Development of a Symbiotic
Algal-Bacterial System for
Nutrient Removal from Wastewater
FRANK J. HUMENIK, Research Associate
GEORGE P. HANNA, JR., Professor
Civil Engineering Department
The Ohio State University
INTRODUCTION
For many years secondary biological waste treatment has been considered
adequate to provide aesthetically acceptable municipal waste effluents, relatively free
of eutrophying nutrients. However, today with our ever increasing volumes and
concentrations of wastes, the contemporary biological methods are falling short of
the need to remove a sufficient amount of these added nutrients in order to adequately maintain the desired quality of the receiving waters. The observations of algal
activity in the nutrient rich receiving waters has led to consideration of third stage
treatment utilizing algal metabolism as the biological means for controlled uptake of
these eutrophying nutrients. This approach poses a further consideration, the subject of this study, directed toward a more comprehensive secondary process involving
more extensive algal participation, that more closely simulates the overall purifying
activity of the natural environment. This process embodies the observed combined
purifying ability of the algae and bacteria in receiving waters through controlled in-
plant operations.
That algae are capable of enhancing the removal of certain wastewater nutrients
is attested to by many investigators who have reported results from studies of algal
oxidation (stabilization) ponds and lagoons (1,2). Gotaas and co-workers (3) showed
that unprocessed sewage provides a very favorable medium for the growth of algal-
bacterial mixed cultures. This suggests an important symbiotic relationship since inorganic carbon, a major requirement for algae, is limited even in sewage with high
natural alkalinity (3, 4, 5).
Ludwig and co-workers (4, 5, 6), investigated the symbiotic activity of algae
and bacteria in aerated laboratory cultures, and reported on the application of algal
symbiosis in oxidation ponds. Recently the concept of "activated algae" was introduced by McKinney and Wahbeh (7), who proposed the combination of bacteria and
algae in a controlled treatment process to remove wastewater components stimulatory
to algal blooms in receiving waters. They reported that the developed biological
system was capable of reducing the BOD, nitrogen and phosphorus in a single unit,
and concluded that the key to this new process was related to the ability of the algae
to "Self-flocculate to form activated algae similar to activated sludge." Goodman and
Weis (8) reported on the preliminary development of a full scale activated algae
process, discussed scale-up difficulties, and indicated lack of information to date to
properly evaluate the feasibility of such a full scale system.
The possible harvest of algal calls for their high nutrient values as established
in several animal feeding trials (9, 10) and nutrition studies (11) has also added to the
attractiveness of waste treatment by nutrient conversion through algal metabolism.
-480-