Increasing the performance of anaerobic digestion: Pilot scale experimental study for thermal hydrolysis of mixed sludge

Abstract

The performance of a pilot plant operation combining thermal hydrolysis (170°C, 30 min) and anaerobic digestion (AD) was studied, determining the main properties for samples of fresh mixed sludge, hydrolyzed sludge, and digested sludge, in order to quantify the thermal pretreatment performance (disintegration, solubilisation, and dewaterability) and its impact on the anaerobic digestion performance (biodegradability, volatile solids reduction, and digester rheology) and end product characteristics (dewaterability, sanitation, organic and nitrogen content). The disintegration achieved during the thermal treatment enhances the sludge centrifugation, allowing a 70% higher total solids concentration in the feed to anaerobic digestion. The digestion of this sludge generates 40% more biogas in half the time, due to the higher solids removal compared to a conventional digester. The waste generated can be dewatered by centrifugation to 7% dry solids without polymer addition, and is pathogen free.

Keywords

anaerobic digestion (AD) / biogas / performance / sludge / thermal hydrolysis