|
The Oxidation Ditch (OD) is a modified form
of the activated sludge system. Oxidation ditches are mechanical
secondary treatment
systems which are tolerant of variations in hydraulic and
organic loads.
The OD consists of a "ring or oval shaped channel" equipped
with mechanical aeration devices. Screened wastewater, which
enters the ditch is aerated and circulated. ODs typically
have long detention times and are capable of removing between
75% and 95% of the Biological Oxygen Demand (BOD).
The proprietary "Orbal System" uses three channels or ditches
concentrically placed. Each channel is independently aerated
and can be configured to act in parallel or series with the
other channels, depending upon the degree of treatment required.
After screening and grit removal, sewage enters the outer
channel where most of the biological reaction takes place.
The second channel is held at a slightly higher dissolved
oxygen content for further BOD and nutrient reduction. The
innermost channel is used for polishing the effluent before
it passes to a clarifier.
Typical figures for ODs are as follows:
|
