A unique autothermal thermophilic aerobic digestion process showing dynamic transition of physicochemical and bacterial characteristics from mesophilic to theromophilic phases.

This study investigated the physicochemical and bacterial community characteristic changes during the full-scale ATAD process operated for approximately 3 weeks in 2 different years. After initiating simultaneous aeration and mixing using an air-inducing circulator (aerator), the temperature autothermally increased rapidly in the first 1-2 d with exhaustive oxygen consumption, leading to a drastic decrease and gradual increase in oxidation-reduction potential in the first 2 d, which reached > 50°C in the middle 4-6 d and remained steady in the final phase. Volatile fatty acids were rapidly consumed and diminished in the first 2 d, whereas the ammonia nitrogen concentration was relatively stable during the process, despite a gradual pH increase to 9.3. Principal coordinate analysis of 16S rRNA gene amplicons using next-generation sequencing divided the bacterial community structures into distinct clusters corresponding to three phases, and they were similar in the final phase in both years despite different transitions in the middle phase. The predominant phyla (closest species, dominancy) in the initial, middle, and final phases were Proteobacteria (Arcobacter trophiarum, 19-43%; Acinetobacter towneri, 6.3-30%), Bacteroidetes (Moheibacter sediminis, 43-54%), and Firmicutes (Thermaerobacter composti, 11-28%, Heliorestis baculata, 2.1-16%), respectively. Two predominant OTUs in the final phase showed very low similarities to the closest species, indicating that the process ...
Source: Applied and Environmental Microbiology - Category: Microbiology Authors: Tags: Appl Environ Microbiol Source Type: research