Decolorization and azo dye degradation by anaerobic/aerobic sequential process
ABSTRACT This study investigates the anaerobic treatability of Reactive Black 5 in an anaerobic/aerobic sequential process. Laboratory scale upflow anaerobic sludge blanket (UASB) reactor/completely stirred tank reactors (CSTR) were operated at different organic loadings and hydraulic retention times (HRT). The effects of shock organic loading on the chemical oxygen demand (COD), color removal, and methane gas production efficiencies were investigated in UASB reactor. The effects of both sludge retention time (SRT) and food to mass (F/M) ratio on the color and COD removal efficiencies were also investigated in aerobic reactor. The reactive dye used in this study contains the groups NN, SO3, SO and is in use in the some textile industries in Turkey. The studies were carried out in continuous mode and the effluent of the UASB reactor was used as feed for the CSTR reactor. COD removal efficiencies decreased from 56 to 27% with increases in COD loadings from 5 to 25 kg COD m−3 per day in the anaerobic UASB reactor. The color removals were 92 and 87%, respectively, for aforementioned organic loadings. The methane percentages were found to be 76 and 60% at organic loading rates of 2.49 and 14.8 kg COD m−3 per day, respectively, in UASB reactor. COD removal efficiencies of 28, 42, and 90% were obtained at SRTs of 1.7, 5.7 and 11 days in the aerobic CSTR reactor. Optimum sludge retention time was 11 days in aerobic reactor. A total of 67 and 28% COD removal efficiencies were obtained at F/M ratios varying between 0.05 and 0.17 and between 0.30 and 1.4 kg COD kg−1 MLSS per day. A 90–95% color and 40–60% COD removal efficiencies were obtained depending on the applied organic loadings in the UASB reactor. The remaining COD was removed with a treatment efficiency of 85–90% in the aerobic CSTR reactor.
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ABSTRACT: The degradation of C.I. Direct red 80, a polyazo dye, was investigated using Bacillus firmus immobilized by entrapment in tubular polymeric gel. This bacterial strain was able to completely decolorize 50 mg/L of C.I. Direct red 80 under anoxic conditions within 12 h and also degrade the reaction intermediates (aromatic amines) during the subsequent 12 h under aerobic conditions. The tubular gel harboring the immobilized cells consisted of anoxic and aerobic regions integrated in a single unit which was ideal for azo dye degradation studies. Results obtained show that effective dye decolorization (97.8%), chemical oxygen demand (COD) reduction (91.7%) and total aromatic amines removal were obtained in 15 h with the immobilized bacterial cell system whereas for the free cells, a hydraulic residence time of 24 h was required for an equivalent performance in a sequential anoxic and aerobic process. Repeated-batch experiments indicate the immobilized cells could decolorize C.I. Direct red 80 and reduce medium COD in five successive batch runs with enhanced activity obtained after each consecutive run, thus suggesting its stability and potential for repeated use in wastewater treatment. UV-visible spectrophotometry and HPLC analysis were used to confirm the partial mineralization of the dye. Data from this study could be used as a reference for the development of effective industrial scale biotechnological process for the removal of dyes and their metabolites in textile wastewater.3 Biotech. 03/2012; 2(1):67-78.
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ABSTRACT: Combinations of sequential anaerobic and aerobic process enhance the treatment of textile wastewater. The aim of this study was to investigate the treatment of diazo dye Reactive Black 5 (RB5)-containing wastewater using granular activated carbon (GAC)-biofilm sequencing batch reactor (SBR) as an integration of aerobic and anaerobic process in a single reactor. The GAC-biofilm SBR system demonstrated higher removal of COD, RB5 and aromatic amines. It was observed that the RB5 removal efficiency improved as the concentration of co-substrate in the influent increased. The alternative aeration introduced into the bioreactor enhanced mineralization of aromatic amines. Degradation of RB5 and co-substrate followed second-order kinetic and the constant (k 2) values for COD and RB5 decreased from 0.002 to 0.001 and 0.004 to 0.001 l/mg h, respectively, as the RB5 concentration increased from 100 to 200 mg/l in the GAC-biofilm SBR system.Water Air and Soil Pollution 03/2012; 223(4):1615-1623. · 1.75 Impact Factor
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ABSTRACT: Azo dyes represent the largest class of industrial colorants. These are no longer used only for the coloration of textiles, plastics, paints, inks, and lacquers, but rather serve as key components in high-tech applications such as optical data storage, reprographics, display devices, dye-sensitized solar cells, energy transfer cascades, light-emitting diodes, laser welding processes, or heat management systems. Azo dyes are also of growing importance in the medical and biomedical fields. In most of these applications, the color is largely irrelevant and it is the ability of the colorants to absorb visible electromagnetic radiation with high efficiency, or other functional property, that is exploited. With the growing awareness and environmental concerns, it is imperative that the hierarchy of reduce, reuse, and degrade be adopted and measures be taken to remove color from the industrial discharge. The present review (a) embodies a comparison of the present decolorization/degradation techniques for water-soluble and insoluble dyes, (b) describes their advantages and limitations, (c) discusses various mechanisms, and (d) focuses on the present literature on microbial decolorization of textile dyes specifically by using bacteria, fungus, yeast, and algae. Also, for the first time an attempt has been made to comprehensively compile chemical and biological decolorization/degradation of disperse dyes. The research on the decolorization of textile dyes has mainly been focused on water-soluble dyes, while decolorization of disperse dyes that are water insoluble have received only scant attention and constitutes a topical area of concern as these dyes persist for a longer duration in textile effluents. Given the limitations (vide infra) of the chemical treatment methods, decolorization using biological means is an interesting option.Critical Reviews in Environmental Science and Technology 05/2011; 41(9):807-878. · 3.38 Impact Factor