Author(s)

R Solera, L I Romero & D Sales

Abstract

This paper describes the determination of the microbial population, in terms of the number, biomass and composition, of single and two phase, laboratory-scale thermophilic (55°C) anaerobic reactors, under steady-state conditions. Epifluorescence microscopy with DAPI (4’,6-diamidine-2-phenylindole) as fluorochrome was used to determine the total number of microorganisms in the reactors, and autofluorescence microscopy for the number of the total methanogenic populations. The results obtained by the direct count methods were compared to the quantity of biomass contained in the system, determined by volatile suspended solids (VSS). The concentration of acidogenic bacteria was estimated by subtraction of the auto fluorescence results from those of the DAPI epifluorescence microscopy. 1 Introduction Complex kinetics, interactions and different steps of anaerobic digestion have been reported by numerous authors [I-61.There are considered to be two main groups of bacteria involved: acidogenic and methanogenic. The stability of the system depends on the viable bacterial groups involved in the process. Understanding the functioning of anaerobic reactors requires quantitative information on microbial numbers, biomass and activities of the bacterial groups

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