Bacterial populations and their roles in a pharmaceutical-waste anaerobic filter

The bacterial populations, their roles and distribution in an anaerobic filter treating a simulated pharmaceutical effluent containing a branched-chain fatty acid (BCFA) were studied. The BCFA degradation pathway and mechanisms were also investigated. The biofilm from the filter was enriched in serum bottle cultures using different BCFAs and fatty acids as the sole carbon source. The anaerobic biofilm was a consortium of (1) BCFA-degrading Syntrophomonas spp. which produced ethanoic acid and H2, (2) H2-utilizing Methanococcus spp. and (3) ethanoate-utilizing Methanothrix spp. Beta-oxidation was proposed as the acidogenic mechanism. The bacterial consortium could degrade BCFAs with tertiary carbon but not those with quaternary carbon. Branching at the alpha or beta position along the carbon chain interfered with the beta-oxidation mechanisms. Bacterial distribution in the filter was uneven, which was attributed to incomplete mixing.