Operation

OPERATION OF THE BIO-WHEEL™

The Bio-Wheel™ consists of a number of cells, which are arranged in a circular fashion around a horizontal
shaft as shown in the schematic drawing. Each cell contains a number of specially profiled polypropylene
plates which form a self supporting segment to provide aeration and mixing as well as a surface area for the
biologically active fixed film. The wheel is submersed to 80% of its diameter in the mixed liquor and is driven by
an easily accessible gear motor and chain drive located above the liquid level on the upper wall of the bio-tank.

Aeration and mixing are provided by the rotation of the Bio-Wheel™. As a cell emerges above the mixed
liquor, the liquid drains out, and the cell is filled with air under normal atmospheric pressure. Because the large
surface of the plate is directly exposed to pressure of the air, immediate saturation of oxygen is obtained.

As the Bio-Wheel™ rotates and the cell segments are submerged into the mixed liquor, the entrapped air is
compressed and forced toward the bottom of the bio-tank. During downward rotation, a portion of the air
escapes to the surface as fine bubbles. The resulting turbulence, combined with the rotation of the wheel,
provides homogeneous mixing in the bio-tank. During upward rotation of the wheel, the partially air filled cell
provides buoyancy and reduces the power required for rotation.

The fixed film on the surface area within the cells is supplied with oxygen while above the surface, and air is
taken in to be compressed and distributed during rotation. This process results in the coincident supply of
oxygen for the fixed film and the activated sludge.

The intake of air is adjusted by the speed of rotation of the Bio-Wheel™. Even with very high loading and
corresponding high oxygen consumption rates, a sufficient supply of oxygen can be transferred. The fixed film
component provides an ideal environment for slow growing nitrifiers to provide stable nitrification. By creating a
separate anoxic zone, complete nitrification and denitrification can be provided with minimal power
consumption by the Bio-Wheel™ system.