B with the enrichment of the microflora by
the formation of self-immobilized (without carrier particle) granules
and the reactor bed was fluidized through the recirculation of
effluent. The reactor had stabile COD removal of 78% up to an OLR
of 8 kg COD m−3 d−1 at HRT of 1.3 d and CH4 production rate was
1.18 m3 CH4 m−3 d−1. The performance of the reactor deteriorated
when HRT was reduced to 0.75 d with an OLR of 14 kg COD m−3 d−1.
Lower HRT favored the growth of particular microorganisms and
loss of slow growing methanogens and it was reported that organic
loading was less effective on microbial diversity.