ABSTRACT

Sludge dewatering is a process to removes the moisture from sludge making it simpler and more economic to transport and disposal. Dewatering is mainly accomplished by drying beds or a physical process, which removes water from the sludge through presses or centrifuges. Generally, chemicals are used to improve the efficiency of processes. Sludge dewatering is necessary for one or more of the following reasons (Campbell & Crescuolo, 1982):

The cost of transporting sludge to the ultimate disposal site becomes substantially lower when dewatering reduces sludge volume.

Dewatered sludge is generally easier to handle than thickened or liquid sludge. In most cases, dewatered sludge may be shovelled, moved about with tractors filled with buckets and blades and transported by belt conveyors.

Dewatering is normally required prior to the heat drying and incineration of the sludge, to increase the calorific value by removal of excess moisture.

In some cases, removal of the excess moisture may be required to render the sludge totally odourless and non-putrescible. This is especially true for sludges stabilised by processes that create high strength recycle flows.

Sludge dewatering is commonly required prior to land filling to reduce leachate production at the landfill site.