AZO DYE REDUCTION AND BIODEGRADABILITY MECHANISMS DURING AN ANAEROBIC PROCESS
Keywords:
Azo dye reduction, biodegradability kinetics, COD fractionAbstract
An anaerobic process for azo dye treatment had a high performance in organic removal with values reaching 85.51% and 90.29% for total chemical oxygen demand (TCOD) and soluble chemical oxygen demand, respectively. At the same time, the process was also capable of color removal. The absorption peak of anaerobic effluent appeared in wavelengths ranging between 195 nm to 246 nm which is identified as being in the aromatic amine regions. The Fourier transform infrared spectrum of anaerobic effluent represented the aromatic region. Therefore, azo dyes were degraded to aromatic compounds during the anaerobic process. The anaerobic influent contained a very high soluble inert chemical oxygen demand (SI) fraction with 60.68% of TCOD. However, the SI fraction was reduced by the anaerobic process at 93.46% removal. It is possible that the SI fraction was adsorbed on the microorganism surface and/or the dead cell composition. The maximum specific growth rate (μmax) and sludge yields were found in the anaerobic influent fed condition that had higher values than in the effluent fed condition. That caused a high organic concentration in the influent. However, the μmax of the heterotroph microorganism was still high at the anaerobic effluent fed condition. This enabled the aerobic treatment to be capable of aromatic amine removal at S0/X0 ratio 0.151-0.156.
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