Optimization of electro-dewatering performance of oily sludge by voltage control and coal-powdered activated carbon (CPAC) addition

Electro-dewatering technology (EDW) exhibits promising prospects for oily sludge reduction treatment, owing to its remarkable dewatering efficiency. Unlike conventional oily sludge dewatering methods, EDW eliminates the need for chemical additives, mitigating the risk of secondary contamination. This study comprehensively investigates the impacts of voltage and coal-powdered activated carbon (CPAC) on the performance of EDW, as well as the properties of the dewatered sludge cake. Moreover, the underlying EDW mechanism is delved into the exploration. The water content decreased from 79.01% to 63.25% with the application of 40 V and 25 kPa pressure, while the dewatering rate increased from 0.025 g/s to 0.055 g/s, with the best electro-dewatering performance. Furthermore, the incorporation of CPAC significantly optimized the electro-dewatering performance, by reducing the viscosity, electrical resistance of the sludge cake and created more mechanical channels for water migration. Introducing 7.5% CPAC (wt.%) achieved the highest dewatering rate of 0.078 g/s with 57.14% final water content of sludge cake. The EDW process enabled discharge of heavy metal ions from oily sludge cake. Additionally, the addition of CPAC contributed to reduced unit energy consumption and improved calorific value of oily sludge cake. This study provides a sustainable and environmentally-friendly technology for the efficient dewatering and subsequent resource utilization of oily sludge, offering considerable potential for both environmental and economic benefits.