A new approach of nonpoint source pollution/stormwater sludge treatment by an integrated thermal plasma system

In this study, we designed and demonstrated the effectiveness of an integrated waste treatment system for contaminated stormwater sludge. The system is comprised of two components: pulsed arc electrohydraulic discharge (PAED) for aqueous-phase treatment and thermal plasma decontamination for solid-phase treatment. PAED provided a reduction of 80 % in total organic carbon (TOC) within a treatment time of 5 min in the aqueous phase. With a prolonged treatment of 30 min, the decontamination of TOC reached over 90 % in the aqueous phase, accompanied with 20 % carbon and 70 % sulfur decreases in weight in the solid phase. A huge weight reduction can be achieved prior to further solid treatment. The solid phase, named as the PAED-treated sludge, was separated by sedimentation and transferred to thermal plasma treatment. The thermal plasma-treated sludge was slightly melted, and the formation of slag was possible. X-ray energy dispersion solid analysis showed that carbon and sulfur were reduced to zero after treatment. Si, Mg, and Al decreased by 25, 30, and 60 %, respectively, while Ca and Fe enriched by 400 and 25 %, respectively. The emission gas analyses demonstrated a possible energy recovery from gaseous compounds with adequate gaseous treatment devices. This research demonstrates an innovative treatment approach of various sludge types, especially those types that contain high water contents and are severely contaminated by toxic organic compounds.