Operating Experience with Bio-Surf Process
Treatment of Food-Processing Wastes
RONALD L. ANTONIE, Manager of Process Engineering
ROBERT J. HYNEK, Manager of Applications and Analysis
Bio-Systems Division
Autotrol Corporation
Milwaukee, Wisconsin 53209
PROCESS DESCRIPTION
The BIO-SURF process is a secondary biological treatment system applicable to all
biodegradable industrial wastes. It consists of 12-foot diameter corrugated polyethylene
media which is mounted on a horizontal shaft up to 25 feet long and placed in a concrete
tank (Figure 1). The media is rotated at l-2rpm while about 40 percent of the surface area is
immersed in the wastewater.
Figure I — BIO-SURF wastewater
treatment plant.
Shortly after start-up, microorganisms begin to grow on the surface of the media. One
to two weeks later, the entire surface area is covered with a 2-4 mm thickness of biomass as
shown in Figure 2. Rotation of the media alternately contacts the biomass with wastewater
for removal of organic materials and exposes it to the air for removal of organic materials
and for absorption of oxygen. The amount of attached biomass is relatively large compared
to the amount of wastewater under treatment — the equivalent of 10,000 to 20,000 mg/l
of mixed liquor volatile solids. This allows high degrees of treatment to be achieved
in relatively short retention times — usually less than six hours for concentrated industrial
wastes.
Rotation of the media at a peripheral velocity of 1.0 foot per second exerts shearing
force on the biomass which strips excess biological growth and prevents clogging. The
mixing action of the media keeps stripped biological solids in suspension until the flow of
treated wastewater carries them to a clarifier for separation and disposal.
HISTORY
The BIO-SURF process was developed initially in Europe in the mid 1950'sand there
are now well over 700 operating installations on both domestic and industrial wastes. The
first installation in the U.S. began operation in 1969 and there are now about 25 operating
on domestic and industrial wastes. One-third of present U.S. installations are on industrial
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