Phosphorus Uptake by P-Starved Algae
HARDAM S. AZAD, Pollution Control Scientist
1711 Golf Road, Apartment 205
Waukegan, Illinois
JACK A. BORCHARDT, Professor
Civil Engineering Department
University of Michigan
Ann Arbor, Michigan
INTRODUCTION
The general problem of eutrophication of our natural waters seems to have
captured the imagination of the public. Certainly lake fertilization as a process
can be readily understood by everyone and equated with damage and loss, at least
on an esthetic basis. But, while this general problem of aging of a lake is a well
recognized environmental problem, the quantitive evaluation of the process itself
is almost impossible to deal with. For example, in a given situation, the question might be asked, what would be the natural rate of eutrophication of the body
of water in question, and how have man's various activities on the tributary
watershed increased nature's rate of change? The answer to this question is presently unavailable, but its definition would immediately provide the means for
assessment of the economic life of the resource. Each improvement in waste
treatment could then be equated with added years of life, and cost-benefit ratios
would be straightforward.
The problem is made up of many facets but, as a first step it seems logical
to consider the impact of phosphorus on an aquatic system. All forms of waste
contain this element (1) in larger or smaller quantities. Over the past twenty
years phosphorus in waste effluents has doubled in concentration. Evidence indicates that the presence of phosphorus is critical in biological energy systems
and, further, that certain controls on the drainage systems are technologically
practical, even though methodology is presently rather imperfectly defined.
At the present time phosphorus removal is being proposed by control agencies
as an objective in waste treatment, purely because it seems necessary to do something, and not because a given removal will produce a known response in the
ecosystem.
This general study (2,3) was initiated to elucidate the cause and effect relationships that exist among the factors that influence the growth of green algae
in the presence of given concentrations of phosphorus in an aqueous environment.
The phase of the work to be reported here is primarily concerned with the response of the starved system to sudden slugs of phosphate.
METHODS
The green algae Chlorella and Scenedesmus were grown as large scale continuous uni-algal-cultures under rigorously controlled environmental conditions.
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