Part A: Sanitization and use of sewage sludge in soil Technical Note 5 - Thermal sludge drying and sanitization

Abstract

Thermal drying of the sludge produced in sewage treatment plants (STPs) is a physical process that allows for a significant reduction of the moisture intrinsic to the material, reducing its mass and volume for handling and final disposal. The process also allows for thermal sanitization of the sludge, dispensing the use of chemical products for that purpose. A fundamental requirement for the operationalization of the process is the availability of heat, which can be obtained, for example, through the energy recovery of biogas and the dry sludge found in STPs, corroborating with the concepts of sustainability, renewable energy and circular economy. Although thermal sludge drying is already consolidated in several countries, it is still not a common practice in Brazil. Therefore, this technical note presents the main topics of interest associated with drying and thermal sanitation of sludge for STPs of different sizes, as well as a review of the fundamentals inherent to the process and the methods for selection of dryers. This document also reports examples of thermal sludge drying and sanitization systems, in addition to important aspects to be considered when implementing the process in STPs.