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J Environ Manage. 2018 Jan 15;206:472-481. doi: 10.1016/j.jenvman.2017.10.062. Epub 2017 Dec 7.

Correlation between system performance and bacterial composition under varied mixing intensity in thermophilic anaerobic digestion of food waste.

Author information

1
Department of Civil & Environmental Engineering, American University of Beirut, Lebanon; Department of Civil & Environmental Engineering, Notre Dame University - Louaize, Lebanon.
2
Department of Civil & Environmental Engineering, American University of Beirut, Lebanon.
3
Biological and Environmental Sciences and Engineering Division, Water Desalination and Reuse Center, King Abdullah University of Science and Technology, Thuwal 23955-6900, Saudi Arabia.
4
Department of Civil & Environmental Engineering, American University of Beirut, Lebanon. Electronic address: mfadel@aub.edu.lb.

Abstract

This study examines the stability and efficiency of thermophilic anaerobic digesters treating food waste under various mixing velocities (50-160 rpm). The results showed that high velocities (120 and 160 rpm) were harmful to the digestion process with 18-30% reduction in methane generation and 1.8 to 3.8 times increase in volatile fatty acids (VFA) concentrations, compared to mild mixing (50 and 80 rpm). Also, the removal rate of soluble COD dropped from 75 to 85% (at 50-80 rpm) to 20-59% (at 120-160 rpm). Similarly, interrupted mixing caused adverse impacts and led to near-failure conditions with excessive VFA accumulation (15.6 g l-1), negative removal rate of soluble COD and low methane generation (132 ml gVS-1). The best efficiency and stability were achieved under mild mixing (50 and 80 rpm). In particular, the 50 rpm stirring speed resulted in the highest methane generation (573 ml gVS-1). High-throughput sequencing of 16S rRNA genes revealed that the digesters were dominated by one bacterial genus (Petrotoga; phylym Thermotogae) at all mixing velocities except at 0 rpm, where the community was dominated by one bacterial genus (Anaerobaculum; phylum Synergistetes). The Petrotoga genus seems to have played a major role in the degradation of organic matter.

KEYWORDS:

16S rRNA gene sequencing; Food waste; Mixing; Thermophilic anaerobic digestion

PMID:
29107803
DOI:
10.1016/j.jenvman.2017.10.062
[Indexed for MEDLINE]

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