Valorization of full-scale waste aerobic granular sludge for biogas production and the characteristics of the digestate

Agnieszka Cydzik-Kwiatkowska; Katarzyna Bernat; Magdalena Zielińska; Mariusz Zygmunt Gusiatin; Irena Wojnowska-Baryła; Dorota Kulikowska

doi:10.1016/j.chemosphere.2022.135167

Valorization of full-scale waste aerobic granular sludge for biogas production and the characteristics of the digestate

Chemosphere. 2022 Sep;303(Pt 2):135167. doi: 10.1016/j.chemosphere.2022.135167. Epub 2022 May 30.

Authors

Agnieszka Cydzik-Kwiatkowska¹, Katarzyna Bernat², Magdalena Zielińska¹, Mariusz Zygmunt Gusiatin¹, Irena Wojnowska-Baryła¹, Dorota Kulikowska¹

Affiliations

¹ University of Warmia and Mazury in Olsztyn, Faculty of Geoengineering, Department of Environmental Biotechnology, Sloneczna 45G, 10-709, Olsztyn, Poland.
² University of Warmia and Mazury in Olsztyn, Faculty of Geoengineering, Department of Environmental Biotechnology, Sloneczna 45G, 10-709, Olsztyn, Poland. Electronic address: bernat@uwm.edu.pl.

PMID: 35653865
DOI: 10.1016/j.chemosphere.2022.135167

Abstract

Despite the dynamic development of aerobic granular sludge (AGS) technology in wastewater treatment, there is limited data on how the different properties of AGS and activated sludge (AS) translate into differences in waste sludge management. Waste sludge generated in both AGS and AS technology is the biggest waste stream generated in wastewater treatment plants (WWTPs). This study aimed to assess biogas production from waste AGS from a full-scale system. Additionally, the properties of the digestate were investigated in terms of its management in line with the assumptions of a circular economy. Both aspects are important because the characteristics of AGS differ from those of AS. Its dense, extracellular-polymer-rich granule structure makes the susceptibility of AGS to anaerobic stabilization lower than that of AS. Given the advantages of AGS for sustainable wastewater treatment and its increasing popularity, waste AGS management will pose a serious challenge for WWTP operators. Therefore, AGS from a full-scale municipal WWTP was valorized for biogas production by increasing the accessibility of the organics in the sludge by homogenization or ultrasound pretreatment. Ultrasound pretreatment released about an order of magnitude more organics from the biomass than homogenization and significantly improved the production of methane-rich biogas (455 L/kg VS, about 66% of CH₄). The digestion time of pretreated AGS was reduced by 25% in comparison with that of untreated AGS making anaerobic digestion of AGS a feasible solution for sludge management. The AGS digestate was rich in Ca (77.0 g/kg TS), Mg (10.9 g/kg TS), N (35.1 g/kg TS) and P (32.4 g/kg TS), whereas its heavy metal levels and biochemical methane potential were low. AGS digestate is not only environmentally safe, but it can serve as a rich source of organics and elements essential for soil fertility and stability.

Keywords: AGS digestate Valorization; EPS; Homogenization; Lignocellulosic compounds; Methane production; Ultrasonic disintegration.

MeSH terms

Anaerobiosis
Biofuels / analysis
Bioreactors
Metals, Heavy*
Methane
Sewage* / chemistry
Waste Disposal, Fluid
Wastewater / chemistry

Substances

Biofuels
Metals, Heavy
Sewage
Waste Water
Methane