Thermal analysis and 454 pyrosequencing to evaluate the performance and mechanisms for deep stabilization and reduction of high-solid anaerobically digested sludge using biodrying process

• Biodrying was firstly used for post-treatment of anaerobically digested sludge (ADS).
• The contribution of the substrates to the heat was analyzed by thermal analysis.
• Microbial community succession was investigated by 454 pyrosequencing technique.
• The ADS mixed with the bulking agent for biodrying gained the desired performance.
• The biodegradation of bulking agent played a key role in the ADS biodrying process.

Biodrying was firstly used for post-treatment of anaerobically digested sludge (ADS) with wheat residues (WR) as bulking agents to improve its quality and reduce its amount. After 18 days of biodrying, water was removed at a rate of 664.4 g kg−1 initial water at the typical ratio of ADS/WR. A separate aerobic incubation test showed that 8.11–14.84% of volatile solid (VS) was degraded in the ADS. The degradation of C- and H-containing materials (e.g., carboxylic acid) accounted for oxygen consumption and VS loss. The WR also showed strong biodegradability, and contributed approximately 86.01% of biogenerated heat during the process. Thermal balance analysis showed that the produced heat was primarily consumed through water evaporation and conductive transfer. 454 pyrosequencing implied the obvious succession from the anaerobic to aerobic microorganisms during the process. Some dominant Firmicutes, such as Clostridium and Bacillales, seemed to relate with organic matter degradation of the substrates.

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