Waste-Activated Sludge Treatment Processes

Abstract

Biological processes are the most common methods to treat wastewater but they produce huge amounts of waste-activated sludge (WAS) as a by-product. WAS generated during wastewater treatment must be stabilized sufficiently prior to ultimate disposal. The most common methods of sludge stabilization are biological processes (aerobic or anaerobic digestion) due to simplicity of the operation, and lower operating and maintenance costs for similar wastes. Anaerobic digestion remains the principal process for the stabilization of sludge solids as organic waste is converted into methane-rich biogas and fertilizer in an oxygen-free environment. However, WAS treatment processes are often a challenging problem. Therefore, the characteristics of WAS are discussed to have a better understanding so as to treat it efficiently. Various kinds of treatment processes such as physicochemical treatment, biological treatment, and combined treatment are the focus of this chapter; however, many concepts developed in this chapter apply to anaerobic digestion to stabilize the WAS.