Anaerobic Co-digestion of Tannery Solid Wastes: A Comparison of Single and Two-Phase Anaerobic Digestion

Performances of single and two-phase mesophilic anaerobic co-digestion of the leather fleshings and the leather industry's wastewater treatment sludge were compared for the first time in this study. With a methane yield of 0.46 m(3)/kg volatile solid, the single-phase digestion system produced 15% more methane gas than that of the two-phase digestion system. However, H2S concentrations, which are over 1% in biogas, was the major problem causing inhibition in the biogas production for the single-phase digestion system. Sulfides, which entered to the reactor with the leather fleshings and caused H2S inhibition, were able to be eliminated easily by rinsing the leather fleshings before being fed to the digester. Although the no H2S inhibition was observed in the two-phase system, the hydrolysis reactor and thus subsequently the methane reactor suffered from serious operational problems causing process failure in the biogas production performance. Regarding methane production performance and simplicity in its operation, the single-phase digestion system is considered to be more convenient for the anaerobic co-digestion of leather fleshings and treatment sludge. [GRAPHICS] .