How is sludge typically treated for disposal?

Sludge treatment is a critical process in sewage treatment, and the method that involves thickening, digestion, and dewatering is the standard approach used to prepare sludge for disposal. Thickening reduces the volume of sludge by removing excess water, making the subsequent treatment steps more efficient. During digestion, bacteria break down organic matter in the sludge, reducing its volume further and stabilizing it, which helps minimize odors and pathogens. Finally, dewatering further reduces the water content through mechanical means, resulting in a solid cake that is easier and less expensive to handle and transport for final disposal or reuse.

The other methods mentioned are not typical for the initial treatment of sludge for disposal. While incineration and chemical stabilization can be used to manage sludge, they're less common than the comprehensive processes of thickening, digestion, and dewatering. Filtration and chlorination are primarily used for treating wastewater rather than sludge itself. Simply dumping sludge in landfills is not a sustainable practice and is discouraged due to environmental and regulatory considerations. Thus, the correct approach combines several treatment processes to effectively manage sludge before disposal.