Influence of porosity and composition of supports on the methanogenic biofilm characteristics developed in a fixed bed anaerobic reactor

This paper reports on the influence of the material porosity on the anaerob ic biomass adhesion on four different inert matrices: polyurethane foam, PV C, refractory brick and special ceramic. The biofilm development was perfor med in a fixed-bed anaerobic reactor containing all the support materials a nd fed with a synthetic wastewater containing protein, lipids and carbohydr ates. The data obtained from microscopic analysis and kinetic assays indica ted that the material porosity has a crucial importance in the retention of the anaerobic biomass. The polyurethane foam particles and the special cer amic were found to present better retentive properties than the PVC and the refractory brick. The large specific surface area, directly related to mat erial porosity, is fundamental to provide a large amount of attached biomas s, However, different supports can provide specific conditions for the adhe rence of distinct microorganism types. The microbiological exams revealed a distinction in the support colonization. A predominance of methanogenic ar chaeas resembling Methanosaeta was observed both in the refractory brick an d the special ceramic. Methanosarcina-like microorganisms were predominant in the PVC and the polyurethane foam matrices.