Facultative lagoons are financially attractive to communities because they
do not require daily attention for maintenance and operation. Since the treated
effluent is discharged for short periods of time in the spring and the fall,
the environment can only be affected during those times.
The quality of a facultative lagoon effluent can be improved by removing
the algae that is produced during the treatment. The algae-laden effluent
can be pumped at a uniform rate to a polishing filter bed consisting of a
12-inch layer of uniform coarse sand underlain by perforated drain tile. The
effluent water will flow through the sand into the drain tile and through
the discharge pipe to the stream. The algae will be captured on the surface
of the sand.
Sand filter beds have been used for many years to dewater liquid sludge
and to polish treated wastewater to a high level of water quality.
The addition of a polishing sand filter bed to a facultative lagoon system
would increase the construction cost of the treatment system by about 9%.
This increase in construction cost is easily justified by the lower annual
operation and maintenance costs, which are only about one-third of those for
a treatment plant.
A. A. Schrage P.E., Inc.
A. A. Schrage, President,
Professional Sanitary Engineer
3368 Galaxy Blvd.
Sterling Heights, MI 48314
Phone: (586)323-0363
Email: aaschrage@sbcglobal.net
