What’s The Sludge Thickening Process?

The thickener is mainly used for wastewater treatment and leachate concentration in mineral processing plants. The increased aspect ratio extends the residence time of fine slurry in the thickener, and the application of polymeric flocculants enhances the slurry coagulation effect, resulting in clearer overflow water and thicker underflow.

The sludge thickening process

The thickening process in wastewater treatment is divided into three stages: settling stage, transition stage, and compression stage. The thickening process of a thickener mainly involves the working process of solid particles in the settling and transition stages. When the thickener is in the settling stage, using flocculants can increase the solid flux of the settling mass. The processing capacity of the thickener and the underflow discharge concentration are mutually restrictive.

As the concentration process enters the compression stage, the sedimentation process of solid particles undergoes a qualitative change, transforming from the sedimentation of solid particles into the process of water being squeezed out of the dense phase layer.

During the compression stage of flocculant concentration, the settling rate and compaction degree of the whole depend on three forces: gravity, the viscosity of the liquid flowing out of the dense phase layer, and the stress between the particles around the dense phase layer. The compression and dehydration of the network structure formed by flocculation and concentration is only related to pressure. The concentration of the dense phase layer can only be significantly increased when the pressure on the concentrated layer exceeds a critical value. In traditional thickeners, the dense phase layer is a homogeneous system, making it extremely difficult to extract water from it using only pressure. While flocculation thickening significantly increases the settling velocity of solid particles, the thickener’s processing capacity remains low due to limitations imposed by the compression process.