The flocculated sludge, once it enters the thickener or dehydrator is transported by a screw. The screw, depending on the type of machine, changes in pitch along its length, thus allowing the thickening or dewatering of the sludge.
During the rotation of the screw at low RPM, the separated water passes through the drum to then be channelled towards the discharge area of the eluate. After reaching the discharge zone, the sludge is conveyed towards the outlet, situated on the bottom of the machine which in the case of the X-RA model can be connected to a pump which transfers the product to a possible subsequent dewatering system, whilst in the X-RAD model, once passed the pneumatic counter pressure system, the sludge is discharged to a skip or similar; or drops into a suitable conveying system such as a screw or belt conveyor, or a cake pump.
To obtain the best performance in terms of sludge dewatering, the two machines can be installed one after the other: first the X-RA to give a thickened sludge of, depending on the model, from 4 to 8% of DS, followed by the X-RAD for dewatering, to a cake of up 25% DS.