General process concept:
To achieve an ideal consistency in the raw or mixed sludge prior to the digestion, as a general rule the excess sludge is mechanically thickened before mixing with the primary sludge. The excess sludge thickening reduces the amount of sludge fed to the digestion tank. This yields considerable energy savings and better use of the digestion system, as well as longer retention times in the digestion process. This results in further reduced digested sludge quantities as well as improved dewatering properties thereof.
Decanters for thickening are not designed according to the classical counter current principle, but according to the direct current principle. Thanks to this design, the suspension passes through the entire length of the centrifugal chamber in the direction of the discharge. The centrate water runs through channels in the direction of the weir openings. The result is a very long clarification section and thus minimal or no polymer as well as achieving the highest separation efficiencies.
Hiller Lysate technology:
The HILLER lysate device is attached in the area of the sludge discharge openings and uses the existing kinetic bowl energy. The disintegration effects in the thickened waste activated sludge (WAS) are mainly caused by impact and shear forces generated by the knife blades rotating at high circumferential velocity in the labyrinth and the lysing chamber. The WAS disintegration is carried out in the full flow of the thick sludge that has entered the lysate device; no lysate enters the separated centrate water.
Advantages:
– Viscosity reduction and better pumping properties at high thickening degrees
– Cell disruption increase resulting in an increased degradation of the organic share
– Gas yield increase
– Improved dewatering behavior
