Solids Thickening

The waste activated sludge from the intermediate clarifiers is sent either to the gravity belt thickeners or to the belt filter presses. 

The gravity belt thickeners separate the biological solids and water, thickening the solids to about 5%.  The water collected is returned to liquids for further processing.  The solids are pumped to a sludge storage tank. 

The belt filter presses also separate the solids from the liquids using a polymer.  The sludge material is thickened to 15 to 17%.  After the sludge is thickened, it is hauled to a landfill for disposal.

Sludge Storage

The partially dewatered sludge from the gravity belt thickeners is stored in an 800,000 gallon capacity tank.  Mechanical mixers in the tank provide constant mixing to produce a homogenous product.

Plate and Frame Filter Press

Sludge from the storage tank is pumped to a conditioning tank where it is mixed with ferric chloride and slate lime, further dewatering the sludge.  The mixed conditioned sludge is pumped to a plate and frame filter press where the water is literally pressed out of the solid material, leaving a plate and frame filter cake content of about 28% to 32%. 

Incineration

The dewatered sludge from the plate and frame filter press is conveyed to the multiple hearth incinerator and is burned.  The ash that is collected at the bottom of the incinerator is hauled to a landfill for disposal.