Bacterial community dynamics during reduction of odorous compounds in aerated pig manure slurry

Aims:  To study the microbial community responsible for the reduction of the polluting load during aerobic digestion of pig slurry.
Methods and Results:  We analysed bacterial succession by nonculture-based methods and determined the physicochemical parameters and polluting substances during 6 days of aerobic digestion. The bacterial subpopulations evolved by aeration, predominantly Bacillus spp., degraded organic matter and vigorously consumed oxygen, as indicated by low oxidation–reduction potential (ORP). In this phase, the volatile fatty acid (VFA) levels drastically decreased, and VFAs were almost depleted on day 4. Simultaneously, the ammonia concentration decreased to its lowest level on day 4; thereafter, it increased until the end of the process. After the decrease in the total organic carbon content in the supernatant of the decomposed slurry, the ORP increased (～0 mV), and the microbial community showed an abundance of lineages belonging to the phylum Proteobacteria.
Conclusions:  Bacillus was the predominant member of the bacterial community driving the VFA-removal process. Their predominance was related to the presence of available carbon, including VFAs and changes in ORP.
Significance and Impact of the Study:  Information on the relationships among the involved microbes, polluting materials and physicochemical parameters will aid process design and retrofitting of the process.