Nutrient Removal by Activated Algae
E. CORBIN McGRIFF Jr., Assistant Professor
Mississippi State University
State College, Mississippi
ROSS E. McKINNEY,    Professor
Department of Civil Engineering
University of Kansas
Lawrence, Kansas
HISTORY
Waste treatment processes in the United States initially consisted of plain
sedimentation or primary treatment, which physically removed suspended settleable
pollutants. As the country became more industrialized and as the population increased,
primary treatment became inutile as a sole source of treatment. The inability of primary
treatment alone to stem the increased pollution engendered biological or secondary
treatment as a process in tandem. Since its inception, biological treatment has played a
major role in the field of water pollution abatement. Biological treatment, which converts
organic matter to ammonia, phosphate, carbon dioxide, and water, generally consists of
either a trickling filter or an activated sludge system. These end products then become the
topic of much discussion since, if not utilized by the biological system, they are discharged
into the receiving stream.
The introduction of effluent from wastewater treatment plants and often the
introduction of raw wastes into water ways tend to degrade the water quality. Raw sewage
obviously degrades the water quality but even the treated effluent contains the above-
mentioned dissolved nutrients. These nutrients are a major factor in promoting algal
blooms, more popularly known as eutrophication. Eutrophication is the major problem
facing the environmental health engineer today.
TERTIARY TREATMENT
For the last quarter century man has observed the changes procreated by excessive
fertilization. Passive realization has finally engendered active concern for effective
methodology for the abatement of excessive fertilization. To combat sewage fertilization,
pollution control authorities began taking action to limit the discharge of sewage
phosphate. In 1964 Virginia became the first state to refuse to grant a permit for a new
sewage treatment plant until the design included phosphate removal. In 1966 the cities of
Detroit, Michigan, and Cleveland, Ohio, were required by their respective state water
pollution control agencies to remove 80 percent of the soluble phosphate present in their
waste water.
In order to meet this phosphate removal requirement, the engineer began to investigate
a third phase of treatment, conveniently called tertiary treatment. Tertiary treatment
incompasses the removal of dissolved nutrients, such as nitrogen and phosphorus, from the
effluent of wastewater treatment systems in order to preclude the proliferation of algae in
the receiving streams.
Algae in the presence of light are photo-lithotrophs, that is, they obtain energy from
light and carbon from inorganic sources, and are therefore able to flourish with an adequate
amount of sunlight and dissolved nutrients. The ultimate result of the copious growth of
algae is a reduction in water quality. Many algae are responsible for tastes, odors, turbidity,
and color in drinking water and for clogging filters in water treatment plants. Floating
layers of algae are particularly disagreeable to  swimmers,  boaters,  fishermen, and
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