Ultrasound-controlled Acidogenic Valorization of Wastewater for Biohydrogen and Volatile Fatty Acids Production: Microbial Community Profiling

Authors and Affiliation:
Omprakash Sarkar*, Leonidas Matsakas, Ulrika Rova, Paul Christakopoulos,

Biochemical Process Engineering, Division of Chemical Engineering, Department of Civil, Environmental, and Natural Resources Engineering, Luleå University of Technology, 971‑87 Luleå, Sweden, Email: [e-mail]

Abstract
The present study explored the influence of ultrasound on acidogenic fermentation of wastewater for the production of biohydrogen and volatile fatty acids. Eight sono-bioreactors underwent ultrasound (20 kHz: 2 and 4W), with an ultrasound duration ranging from 15 minutes to 30 days, and the formation of acidogenic metabolites. Long-term continuous ultrasonication enhanced biohydrogen and volatile fatty acid production. Specifically, ultrasonication at 4W for 30 days increased biohydrogen production by 3.05-fold compared to the control, corresponding to the hydrogen conversion efficiency of 58.4%; enhanced volatile fatty acid production by 2.49-fold; and increased acidification to 76.43%. The observed effect of ultrasound was linked to enrichment with hydrogen-producing acidogens such as Firmicutes, whose proportion increased from 61.9% (control) to 86.22% (4W, 30 days) and 97.53% (2W, 30 days), as well as inhibition of methanogenic activity. This result demonstrates the positive effect of ultrasound on the acidogenic conversion of wastewater to biohydrogen.