ABSTRACT
The principal sources of sludge at municipal wastewater treatment plants are the primary sedimentation basin and the secondary clarifiers. Sludge contains large volumes of water. The small fraction of solids in the sludge is highly offensive. Thus, the problems involved with handling and disposal of sludge are complex. Common sludge management processes include thickening, stabilization, dewatering, and disposal. This chapter describes the basic characteristics of sludge produced in the primary and secondary treatment processes. It presents a general overview of sludge pumping and processing systems and environmental control measures. The chapter also describes various sludge-thickening methods, and provides the step-by-step design procedure of a gravity thickener in the design example. It summarizes the characteristics of wastewater residues and their production rates from various treatment processes. The chapter considers typical physical characteristics of sludge from different treatment processes, and chemical compositions of raw and digested sludges. It includes maximum allowable heavy metals concentration in biosolids for land application and governing regulations.
