Characterisation by image analysis of anaerobic sludge under shock conditions

In the present work the characterisation by image analysis of anaerobic bio mass under organic and hydraulic shocks was performed. The digester was fed with a synthetic substrate, containing 50% oleic acid (as COD). Organic an d hydraulic shocks were performed by stepwise increasing the substrate conc entration or by reducing the hydraulic retention time. In both cases the or ganic loading rate changed from 6 to 30 kg COD/m(3).d. Hydraulic shock indu ced a fast decrease in the number of free filaments and in total filament l ength, which attained a minimum value 51 hours after beginning the shock. T he initial filament values were not recovered 340 hours after the hydraulic shock. In the organic shock, the minimum values of these parameters were d etected 200 hours after beginning the shock and initial values were recover ed 840 hours after. During the hydraulic shock the methanogenic acetoclasti c activity was directly correlated to the number and length of free filamen ts. This result suggests that filaments are predominantly acetoclastic bact eria. probably Methanosaeta.