CBU is a combined unit used to pre-treat wastewater before it enters the waste water treatment plant. It performs three operations: screening; grit removing and grease removing.
Wastewater passes through the screen, where bigger particles are removed: the screw screen also washes and compacts the screenings before discharge. The efficiency depends on the screen perforation, as well as the capture rate.
Inlet screen can be a spiral screen TSS or SSS type; a rotary drum screen TR type, and the screen tank can be provided with a by-pass tank with manual screen inside. the screen basket or the screen drum can be made of perforated plate or wedge wire.
After the screening section, the wastewater flows toward the settling tank, where the grit sedimentation takes place. In order to improve this process a special baffle is used to obtain a laminar flow as well as to reduce the temperature gap.
Settled grit is collected toward the accumulation pit and then removed by an inclined screw conveyor (grit classifier). This can eventually be provided with a washing system.
Suspended particles, such as oil, grease and other matters, are removed by stainless steel wire driven paddles system.
The settling tank is provided with an air blower to increase the organic matter separation and grit settlement. Bigger units can be provided with two blowers.
The unit can be manufactured in stainless steel grade 304 or 316, with spiral in carbon steel or stainless steel and/or many combination of the two materials.
In those case where the grease removing system is not required, the unit is not provided with the paddle and is named CBU2.
Different combinations of treatments can be provided: the unit can performs the following solutions:
– screening, grit, grease removing
– screening and grit removing
– grit removing
– grease and grit (no screening)
Upon request the unit can be supplied provided with a control panel, which can be electromechanical or PLC controlled.