Hydrodynamic cavitation pre-treatment of urban waste: Integration with acidogenic fermentation, PHAs synthesis and anaerobic digestion processes

• Published in: Chemosphere (Oxford) Vol. 301; p. 134624
• Main Authors: Lanfranchi, A., Tassinato, G., Valentino, F., Martinez, G.A., Jones, E., Gioia, C., Bertin, L., Cavinato, C.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.08.2022
• Subjects: Cavitation; Organic waste; PHAs; Sludge; VFAs; OFMSW; Organic waste; VW; F/M; HRT; FR; TVS; FW; tCOD; OLR; pCOD; GC; OL; HPLC; OAs; SS; AC; AD; BMP; VFAs; Sludge; Cavitation; PHAs; sCOD; WWTP; TKN; HC; TS
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2022.134624

Urban waste can be valorized within a biorefinery approach, producing platform chemicals, biopolymers and energy. In this framework, hydrodynamic cavitation (HC) is a promising pre-treatment for improving biodegradability due to its high effectiveness and low cost. This paper deals with the effect of HC pre-treatment on the acidogenic co-fermentation process of thickened sewage sludge from a WWTP and seasonal vegetable waste from a wholesale market. Specifically, HC was assessed by testing two sets of parameters (i.e., treatment time of 30 and 50 min; vacuum pressure 1.4 and 2.0 bar; applied power 8 and 17 kW) to determine its effectiveness as a pre-treatment of the mixture. The highest increase in sCOD (+83%) and VFAs (from 1.93 to 17.29 gCODVFA L−1) was gained after 50 min of cavitation. Fermentations were conducted with not cavitated and cavitated mixtures at 37 °C on 4 L reactors in batch mode, then switched to semi-continuous with OLR of 8 kgTVS m-3 d−1 and HRT of 5–6.6 d. Good VFAs concentrations (12.94–18.27 gCODVFA L−1) and yields (0.44–0.53 gCODVFA gVS(0)−1) were obtained, which could be enhanced by pre-treatment optimization and pH control. The organic acid rich broth obtained was then assessed as a substrate for PHAs storage by C. necator. It yielded 0.37 g g−1 of polyhydroxybutyrate, such biopolymer resulted to have analogous physicochemical characteristics of commercial equivalent. The only generated side-stream would be the solid-rich fraction of the fermented effluent, which valorization was assessed through BMP tests, showing a higher SGP of 0.42 Nm3 kgTVS−1 for the cavitated. [Display omitted] •A mixture of sewage sludge and vegetable waste was pre-treated with cavitation.•Cavitation pre-treatment raised the VFAs content of the mixture by nine folds.•Cavitation-fermentation derived broth resulted performant for PHAs production.•Cavitation raised the SGP of the solid-rich fraction of the fermented broth.