STAGED AND NON-STAGED ANAEROBIC FILTERS - MICROBIAL ACTIVITY SEGREGATION, HYDRODYNAMIC BEHAVIOR AND PERFORMANCE

This work describes a comparative study of staged and non-staged anaer obic filters for treating a synthetic dairy waste under similar operat ing conditions. The effect of increasing the substrate concentration f rom 3 to 12 g COD dm(-3) at a constant hydraulic residence time (HRT) of 2 days was evaluated with respect to overall reactor performance, b iogas production, volatile fatty acids profiles along the height, meth anogenic and acidogenic activity distribution, and hydrodynamic behavi our. The potential maximum specific methanogenic activity against acet ate, hydrogen, propionate and butyrate and the lactose specific activi ty were determined for sludge sampled from three different points in e ach reactor, under two operating conditions (influent COD of 3 and 9 g COD dm-3). Although all trophic groups involved in the anaerobic proc ess were found throughout the reactors, it was possible to identify di fferent specific sludges at different heights in both reactors. Perfor mances of the two configurations were very similar under the operating conditions tested and the plug flow behaviour of the staged reactor w as clearly reduced when the influent concentration increased from 3 to 9 g COD dm(-3). (C) 1998 Society of Chemical Industry.