Sludge thickening in a wastewater treatment plant using a modified hydrocyclone

The main application of hydrocyclones in most industry sectors is the separation of particles from liquids. For thickening, however, the separation properties of the cyclone should be adjustable, which requires a different operating mode. Therefore, we investigated an add-on thickening module, consisting of a conical plug and a secondary vortex finder in the underflow of the hydrocyclone. Laboratory scale experiments are carried out to investigate the function of the concept of annular gap modification by the use of the thickening module. In the second step, we transferred this concept to industrial scale for field tests at a municipal wastewater treatment plant. In the field tests, geometrical properties (annular gap modification) and operational parameters (volume flow rate, sludge type) were investigated. The results show that thickening in terms of increasing the total solids content of sludge is possible with the modified hydrocyclone. In the field tests, a thickening factor (total solids content of thickened sludge related to feed sludge) of 1.31 (average) was reached for digested sludge. Hence, a hydrocyclone could be a promising addition in wastewater treatment plants for dewatering of sludge.