Physical and Chemical Features of the Thermolysis of Wastewater Sludge
Abstract
The global concern regarding the disposal of municipal wastewater sludge is pressing. Contaminated water influxes into wastewater treatment channels, causing a surge in sludge volume and requiring additional processing. Pyrolysis of domestic wastewater sludge emerges as a promising solution, transforming waste sludge into reusable secondary raw materials. Our study employs a uniquely designed batch reactor system to uncover outcomes from laboratory-based thermal processing of domestic wastewater sludge. Within the reactor, the feedstock undergoes a series of processes, including dehydration, depolymerization, partial decomposition, and the removal of water. Additionally, decarboxylation occurs, leading to the formation of pyrolysis resins, achieved by combining dehydration and decarbonylation processes. This comprehensive process yields solid, liquid, and gaseous carbonaceous hydrocarbon residues. The chemical composition, structure, and properties of these pyrolysis products are thoroughly examined through analytical characterization techniques. Our findings reveal that sludge pyrolysis accomplishes thermal sterilization, resulting in valuable carbonaceous residue with potential applications as fuel or raw materials for petrochemical synthesis. Moreover, during pyrolysis, heavy metals such as cadmium and mercury can be extracted from the carbonaceous residue. Importantly, this process generates additional energy, and operating below 500°C prevents dioxin contamination in the environment.