Effect of the hydraulic retention time on the acidogenic fermentation of sewage sludge, wine vinasse and poultry manure for biohydrogen production

Abstract

The present work aims to study the performance of the co-fermentation of sewage sludge, wine vinasse and poultry manure to generate volatile fatty acids (VFA) and biohydrogen at different hydraulic retention times (HRT: 10, 8, 6, 5 and 3 days). The study was carried out in constant agitated reactors at laboratory scale. The feeding consisted of a mixture of sludge:vinasse (50:50) with 10 g/L of poultry manure. The reactors operated under thermophilic conditions (55 °C) and pH of 5.5.The results showed an increase in hydrogen production and specific hydrogen production, 1.18LH2/L/d and 40.41 mLH2/gVSadded respectively, as HRT decreased from 10 to 5 days of HRT. The volatile solids (VS) removal (33.32%VSr) and 71.24% soluble chemical oxygen demand (SCOD) were observed at HRT of 5 days, with the highest butyric acid/acetic acid ratio (HBu/HAc) value of 2.09. As HRT drops below 5 days, yields and hydrogen production drop. The highest activity of the microorganisms was observed for a HRT of 5 days (5.64E-11 LH2/Cells), with a higher proportion of Eubacteria than Archaea (74:26) and higher concentration of Butyrate-utilizing Acetogens (BUA) than Propionate-utilizing Acetogens (PUA) (18.60 and 12.18% respectively). Therefore, this technology, in a 5-day HRT, could be a viable alternative for the production of bioenergy in the biorefinery concept.