ISOLATION AND IDENTIFICATION OF DOMINANT MICROORGANISMS IN ACTIVATED SLUDGE OF ABS EFFLUENT TREATMENT PLANT AND EVALUATION OF THEIR POTENTIAL FOR ACRYLONITRILE BIODEGRADATION

Acrylonitrile is widely used as the main raw material in the production of Acrylonitrile butadiene styrene (ABS). It can be considered as pollutant in ABS process effluent. Since the importance of biological systems to treatment the ABS effluents, this study aimed to identify the dominant microorganisms in biological wastewater treatment plant and to evaluate the potential for biodegradation of acrylonitrile.
Microbial populations in the biological unit were examined during 8 runs of sampling. The culture media including PCA, R2A, Sabouraud Dextrose Agar and Rose Bengal were used for bacterial and fungal culturing. Biochemical tests were used to identify bacterial genus and the culturing was used for fungal identification. The potential of acrylonitrile biodegradation was assessed through the measurement of the concentration of acrylonitrile, acrylamide and acrylic acid.
A total of 20 bacteria isolated, 7 genera including Neisseria, Moraxella, Alcaligenes, Bacillus, Pseudomonas, Shigella and Staphylococcus were identified as dominant. The fungal genera including Aspergillus, Cladosporium, Trichoderma, and Penicillium were also identified as dominant. From a total of 71% acrylonitrile in biological unit. Acrylic acid concentration as breakdown product of acrylonitrile in influent and effluent were 39 and 94 mg/l, respectively. However, acrylamide concentration as a byproduct was almost constant.
Dominant bacterium and fungi are identified as Pseudomonas and Aspergillus, respectively. Among the isolated bacteria, the genera of Alcaligenes, Pseudomonas, Bacillus and Moraxella belong to heterotrophic nitrifying bacteria that have the ability to breakdown nitrogen compounds such as acrylonitrile.