Anaerobic color removal

Factors Effecting Anaerobic Color Removal Efficiency. 62... 

Acid Orange 7 Sludge originally collected from a pulp and paper wastewater treatment plants Color removal of 96% was achieved in the presence of liposomes that facilitated uptake of dyes by anaerobic biomass, leading to a fast decolorization. Amines such as sulfanilic acid and aniline were mineralized by inocula with high microbiological diversity, even with domestic effluent. Orthanilic and metanilic acids and 1-amino-2-naphtol were persistent under tested conditions [176]... 

Reactive Black 5 Activated sludge batch reactor Color removal occurred under anaerobic environment, while a slight attenuation was noticed under the aerobic condition [136]... 

Simulated textile Inclined Tubular A 78% color removal by anaerobic [190]... 

Anaerobic stages of SBR studies have been shown efficient with color removal rates mostly higher than 70% [3, 18-20], Meanwhile, COD removal efficiency of anaerobic phase of SBR was found to depend on dyestuff type, amount of initial COD concentration, anaerobic cycle time, etc. Nevertheless, there are also reports about no efficient COD removal in anaerobic cycle of SBR [21, 22],... 

Though cycle time plays an important role in the SBR for the decolorization process, not many reports are found in the literature. The long retention times are often applied in the anaerobic phase of the reactor studies, such as 18 and 21 h. In several studies, it was reported that there is a positive correlation between the anaerobic cycle time and the color removal [30, 31]. Indeed, in combined anaerobic-aerobic SBRs, since bacteria shifted from aerobic to anaerobic conditions, or vice versa, anaerobic azo reductase enzyme can be adversely affected by aerobic conditions, which is essential for aromatic amine removal, thereby resulting in insufficient color removal rate. To investigate the effect of cycle time on biodegradation of azo dyes, inar et al. [20] operated SBR in three different total cycle times (48-, 24- and 12-h), fed with a synthetic textile wastewater. The results indicated that with a... 

Since anaerobic azo dye reduction is an oxidation-reduction reaction, a liable electron donor is essential to achieve effective color removal rates. It is known that most of the bond reductions occurred during active bacterial growth [48], Therefore, anaerobic azo dye reduction is extremely depended on the type of primary electron donor. It was reported that ethanol, glucose, H2/CO2, and formate are effective electron donors contrarily, acetate and other volatile fatty acids are normally known as poor electron donors [42, 49, 50]. So far, because of the substrate itself or the microorganisms involved, with some primary substrates better color removal rates have been obtained, but with others no effective decolorization have been observed [31]. Electron donor concentration is also important to achieve... 

Previous studies suggested that enzymes responsible for the aromatic amine removal become more active when the color removal rates are high, which resulted in more aromatic amine production within the SBR. Beside this, adverse effect of anaerobic conditions on aerobic enzymes was also reported, and results indicated that their activities increased in aerobic stage and decreased in anaerobic stages due to the absence of dissolved oxygen [20, 69]. Viliesid and Lilly [70] found that the activity of catechol 1,2-dioxygenase is dependent on the dissolved oxygen... 

Though treatment of azo dye-containing wastewaters needs combined anaerobic-aerobic phases, microorganisms are subjected to continually alternating anaerobic and aerobic conditions. Thus, it is presumable that anaerobic enzymes involved in the azo dye reduction may be adversely affected by aerobic conditions, as well as aerobic enzymes involved in the aromatic amine mineralization may be adversely affected by anaerobic conditions. Since little is known about the regulations of the enzymes involved in complete biodegradation of colored wastewaters, this approach seems to need advanced investigation to improve color removal and aromatic amine mineralization. 

Luangdilok W, Paswad T (2000) Effect of chemical structures of reactive dyes on color removal by an anaerobic-aerobic process. Water Sci Technol 42(34) 377-382... 

Anaerobic Aerobic Wastewater characteristics Color removal Aromatic amines References... 

Depending on dye concentration and HRT. All dyes >80% decolorization at high HRT Complete removal of the metabolites from anaerobic treatment, probably mostly due to autoxidation Presumably no removal of dye metabolites hardly any DOC removal and only slight decrease of toxicity Data refer to fully hydrolyzed RBk5, less color removal for partially hydrolyzed RBk5... 

Several studies have reported a positive relationship between the hydraulic retention time of the anaerobic stage and the color removal efficiency [95],... 

Under aerobic conditions Reactive Black 5 maximum total color removal was 92%. The authors attributed initial rapid loss primarily to adsorption to sludge biomass. Hydrolyzed Reactive Black 5 showed little color removal, adsorption, or degradation. Navy 106 also exhibited a loss of color over time. The initial rapid loss was likely adsorption to sludge, but the subsequent decrease may have been due either to anaerobic transformation of dyes in microanaerobic zones of the aerobic system, or to aerobic microbial degradation. 

Shewanella decolorationis S12 Fast Acid Red GR After 4 h incubation, more than 90% of the color was removed under anaerobic conditions while 12.8 and 33.7% decolorizing rates were observed under aerobic and microaerophilic conditions [84]... 

Shewanella J18 143 Remazol Black B, Acid Orange 7 Anaerobic cultures of Shewanella strain J18 143 rapidly removed color from the azo dye Remazol Black B in the growth medium to produce an absorbance at 597 nm of less than 1 in under 40 min [86]... 

Industrial wastewater containing precursors and synthesis products of 15 sulfonated azo dyes Anaerobic baffled reactor containing mixed sulfate reducing bacteria, and methanogens In an anaerobic baffled reactor, almost a complete removal of color was observed in the reactor within 100 days of operation [182]... 

Kapdan IK, Alparslan S (2005) Application of anaerobic-aerobic sequential treatment system to real textile wastewater for color and COD removal. Enz Microbial Technol 36 273-279... 

Using standard anaerobic techniques, a 100-mL Schlenk flask equipped with a stir bar is charged with 50 mL dry benzene and 2 mL (1.96 g, 0.0172 mol) distilled free amine. If crude daco is used, the product will be less pure and of lower yields. The mixture is warmed to 50-60°C under N2. Three 1-mL (0.05 mol) portions of ethylene sulfide are added, allowing 20 min reaction time between additions. The mixture is then heated under N2 for 1 h. Complete reaction is indicated by the formation of a finely divided white precipitate after the final addition. The reaction mixture is filtered anaerobically through a bed of celite in a glass-fritted funnel. Solvent is removed under vacuum while continuing to heat at 50-60°C. The H2-bme-daco is obtained as a colorless to pale yellow oil. Irrespective of color, this material is of suitable quality to be converted to the nickel complex. If distilled daco is used, the product is quite pure. Attempts at vacuum distillation (bpo.immHg = 135°C) resulted in partial decomposition. Yield 3.21 g (80%). 

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