| The biological microbial processes, which are considered as an environmental friendly technique, are widely used for the treatment of different kind of wastewaters. Anaerobic microbial treatment has added advantages over aerobic treatment methods since it can be used in the broad spectrum of wastewaters containing recalcitrant compounds and produce methane, which can replace the energy requirements involved in the treatment process.In this work, the series of experiments were carried out to investigate the use of one of the famous reactor, upflow anaerobic sludge blanket (UASB), for the treatment of textile wastewaters containing different types of dyes using anaerobic granular mixed cultures in mesophilic temperature. In first part, the single dye containing simulated textile wastewaters (STW) were prepared by using three different dyes (acid red 131(AR131), acid yellow 79 (AY79) and acid blue (AB204))having different chemical structures belong to different chemical groups and fed to laboratory scale UASB reactor. The colour and chemical oxygen demand (COD) removal efficiency and process stability were monitored and found that AR131 and AY79 were decolourized achieving over 95% colour removals owing to biodegradation. The observed colour removal of AB204 was merely due to the adsorption of dye on to microbial granules. The COD removal of AR131 and AY79 containing STW were 80% and 89%, respectively, at 300 mg/L dye concentration. Although AB204 showed a little inhibition over methanogenic consortia, over 93% COD removal was observed at 100 mg/L dye concentration. The alkalinity, accumulation of volatile fatty acids (VFA) and pH were in the desirable limits for anaerobic digestion process.The rate of biodegradation and inhibition caused to microorganisms over substrate removal by dyes were investigated in anaerobic batch reactors. This investigation confirmed the results obtained in the previous study that AR131 and AY79 could be biodegraded leading to decolourization while AB204 could not be biodegraded, however, considerable colour removal was observed due to adsorption. The AR131 biodegradation followed the first order kinetic model with respect to dye concentrations while AY79 biodegradation approximated to second order kinetic model. The substrate removal with AR131 and AY79 was followed the first order kinetic model at low dye concentrations whereas it tends to approach to second order kinetic model at increased dye concentrations. The substrate degradation in AB204 containing reactors can more suitably explained by second order kinetic model throughout all studied dye concentrations. The kinetic constants and VFA accumulation in reactors showed that substrate degradation could be inhibited by increased dye concentrations. The AB204 caused to create higher inhibitive effects to substrate removal over other dyes studied. To find out the combination effects of dyes on colour and COD removal in UASB reactor with different COD levels, the separate investigation was carried out using STW, which was prepared by mixing of three dyes in equal quantities, in different dye concentrations.No any negative and positive effects over colour and COD removals were found in this investigation. Over 85% colour removal was achieved at 300 mg/L dye concentration, regardless of the influent cosubstrate (COD) concentrations. The specific methanogenic activity (SMA) determined at the beginning and end of the experimental stages showed that it was not considerably affected by the mixture of dyes, however, SMA was... |
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