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9 Páginas.-- 4 Figuras.-- 1 Tabla, Facilitating the anaerobic degradation of long chain fatty acids (LCFA) is the key to unlock the energy potential of lipids-rich wastewater. In this study, the feasibility of psychrophilic anaerobic treatment of LCFA-containing dairy wastewater was assessed and compared to mesophilic anaerobic treatment. The results showed that psychrophilic treatment at 15 ℃ was feasible for LCFA-containing dairy wastewater, with high removal rates of soluble COD (>90%) and LCFA (∼100%). However, efficient long-term treatment required prior acclimation of the biomass to psychrophilic temperatures. The microbial community analysis revealed that putative syntrophic fatty acid bacteria and Methanocorpusculum played a crucial role in LCFA degradation during both mesophilic and psychrophilic treatments. Additionally, a fungal-bacterial biofilm was found to be important during the psychrophilic treatment. Overall, these findings demonstrate the potential of psychrophilic anaerobic treatment for industrial wastewaters and highlight the importance of understanding the microbial communities involved in the process., The authors thank Arrabawn Dairies and Dairygold Co-Operative Society for providing the inoculum; Sandra O’Connor, Alison Graham, and Andrew Bartle for assisting reactor operations and Dr Anna Christine Trego for scientific discussions. The authors acknowledge the facilities and scientific and technical assistance of the Centre for Microscopy & Imaging at University of Galway (www.imaging.universityofgalway.ie). This work was supported by the Enterprise Ireland Technology Centres Programme (TC/2014/0016) and Science Foundation Ireland (19/FFP/6746 and 16/RC/3889), as well as the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie grant agreement N° 101033411

More than 400 papers in the last 5 years have been published on FW into energy. Food waste complexity and composition affects anaerobic conversion. Scaling up of the AD process is fundamental to assess the real methane potential. Methanogenesis is often rate limiting step leading to pH drop and instability. Strategies to improve AD performances and stability are here reviewed.

High-frequency ultrasounds have recently gained interest as oxidative technique for sonochemical degradation of organic contaminants in water. In this study an innovative approach applying 200. kHz ultrasounds to improve both sludge anaerobic biodegradability and decontamination is proposed. Digestion tests were performed on batch reactors fed either with untreated or sonicated sludge, at different food/inoculum (F/I) ratio, in the range 0.3-0.9. First order kinetic highlighted a decreasing trend of the hydrolysis rate by increasing F/I, both for untreated and sonicated sludge. Positive effect of ultrasounds on specific biogas production was evident, but the conversion rate for pretreated sludge was strongly affected by F/I, and decreased by increasing F/I. Anionic surfactants anaerobic removal occurred in all tests, but the effect of ultrasounds was significant only at F/I. = 0.3. By pretreating sludge with high frequency ultrasounds, low F/I was the ideal ratio improving both sludge anaerobic digestion and decontamination. © 2014 Elsevier Ltd.

Olive husks, typical solid by-products from the olive oil industry, were selected to carry out anaerobic digestion tests. Before digestion, olive husks were subjected to ultrasonic or thermal pretreatments in order to release the organic matter into solution. Both sonication and thermal pretreatment allowed to solubilize the particulate matter with 22% and 72% increase in soluble organics of olive husks, respectively. Nevertheless, such pretreatments caused the release of unwanted molecules in solution, with the related risks of inhibition of the methanogenic process. Biochemical Methane Potential (BMP) tests on olive husks mixed with olive-mill wastewater and dairy wastewater, either pretreated or not, showed that ultrasound pretreatment resulted in 15% increase in volatile solids reduction and a 13% increase in biogas production, while after thermal pretreatment no benefits were observed.

In this work the potential of high frequency ultrasounds as pretreatment for sludge anaerobic digestion has been assessed. Irradiation with 200 kHz ultrasounds was efficient in disintegrating the floc structure increasing the available fraction of soluble organic matter (up to seven times at 25,000 kJ/kg TS). Batch anaerobic digestion tests were carried out on lab-scale reactors fed either with untreated or disintegrated sludge inoculated with anaerobic sludge, at different feed/inoculum ratio (F/I = 0.5 and 1). Degradation of particulate matter, biogas production and related microbial community composition (estimated by fluorescence in situ hybridization, FISH) were investigated. Sludge ultrasounds pretreatment led to an overall improvement of the digestion performances, with a maximum biogas gain of 40% at F/I = 0.5. FISH showed a key-role of Methanosarcina spp. in the main reactions of biogas synthesis.

The objective of this work was to maximize the digestibility of biological sludge to elucidate the feasibility of a new sludge management strategy to recover good quality sludge for agricultural use. The combined effects of organic loading rates (from 0.7 to 2.8 g VS L −1 d −1 ) and the degree of disintegration by anaerobic digestion of sonicated activated sludge were discussed, and the thermal and energetic balances were evaluated. Despite low sonication inputs, sludge digestion performance improved in terms of solids degradation and biogas production depending on the soluble organic load. The biogas production by sonicated sludge was higher (up to 30%) with respect to the control. Filterability improved during digestion of sonicated sludge at medium OLR due to a significant abatement of the fines. Thermal balances indicated that sonication may be a proper system to guarantee self-sustaining WAS mesophilic digestion. Nevertheless, thickening is a pre-requisite to achieve a positive energy balance.

Degradation kinetics of particulate matter in anaerobic digestion of secondary sludge, untreated and sonicated, was investigated by carrying out batch tests at different feed/inoculum ratio (F/I) (in the range of 0.1-4.0). Particulate COD degradation data were analysed using the four equations most widely utilized to model the hydrolysis process and the related kinetic parameters were evaluated. The increase of F/I results in a correspondent increase of the process rate up to one order of magnitude in the investigated interval for both untreated and sonicated sludge. The maximum step increase is observed in the range of 0.1-2.0 while for F/I varying from 2.0 to 4.0 only a modest enhancement of the process kinetics is detected. The effect of sonication on kinetics is not appreciable at low F/I, due to the low fraction of fed sludge and to the consequent strong substrate limitation, whereas at high F/I a slight increase is evidenced.