Batch and semi-continuous anaerobic codigestion of Olive mill wastewaters and diluted poultry manure: a laboratory scale optimal ratio evaluation

The anaerobic codigestion of olive mill wastewater (OMWW) and poultry manure (PM) was investigated in order to determine the appropriate mixture ratio with a focus on total and OMWW organic load contribution. Codigestion was first explored through batch tests using a combination of four PM dry basis ratios (1 to 4%) and four volumetric OMWW ratios (0 to 15%). Thereafter, codigestion was attempted at semi-continuous mode, at batch identified appropriate PM ratio, using a gradual OMWW increase up to 20%. Results showed that the maximum BMP was recorded with PM monodigestion with biogas peak of 410.48 mL/gVS at 5.38 gVS/L. Under the semi-continuous conditions, increasing OMWW fed ratio improved biogas yield up to total feed of 1.57 gVS/L.d achieving a maximum production of 215.85 +/- 23.56 mL/gVS.d. The codigestion of OMWW and PM was possible up to a critical OMWW VS contribution of 40% to 50%.