1. Dewatering is accomplished either by air drying in Sand drying beds or by mechanical means using Vacuum filtration, centrifugation, heat drying etc.
   1. Dewatered sludge may some times require further treatment such as incineration to reduce the volume and the organic content of sludge.
   2. Incineration involves the combustion of the sludge in a reactor under high temperature along with auxiliary fuels if needed.
   3. The ultimate disposal of dewatered sludge or the ash after incineration may be onto the land or into the sea.

The methods are:

1. In Vacuum filtration process, the sludge is first mixed with a coagulant such as ferric chloride and then conveyed to a vacuum filter, consisting of a hollow rotating drum covered with a replaceable filter cloth.
2. The drum rotates partly submerging into sludge.
3. The vacuum created by a pump within the drum draws the moisture from the sludge through the cloth.
4. The sludge cake which is formed on the outside of the drum is removed by a scraper as the drum rotates.
5. High speed centrifuges are also used for drying of raw or digested sludges and are becoming more popular because of small area requirements. These methods may remove about 50% moisture.
6. Vacuum filtration or centrifugation of raw sludge is often adopted in situation where sludge is to be disposed of by incineration.
7. These mechanical methods of drying are generally used when the available area is less than that required for sludge drying beds or where the climates are too cold or at places where rains are frequent as not to permit natural drying or as a preliminary to heat drying for making fertiliser.