Microbiological evaluation of sludge during an improvement process applying the washing technique (selective pressure)

In this investigation, the microbial consortiums were evaluated by using characterization by trophic groups and related groups by their sensibility to oxygen, as well as the specific methanogenic activity (SMA) of an acclimated sludge, starting from an aerobium sludge corning from a residual water treatment plant. Later, the technique of improvement by washing was applicated to this sludge, getting inoculum for the starting of an anaerobic reactor of the kind UASB (treatment reactor). At the same time, a control reactor was operated, inoculated with acclimated sludge. Both reactors were operated during 120 days, using brown sugar as substrate, the experimental phase included dates up to 70 operation days, characterizing the sludge at the end of this period. The SMA was analysed using acetic and formic acids as substrates. The results showed activities between 0,45 and 1,39 g DQO-CH4/SSV -d. for both substrates. At the end of the experimental phase of the UASB reactor, the sulphate reducer bacteria from the acetate and the lactate were observed as predominant group, followed by the methanogenic hydrogenophilic bacteria. It is important to notice that, with the application of the sludge washing technique, all the tropic groups were increased, with the exception of the lactate fermentative bacteria