Characterization and Biological Treatment of Thermal Hydrolysis Pretreated Anaerobic Digestion Centrate: A Size Distribution Study

Thermal hydrolysis (TH) is a sludge pretreatment method that utilizes high pressure and temperature to hydrolyze sludge prior to anaerobic digestion. It results in increased volatile solids destruction, higher biogas production and improved cake dewaterability. Disposal of the centrate/filtrate produced by the dewatering of the sludge is a major concern for treatment plants because the presence of UV quenching substances in the centrate/filtrate might interfere with UV disinfection. Also, with the lowering of effluent nitrogen standards in some locations, development of treatment techniques for nitrogen-containing organics in the recycle flow is required. In this study, the particle size based fractions were characterized by their total organic carbon, UV absorbance and organic nitrogen. This study also investigated the impact of aerobic biological treatment on the different particle size based fraction. Aerobic biological treatment was found to be effective for the removal of particles < 300 kDa.