Sludge handling
Ing. Zdeněk Sekerka – ADOS (Czech utility model pending No. 2004-14997)
Sludge handling – sludge pre-thickener and automatic sludge thickener AZK
Introduction
The excess sludge produced at the treatment plants must be stored and it is therefore necessary to minimize its water content. The sludge prethickener is used for thickening the sludge to roughly 2-4% of solids. Automatic sludge thickener is used for dewatering the sludge to 15-25% of solids.
Process
The sludge prethickener automatically thickens the sludge to 2-4 % of solids from the activation process using gravity. The prethickener is placed directly in the activation tank. The supernatant water from the prethickener is returned to the treatment process.
The automatic sludge thickener AZK dewaters the activated sludge to 15-20% of solids. The unit must be placed inside an operating building and requires a roofed container where further thickening takes place.
Advantages
1) Withdrawal on the sludge from the aerated section of activation: when the sludge is removed from the aerated section of activation the polyphosphates in the sludge water are removed at a higher rate, which decreases phosphorus content in the whole treatment process.
2) The excess sludge is pumped at a higher concentration than operating concentration: Operating sludge concentration in the process is usually 2-5 g/l, in the prethickener the sludge is thickened to 20 – 30 g/l – sludge with lower water content is pumped which saves polycoagulant during further dewatering.
3) Use of automatic sludge thickener AZK: The automatic sludge thickener AZK dewaters the activated sludge to 15-20% of solids. It does not require any special filtering cloths. The system is equipped with a steel filter and the thickened sludge is pumped into a container.
Technology Description
Introduction
The prethickener is a plastic or stainless steel tank inserted into the activation area and equipped with a pump.
Automatic sledge thickener AZK is made of stainless steel.
System Description
The plastic or stainless steel prethickener tank is equipped with two check gates at the top and in the middle of the tank. The gates are used for regulating the mixed liquor inflow. The pump placed at the bottom of the prethickener is timer controlled and pumps the thickened sludge to the sludge storage.
The sludge pumped into the automatic sludge thickener AZK is mixed with organic flocculant and once mixed follows to the thickener AZK itself. The supernatant is separated from the sludge and is pumped back to the treatment process. After substantial thickening the dewatered sludge is pumped via screw pump to a container for further thickening.
Efficiency:
The sludge prethickener gravitationally thickens the sludge to 2-4 % of solids.
The automatic sludge thickener AZK dewaters the activated sludge to 15-20% of solids.