A Versatile Activated
Sludge Pilot Plant — Its Design,
Construction and Operation
MICHAEL C. MULBARGER, Sanitary Engineer
J. A. CASTELLI, Mechanical Engineer
Chemistry and Physics Activities
Basic and Applied Sciences Program
Cincinnati Water Research Laboratory
Federal Water Pollution Control Administration
Cincinnati, Ohio
INTRODUCTION
A successful and consistently-operating pilot plant is an important phase of the
total integrated research project. Jones (1) and Ludzack (2) have discussed in detail pilot plant methods, considerations, and problems. This paper is intended to
go one step farther and provide detailed directions for building and operating a
versatile, experimental activated sludge pilot plant.
EXPERIMENTAL PILOT PLANT
The pilot plant, designed for an average flow rate of 500 ml/min, has the
following design objectives: 1) Service on unrelated projects for a number of years;
2) a degree of portability, allowing the unit to be transported into the field by
conventional carriers such as small vans and panel or pick-up trucks; 3) Maintenance and operation time at a practical minimum; 4) Ability to operate, unattended,
for periods of 16 to 24 hrs; 5) Automatic representative sampling of the process
streams; 6) Ability to vary the hydraulic and organic load in the approximation of
actual operating experiences; 7) Ability to change from "plug" to "uniformly
mixed" aeration flow patterns; and 8) Ability to vary each unit's detention time
independently of the flow rate.
In the following sections, the design, construction, and operation of the settlers, aeration tank, pumps, and samplers are discussed, supplemented by detailed
construction drawings and a bill of materials.
SETTLING TANKS
It is impossible to retain in a pilot sedimentation unit the same surface loading, transverse liquid velocity, retention time, and geometric proportions that are
encountered in full-scale practice. Practical operational considerations demand
that the sludge be settled, concentrated, and drawn-off at one location. The
settler design, shown in Figure 1, is a compromise of desired characteristics and
practical operational and construction limitations. The unit is designed as a right
rectangular pyramid with steep side walls to prevent solids "hang-up" and to enhance the solid-liquid separation phase.
Influent and effluent structures were designed to minimize stray current problems caused by the proximity of inlets and outlets.   The influent nipple on the
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