Preliminary Results of a
New Approach in the Aerobic Biological
Treatment of Highly Concentrated Wastes
FRED M. WELCH, Program Manager
Research Division
Allis-Chalmers Manufacturing Company
Milwaukee, Wisconsin
INTRODUCTION
In the early 1960's Allis-Chalmers initiated an experimental program utilizing a device termed the Two-Phase Contactor (TPC). The Two-Pnase Contactor
as the name denotes is a mass transfer device for contacting one fluid with another. In most instances this has been a liquid with a gas. The TPC consists
basically of a series of rotating discs which are partially submerged in one fluid
and as the discs are rotated, carry a thin film of fluid up into contact with the upper fluid.
Following some successful experiments using the Two-Phase Contactor as an
aeration or gas transfer device it was decided to field test a TPC in various processes for treating wastewater. Initially, two TPC units were taken to a local
waste treatment plant where they were arranged to test various waste treatment
processes. One series of tests required the establishment of a biological lawn or
film on the discs of a TPC unit. In this manner, the rotating disc functioned as
a support media for the biomass, an aeration mechanism and a controlled means
for contacting the biomass with the sewage. From this description was coined the
terms Rotating Biological Contactor or RBC. During the ensuing testing program
which tested the efficiency of the Two-Phase Contactor as an aeration device and
as a Rotating Biological Contactor, it was possible to examine and evaluate each
of the proposed processes. All of the various processes tested during the initial
program, which utilized the TPC as an aeration device and biological contactor
for treating municipal wastewater, were successful. The most promising process
of the initial program was the one which incorporated the bio-lawn or RBC concept and was so encouraging that further testing was warranted. However, during
the early testing program at the municipal wastewater treatment plant, wide variations in flow rates and concentrations of the primary treated sewage were encountered. Therefore, it was proposed that in order to better examine the various parameters that effect the RBC a synthetic sewage should be incorporated into
the testing program.
EXPERIMENTAL EQUIPMENT AND PROCEDURES
Various synthetic sewages and test programs that utilize such sewage were investigated. As a result of this search for a simple yet practical means of testing
a waste treatment device using synthetic sewage a formula devised by the Sanitary Engineering Department at the University of Wisconsin, Madison, which
utilizes dry dairy solids was formally adopted. The formula for the synthetic
sewage consisted of: 1) dairy solids, which supplied the source of carbohydrates
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