Fermentative and sulphate-reducing bacteria associated with treatment of an industrial dye effluent in an up-flow anaerobic fixed bed bioreactor

This work aims to study effects of increasing wastewater loading rates (WLRs) on the performance of an up-flow anaerobic fixed bed bioreactor and on the dynamics of the bacterial community of the sludge using polymerase chain reaction–single stranded conformation polymorphism (PCR–SSCP) methods. The analysis showed that WLRs variations influence the bacterial community structure and affect the bioreactor performance. For WLRs of 0.34–0.85 g l−1 d−1, the bioreactor showed a high performance and maintained highest colour and chemical oxygen demand (COD) removal yields with average values of 95% and 90%, respectively. The molecular fingerprint revealed a positive correlation between the diversity and the bioreactor performance. Increasing the WLR to 1.7 g l−1 d−1 affected significantly the bioreactor performance, the colour and COD removal efficiencies dropped to average values of 75% and 70%, respectively and bacterial and archaeal communities’ profiles changed.The gas production rates increased when WLR increased. The highest value of 0.68 l l−1 d−1 was obtained at an hydraulic retention time (HRT) of 1 day. The use of molecular and microbiological methods to recover bacterial populations involved in this anaerobic process showed that fermentative (Clostridium spp.) and sulphate-reducing bacteria (SRB) (Desulfovibrio spp.) were the prominent members of the bioreactor bacterial community.