Oxygen limitation in aerobic polyhydroxyalkanoates production from sewage sludge anaerobic fermentation liquids under low and medium organic loading rate

Marco Gottardo; Silvia Zanatta; Michele Modesti; Laura Lorini; Paolo Pavan; Francesco Valentino

doi:10.1016/j.chemosphere.2023.139468

Oxygen limitation in aerobic polyhydroxyalkanoates production from sewage sludge anaerobic fermentation liquids under low and medium organic loading rate

Chemosphere. 2023 Oct:338:139468. doi: 10.1016/j.chemosphere.2023.139468. Epub 2023 Jul 11.

Authors

Marco Gottardo¹, Silvia Zanatta², Michele Modesti³, Laura Lorini⁴, Paolo Pavan⁵, Francesco Valentino⁵

Affiliations

¹ Department of Environmental Sciences, Informatics and Statistics, Ca' Foscari University of Venice, Via Torino 155, 30170 Mestre-Venice, Italy. Electronic address: marco.gottardo@unive.it.
² Department of Industrial Engineering, University of Padova, Via Marzolo 9, 35131 Padua, Italy.
³ Department of Industrial Engineering, University of Padova, Via Marzolo 9, 35131 Padua, Italy; Centre for Mechanics of Biological Materials, Department of Industrial Engineering, University of Padova, Via Marzolo 9, 35131 Padua, Italy.
⁴ Department of Chemistry, La Sapienza University of Rome, P.le Aldo Moro 5, 00185 Rome, Italy.
⁵ Department of Environmental Sciences, Informatics and Statistics, Ca' Foscari University of Venice, Via Torino 155, 30170 Mestre-Venice, Italy.

PMID: 37442385
DOI: 10.1016/j.chemosphere.2023.139468

Abstract

The present study describes the microbial production of polyhydroxyalkanoates (PHA) from thermally pre-treated sewage sludge at pilot scale level, investigating for the first time the effect of the organic loading rate (OLR) under oxygen limitation on biomass storage properties and kinetics. Polymer characteristics have been also evaluated. The selection/enrichment of PHA-storing biomass was successfully achieved in a Sequencing Batch Reactor (SBR) under short hydraulic retention time (HRT; 2 days). Low OLR (2.05 g COD/L d) was ideal for the selection of an efficient PHA-producing consortium cultivated under limited oxygen availability. In the fed-batch accumulation conducted under high DO regime, such biomass was characterized by 51% of PHA content on cell dry weight, with a related storage yield (Y_P/S^batch) of 0.61 COD_PHA/COD_S. On the contrary, medium OLR (4.56 g COD/L d) was not technically feasible to sustain the required consortium's selection under low DO regime. The PHA produced by biomass cultivated under low DO regime was characterized higher thermal stability and crystalline domain compared to PHA traditionally produced under high DO regime. The mass balance assessment highlighted a global yield of 51 g PHA/kg VS (volatile solids of thickened sludge), which was 9% lower than yield obtained under high DO regime, in the face of a realistic reduction of the energy cost of the process.

Keywords: Oxygen limitation; PHA properties; Polyhydroxyalkanoates; Sewage sludge.

MeSH terms

Anaerobiosis
Biomass
Bioreactors
Fermentation
Oxygen
Polyhydroxyalkanoates*
Sewage*

Substances

Sewage
Polyhydroxyalkanoates
Oxygen