatment and energy production. The independent variables were wastewater type, electrode array, and amount of sulfate-reducing inhibitor, while the dependent variables were azo dye removal, maximum power density, chemical oxygen demand (COD) removal, and coulomb efficiency. The effect of variables on all responses was determined using Analysis of Variance (ANOVA) and 3-dimensional (3D) graphs. The suitability of the models was tested by verification experiments under the determined optimum conditions (OPT 1, 2 and 3). Optimum experiments were ranked with the PROMETHEE approach according to azo dye removal (mg/L), maximum power density (mW/m2), COD removal (g/L), coulombic efficiency (%), and electrode cost (€/m2) criteria. The preference order of the optimum experiments was determined as OPT 1>OPT 2>OPT 3. With OPT 1, azo dye removal of 16.8 mg/L, maximum power density of 95.34 mW/m2, COD removal of 5.8 g/L and coulombic efficiency of 0.23 % were achieved. With a 1000 Ω external resistor, the maximum power density and coulombic efficiency increased to 147 mW/m2 and 1.5 %, respectively. In addition, the determined optimum experiments were examined using polarization curve and Electrochemical Impedance Spectroscopy.

Synchronous reinforcement azo dyes decolorization and anaerobic granular sludge stability by Fe, N co-modified biochar: enhancement based on extracellular electron transfer

Anaerobic digestion (AD) treatment of azo dyes wastewater often suffers from low decolorization efficiency and poor stability of anaerobic granular sludge (AnGS). In this study, iron and nitrogen co-modified biochar (FNC) was synthesized based on the secondary calcination method, and the feasibility of this material for enhanced AD treatment of azo dye wastewater and its mechanism were investigated. FNC not only formed richer conducting functional groups, but also generated Fe2+/Fe3+ redox pairs. The decolorization efficiency of Congo red and AD properties (e.g., methane production) were enhanced by FNC. After adding FNC, the content of extracellular polymeric substances (EPS) and the ratio of proteins remained stable under the impact of Congo red, which greatly protected the internal microbial community. This was mainly contributed to the excellent electrochemical properties of FNC, which strengthened the microbial extracellular electron transfer and realized the coupled mechanism of action: On the one hand, an electron transfer bridge between decolorizing bacteria and dyes was constructed to achieve rapid decolorization of azo dyes and mitigate the impact on methanogenic bacteria; On the other hand, the stability of AnGS was enhanced based on enhanced extracellular polymeric substances secretion, microbial community and direct interspecies electron transfer (DIET) process. This study provides a new idea for enhanced AD treatment of azo dyes wastewater.

Electrochemical treatment of azo dye wastewater by dynamic flow diaphragm system: Response surface methodology optimization and energy consumption analysis

In this experiment, the degradation process of azo dye wastewater was studied based on the diaphragm double chamber electrochemical reactor, taking the mono azo dye amaranth as an example. Through the circulation flow of appropriate volume of wastewater in the cathode and anode chamber, the simultaneous action of cathode and anode was realized, and the degradation and decolorization efficiency of azo wastewater was improved while reducing energy waste. The optimal reaction conditions optimized by response surface methodology were as follows: the voltage was 20.74 V, the plate spacing was 4.89 cm, and the cycle speed was 60.66 rad / min. The optimal decolorization rate was 99.66 %. The energy consumption analysis of the dynamic flow diaphragm system electrochemical method and the static flow diaphragm system electrochemical method for the treatment of azo dye wastewater was compared and analyzed. In addition, the possible degradation process of azo dye wastewater by dynamic flow electrochemistry was inferred by ultraviolet spectroscopy and mechanism prediction analysis. The experimental results show the great potential of the dynamic flow membrane system process in the treatment of azo dyes.

A Zn-Ca-Based Metallic Glass Composite Material for Rapid Degradation of Azo Dyes.

The catalytic capabilities of metals in degrading azo dyes have garnered extensive interest; however, selecting highly efficient metals remains a significant challenge. We have developed a Zn-Ca-based metallic glass composite which shows outstanding degradation efficiency for Direct Blue 6. This alloy comprises a Zn2Ca crystalline phase and an amorphous matrix, allowing for the degradation of azo dyes within minutes in a wide temperature range of 0-60 °C. Kinetic calculations reveal an exceptionally low activation energy of 8.99 kJ/mol. The rapid degradation is attributed to the active element Ca and the unique amorphous structure of the matrix, which not only facilitates abundant redox conditions but also minimizes the hydrolysis of the active element. The newly developed metallic glass composite exhibits a notably higher azo dye degradation rate compared to those of general metallic glasses, offering a new avenue for the rapid degradation of azo dyes. This paper holds significant importance for the development of novel azo dye wastewater treatment agents.

Decolorization and detoxification of Brilliant Crocein GR by a newly enriched thermophilic consortium

The environmental pollution caused by azo dyes at high temperatures has become an urgent problem. However, little attention has been paid to decolorizing azo dyes by thermophilic consortiums. In this study, a thermophilic bacterial consortium (BCGR-T) mainly composed of two genera, namely, Caldibacillus (70.90%) and Aeribacillus (17.63%) was first enriched, which can decolorize Brilliant Crocein GR (BCGR) at high temperatures (50–75 °C), pH values of 6∼8, dye concentrations (100–400 mg/L) and salinities (1–5%, w/v). The enzyme activity results showed that the azoreductase activity was nearly 8.8 times that of the control (p < 0.01), and the intracellular lignin peroxidase was also highly expressed with enzyme activity of 5.64 U (min−1 mg−1 protein) (p < 0.05), indicated that both azoreductase and intracellular lignin peroxidase played an important part in the decolorization process. Furthermore, seven new intermediate metabolic products, including aniline, phthalic acid, 2-carboxy benzaldehyde, phenylacetic acid, benzoic acid, toluene, and 4-methyl-hexanoic acid, were identified. In addition, functional genes related with the azo dye decolorization, such as those encoding the azoreductase, laccase, FMN reductase, NADPH-/NADH-quinone oxidoreductases and NADPH-/NADH dehydrogenases, catechol dioxygenase, homogentisate 1,2-dioxygenase, protocatechuate 3,4-dioxygenase, gentisate 1,2-dioxygenase, azobenzene reductase, naphthalene 1,2-dioxygenase, benzoate/toluate 1,2-dioxygenase, and anthranilate 1,2-dioxygenase and so on were found in the metagenome of the consortium BCGR-T. Finally, a new decolorization pathway of the thermophilic consortium BCGR-T was proposed. In addition, the phototoxicity of BCGR decreased after decolorization. Overall, the thermophilic consortium BCGR-T could be a promising candidate in the treatment of high concentration azo dye wastewater at high temperatures.

Azo dye wastewater treatment in a novel process of biofilm coupled with electrolysis

Azo dye wastewater treatment in a novel process of biofilm coupled with electrolysis

Kinetic analysis of electron transfer process in decolorization of azo dyes by Shewanella combined with porous organic polymers in MFCs

Two-dimensional nanostructured materials have emerged as very promising electrode materials for bioelectrochemical systems, enabling high bioelectrical output. We constructed air-cathode microbial fuel cells (MFCs) with electrical energy storage material POPM-TFP-rGO modified anodes for methyl orange (MO) decolorization and investigated the MFC performance. The kinetics of these processes were further analyzed. The results showed that MO decolorization efficiency in the POPM-TFP-rGO material-modified anode MFC reached 69.5% at 10 h. Compared with the unmodified electrode MFC, the efficiency and the kinetic constant of MO decolorization increased by 26.4% and 219%, respectively. Compared with control (40.5 mA m-2, 4.16 mW m-2), the stable current density and maximum power density (162.5 mA m-2, 48.84 mW m-2) were enhanced by 301% and 1070%, respectively. Further analysis of extracellular electron transfer kinetics showed that after modification of POPM-TFP-rGO, the number of electrons n and the charge transfer coefficient α (4, 0.56) increased by 74% and 65%, respectively, compared with control (2.3, 0.34). Therefore, POPM-TFP-rGO could be considered as a suitable and effective option for azo dye wastewater treatment by MFCs.

Expansion of carbon source utilization range of Shewanella oneidensis for efficient azo dye wastewater treatment through co-culture with Lactobacillus plantarum.

Shewanella oneidensis has demonstrated excellent potential for azo dye decolorization and degradation. However, in anaerobic environments, S. oneidensis has a narrow carbon source spectrum, which requires additional electron donors, such as sodium lactate. This increases the practical application costs for wastewater treatment. Here, we aimed to expand the carbon source utilization range of S. oneidensis FJAT-2478 by co-culturing it with Lactobacillus plantarum FJAT-7926, leveraging their commensalism relationship to develop a metabolic chain. Results showed that a 1:2 initial ratio of L. plantarum FJAT-7926 to S. oneidensis FJAT-2478 achieved a 97.16% decolorization rate of methyl orange when glucose served as the sole carbon source. This co-culture system achieved a decolorization rate comparable to that obtained using sodium lactate as an electron donor and was significantly higher than that achieved by L. plantarum FJAT-7926 (7.88%) or S. oneidensis FJAT-2478 (6.89%) alone. After undergoing five cycles, the co-culture system continued to exhibit effective decolorization. It was demonstrated that the co-culture system could use common and inexpensive carbon sources, such as starch, molasses, sucrose, and maltose, to decolorize azo dyes. For instance, 100mg/L methyl orange could be degraded by over 98.05% within 24h. The results indicated that the degradation rates of methyl orange were higher when L. plantarum was inoculated first, followed by a subsequent inoculation of S. oneidensis after 2h. The co-culturing of L. plantarum FJAT-7926 and S. oneidensis FJAT-2478 proved to be an effective strategy in treating azo dye wastewater, expanding the potential practical applications of S. oneidensis.

Adsorption of Amido Black 10B by Zinc Ferrite and Titanium Dioxide

This study focuses on the comprehensive recycling and utilization of zinc ferrite, a by-product of wet zinc refining, for the treatment of azo dye wastewater. It explores the adsorption performance of various materials on Amido Black 10B and analyzes the factors that influence the adsorption process. Zinc ferrite derived from the by-products of wet zinc refining, zinc ferrite synthesized via calcination, and titanium dioxide prepared using the sol–gel method are utilized as adsorbents, specifically targeting Amido Black 10B. By adjusting factors such as calcination temperature, mixing ratio, initial pH, adsorbent dosage, adsorption time, initial concentration, and reaction temperature, the effects on the adsorption of Amido Black 10B are studied. Additionally, the performance of composite materials consisting of different crystalline forms of titanium dioxide and purified zinc ferrite is examined. Furthermore, the adsorption process of Amido Black 10B by purified zinc ferrite/titanium dioxide is analyzed in terms of kinetics and thermodynamics. The results show that titanium dioxide and purified zinc ferrite, prepared at temperatures of 300 °C to 550 °C, achieve over 90% removal efficiency when co-adsorbing Amido Black 10B. The best performance is observed at a ratio of 4:6 for purified zinc ferrite to titanium dioxide, with removal efficiency exceeding 80%. The second-order kinetic model fits the adsorption data well, and higher initial solution concentrations lead to decreased adsorption rates. The adsorption process of purified zinc ferrite/titanium dioxide on Amido Black 10B is spontaneous, exothermic, and reduces system disorder. Higher temperatures negatively impact the adsorption process.

Performance and response of coupled microbial fuel cells for enhanced anaerobic treatment of azo dye wastewater with simultaneous recovery of electrical energy.

The anaerobic baffled reactor (ABR) is an anaerobic bioreactor that uses baffles to separate the working area into multiple reaction zones. The ABR-microbial fuel cell (MFC) reactor was constructed by embedding MFC in each reaction zone of the ABR. Its degradation of azo dye type (acid mordant red) wastewater and microbial power generation performance were investigated. For different electrode area ratios, the best enhanced treatment and electrical energy output of the coupled system was achieved with an anode/cathode area ratio of 1:1. Compared with the electrode area ratio of 2:1 and 1:2, the power density increased by 82.5% and 80.6%, and the Coulomb efficiency increased by 133.3% and 64.7%. In addition, the best enhanced treatment of printing and dyeing wastewater was achieved by ABR-MFC at 1:1. At a dye concentration of 200 mg/L and a sucrose concentration of 1000 mg/L, the coupled system obtained a COD removal of 92.85% and a chromaticity removal of 96.2%, which achieved a relative COD and chromaticity removal improvement of 1.82% and 2.64%, respectively, relative to the ABR. Scanning electron microscopy (SEM) observation of the electrodes at 1:1 revealed that more microorganisms were attached to the anode surface of the coupled system, the particle size of the granular sludge within the system was larger, and the UV scanning pattern showed lower dye concentration in the water. In conclusion, the microbial fuel cell enhanced anaerobic treatment of dyeing wastewater was the most effective when the electrode area ratio was 1:1, and the best electrical energy output was obtained at the same time. ABR-MFC provides a new idea for the enhanced treatment of dyeing wastewater and electrical energy production.

Upcycling polyvinyl chloride waste into highly efficient amine-functionalized nanofiber membrane adsorbent through the dissolution-modification-reforming process

Polyvinyl chloride (PVC) waste recycling is a challenging task and there is a great lack of convenient, feasible, and effective methods. In this work, a dissolution-modification-reforming process was proposed to upcycle PVC into highly efficient adsorbents (polyethylenimine-crosslinked PVC nanofiber membranes (PEI/PVC NFMs)). The effect of PEI to PVC mass ratio on the preparation of PEI/PVC NFMs was estimated. The adsorption performance of azo dyes on PEI/PVC NFMs was evaluated using Reactive Black 5 (RB5). The acid/alkali resistance of PEI/PVC NFM and its adsorption potential for various ionic pollutants were also investigated. Here are the results: The PEI/PVC NFMs exhibited high RB5 uptake within pH 2 to 8. The amine groups content in PEI/PVC NFM increased with increasing of PEI to PVC mass ratio, resulting in faster adsorption rates and higher adsorption capacity. With the mass ratio of PEI to PVC increased from 0.5:1.0 to 2.0:1.0, the adsorption equilibrium time reduced from 480 to 120 min, while the maximum RB5 uptake increased from 314.5 to 1036.7 mg/g. The adsorption isotherms and thermodynamic analysis revealed that physisorption dominated the adsorption process. The PEI/PVC NFM also exhibited good adsorption potential for various ionic pollutants, including per-/poly-fluoroalkyl substances (PFAS) and heavy metals (Pb2+, H2AsO4−, Co2+, and Ni2+). The 30-d acid/alkali resistance test confirmed that the PEI/PVC NFM has better stability at higher pH conditions. The PEI/PVC NFM exhibited good recyclability in azo dye wastewater treatment. In conclusion, this study demonstrates that the dissolution-modification-reforming process is a viable route for PVC waste upcycling. This pathway allows the conversion of PVC waste into highly efficient adsorbents for the elimination of ionic pollutants from water.

Adsorption and Degradation of Methylene Blue Aqueous Solution by Fe‐based Amorphous Alloy

Fe‐based amorphous ribbons with the brand name 1K101 can adsorb methylene blue (MB) solution. The adsorption reaction is multilayer adsorption, in which chemical adsorption plays a major role. There are also some processes like physical adsorption, liquid phase diffusion, and internal diffusion of particles. The adsorption reaction is exothermic and spontaneous, which is more favorable at low temperatures. During the adsorption process, the entropy value decreases, the degree of disorder and freedom of the solution decreases, and the structure also changes. What's more, H2O2, pH, ribbons's dosage, dye's concentration, and temperature affect the degradation performance of 1K101 on MB. Degradation reactions are mainly controlled by surface chemical reactions, including chemical reduction reactions and adsorption. When c(H2O2) is 15 mm, pH is 2, ribbons’ dosage is 0.9 g, c(MB) is 20 mg L−1, temperature is 338 K, the degradation effect is the best. The optimal conditions with lowest overall cost obtained under the orthogonal experiment are: c(H2O2) = 20 mm, pH = 2, ribbons's dosage = 0.7 g, c(MB) = 20 mg L−1, and T = 338 K. Overall, 1K101 amorphous ribbon can be utilized to treat MB solution, and its degradation effect is better than adsorption effect, which can provide new ideas for the reuse of waste amorphous ribbon and the treatment of azo dye wastewater.

Effect of Enhanced Hydrolytic Acidification Process on the Treatment of Azo Dye Wastewater.

The hydrolysis acidification process is an economical and effective method, but its efficiency is still low in treating azo dye wastewater. It is therefore crucial to find more suitable and efficient means or techniques to further strengthen the process of treating azo dye wastewater by a hydrolytic acidification process. In this study, a hydrolytic acidification aerobic reactor was used to simulate the azo dye wastewater process. The change of wastewater quality during the reaction process was monitored, and the deep enhancement effect of single or composite biological intensification technology on the treatment of azo dye wastewater by the hydrolytic acidification process was also explored. Co-substrate strengthening and the addition of fructose co-substrate can significantly improve the efficiency of hydrolytic acidification. Compared with the experimental group without the addition of fructose, the decolorization ratio of wastewater was higher (93%) after adding fructose co-substrate. The immobilization technology was strengthened, and the immobilized functional bacteria DDMZ1 pellet was used to treat the simulated azo dye wastewater. The results showed that the composite technology experimental group with the additional fructose co-matrix had a better decolorization efficiency than the single immobilized bio-enhancement technology, with the highest decolorization ratio of 97%. As a composite biological intensification method, the fructose co-matrix composite with immobilized functional bacteria DDMZ1 technology can be applied to the treatment of azo dye wastewater.

Mass-producible low-cost flexible electronic fabrics for azo dye wastewater treatment by electrocoagulation

Electrocoagulation is progressively becoming an ecologically friendly water treatment method owing to its lack of secondary pollution, high active ingredient concentration, high treatment effectiveness, simple equipment, and simplicity of automated control implementation. Herein, electrocoagulation is offered as a method for treating wastewater containing azo dyes using a revolutionary flexible electronic fabric that can be mass-producible at a reasonable price. A computer-controlled machine embroiders 316L stainless steel fiber (316L SSF) onto an insulating fabric to manufacture a flexible electronic device of cathode and anode with a monopolar arrangement on the fabric surface. Using methyl orange (MO) solution to simulate azo dye wastewater, the decolorization rate of 500 ml MO reached 99.25% under the conditions of 50 mg·L−1 initial mass concentration, 120 min electrolysis time, 15 mA·g−1 current density, 1 cm electrode spacing, 0.1 mol·L−1 NaCl, pH 7.6, 200 r·min−1 rotational speed of the stirrer, and 22−25 °C room temperature. In addition, it is feasible to embroider flexible electronic fabrics with varied sizes and numbers of electrodes based on the amount of treated sewage to increase the degradation rate, which has significant practical application value.

Refractory azo dye wastewater treatment by combined process of microbial electrolytic reactor and plant-microbial fuel cell

An innovative design of microbial electrolytic reactor (MER) coupled with Ipomoea aquaticaForsk. plant microbial fuel cell (IAF-PMFC) was developed for azo dye wastewater treatment and electricity generation. This study aims to assess the sequential degradation of azo dye and the feasibility of energy self-sufficiency in the MER/IAF-PMFC system. The decomposition of azo dye into aromatic amines and dye decolorization occurred in the MER at high hydraulic loading of 0.28 m3/(m2·d), while dye intermediates were mainly mineralized in the IAF-PMFC at low hydraulic loading of 0.06 m3/(m2·d). The final decolorization efficiency and COD removal of the combined system reached 99.64% and 92.06% respectively, even at influent dye concentration of 1000 mg/L. The effects of open/closed circuit conditions, presence/absence of aquatic plant and different cathode areas on the performance of the IAF-PMFC for treating the effluent of the MER were systematically tested, and the results showed that closed-circuit condition, plant involvement and larger cathode area were more beneficial to decolorization, detoxification and mineralization of dye wastewater, bioelectricity output, plant growth and photosynthetic rate. The power consumption by the MER was 0.0163 kWh/m3 of dye wastewater, while the highest power generation of the IAF-PMFC reached 0.0183 kWh/m3. The current efficiency of the MER for dye decolorization was as high as 942.83%, while the maximum coulombic efficiency of the IAF-PMFC for intermediates metabolism was only 6.30%, which still had much space of bioelectricity generation promotion. The MER/IAF-PMFC technology can simultaneously realize refractory wastewater treatment and balance of electricity production and consumption.

Effective removal of Orange II dye by porous Fe-base amorphous/Cu bimetallic composite

Azo dye wastewater is a worldwide problem with substantial deleterious environmental effects. Fe-based amorphous alloys have shown potential in azo dye wastewater treatment. However, their slower degradation rate and narrow working pH range hinder their wide application. Therefore, we designed a new porous Fe-base amorphous/Cu (Feam/Cu) bimetallic composite ribbon and prepared them using the chemical replacement copper plating method to remove the Orange II dye. The designed bimetallic composite ribbons can enhance the removal rate of azo dyes to various extents. The kinetic reduction rate (kobs) of the porous Feam/Cu bimetallic composite is 0.217 min−1 at pH= 7, a 92 % improvement compared to the kobs of Feam. Moreover, the porous Feam/Cu bimetallic composite shows a more comprehensive adaptability range of pH = 3–11 compared with many Fe-based amorphous catalysts. During kinetic analyses, the decolorization rates fitted well with both the pseudo-first-order reduction and pseudo-second-order adsorption models, implying that the removal of Orange II by porous Feam/Cu bimetallic composite involves both adsorption and catalytic modes of reduction. The strategy using the chemical replacement copper plating method to obtain porous Feam/Cu bimetallic composite is simple, cost-effective, and environmentally benign, making the large-scale production of porous Feam/Cu bimetallic composite possible for field remediation.

Electrostimulation for promoted microbial community and enhanced biodegradation of refractory azo dyes

Excess azo dyes are detrimental to natural water systems and human health. To effectively treat dye wastewater, two-dimensional cylindrical electrodes were introduced into traditional biofilm reactor (BR), and thus a novel two-dimensional biofilm electrode reactor (2D-BER) was developed. In the 2D-BER, at low current density from 0.53 ± 0.05 mA m-2 to 12.61 ± 1.24 mA m-2, the electrostimulation increased microbial growth; while at higher current density above 12.61 ± 1.24 mA m-2, the electrostimulation exhibited an inhibition effect to microorganisms. Microbial decolorization in the 2D-BER demanded the participation of co-substrate as carbon source, and the order of decolorization with different co-substrates was glucose > sucrose > starch. An appropriate concentration of glucose improved dye decolorization, but high level of glucose (1 g/L) resulted in a slight decline of decolorization. UV-Vis, FT-IR and GC-MS analysis showed that azo dye was firstly decomposed into various aromatic anilines and then degraded into small molecules. By analyzing the differences in the microbial communities in the 2D-BER and BR, it was found that the electrostimulation prompted the growth and proliferation of electroactive decolorization bacteria, such as Bellilinea, Desulfobulbus, Geobacter and Desulfovibrio, thus leading to high decolorization rate constant of 0.0313 h-1 in the 2D-BER. Considering the excellent decolorization due to the synergism of bioelectrochemistry and microbial catalysis, the electrostimulation technology shows good application prospects in azo dye wastewater treatment.

Biodegradation, Decolorization, and Detoxification of Di-Azo Dye Direct Red 81 by Halotolerant, Alkali-Thermo-Tolerant Bacterial Mixed Cultures.

Azo dyes impact the environment and deserve attention due to their widespread use in textile and tanning industries and challenging degradation. The high temperature, pH, and salinity used in these industries render industrial effluent decolorization and detoxification a challenging process. An enrichment technique was employed to screen for cost-effective biodegraders of Direct Red 81 (DR81) as a model for diazo dye recalcitrant to degradation. Our results showed that three mixed bacterial cultures achieved ≥80% decolorization within 8 h of 40 mg/L dye in a minimal salt medium with 0.1% yeast extract (MSM-Y) and real wastewater. Moreover, these mixed cultures showed ≥70% decolorization within 24 h when challenged with dye up to 600 mg/L in real wastewater and tolerated temperatures up to 60 °C, pH 10, and 5% salinity in MSM-Y. Azoreductase was the main contributor to DR81 decolorization based on crude oxidative and reductive enzymatic activity of cell-free supernatants and was stable at a wide range of pH and temperatures. Molecular identification of azoreductase genes suggested multiple AzoR genes per mixed culture with a possible novel azoreductase gene. Metabolite analysis using hyphenated techniques suggested two reductive pathways for DR81 biodegradation involving symmetric and asymmetric azo-bond cleavage. The DR81 metabolites were non-toxic to Artemia salina nauplii and Lepidium sativum seeds. This study provided evidence for DR81 degradation using robust stress-tolerant mixed cultures with potential use in azo dye wastewater treatment.

Simultaneously enhanced treatment efficiency of simulated hypersaline azo dye wastewater and membrane antifouling by a novel static magnetic field membrane bioreactor (SMFMBR)

Operation performance and membrane fouling of a novel static magnetic field membrane bioreactor (SMFMBR) for treatment of hypersaline azo dye wastewater was investigated. The results showed that SMFMBRs possessed higher efficiency of dye decolorization, COD removal and detoxification than the control MBR without SMF. The (3#) SMFMBR equipped with 305.0 mT (the highest intensity) SMF displayed the best treatment performance among all the four reactors (named as 0#–3#, equipped with SMFs of 0 mT, 95.0 mT, 206.3 mT and 305.0 mT, respectively). Potentially effective microbes belonging to Rhodanobacter, Saccharibacteria genera incertae sedis, Defluviimonas, Cellulomonas, Cutaneotrichosporon, Candida and Pichia were enriched in three SMFMBRs, in both of suspended sludge and bio-cakes. The relative abundance of Candida and Pichia in suspended sludge of 3# SMFMBR was the highest among all the four reactors, suggesting their successful colonization and potentially persistent effect of bioaugmentation. On the other hand, SMF of higher intensity effectively mitigated membrane fouling. Less production of soluble microbial products (SMP) and extracellular polymeric substances (EPS), lower protein/polysaccharide (PN/PS) ratio in SMP and EPS, looser structure of bio-cakes on membrane surface, as well as lower relative abundance of potential fouling causing microbes (mainly bacteria) in microbial communities were determined in 3# SMFMBR than the other three groups.

Azo dye wastewater treatment in a novel three-dimensional electrode reactor

Azo dye wastewater treatment in a novel three-dimensional electrode reactor