chapter  1
Biosolids Characterization, Treatment and Use: An Overview
BySystems Inc
Pages 20

Municipal wastewater treatment produces two products: clean water and water slurries which are usually referred to as sludges.

While clean water is disposed of directly into the environment, it is not feasible, environmentally or economically, to do so with the solids generated by wastewater treatment processes. They must be treated prior to disposal or beneficial use to comply with public health, safety, environmental and economic considerations.