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.

Certain industrial wastewaters have posed a big challenge to biological water treatment systems because of their high toxic organic compounds concentration (e.g. phenol) and high salinity. The maximum biomass specific phenol bioconversion rate (PhCR) of a mesophilic (35 °C) anaerobic membrane bioreactor (AnMBR) under high sodium concentration [18.6 g Na+/L] condition was studied by an increase in the biomass specific phenol loading rate (PhLR) through hydraulic retention time (HRT) decrease. The maximum PhCR achieved in our research was 73 mg Ph-COD/gVSS-COD.d, with acetate as co-substrate [2g AC-COD/L]. This result was lower than that reported by the previous study of Bioxtreme (193 mg Ph-COD/gVSS-COD.d) at lower sodium concentration [8.0 g Na+/L].
On the other hand, a simplified ADM1 model was used to model the conversion of acetate to methane in batch experiments, among which, the inhibition of substrate (acetate or phenol) on microbial growth rate was described by Haldane equation. The kinetic parameters for acetate degradation were Ks,AC=300 mg COD/L, KI,AC=821mg COD/L, km,AC I =0.246 mg COD/mg COD.h without phenol addition and Ks,AC=300 mg COD/L, KI,AC=806 mg COD/L, km,AC I=0.236 mg COD/mgCOD.h with the addition of 714 mg Ph-COD/L (300 mg Ph/L) at sodium concentration of 18.6 g Na+/L, while it was Ks,AC=6.7 10-9 mg COD/L, KI,AC=5670 mg COD/L, km,AC I=0.043 mg COD/mgCOD.h at lower sodium concentration [8.0 g Na+/L] without phenol addition.
The kinetic parameters estimated for the batch experiments were applied in a mathematical model describing a dynamic experiment carried out in the AnMBR1 and validated with different HRTs. In the model, the conversion from phenol to acetate was considered and the kinetic parameters estimated for phenol degradation were Ks,Ph=20 mg COD/L, KI,Ph=300 mg COD/L, km,Ph I=0.008 mg COD/mgCOD.h. It was proved that the simplified ADM1 model could well predict the phenol and acetate concentrations in the reactor at different PhLRs.
This research has provided an experimental and modeling approach for the maximum PhCR determination and could contribute to the understanding of the inhibition effect of sodium and phenol on PhCR in the treatment process of saline phenolic wastewater.

This study is part of a project titled: “Phenolic compounds degradation in AnMBR under mesophilic and thermophilic operation: BioXtreme-following up”.
Phenol is a toxic contaminant found widely in industrial effluents. It is toxic to humans and animals even at very low concentrations. Anaerobic digestion uses phenol as a carbon source and then to degrade it to non-toxic products for lower costs. Industrial effluents are also likely to have high concentrations of salinity which causes inhibition at high concentrations. Anaerobic membrane bioreactors are an attractive method as it enables biomass retention for biomass. The aim of this study is to understand the effect of Na+ concentration in a batch phenol degradation by phenol adapted mesophilic AnMBR biomass. NaCl concentration ranging from 0-90 g/L were tested on adapted AnMBR biomass. COD, phenol degradation, particle size distribution and methane production of adapted AnMBR biomass were analysed. The results from the batch test were used to model kinetic parameters. The biomass was acclimatized to 30 g/L of NaCl in AnMBR. Phenol removal of 98% was observed at 30 g/LNaCl and it decreased further with elevated salinity. Similarly, biogas production was also highest for 30g/L NaCl and decreased further with higher NaCl concentration. The highest value for SMA of 0.10 ± 0 gCOD-CH4.gVSS-1 d -1 was observed for 30g/L. However, the data did not indicate a specific trend with increasing salinity and showed high variability. The data showed poor fit to both Haldane and Monod growth model as these models were used for substrate inhibition. Modelling with modified Gompertz equation also failed to yield any conclusive results.

Certain industrial wastewaters have posed a challenge to water treatment systems because of their composition. The bitumen from the reclaimed asphalt process is heated by the BAM Infra Asfalt and produces fumes, which are usually sent to the air filters and then out through the chimney. To recover the heat lost through the fume, it is condensed. The bitumen fume condensate contains aromatic hydrocarbons of petroleum origin and this poses a threat to health and the environment. The removal of these compounds by anaerobic biodegradation was assessed with a mesophilic anaerobic membrane bioreactor (AnMBR). The bitumen condensate contained over 800 compounds, out of which some were p-cresol, o-cresol and 2-napthalenemethanol. The inhibition to the methanogenic activity and toxicity to the biomass of this wastewater on three different inocula were studied under batch-test conditions. A phenol-degrading sludge was less inhibited (IC₅₀= 870 mg COD_bitumen/L) and more resistant to the toxicity than granular sludge from a petrochemical wastewater treatment plant (IC₅₀= 187 mg COD_bitumen/L) and a municipal sludge (sludge from a municipal wastewater treatment plant, IC₅₀= 127 mg COD_bitumen/L). In continuous operation, the bitumen condensate was degraded efficiently with 89%±12% (S.D)COD removal from the influent of the AnMBR. Maximum organic conversion rate of the bitumen condensate was 26.0 mg COD/g VSS.d. This research demonstrated the efficiency of AnMBR technology to degrade bitumen condensate. Further research must be done to improve the organic conversion rate and optimise the technology for large scale implementation.