shows SEM pictures of the anaerobic sludge (AS) sample
used as inoculum and sludge samples obtained from R1 and R2
at the end of the experiment. 300 pictures gave us a general overview
of the different sludges developed in the reactors. AS sample
presented a homogenous appearance. Baharuddin et al. [24] reported
a similar appearance analyzing a palm oil mill effluent
anaerobic sludge by SEM. On the contrary, anaerobically digested
matrixes for R1 and R2 presented a heterogenous structure with
different sized particles. Those particles may correspond to lignin
and cellulose structures. For instance, R2 picture (300) presented
a trachea, which is xylem cells with lignified walls typically
encountered in vegetable structure