Improved hydrolysis of sewage sludge by air-assisted non-thermal plasma for enhanced biomethane recovery

Conventional pretreatment technologies have been assessed to resolve the slow hydrolysis of sewage sludge, but high operating costs have prevented their wide use. This study investigated non-thermal plasma (NTP) technologies as an alternative to promote anaerobic digestion (AD). Various contact time (CT) and temperature (T) conditions were used to assess how NTP pretreatment improves the methane conversion of organics in sewage sludge. A multi-response surface model (RSM) using a central composite design (CCD) identified the optimal CT (4.6 h) and T (45 °C). This statistical optimization of NTP pretreatment led to an enhanced biochemical methane potential of 297 ± 46 mL CH₄ g^–1 COD by reducing operating cost as power consumption as low as 0.08 USD L^–1. The result was comparable to those of other advanced oxidation processes (0.14 – 0.60 USD L^–1) demonstrating that accelerated hydrolysis of sewage sludge using NTP pretreatment show potential for improving renewable energy recovery from sewage sludge.