Wastewater decolorization

Chen BY, Chen SY, Chang JS (2005) Immobilized cell fixed-bed bioreactor for wastewater decolorization. Process Biochem 40 3434-3440... 

Takaoka S. Electrode configuration in dyeing wastewater decolorization by electrolysis. Japan Patent JP 08267073 A2, 1996. 

Model Bleach Plant Wastewater Decolorization using Fe-TAML/HiOi... 

Although it has been reported (138) that decolorization of wastewater containing reactive azo dyes with sodium hydrosulfite is possible only to a limited extent, others have demonstrated good reduction (decolorization). For example, using zinc hydrosulfite for the decolorization of dyed paper stock (139) resulted in color reduction of 98% for azo direct dyes (139). A Japanese patent (140) describes reducing an azo reactive dye such as Reactive Yellow 3 with sodium hydrosulfite into its respective aromatic amines which ate more readily adsorbable on carbon than the dye itself. This report has been confirmed with azo acid, direct, and reactive dyes (22). 

The following are some of the typical industrial applications for liquid-phase carbon adsorption. Generally liquid-phase carbon adsorbents are used to decolorize or purify liquids, solutions, and liquefiable materials such as waxes. Specific industrial applications include the decolorization of sugar syrups the removal of sulfurous, phenolic, and hydrocarbon contaminants from wastewater the purification of various aqueous solutions of acids, alkalies, amines, glycols, salts, gelatin, vinegar, fruit juices, pectin, glycerol, and alcoholic spirits dechlorination the removal of... 

Diatomaceous earths may resemble the forms of the charcoals. The earths are primarily filter aids, precoats or adsorbents, the hmction of the filter medium being secondary. Fuller s earth and clays are used for decoloring applications diatomaceous earths are used for clarification. The adsorbtivity of diatomaceous earth works in the same fashion as activated carbon, but isotherms (affinity) for many chemical species like the hydrocarbons is weaker. For this reason, activated charcoal or carbon is much preferred in wastewater treatment applications expecially when taste and odor issues are priorities. 

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]... 

Acid Orange 7 and many other dyes Bacterial consortium TJ-1 consisting of Aeromonas caviae, Proteus mirabilis, and Rhodococcus globerulus Decolorization of Acid Orange 7 was significantly higher with the consortium as compared to the individual strains. More than 90% decolorization could be achieved even at 200 mg L 1 within 16 h. The consortium also decolorized 15 other azo dyes individually as well as a simulated wastewater containing a mixture of all the 16 azo dyes [58]... 

Direct Fast Scarlet 4BS Consortium of a white-rot fungus and Pseudomonas 1-10 isolated from wastewater The microbial consortium showed a significant improvement in dye decolorization rates under either static or shaking culture. The 4BS was mineralized completely [89]... 

Dye-containing wastewater and Reactive Red 22 Mixed cultures of Pseudomonas luteola and E. coli DH5a Presence of E. coli DH5a increased the decolorization efficiency of P. luteola even though DH5a was an inefficient decolorizer in this consortium [42, 95]... 

Textile wastewater Activated sludge and Over 90% decolorization was [17]... 

Xu M, Guo J, Cen Y et al (2005) Shewanella decolorationis sp. nov., a dye-decolorizing bacterium isolated from activated sludge of a wastewater treatment plant. Int J Syst Evol Microbiol 55 363-368... 

Adedayo O, Javadpour S, Taylor C, Anderson WA, Moo-Young M (2004) Decolorization and detoxification of methyl red by aerobic bacteria from a wastewater treatment plant. World J Microbiol Biotechnol 20 545-550... 

Sandhya S, Swaminathan K, Swaminathan T (2007) Decolorization and treatment of recalcitrant dye industry wastewater containing azo dyes. In Trivedi PC (ed) Industrial pollution and its management. Aavishkar, India, pp 148-171... 

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... 

Nitrate is normally found in textile processing wastewaters and generally comes from salts such as sodium nitrate, which is included in the dye baths for the improvement of dye fixation to the textile fibers. Nitrate concentrations used in textile processing can reach 40-100 g/L [35], The importance of nitrate in anaerobic phase of SBR is that nitrate can compete with the azo dye for reducing the equivalents formed, resulting in decreasing decolorization [2, 5, 7, 35, 36], Wuhrmann et al. [5] reported that azo dye cannot be decolorized until denitrification ends up. 

Azo dye-containing wastewaters seems to be one of the most polluted wastewaters, which require efficient decolorization and subsequent aromatic amine metabolism. On the basis of the available literature, it can be concluded that anaerobic-aerobic SBR operations are quite convenient for the complete biodegradation of both azo dyes and their breakdown products. Nevertheless, like the other methods used for biological treatment, SBRs treating colored wastewaters have some limitations. Presence of forceful alternative electron acceptors such as nitrate and oxygen, availability of an electron donor, microorganisms, and cycle times of anaerobic and aerobic reaction phases can be evaluated as quite significant. 

Kapdan IK, Tekol M, Sengul F (2003) Decolorization of simulated textile wastewater in an anaerobic-aerobic sequential treatment system. Process Biochem 38(7) 1031-1037... 

Anaerobic decolorization of azo dyes was started back in the 1970s. Reticulated sintered glass was used as immobilization of anaerobic bacteria for the decolorization of wastewater and transformation of the azo dye to degradable products [58], Full decolorization was achieved in less than 4 h HRT, and in addition to it, methane as biogas was also produced. 

Georgiou D, Hatiras J, Aivasidis A (2005) Microbial immobilization in a two stage fixed bed reactor pilot plant for onsite anaerobic decolorization of textile wastewater. Enzyme Microb Technol 37 597-605... 

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