Effects of Refrigerated Storage on the
Characteristics of Waste
FRANKLIN J. AGARDY, Associate Professor
Department of Civil Engineering
San Jose State College
San Jose, California
MICHAEL L. KIADO, Graduate Student
University of California
Berkeley, California
INTRODUCTION
The characterization of a waste, whether it be domestic or industrial in origin,
begins with the sample. When numerous samples are taken and many analyses required, it is customary to store samples and program the analyses as time allows.
This storage is almost universally carried out under refrigeration. Further, refrigerated storage is usually an intrinsic part of the collection of time-composite
samples. The inherent assumption is that the sample will remain "static" if refrigerated. Standard Methods (1) recommends that samples requiring storage should
be stored at low temperatures (0 - 10 C) and in the dark.
It is recognized that samples held at room temperature will undergo changes
as a result of: 1) volatilization; 2) biological activity; and 3) chemical activity.
The assumption that refrigerated storage will curtail these activities requires further discussion and investigation.
REFRIGERATION WITHOUT FREEZING
Many laboratories store samples at 4 C, a temperature recommended in Standard Methods (1) for the storage or compositing of industrial wastes. This temperature is also specifically recommended for storage of samples held for subsequent
BOD analysis. However, Gotaas(2) demonstrated that BOD values, as determined
by Warburg analysis, were subject to error when samples were held at temperatures
as low as 5 C. Ellison (3) also found evidence of biological activity at storage
temperatures of 6 C. These investigations merely substantiated the fact that psy-
chrophilic bacteria can metabolize at temperatures as low as 5 C. As a result of
studies of this type, it is generally felt that storage should not exceed one day.
Having established the fact that chilling will not stop metabolism, it can be
assumed that continuing biological activity can change the biological, physical,
and chemical characteristics of the waste when stored at low temperature. The
question to be answered concerns the degree to which these changes occur during
the storage interval.
FROZEN STORAGE
It has been fairly well established that freezing will curtail biological activity. Most bacteriology laboratories use this method of storage to preserve bacterial
cultures. However, experiments carried out by Morgan and Clarke (4) and Fogarty
and Reeder (5) indicate that significant errors will occur in certain analyses per-
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