Novel bioaugmentation strategy boosted with biochar to alleviate ammonia toxicity in continuous biomethanation

Abstract

<p>This study investigated for the first time if ammonia tolerant methanogenic consortia can be stored in gel (biogel) and used in a later time on-demand as bioaugmentation inocula, to efficiently relieve ammonia inhibition in continuous biomethanation systems. Moreover, wood biochar was assessed as a potential enhancer of the novel biogel bioaugmentation process. Three thermophilic (55 °C), continuous stirred-tank reactors (R<sub>Bgel</sub>, R<sub>Char</sub> and R<sub>Mix</sub>), operated at 4.5 g NH<sub>4</sub><sup>+</sup>-N L<sup>-1</sup> were exposed to biogel, biochar and mixture of biogel and biochar, respectively, while a fourth reactor (R<sub>Ctrl</sub>) was used as control. The results showed that the methane production yields of R<sub>Mix</sub>, R<sub>Char</sub> and R<sub>Bgel</sub> increased by 28.6%, 20.2% and 10.7%, respectively compared to R<sub>Ctrl</sub>. The highest methane yield was achieved by the synergistic interaction between biogel and biochar. Additionally, biogel stimulated a rapid recovery of Methanoculleus thermophilus sp. and syntrophic acetate oxidising bacteria populations.</p>