Biodegradability Assessment of Aniline under Methanogenic and Saline Conditions in Batch and AnMBR

Abstract

Aniline, a toxic aromatic amine present in certain wastewaters from the petroleum-, pharmaceutical- , and textile industry is regarded recalcitrant under strict anaerobic conditions. This study assessed the feasibility of methanogenic aniline biodegradation under saline (8 gNa+/L) conditions (1) by performing biodegradability batch assays using biomass from three different origins, and (2) by treating aniline-containing synthetic wastewater in a continuous anaerobic membrane bioreactor (AnMBR), seeded with granular sludge coming from an up-flow anaerobic sludge blanket (UASB) reactor treating petrochemical wastewater. In addition, the inhibitory effect of aniline and phenol on the aceticlastic methanogenesis, as well as the toxic effect on the integrity of cell membranes of the anaerobic biomass were assessed. Methanogenic biodegradation of aniline was not observed in the AnMBR, nor in the biodegradability assays. However, the results from the AnMBR operation fed with synthetic wastewater (20-200 mg aniline/L) demonstrated a 10-20% aniline removal, which was mainly attributed to volatilisation of aniline. Results from specific methanogenic activity (SMA)-inhibition tests demonstrated a half maximal inhibitory concentration (IC50) of aniline for the aceticlastic methanogenesis of 2.5 g aniline/L. The IC50 of phenol for the aceticlastic methanogenesis was 1.0 g phenol/L. The cell membrane integrity (CMI) of the anaerobic biomass was not significantly affected after 72 hours of exposure to 4 g aniline/L or 2 g phenol/L. This research constituted the first report demonstrating the application of an AnMBR with the aim to biodegrade aniline-containing synthetic wastewater under methanogenic saline conditions. The results of this research demonstrated that, after 200 days of AnMBR operation, the methanogenic enrichment culture was not able to biodegrade aniline.