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

Abstract

Abstract To resolve the slow hydrolysis of sewage sludge, various pre-treatment technologies have been assessed but high operating costs prevent active application. To mitigate the cost-effectiveness of pre-treatment and to promote anaerobic digestion (AD), this study investigates non-thermal plasma (NTP) technologies as an alternative. Experimental design under various contact time (CT) and temperature (T) conditions tests how NTP pre-treatment improves the methane conversion of organics in sewage sludge. By building a multi-response surface model (RSM) using a central composite design (CCD), optimal CT and T were revealed as 4.6 h and 45°C, respectively. This statistical optimization of NTP pre-treatment led to enhanced biochemical methane potential of 297 ± 46 mL CH4/g COD keeping the cost due to power consumption as low as 0.06 US$/L, which is comparable to those of other advanced oxidation processes (0.11 ~ 0.44 US$/L). The results demonstrate that accelerated hydrolysis of sewage sludge using non-thermal plasma pre-treatment might benefit better renewable energy recovery from sewage sludge.