Understanding Of Microbial Structure Research Articles

Simultaneous nitrogen and carbon removal in a packed A/O reactor: effect of C/N ratio on microbial community structure.

In this research, a novel packed anoxic/oxic moving bed biofilm reactor (MBBR) was established to achieve high-organic matter removal rates, despite the carbon/nitrogen (C/N) ratio of 2.7-5.1 in the influent. Simultaneous nitrification-denitrification (SND) was investigated under a long sludge retention time of 104days. The system exhibited excellent performance in pollutant removal, with chemical oxygen demand and total nitrogen (TN) enhanced to 93.6-97.4% and 34.4-60%, respectively. Under low C/N conditions, the nitrogen removal process of A/O MBBR system was mainly achieved by anaerobic denitrification. The increase of C/N ratio enhanced SND rate of the aerobic section, where dissolved oxygen was maintained at the range of 4-6mg/L, and resulted in higher TN removal efficiency. The microbial composition and structures were analyzed utilizing the MiSeq Illumina sequencing technique. High-throughput pyrosequencing results indicated that the dominant microorganisms were Proteobacteria and Bacteroidetes at the phylum level, which contributes to the removal of organics matters. In the aerobic section, abundances of Nitrospirae (1.12-29.33%), Burkholderiales (2.15-21.38%), and Sphingobacteriales (2.92-11.67%) rose with increasing C/N ratio in the influent, this proved that SND did occur in the aerobic zone. As the C/N ratio of influent increased, the SND phenomenon in the aerobic zone of the system is the main mechanism for greatly improving the removal rate of TN in the aerobic section. The C/N ratio in the aerobic zone is not required to be high to exhibit good TN removal performance. When C/NH4+ and C/TN in the aerobic zone were higher than 2.29 and 1.77, respectively, TN removal efficiency was higher than 60%, which means that carbon sources added to the reactor could be saved. This study would be vital for a better understanding of microbial structures within a packed A/O MBBR and the development of cost-efficient strategies for the treatment of low C/N wastewater.

Performance and microbial diversity of palm oil mill effluent microbial fuel cell

To evaluate the bioenergy generation and the microbial community structure from palm oil mill effluent using microbial fuel cell. Microbial fuel cells enriched with palm oil mill effluent (POME) were employed to harvest bioenergy from both artificial wastewater containing acetate and complex POME. The microbial fuel cell (MFC) showed maximum power density of 3004 mW m(-2) after continuous feeding with artificial wastewater containing acetate substrate. Subsequent replacement of the acetate substrate with complex substrate of POME recorded maximum power density of 622 mW m(-2). Based on 16S rDNA analyses, relatively higher abundance of Deltaproteobacteria (88.5%) was detected in the MFCs fed with acetate artificial wastewater as compared to POME. Meanwhile, members of Gammaproteobacteria, Epsilonproteobacteria and Betaproteobacteria codominated the microbial consortium of the MFC fed with POME with 21, 20 and 18.5% abundances, respectively. Enriched electrochemically active bacteria originated from POME demonstrated potential to generate bioenergy from both acetate and complex POME substrates. Further improvements including the development of MFC systems that are able to utilize both fermentative and nonfermentative substrates in POME are needed to maximize the bioenergy generation. A better understanding of microbial structure is critical for bioenergy generation from POME using MFC. Data obtained in this study improve our understanding of microbial community structure in conversion of POME to electricity.