Solubilization of waste activated sludge by alkaline pretreatment and biochemical methane potential (BMP) tests for anaerobic co-digestion of municipal organic waste

Abstract

Biochemical methane potential (BMP) tests have been carried out to determine the anaerobic digestibility of the waste activated sludge (WAS) and the sludge pretreated by NaOH (PWAS). The optimal NaOH dosage was determined to be 45 meq NaOH/L. The maximum SCOD solubilization was 27.7, 31.4 and 38.3% at the temperatures of 25, 35 and 55°C respectively after 4 hours reaction. The final methane yield of simulated food waste (SFW) was 430 ml CH4/g VSadded, and those of PWAS (25°C), PWAS (35°C) and PWAS (55°C) was 274, 286 and 310 ml CH4/g VSadded respectively after 20 days. The figures were 66%, 73% and 88% higher than that of WAS. The methane production in anaerobic co-digestion is considerably affected by the fraction of SFW and PWAS in the feed. The anaerobic digestibility of the feed mixture (SFW with PWAS) is higher than that of the feed mixture (SFW with WAS). Anaerobic co-digestion of food waste with the PWAS is found to be an attractive option to reduce the solid waste volume with improved methane recovery.