MANAGEMENT OF BIOLOGICAL TREATMENT PLANT UPSETS:
AVOIDANCE, DETECTION AND MINIMIZATION
Brian P. Flynn, Chemical Engineer
Environmental Resources Management, Inc.
West Chester, Pennsylvania 19380
INTRODUCTION
The continued application of the Water Pollution Control Act of 1972 (PL 92-500)
has resulted in the imposition of effluent standards on virtually every municipal and industrial point source discharge in the United States. Recent reports have indicated that many
publicly owned treatment works (POTW) are not achieving their effluent limits. Along
with numerous enforcement actions against industrial dischargers operating their own
treatment plants, it has become obvious that a great deal of effort must be expended
towards proper treatment plant operation, shifting emphasis away from simple capital construction. Since many treatment plants are biologically based and operating within their
design limits, the avoidance, detection, and/or minimization of biological upsets has
become a critical element in achieving effluent limitations.
This chapter wdl detad the many causes of biological upsets and wdl present a basic,
integrated, three-step approach to avoiding or minimizing their impact. The three steps
are:
1. Avoidance. Means are available to prevent many potential biological upsets.
2. Detection. Most biological upsets can be "seen" by one or more methods as they
start to occur. Sometimes, the upset can then be avoided. Certainly, it can be
minimized.
3. Minimization. Within limits, upsets can be managed to minimize their adverse
effects on the environment and permit limits.
Two useful case histories, one real and one theoretical, wdl be detaded in order to
yield insight into the overall management technique.
DISCUSSION
Avoidance
Upsets occur in waste treatment plants due to improper operation or the nature of the
wastewater. It follows that the first step to be taken to avoid upsets is proper operation,
/.<?., elimination of self-induced upsets. Table I summarizes the more common operating
parameters which must be kept under control. One frequent mistake is to assume a
parameter is in range and not check it, e.g., an industrial activated sludge plant may normally receive adequate phosphorous, but due to the shutdown of a phosphorous waste
producing manufacturing process (unnoticed by treatment plant personnel) may become
phosphorous deficient, thus inducing an upset. Table II summarizes the type and frequency
of data collection and analysis that should be maintained in order to assure that treatment plant operation is adequate. Without this data it is sometimes impossible to define
the cause of an upset after it occurs.
The second step to be taken to avoid upsets is to manage the wasteload. At industrial
sites the wastewater treatment plant is usually the only major process which has no control over its major raw material-the wastewater! This lack of control can be avoided
without undue stress on manufacturing schedules. Individual or aggregate waste streams
can be defined for each product, i.e., a waste standard. See Table III for an example.
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