Potential of high-frequency ultrasounds to improve sludge anaerobic conversion and surfactants removal at different food/inoculum ratio

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Microbial diversity in innovative mesophilic/thermophilic temperature-phased anaerobic digestion of sludge

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Polyhydroxyalkanoates production by mixed microbial cultures in sequencing batch reactors operated under different feeding conditions

The production of polyhydroxyalkanoates (PHA) by mixed microbial cultures (MMC) requires a multistage process, whereby the microbial selection of PHA-storing microorganisms plays a key role on the overall performance. A strategy to favor the microbial selection consists in the alternance of excess (feast phase) and absence (famine phase) of the external carbon source. In this work, three runs of a lab-scale Sequencing Batch Reactor (SBR) operated under different working conditions for the establishment of the feast and famine (F/F) regime were analyzed. A fixed organic loading rate of 4.25 gCOD (Chemical Oxygen Demand)/L d, and a fixed cycle length of 12 h were applied to the SBR. The F/F regime consisted of fully aerobic dynamic (ADF) or aerobic/anoxic (AE/ANOX) conditions. Results showed an intracellular PHA content as high as 40 ± 2 (%, w/w) when ADF conditions were applied with the organic feeding solution made of acetate (85 % on COD basis) and propionic (15%) acids. The hydroxyvalerate content in the stored polymer increased (from 25 ± 1 to 41 ± 3, % w/w) by increasing the propionic fraction (up to 35%) in the feeding solution. The AE/ANOX condition resulted in a lower PHA-storing ability which warrants further investigations

Hygienization performances of innovative sludge treatment solutions to assure safe land spreading

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Food waste valorisation through anaerobic processes: thermal pretreatment or co-digestion?

Anaerobic digestion of Food Wastes (FW) was investigated in batch mesophilic tests. Scope of this work was to evaluate the efficiency of thermal pretreatment on the solubilisation degree of FW, alone or mixed with typical Mediterranean agro-wastes as olive husks (OH), and to evaluate the digestion enhancement potential of pretreatment and co-digestion strategy in terms of methane and hydrogen conversion rates of FW. Co-digestion was carried out by mixing FW and olive husks, untreated or thermal pre-treated. Thermal pretreatment was efficient in solubilising the organic material of FW (soluble COD increase up to 35%) and of the mixture FW and OH (up to +96%), in particular carbohydrates. After 30 days of digestion, an overall good anaerobic biodegradability of FW alone was observed, with methane yields in the range 0.350 – 0.592 Nm3/kgVSfed, overshadowing the effect of pretreatment, that affected positively only the hydrogenogenic phase. Moreover, also co-digestion with OH was a successful option for encouraging hydrogen conversion rate, which was found to be more than double compared to sole FW substrate digestion. Nevertheless, thermal pretreatment coupled with high sugars substrates as OH set the conditions for Maillard reactions occurrence, decreasing the conversion to methane