Influence of the organic loading rate on the anaerobic treatment of winery effluents applying one and two stages

Wineries must comply with wastewater discharge standards, and anaerobic digestion can help meet the regulatory requirements. One or two-stage processes have been proposed for winery effluent treatment, and analyzing which method is more suitable for COD removal. This study evaluates one and two-stage anaerobic processes focused on COD removal, varying the organic loading rate in continuous reactors using two types of winery effluents with different initial concentrations. A low-concentration wastewater (8.7 g COD/L) was assessed under one and two-stage processes, whereas a high-concentration effluent (23 g COD/L) was studied using two stages. Results showed that both configurations present excellent organic matter removal, as high as 88% in the case of high-concentration wastewater and from 93 to 97% removal for low-concentration wastewater. Methane productivities varied from 362 to 718 NmL CH₄/L_reactor·day, methane yield from 291 to 312 NmL CH₄/g COD, and the concentration of total suspended solids in the effluent from 80 to 610 mg/L. A one-stage process is recommended when the initial concentration of the effluent is relatively low; however, when treating effluents with elevated initial concentration, a two-stage system is more convenient because it avoids stability problems.