دانلود رایگان مقاله آنالیز جامعه میکروبی گرانول بی هوازی در فنل تخریبی UASB

Abstract

The objective of this study was to investigate microbial communities in a continuous anaerobic phenol-degrading system using a next generation sequencing tool. The anaerobic granules adapted to phenol were first obtained by repeated-batch operation, which were then inoculated in an up-flow anaerobic sludge blanket reactor (UASB) operated at various organic loading rates (OLRs). Lag periods for both phenol degradation and CH4 production decreased as batch fermentation was repeated, indicating a progressive adaptation of the granules to phenol. In the UASB operation, the highest OLR handled was 6 kg COD/m3/d, in which the attained biogas production rate, phenol degradation, and CH4 contents were 2.1 m3/m3/d, 79.0%, and 75.3%, respectively. Syntrophorhabdus and Clostridium were found to be the dominant bacteria, whose sum occupied around 60% of total bacterial sequences. In particular, there was a significant increase in Syntrophorhabdus (39.2% of total bacterial sequences), known to degrade phenol to benzoate and subsequently to acetate and hydrogen in syntrophic association with a hydrogenotrophic methanogen. In terms of archaea, Methanosaeta (42.1% of total archaeal sequences), and Methanobacterium (24.5% of total archaeal sequences) became dominant as operation continued, which were negligible in the inoculum.

4. Conclusions

The progressive adaptation of granules was observed as phenol addition was repeated. At an OLR of 6 kg COD/m3/d, the performance of UASB was 2.1 m3 biogas/m3/d with 79% phenol degradation. At higher OLR, a phenol degradation efficiency dropped down to 40%, and a considerable amount of benzoate and acetate were detected in the effluent. The NGS results showed that Syntrophorhabdus, which is known to degrade phenol to benzoate and subsequently to acetate and hydrogen, was the main genus, accounting for 39.2% of the total bacterial sequences. The existence of acetoclastic methanogens was negligible in the inoculum, but it significantly increased to 42.1% (mainly Methanosaeta) of the total archaeal sequences. The main hydrogenotrophic methanogen was found to be Methanobacterium, occupying 24.5% of the total archaeal sequences.