High-solids anaerobic co-digestion of seven kinds of waste biomass mainly consisting of dewatered sludge produced in an oxidation-ditch process and waste fried Tofu.

Abstract

 To achieve concentrated treatment of several organic wastes and promote the recycle of waste biomass in local towns, a high concentrated continuous co-digestion experiment was conducted in a 1m³ of mesophilic digester. The waste biomass mixture of which TS was approximately 8.8% consisted of waste sludge from an oxidation ditch process (OD), a contact aeration process and a septic tank, human waste, kitchen garbage and two kinds of fried tofu (raw type and dry type). With an average organic loading rate of 2.5 kg-VS/m³/d, digestion operated stably. Biogas yield of waste mixture was 0.29 Nm³/kg-VS, and average VS removal ratio was 37%. No significant difference was shown of the dewatering characteristics of digested sludge, compared to the input OD sludge. Fertilizer effect analysis shows that digested sludge quality met the Fertilizer Control Act, , and high fertilizer efficicency was suggested.