Which of the following is not a major solids treatment method?

Concentration is not considered a major method for treating solids in wastewater management. The primary methods of solids treatment focus on reducing the volume, improving the quality, and preparing solids for disposal or further processing.

Thickening involves increasing the solid content of sludge, making it more manageable and reducing the volume for subsequent treatment. Dewatering is the process of removing water from sludge to lower its volume and weight, which facilitates easier handling and transportation. Stabilization refers to the treatment of sludge to reduce pathogens, odors, and organic material, making it safer and more stable for disposal or reuse.

In contrast, concentration is more about the separation and increase of specific solids, but it does not directly involve the standardized treatment processes aimed at reducing waste volume and improving the handling of solids. Thus, concentration does not fit within the main treatment methods used for managing solids in wastewater treatment operations.