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An Upflow Anaerobic Sludge Blanket Reactor/Continuous Stirred Tank Reactor was used sequentially to decolorize and mineralize C.I. Direct Black 38 azo dye (3200 mg/L) in a synthetic wastewater containing glucose as co-substrate. At the steady state conditions color was effectively removed under anaerobic condition, while the total aromatic amines a...
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... (1) (2)), under anaerobic and aerobic conditions, respectively. These results and the mass spectra in aerobic effluents show that DB 38 azo dyes could not be completely mineralized by means of anaerobic/aerobic sequential process. The proposed intermediates produced from the sequential anaerobic/aerobic degradation of DB 38 are illustrated in Fig. 7 [48,49]. As shown in this figure 1,2,5-triaminobenzene, benzidine, 2,8,9-triamino-1-hydroxynaphthalene-3,7-disulphonic acid and aniline were produced under anaerobic conditions while SO 3 − , Na + , NH 3 , NO 2 − ,NO 3 − , CO 2 , H 2 O and OH − were released through aerobic stage. In a study performed by Bradford et al. [30] it was ...
Citations
... [33] Azo dyes are comprised of an amine or phenol linked to a diazotized amine. [34] A single azo group makes up the majority of azo dyes, although others include two (disazo), three (trisazo), or even more [31,35] Based on the exact structure of the molecule, azo dyes can produce a full spectrum of colors. Azo dye compounds may be found in the colors yellow, orange, red, brown, and blue [36]. ...
... There are three primary steps in the azoic dyeing process. [33,34,72] They are a) Naphtholation, b) Diazotisation, and c) Coupling Naphtholation Naphthols are insoluble in water and require the treatment of an alkali to become soluble in water. [73] Fabric is impregnated with this salt solution. ...
... The damaged dye, once separated, can cause serious pollution problems when released into the environment. In many cases, the toxicity of the destroyed dye molecules is much greater than that of the dye molecules themselves (Işık and Sponza, 2004). ...
... Concerning organic compounds, most studies have assessed pesticides only, with significant knowledge gaps noted for other chemical classes, such as Polychlorinated biphenyl, Polybrominated diphenyl ethers, polycyclic aromatic hydrocarbons, and Perfluoroalkyl and Polyfluoroalkyl Substances. In one study, in vitro inhibition was noted in CA purified from Acipenser gueldenstaedtii (Danube Sturgeon) erythrocytes following exposure to several pesticides (2.4-dichlorophenol, dithiocarbamates, parathion, and carbaryl) (Kolayli et al., 2011), while in other assessment various pesticides (nuarimol, fenarimol, parathion-methyl, and 2,4-dichlorophenoxy acetic acid, delthametric) inhibited CA activity in freshwater and seawater fish erythrocytes (Isik and Sponza, 2004;Dogan et al., 2006) and erythrocytes purified from Oncorhynchus mykiss (Rainbow Trout) gills (Ceyhun et al., 2010) to different degrees. However, no similar studies in elasmobranchs have been conducted to date, indicating a significant knowledge gap in this regard and potential aggravated risks to the health and resilience of this group. ...
The enzyme carbonic anhydrase (CA) has well-known functions in acid-base balance, respiratory gas exchange, and osmoregulation in teleost fishes. However, studies concerning the role of CA in elasmobranchs are still scarce. Therefore, the aim of this study is to present the current status of CA studies in sharks and rays, as well as to identify gaps and emerging needs, in order to guide future studies. This review is organized according to the main roles of CA, with further considerations on climate change and CA effects indicated as paramount, as strategies in the face of climate change can be crucial for species response. The literature review revealed a reduction in publications on CA over the years. In addition, a historical research differentiation is noted, where the first assessments on the subject addressed investigations on basic CA functions, while the most recent studies present a comparative approach among species as well as interdisciplinary discussions, such as ecology and phylogeny. Considering that most elasmobranchs are threatened, future studies should prioritize non-lethal methodologies, in addition to expanding studies to climate change effects on CA.
... Within latter, the post-tanning process is present, where re-tanning, dyeing, bleaching and fatliquoring take place. Therefore in post-tanning, different chemicals are used (Saxena et al., 2016); including tannins and resins (Lofrano et al., 2013), greases and oils (Kalyanaraman et al., 2013), and dyes (Işik and Sponza, 2004). Due to variation in input materials, processes, chemicals, and water consumption, chemical load and residues change greatly, wastewater characterization should be followed. ...
Post-tanning process in the tannery industry generates complex wastewater. Continuous electrocoagulation (EC) with carbon-steel electrodes was used to treat synthetic/post-tanning wastewater. Research surface methodology, based on central composite design (RSM-CCD), was used for variables optimization and analysis of variance (ANOVA) to relate all parameters. Optimal variables were identified as initial pH 3.0, current density 6.4 mA m⁻², initial dye concentration 125 mg L⁻¹, NaCl concentration 1,000 mg L⁻¹, and inlet flow rate 176 mL min⁻¹ to produce 71% dye removal, operational costs (OC) 0.05 US$ m⁻³, power consumption 1.3 kWh m⁻³, iron consumption 0.05 kg m⁻³, dye removal capacity per dissolved mg iron (qe) 4.3 mg Dye L⁻¹ C⁻¹ and total dissolved solids (TDS) removal 43.5%. Best process conditions were used to treat real post-tanning wastewater and resulted in carbon oxygen demand (COD) and TDS abatement (23% and 76%, respectively), as well as low OC (0.84 US$ m⁻³) and energy consumption (20.6 kWh m⁻³). Pseudo-first-order kinetic model was found fitting experimental results, having electrical energy per order (EEO) of 1 kW h m⁻¹ order⁻¹ with a higher k =1.14 min⁻¹. Scanning electron microscopy analysis suggested the presence of iron nanoparticles within the sludge. All input and output parameters resulted in statistically significant where TDS and qe were the most valued for effective pollutant removal optimization and prevention of TDS increase in treated water. The outcomes of this study suggest EC as a suitable treatment for post-tanning wastewater and further knowledge of steel-carbon EC reactor design and sludge reusing purposes.
... Applications of laboratory-and pilot-scale up-flow anaerobic sludge blanket reactors (UASB) and activated sludge processes for decolorization of synthetic dye mixtures and textile industry effluents are reported [13,14]. These reactors have been inoculated with anaerobic granular/activated sludge and hence the microorganisms responsible for dye decolorization were unknown. ...
A fixed bed biofilm reactor (FBBR) was developed and its performance in decolorizing synthetic dye mixture and textile industry effluents was evaluated in both batch and continuous modes. It was observed that yeast extract was important as the carbon source in the FBBR feed for color removal. However, the requirement for yeast extract in FBBR is very small compared to that in suspended cell cultures. Structural changes in dyes due to biological treatment were assessed from ultraviolet‐visible spectral and high‐performance liquid chromatography (HPLC) analyses. Gas chromatography‐mass spectrophotometry (GC‐MS) investigations confirmed the metabolites formed were non‐toxic and benign.
... Among the physicochemical characteristics, the composition of the effluents is highly variable; being the concentration of the parameters very different between the studies available in literature. This type of effluent are characterized for having a wide range of pH between values of 5 and 12 (Singh and Singh, 2017;Paździor and Bilińska, 2020;Samuchiwal et al., 2021), elevated chemical oxygen demand (COD) from 10 to 2250 mgO 2 L −1 (Ghaly et al., 2014;Singh and Singh, 2017;Paździor and Bilińska, 2020;Samuchiwal et al., 2021), biochemical oxygen demand (BOD) among 100 and 3000 mgO 2 L −1 (Işik and Sponza, 2004;Paździor and Bilińska, 2020), suspended solids, heavy metals and salts (Saratale et al., 2011;Singh and Singh, 2017;Vikrant et al., 2018;. Regarding to dye concentration, they are highly colored. ...
... Among the physicochemical characteristics, the composition of the effluents is highly variable; being the concentration of the parameters very different between the studies available in literature. This type of effluent are characterized for having a wide range of pH between values of 5 and 12 (Singh and Singh, 2017;Yaseen and Scholz, 2019;Paździor and Bilińska, 2020;Samuchiwal et al., 2021), elevated chemical oxygen demand (COD) from 10 to 2250 mgO 2 L −1 (Ghaly et al., 2014;Singh and Singh, 2017;Paździor and Bilińska, 2020;Samuchiwal et al., 2021), biochemical oxygen demand (BOD) among 100 and 3000 mgO 2 L −1 (Işik and Sponza, 2004;Paździor and Bilińska, 2020), suspended solids, heavy metals and salts (Saratale et al., 2011;Singh and Singh, 2017;Vikrant et al., 2018;Yaseen and Scholz, 2019). Regarding to dye concentration, they are highly colored. ...
Wastewater discharge is a matter of concern as it is the primary source of water pollution. Consequently, wastewater treatment plays a key role in reducing the negative impact that wastewater discharge produce into the environment. Particularly, the effluents produced by textile industry are composed of high concentration of hazardous compounds such as dyes, as well as having high levels of chemical and biological oxygen demand, suspended solids, variable pH, and high concentration of salt. Main efforts have been focused on the development of methods consuming less water or reusing it, and also on the development of dyes with a better fixation capacity. However, the problem of how to treat these harmful effluents is still pending. Different treatment technologies have been developed, such as coagulation-flocculation, adsorption, membrane filtration, reverse osmosis, advanced oxidation, and biological processes (activated sludge, anaerobic-aerobic treatment, and membrane bioreactor). Concerning to biological treatments, even though they are considered as the most environmentally friendly and economic methods, their industrial application is still uncertain. On the one hand, this is due to the costs of treatment plants installation and, on the other, to the fact that most of the studies are carried out with simulated or diluted effluents that do not represent what really happens in the industries. Integrated treatment technologies by combining the efficiency two or more methodologies used to be more efficient for the decontamination of textile wastewater, than treatments used separately. The elimination of hazardous compounds had been reported using combination of physical, chemical, and biological processes. On this way, as degradation products can sometimes be even more toxic than the parent compounds, effluent toxicity assessment is an essential feature in the development of these alternatives. This article provides a critical view on the state of art of biological treatment, the degree of advancement and the prospects for their application, also discussing the concept of integrated treatment and the importance of including toxicity assays to reach an integral approach to wastewater treatment.
... De Jager et al. [26] demonstrated that degradation of aromatic amines in an aerobic tank caused increase in nitrate level to 3 mg·L −1 when real textile was treated. Increase in nitrate concentration from 16 to 83 mg·L −1 was observed during decolorization of Direct Black 38 in anaerobic/aerobic sequential reactors [59]. Distinctive microbial community in biofilm and suspended sludge has been observed in hybrid suspended growth -biofilm wastewater treatment system [48]. ...
In this study, the effect of number of stages and bioreactor type on the removal performance of a sequential anaerobic-aerobic process employing activated sludge for the treatment of a simulated textile dyeing wastewater containing three commercial reactive azo dyes was considered. Two stage processes performed better than one stage ones, both in terms of overall organic and color removal, as well as the higher contribution of anaerobic stage to the overall removal performance, thereby making them a more energy efficient option. The employment of a moving bed sequencing batch biofilm reactor, which uses both suspended and attached biomass, for the implementation of the anaerobic stage of the process, was compared with a sequencing batch reactor that only employs suspended biomass. The results showed that, although there was no meaningful difference in biomass concentration between the two bioreactors, the latter reactor had better performance in terms of chemical oxygen demand (COD) removal efficiency and rate and color removal rate. Further exploratory tests revealed a difference between the roles of suspended and attached bacterial populations, with the former yielding better color removal whilst the latter had better COD removal performance. The sequential anaerobic-aerobic process, employing an aerobic membrane bioreactor in the aerobic stage resulted in COD and color removal of 77.1±7.9% and 79.9±1.5%, respectively. The incomplete COD and color removal was attributed to the presence of soluble microbial products in the effluent and the autoxidation of dye reduction metabolites, respectively. Also, aerobic partial mineralization of the dye reduction metabolites, was experimentally observed.
... Received 14 January 2020; Received in revised form 27 February 2020; Accepted 1 March 2020 close to neutrality [8]. However, during biological treatments not only dye mineralization is rarely reached, but many dyes and especially their reduction products lead to the formation of toxic and carcinogenic aromatic amines [13][14][15]. Otherwise, physical-chemical methods, as adsorption, are excellent for decolorization. However, they are not destructive, only transferring the pollutant from one phase to another, generating solid waste [16]. ...
... According to Figure S2 it was possible to identify some fragments referring to the cleavage of dye molecule DB22 by free radicals (O 2 − and % OH) generated by the composite, suggesting a simple fragmentation route [32]. During the biological treatment it is suggested the formation of fragments similar to those described in Fig. 11 route a, by the cleavage of terminal nitrogen groups [15,50]. It is widely reported that many bacterial strains can produce specific enzymes, which are capable of cleaving amino bonds. ...
The disposal of wastewater containing large amounts of dyes is a public health and environmental problem, due to its toxicity into the aquatic biota, the reduction in sunlight penetration, which consequently interference in photosynthetic activity. In the present study a new composite, based on the heterojunction of reduced graphene oxide (rGO) and chalcopyrite (CuFeS2), was developed to treat a real textile wastewater (RW). The efficiency of the composite assisted by microwave irradiation was evaluated to catalyze the decolorization and degradation of RW containing a high concentration of the azo Direct Black 22 (DB22). A small amount (0.5 w/w%) of rGO on CuFeS2 was enough to uplift the efficiency of decolorization to 74 % of DB22 and 97 % TOC in the RW, only in the first min of treatment, and 97 % and 99 %, respectively, at 6 min. The improvement in catalytic activity can be attributed to the dipolar polarization effect, hot spots and the generation of hydroxyl radicals. Additionally, a synergistic effect between the composite and microwave irradiation, assisted by hydrogen peroxide, reduced the RW phytotoxicity, improving the radicle length of Lactuca sativa three times (from 0.87 cm to 2.65 cm with the application of a single minute of treatment). The reduction in phytotoxicity led to an increase in the germination percentage from 36 % to 53 %. Finally, the use of MW irradiation coupled to a novel rGO-CuFeS2 composite, in presence of H2O2 under acid medium, provides a feasible and highly rapid method to treat RW, reducing its phytotoxicity.
Capsule: A novel rGO-CuFeS2 catalyst was developed and applied together with microwave irradiation for an ultra-fast degradation treatment (6 min) in real textile wastewater.
... Received 14 January 2020; Received in revised form 27 February 2020; Accepted 1 March 2020 close to neutrality [8]. However, during biological treatments not only dye mineralization is rarely reached, but many dyes and especially their reduction products lead to the formation of toxic and carcinogenic aromatic amines [13][14][15]. Otherwise, physical-chemical methods, as adsorption, are excellent for decolorization. However, they are not destructive, only transferring the pollutant from one phase to another, generating solid waste [16]. ...
... According to Figure S2 it was possible to identify some fragments referring to the cleavage of dye molecule DB22 by free radicals (O 2 − and % OH) generated by the composite, suggesting a simple fragmentation route [32]. During the biological treatment it is suggested the formation of fragments similar to those described in Fig. 11 route a, by the cleavage of terminal nitrogen groups [15,50]. It is widely reported that many bacterial strains can produce specific enzymes, which are capable of cleaving amino bonds. ...
The novelty of this work lies in the use of a real textile wastewater (RTW), without a pretreatment, without additional carbon sources and undiluted, with coupling a photocatalysis by using an unprecedented composite for this application. The collected RTW containing the azo dye Direct Black 22 (205.15 mg L⁻¹ TOC: 672.7 mg L⁻¹), was treated with a bacterial consortium and after 96 h the sequential photocatalysis process was employed using ZnO/Polypyrrole during 60 min. The coupling of both treatment processes resulted in a total decolorization efficiency of 95.7 % and 99.8 % of TOC degradation (8.76 mg L⁻¹ TOC: 1.33 mg L⁻¹). Degradation product analysis was carried out by LC–MS/MS and a degradation pathway is proposed. The textile wastewater treatment proposed in this work is an attractive alternative and it is highly recommended to apply this system before the disposal of textile effluents in water bodies.
