Disintegration of digested sludge with the thermal alkaline process to enhance the biogas production

Digested sludge (DS) has a high organic content, and due to its large amounts to be disposed of, the post-thermal alkaline process (post-TAP) is investigated for DS disintegration, targeting to improve the organic solubilization for subsequent anaerobic digestion (AD) and reduce sludge volume. Seven DSs were treated at 160 °C for 30 min under pH 9-12 and then anaerobically digested. The maximum biogas yield of post-treated DSs reached 314-361 L/kg VS_added with TAP at pH 9, and the biogas production could be improved by 364-4,423 m³/d in the seven wastewater treatment plants (WWTPs) investigated. Besides, an additional electricity generation of 34% and a reduced sludge volume of 22% could be achieved in a model WWTP. Furthermore, in a model incineration plant with extended TAP and AD, the electricity balance of dewatered DS with 25% total solids (TS) was enhanced by 84.4 kWh/m³.