Mesophilic and thermophilic anaerobic co-digestion of waste activated sludge and source sorted biowaste in pilot- and full-scale reactors

The paper presents the results of a pilot- and full-scale experimental campaign on the anaerobic co-digestion of waste activated sludge and biowaste both in mesophilic and thermophilic conditions. The study demonstrated the possibility to increase the specific biogas production from 0.34 to 0.49 m3/kgTVS and the gas production rate from 0.53 to 0.78 m3per m3 of reactor per day changing the reactor temperature from the mesophilic (37 °C) to the thermophilic (55 °C) range. The experimental work was carried out at pilot-scale, and the results match the full-scale behaviour. Ammonia nitrogen recycled from the anaerobic digestion section to the wastewater treatment plant accounted for about 4% of the total nitrogen loading. Digestate characteristics in terms of biological stability and heavy metals content suggested the opportunity of a short time post-aerobic stabilisation, leading to a high quality compost product.

► Sustainability of anaerobic digestion process changing temperature from 35 to 55 °C. ► Anaerobic digestion autothermal condition at 55 °C. ► Effluent quality of integrated anaerobic digestion-composting process. ► Low impact of Nitrogen extra-load on wastewater treatment plant.