Case specific: Addressing co-digestion of wastewater sludge, cheese whey and cow manure: Kinetic modeling
Blaž Stres,
Artin Hatzikioseyian,
Pavlina Kousi,
Emmanouella Remoundaki,
Leon Deutsch,
Katarina Vogel Mikuš,
Gašper Rak,
Sabina Kolbl Repinc
Affiliations
Blaž Stres
Department of Environmental Civil Engineering / Faculty of Civil and Geodetic Engineering, University of Ljubljana, Jamova 2, SI-1000, Ljubljana, Slovenia; Department of Animal Science, Group for Microbiology and Microbial Biotechnology / Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia; National Institute of Chemistry, Department of Catalysis and Chemical Reaction Engineering, Hajdrihova ulica 19, 1000, Ljubljana, Slovenia
Artin Hatzikioseyian
Laboratory of Environmental Science and Engineering, School of Mining and Metallurgical Engineering, National Technical University of Athens (NTUA), Heroon Polytechniou 9, 15780, Zografou, Athens, Greece
Pavlina Kousi
Laboratory of Environmental Science and Engineering, School of Mining and Metallurgical Engineering, National Technical University of Athens (NTUA), Heroon Polytechniou 9, 15780, Zografou, Athens, Greece
Emmanouella Remoundaki
Laboratory of Environmental Science and Engineering, School of Mining and Metallurgical Engineering, National Technical University of Athens (NTUA), Heroon Polytechniou 9, 15780, Zografou, Athens, Greece
Leon Deutsch
Department of Animal Science, Group for Microbiology and Microbial Biotechnology / Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia; The NU B.V., J.H. Oortweg 21, 2333CH, Leiden, the Netherlands
Katarina Vogel Mikuš
Department of Biology, Chair of Botany and Plant Physiology / Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia
Gašper Rak
Department of Environmental Civil Engineering / Faculty of Civil and Geodetic Engineering, University of Ljubljana, Jamova 2, SI-1000, Ljubljana, Slovenia
Sabina Kolbl Repinc
Department of Environmental Civil Engineering / Faculty of Civil and Geodetic Engineering, University of Ljubljana, Jamova 2, SI-1000, Ljubljana, Slovenia; National Institute of Chemistry, Department of Catalysis and Chemical Reaction Engineering, Hajdrihova ulica 19, 1000, Ljubljana, Slovenia; Corresponding author.
The study investigated the methane production efficiency in a semi-continuous laboratory experiment with periodic feeding of wastewater sludge (WWS) as primary substrate and addition of whey (CW) and cow manure (CM). The short-term behavior of a real-scale anaerobic digester with WWS and the methane production improvements with different feeding mixtures of WWS, CW and CM were addressed. Gradual addition of CW to WWS (WWS:CW:CM = 70:20:0 to 70:55:0) increased the average daily methane production to 48.6 mL CH4/g COD/day and prevented reactor failure, but high VOA/TIC values showed that the reactors were conditionally stable evolution at an OLR of 8 g COD/L/day. Reactors that were additionally supplemented with CM (WWS:CW:CM = 70:55:10) achieved at least 12.3 % more methane than the reactors supplemented with WWS and CW alone. The highest methane production and process evolution in the reactors were achieved at OLRs between 7.5 and 8.7 g COD/L per day. After day 50, the addition of double the amount of CW further increased the methane production and VOA/TIC ratios. In this case, the OLR increased from 6.3 to 9.3 g COD/L/day. The concentration of propionic and acetic acid in all reactors increased above the recommended values and caused inhibition and instability. A strong positive Pearson correlation was found between the trace elements (Fe, Cu, Zn, Mn) detected by XRF. TE contributed to methane production, but to a lesser extent than TIC and NH4+-N. The simplified model successfully predicted methane production under a periodic feeding regime.
