Laboratory Procedures for
Bio-Oxidation Design
W. WESLEY ECKENFELDER, Associate Professor of Civil Engineering
EDWIN L. BARNHART, Research Assistant
Manhattan College
New York 71, New York
The use of batch and continuous laboratory studies to evaluate biological
oxidation systems and to provide design criteria for either pilot or full-scale
treatment systems provides an economic approach to many waste treatment
problems. The results of batch studies may, under favorable conditions, provide reliable data for bio-oxidation design. The studies of Weston and Stack
(1) and Busch et al (2) provide detailed discussion of the points for and against
the use of batch studies in biological systems.
To provide the maximum information from limited laboratory studies,
procedures must be developed which consider a maximum number of the pertinent variables without requiring an unreasonable amount of work. In this
paper the authors shall present procedures for three types of systems-, conventional activated sludge, high-rate activated sludge, and aerated lagoons.
The author believes that these procedures provide the maximum of usable
information without necessitating unusual laboratory work.
GENERAL
Sludge Acclimitization
The first step in any investigation of biological system is to provide a
sludge which is properly acclimitized to the waste feed. Not only the type
of feed but also the loading rate and the feeding schedule will influence the
type and efficiency of the sludge culture developed. Wherever possible,
sludge acclimitization should be carried on in a continuous system. Often,
however, such a system may not be possible with the limited faculties available in field tests. In such cases, a batch-fed system, utilizing proper loading levels, reasonable aeration periods, and settling times similar to those in
practice, may be employed.
The magnitude of loading levels, etc., must be defined by experience
with similar wastes or the expected operation of the system.
The proper acclimitization of a sludge is defined by uniform: BOD removal, oxygen utilization rate, settling characteristics, and solids buildup.
For most systems the time of acclimitization will vary from five to 10 days.
Acclimitization procedures have been described by Sawyer (5) and Heukelekian (6).
Test Methods and Equipment
Tests for BOD, suspended solids, etc., are conducted in accordance with
Standard Methods (3) procedures. The oxygen utilization rate can be measured polarographically as described by Eckenfelder and Buris (4) or employing
oxygen utilometers. It has been found convenient to carry on aeration in
tubes with rounded bases to eliminate "dead spots." Aloxite stones located
in the base of such tubes provide sufficient air to maintain aerobic conditions.
Enough care must be taken during test runs to prevent high foaming which will
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