Use of Algal Assays in Studying Eutrophication Problems
207
test flasks, an inoculum of the same age and concentration, and the same methods for
sample preparation. In the first in t erlab oratory test, algal growth responses in various
concentrations of the culture medium were evaluated as well as growth responses in the
culture medium with important nutrients deleted and added back in varying
concentrations. In the second interlaboratory test, two natural lake water samples were
assayed; one from a common source, collected from a lake near Corvallis, Oregon, and
another collected from a lake located in the vicinity of the participating laboratory. Each
sample was treated prior to assaying by both autoclaving and membrane filtration and
additions (spikes) of various concentrations of nutrients were made to the treated waters.
Excellent agreement in the data was obtained among the participating laboratories and it
was felt that the Bottle Test had undergone sufficient evaluation and refinement to be
considered reliable. As a result the Algal Assay Procedure: Bottle Test (2) was published
in August, 1971.
PRACTICAL APPLICATION OF ASSAY PROCEDURE
Assessment of Effects of Changes in Waste Treatment Processes on Receiving Waters
At our laboratory we have been using the Bottle Test assay as a tool in solving several
practical problems relating to eutrophication. We are, for example, involved in several
projects concerning the restoration of lakes. One of these projects is located at Shagawa
Lake, Minnesota. Shagawa Lake at normal level has an area of 2,337 acres (946 ha), a
mean depth of 22 feet (6.7 m) and a capacity of 45,000 acre-feet (5,553,000 m
3 ). The
retention time is approximately one year. The lake received primary wastewater effluent
from the City of Ely from 1903 to 1954 and secondary wastewater effluent since 1954.
Nutrient budgets on the surface inflow indicate that about 70 percent of the total
phosphorus and about 25 percent of the total nitrogen are from the wastewater treatment
plant. About 80 percent of the surface inflow of water to the lake comes from Burntside
River, its main tributary, and about two percent from the wastewater treatment plant. In
1968 the National Eutrophication Research Program began operation of a pilot scale
advanced waste treatment plant, essentially designed for phosphorus removal, and using
the city's secondary wastewater as the feed source. The principal aim of the project was
to estimate, through laboratory and in situ algal assays in conjunction with chemical and
physical analysis and limnological investigations, whether or not the lake would recover
from its present advanced stage of eutrophication if all the secondary wastewater effluent
entering the lake were similarly stripped of phosphorus (3). The phosphorus stripped
effluent is referred to as "tertiary wastewater" in this paper.
In laboratory assays the samples tested included secondary wastewater effluent,
tertiary wastewater effluent, Shagawa Lake water, and Burntside River water collected at
several times during the year. Additions to the lake and river waters included phosphorus
(as K 2 HP0 4 ) in concentrations ranging from 0.02 to 0.06 mg P/1 and/or nitrogen (as
NaNÖ 3 ) in concentrations ranging from 0.5 to 1.0 mg N/1 as well as the wastewater
effluents. Carbon (as NaHC0 3 ) was added in concentrations ranging from 10 to 20 mg
C/1. PAAP culture medium in several dilutions, served as a control. Table 2 shows the
growth (mg dry wt/1) of Selenastrum capricornutum obtained in membrane filtered
Shagawa Lake and Burntside River waters with the various nutrient additions. Shagawa
Lake water supported over 12 times the amount of algal growth produced in Burntside
River water. The data show that Burntside River water is phosphorus-limited for algal
207
test flasks, an inoculum of the same age and concentration, and the same methods for
sample preparation. In the first in t erlab oratory test, algal growth responses in various
concentrations of the culture medium were evaluated as well as growth responses in the
culture medium with important nutrients deleted and added back in varying
concentrations. In the second interlaboratory test, two natural lake water samples were
assayed; one from a common source, collected from a lake near Corvallis, Oregon, and
another collected from a lake located in the vicinity of the participating laboratory. Each
sample was treated prior to assaying by both autoclaving and membrane filtration and
additions (spikes) of various concentrations of nutrients were made to the treated waters.
Excellent agreement in the data was obtained among the participating laboratories and it
was felt that the Bottle Test had undergone sufficient evaluation and refinement to be
considered reliable. As a result the Algal Assay Procedure: Bottle Test (2) was published
in August, 1971.
PRACTICAL APPLICATION OF ASSAY PROCEDURE
Assessment of Effects of Changes in Waste Treatment Processes on Receiving Waters
At our laboratory we have been using the Bottle Test assay as a tool in solving several
practical problems relating to eutrophication. We are, for example, involved in several
projects concerning the restoration of lakes. One of these projects is located at Shagawa
Lake, Minnesota. Shagawa Lake at normal level has an area of 2,337 acres (946 ha), a
mean depth of 22 feet (6.7 m) and a capacity of 45,000 acre-feet (5,553,000 m
3 ). The
retention time is approximately one year. The lake received primary wastewater effluent
from the City of Ely from 1903 to 1954 and secondary wastewater effluent since 1954.
Nutrient budgets on the surface inflow indicate that about 70 percent of the total
phosphorus and about 25 percent of the total nitrogen are from the wastewater treatment
plant. About 80 percent of the surface inflow of water to the lake comes from Burntside
River, its main tributary, and about two percent from the wastewater treatment plant. In
1968 the National Eutrophication Research Program began operation of a pilot scale
advanced waste treatment plant, essentially designed for phosphorus removal, and using
the city's secondary wastewater as the feed source. The principal aim of the project was
to estimate, through laboratory and in situ algal assays in conjunction with chemical and
physical analysis and limnological investigations, whether or not the lake would recover
from its present advanced stage of eutrophication if all the secondary wastewater effluent
entering the lake were similarly stripped of phosphorus (3). The phosphorus stripped
effluent is referred to as "tertiary wastewater" in this paper.
In laboratory assays the samples tested included secondary wastewater effluent,
tertiary wastewater effluent, Shagawa Lake water, and Burntside River water collected at
several times during the year. Additions to the lake and river waters included phosphorus
(as K 2 HP0 4 ) in concentrations ranging from 0.02 to 0.06 mg P/1 and/or nitrogen (as
NaNÖ 3 ) in concentrations ranging from 0.5 to 1.0 mg N/1 as well as the wastewater
effluents. Carbon (as NaHC0 3 ) was added in concentrations ranging from 10 to 20 mg
C/1. PAAP culture medium in several dilutions, served as a control. Table 2 shows the
growth (mg dry wt/1) of Selenastrum capricornutum obtained in membrane filtered
Shagawa Lake and Burntside River waters with the various nutrient additions. Shagawa
Lake water supported over 12 times the amount of algal growth produced in Burntside
River water. The data show that Burntside River water is phosphorus-limited for algal