Anaerobic co-digestion of acerola (Malphigia emarginata) agro-industry effluent with domestic sewage at mesophilic and thermophilic conditions.

This study evaluated the effect of temperature on the anaerobic co-digestion of acerola agro-industry effluent (EAV) and domestic sewage (EDT). The assays were performed in triplicates of reactor flasks using treatments with different mixture compositions (T1= 5% EDT + 95% EAV; T2= 20% EDT + 80% EAV; T3= 30% EDT + 70% EAV) and anaerobic sludge as inoculum (5 g.L−1 ), at mesophilic (35 °C) and thermophilic (55 °C) temperatures. The analyses of soluble chemical oxygen demand (CODs) and volatile fatty acids (VFA) were performed by etermining the removal efficiency of the CODs, the decay rate constant of the COD (Kd), and the percentages of anaerobic biodegradability (%BD) and methanation (%M). The inoculum biomass of the treatments was observed through scanning electron microscopy (SEM) at the end of the degradation process (12 days). Regardless of the temperature, the anaerobic digestion was considered efficient, with biodegradability above 60%. The mesophilic temperature favored the anaerobic co-digestion for all mixture compositions, presenting more diversified and structured biomass at the end of the assays, as well as higher removal efficiencies of the CODs and methanization, especially for T3 at 35 °C (63% and 51%, respectively). Furthermore, the kinetics of the degradation process proved to be more accelerated at mesophilic conditions (Kd 0.1d−1 ) and in the treatments with a higher percentage of sewage (T2M and T3M)