Improvement of the anaerobic digestion of sewage sludge by co-digestion with wine vinasse and poultry manure: Effect of different hydraulic retention times

Abstract

This study arose in response to the management of different organic wastes generated locally, which cause environmental damage. These wastes could be used to obtain biogas and class A biosolids through anaerobic digestion. For this purpose, the mesophilic anaerobic tri-digestion of sewage sludge (S), wine vinasse (V) and poultry manure (PM) (49.5:49.5:1) was studied to obtain biogas in an improved way compared to bi-digestion of SV (50:50) and mono-digestion of S. Tests were carried out in anaerobic digesters, at laboratory scale, to compare the benefits at different hydraulic retention time (HRT) (20, 15, 13, 10, 8 and 6 days). From the results obtained, anaerobic tri-digestion of the waste gave the best results, with a total chemical oxygen demand (TCOD) removal efficiency of 51%, volatile solids (VS) removal efficiency of 57%, and methane yield values of 261 mLCH4/gVSadded at a HRT of 13 days. In relation to the pathogens, both co-digestion studies addressed managed to inactivate enough pathogens in the effluent to be classified as class A biosolids. This would allow considering the anaerobic tri-digestion as a promising technology, which allows valorizing organic waste, obtaining biogas and class A biosolids, moving towards a circular bioeconomy.