Reduction of water content in sludge

Any waste-sludge handling requires separation of the maximum content of sludge water. It is necessary to differentiate the terms thickening and dewatering . 

Sludge thickening denotes removal of water by gravitation (in settlers). Dewatering is usually performed by means of mechanical systems (centrifuges, filter presses, filters, etc.), or by natural dewatering. 

By thickening, the water content is reduced to 80-85%, by dewatering to 60%. During drying or incineration the water content is reduced to 40% or less. 

The simplest technological procedures is thickening by settling employing the sedimentation properties of suspensions. Thickeners are designed for either discontinuous or continuous operation. 

The sludge fields are flat earth or concrete basins whose bottom is formed by dewatered filtration gravel sand. The cycle of a sludge field operation has the following stages  

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