DEVELOPMENT OF BIOFILM IN THE ANAEROBIC ROTATING
BIOLOGICAL CONTACTOR PROCESS
Mark J. Laquidara, Laboratory Supervisor
Frederic C. Blanc, Professor
James O'Shaughnessy, Associate Professor
Department of Civil Engineering
Northeastern University
Boston, Massachusetts 02115
INTRODUCTION
Over the last ten years, operation and maintenance costs of conventional waste treatment have
risen drastically. Thus, alternative waste treatment processes have gained popularity. The most promising alternative to conventional waste treatment for many industrial wastes is some type of fixed
film anaerobic system. Some important advantages include the following:
• High organic removal efficiencies can be achieved at high organic loading rates.
• Fixed film systems retain biomass well, thus mean cell residence times are less dependent of hydraulic
detention limes.
• Fixed film systems recover quickly from both organic overloads and toxic substance shock loads.
• Anaerobic treatment systems produce low quantities of waste biological solids.
• Anaerobic treatment processes produce a usable product, methane gas.
Extensive process design information is as yet unavailable. Therefore, before widespread fixed
film anaerobic process use occurs, a good deal of process design information must be developed.
The objectives of this study were to develop design information with respect to biofilm attachment
patterns for the Anaerobic Rotating Biological Contactor (AnRBC) process. Information such as
attached biofilm growth kinetics, attached biofilm characteristics and properties, and sloughed biofilm properties and characteristics were evaluated. The results obtained will provide information so
that rational attempts can be made to design full-scale AnRBC systems.
BACKGROUND
Anaerobic Rotating Biological Contactor Process
The AnRBC process, an immobilized cell system, was developed by Friedman and Tait [1). The
configuration of the AnRBC process is very similar to the aerobic rotating biological process except
that the reactor is covered and sealed, an anoxic atmosphere exists above the liquid surface, and disk
submergence is greater than in aerobic systems since oxygen transfer is not a consideration. The
process has shown promise, since a high SRT/HRT ratio is achievable. In addition, clogging by
bridging can be eliminated if disk rotation is kept high enough to create shear forces large enough
to slough off large loosely attached biofilm clumps and create completely mixed conditions in the
reactor vessel. Reactor design should possess the ability to pass nonreactive solids through the reactor
so that nonreactive solids clogging will not occur.
Type and Quantity of Biofilm in Immobilized Cell Systems
A summary of reactor types, loading rates, and removal rates based on laboratory studies is
presented in Table I [2,3,4]. One problem associated with laboratory attached biofilm systems which
utilize mechanical motion to achieve mixing is that, when compared to full scale systems, an unrealistic portion of suspended growth, or suspended-loosely attached growth, may occur. Therefore,
additional research with respect to biofilm development patterns is necessary.
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