EPA-R3-72-001
August 1972 Ecological Research Series
Role of Phosphorus in Eutrophication
National Environmental Research Center
Office of Research and Monitoring
U.S. Environmental Protection Agency
Corvallis, Oregan 97330
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and
Monitoring, Environmental Protection Agency, have
been grouped into five series. These five broad
categories were established to facilitate further
development and application of environmental
technology. Elimination of traditional grouping
was consciously planned to foster technology
transfer and a maximum interface in related
fields. The five series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
This report has been assigned to the ECOLOGICAL
RESEARCH series. This series describes research
on the effects of pollution on humans, plant and
animal species, and materials. Problems are
assessed for their long- and short-term
influences. Investigations include formation,
transport, and pathway studies to determine the
fate of pollutants and their effects. This work
provides the technical basis for setting standards
to minimize undesirable changes in living
organisms in the aquatic, terrestrial and
atmospheric environments*
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EPA-R3-72-001
August 1972
ROLE OF PHOSPHORUS
IN
EUTROPHICATION
A. F. Bartsch
National Environmental Research Center
200 S. W. 35th Street
Corvallis, Oregon 97330
Program Element 328201
NATIONAL ENVIRONMENTAL RESEARCH CENTER
OFFICE OF RESEARCH AND MONITORING
U.S. ENVIRONMENTAL PROTECTION AGENCY
CORVALLIS, OREGON 97330
For sale by the Superintendent of Documents, U.S. Government Printing Office
Washington, B.C., 20402 - Price 55 cents
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ABSTRACT
The process of eutrophication is a natural one, often accelerated
greatly by man's activities that contribute nutrients. The key nutrient
is phosphorus. Although there is no simple relationship, it is clear
that increasing phosphorus content frequently leads to accelerated
eutrophication. Of all important nutrients, phosphorus is most
controllable.
Sources of phosphorus include runoff from undisturbed agricultural
and urban lands; waste from water craft; industrial and domestic
wastes; biological sources; and precipitation. Also, the most important
single source is municipal sewage, fortunately, the most potentially
controllable of all inputs.
Control efforts follow five basic directions: Limiting fertility;
improving food webs; stimulating plant diseases and parasites;
recycling nutrient-laden water to agricultural and forest lands;
and using toxic chemicals to kill vegetation. Limitation of nutrients
is the most desirable approach, particularly through curtailing
phosphorus inputs.
m
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CONTENTS
Section Page
I Conclusions 1
II Introduction 3
III Causes of Eutrophication 7
IV Significance of Phosphorus 11
V Sources of Phosphorus 21
33
VI Control of Eutrophication
39
VII References
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FIGURES
PAGE
1 PROGRESSIVE CHANGES IN NATURAL EUTROPHI CATION 7
2 INCREASING PHOSPHORUS CONCENTRATIONS IN
PHOSPHORUS-POLLUTED LAKES 15
3 ALGAL YIELDS, AS DRY WEIGHT PER LITER,
IN OREGON LAKE WATERS HAVING PHOSPHORUS
CONTENT AS SHOWN 17
4 THE RELATIONSHIP BETWEEN PHOTOSYNTHESIS AT
OPTIMAL ILLUMINATION AND CONCENTRATIONS OF
TOTAL PHOSPHORUS IN SURFACE SAMPLES FROM 11
LOCALITIES IN LAKE MINNETONKA 19
VI
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TABLES
No. Page
1 Elemental Composition of Freshwater Algae 8
2 Photosynthetic Rates of Phytoplankton in
Oligotrophic and Eutrophic Lakes 9
3 Nitrogen and Phosphorus Concentrations
in the Great Lakes 11
4 Permissible Loading Levels for Total Nitrogen
and Total Phosphorus 12
5 Algal Stimulation by Tertiary Effluent
Containing Restored Phosphorus 16
6 Mean Concentration Cvg/1) of Chlorophyll a_
and Phosphorus in Surface Waters at 11
Localities in Lake Minnetonka during July
and August, 1968 and 1969 18
7 Commercial Phosphorus Consumption in the
United States (million pounds) 24
8 Phosphorus Concentrations in German Industrial
Wastes 24
9 Estimated Quantity of Phosphorus Discharges
to Receiving Waters in the U. S. in 1968 from
the Sewered Population 26
10 Estimated Phosphorus Removals by Municipal Sewage
Treatment in 168 27
11 Detergent History 29
12 Synthetic Detergent Formulas 30
13 Concentration of Phosphorus in Detergent Formulation
as Percent Phosphorus 31
14 Comparison of Various Plant Nutrients in Respect to
(A) Whether They are Ever Growth-Controlling in Lakes
and CB) Whether They are Controllable by Man. Elements
Listed in Order of Increasing Atomic Weight. Note that
Phosphorus is the Only Element Meeting Both Requirements 35
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SECTION I
CONCLUSIONS
In light of our present knowledge of eutrophication, its causes
and prospects for control, following are appropriate conclusions:
1. It is affirmed that limiting phosphorus availability in
lakes is the single, most important and necessary step to be taken
now in eutrophication control.
2. The most effective way to do this is to reduce phosphorus
inputs.
3. Because all inputs are additive, and therefore potentially
significant, all should be considered for control.
4. Municipal sewage is the major point source. All such
discharges to lakes and other susceptible waters should be treated
to reduce phosphorus content to realistic target leve.ls.
5. Phosphorus contributions to sewage should be reduced in every
feasible way.
6. Nutrient budgets should be established for all major lakes to
facilitate curtailing nutrient inputs from all significant diffuse and
point sources.
7. Technology, where not at hand, must be developed to effectively
curtail phosphorus inputs from all significant point and diffuse sources.
8. Where slow flushing impedes improvement from curtailed
phosphorus inputs, accessory steps to inactivate, harvest, or otherwise
retrieve nutrients from lakes must be considered.
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SECTION II
INTRODUCTION
During the past several decades a growing anxiety has appeared among
environmentalists, government officials, and the general public over
the obvious and continuing deterioration of the Nation's lakes. In
many of them, changes in water quality and usefulness have been perceptible
in a single human lifetime, and in some lakes, such as Lake Erie, change
has been even more rapid. These changes are eutrophication, which has
many symptoms. Excess growths of algae and other aquatic plants are
the most destructive and distasteful ones.
Many interacting factors contribute to the overall process of eutro-
phi cation--a term known more widely now to mean the nutrient enrichment
of waters. Once in motion, eutrophication brings on a number of related
changes in addition to increased production of algae and other aquatic
plants—deterioration of desirable fisheries and water quality, and
other responses that impair water uses and are found objectionable.
In whatever way lakes originated, they soon acquired nutrients from
the earth, the air, and the remains of plants and animals. If sufficient
in amount, these nutrients supported growing aquatic plants. As inputs
continued, fertility and productivity increased, in many cases reaching
considerable levels. Changes like these still go on but at differing
paces in different lakes, the rate varying at different times, sometimes
the direction of change even reversing. Natural factors that functioned
during past centuries or millenia have left some lakes relatively untouched
as pristine lakes—Lake Tahoe in California, Crater and Waldo lakes
in Oregon, for example. Others, exposed during a similar time span,
have reached advanced stages of natural eutrophication. In their new
eutrophic character, such lakes now range from ones with the blemish
of frequent dense algal blooms* to a plot of dry land that shows where
the now extinct lake once had been.
It has been known for at least 50 years that people accelerate eutro-
phication. Such resulting change can be rapid and occur in years to
tens of years where human populations are sufficiently dense. Rarely
is the human influence as bizarre or direct as in the Lake of Blood
(Lago Yarquacocha) high in the Andes (1). Here, according to legend,
the continual bloom of blue-green algae depends on a persistent rich
supply of nitrogen and phosphorus from the time, during the Inca wars,
when 10,000 dead warriors were thrown into the lake.
Thus, one can distinguish "natural" from "accelerated," "artificial,"
or "cultural" eutrophication. But such changes can be largely reversed
*Dense populations of free-floating algae that give the water a greenish,
often peasoup, appearance.
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if the human influence is eliminated in time. At least some lakes are
changing faster under the influence of people than the rate of human
population growth. Unless resolute steps are taken, further impacts
on lakes and increasing threats of destruction must be expected. Very
likely, also, these influences will intensify as population grows beyond
the present 205,000,000 persons. The human influence of greatest concern
is our persistent habit of augmenting lake fertility far beyond the
pace of natural contributions. It is readily apparent that this human
threat is real and cause for national concern.
Eutrophication is a worldwide problem. Because the human influence
has prevailed longer in some other countries, they also have a longer
recorded history of cultural eutrophication than the United States.
But here, too, the problem is growing more prominent and widespread
than a few decades ago. Through the press, many persons now are aware
of trouble in the Great Lakes, the St. Lawrence River, the Potomac Estuary,
and many other threatened waters. While it is not known how many of
this Nation's 100,000 small lakes are afflicted, a recent preliminary
survey (2) shows the problem occurring with some intensity in at least
40 of the 50 states. In states well endowed with lakes which contribute
substantially to the economy, the dollar losses from impaired recreation,
depressed resort patronage, property depreciation, and costs of ameliorating
the problem certainly must extend to hundreds of millions of dollars
annually. In these states, and especially in others not so well endowed
with water where the competition for it is more keen, the loss of lakes
for citizen use is perhaps even more serious.
Full-blown eutrophication is obvious to most people, but when it is
only beginning, the scientist must search out the more subtle symptoms
for signals of impending trouble. They include (3, 4, 5, 6, 7, 8):
(a) analytical detection of increased amounts of nutrients, (b) measurable
increases in algal populations, (c) decreasing transparency of the water,
(d) in deep lakes that stratify thermally, gradually decreasing dissolved
oxygen in the bottom water, (e) decreasing organism diversity, sometimes
preceded briefly by increasing diversity, (f) appearance of new, undesirable
species and disappearance of old ones, and (g) increased silting and
accelerated accumulation of bottom sediments which add to the other
signs that eutrophication progress should be a matter of public concern.
Publications related to this subject number in the thousands. It is
not possible, therefore, to cite here more than a handful that bear
in some important way on the significance of phosphorus in eutrophication.
The serious student is referred to the Eutrophication Information Center
at the University of Wisconsin as a national repository for much of
the world's pertinent literature. For the interested reader, the following
would give general or comprehensive coverage of eutrophication:
Eutrophication: Causes, Consequences, Correctives (9)
Science Year, 1971 (10)
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Algae and Metropolitan Wastes (11)
Environmental Requirements of Blue-Green Algae (12)
Eutrophication - A Review (13)
Modeling of the Eutrophication Process (14)
Scientific Fundamentals of the Eutrophication of Lakes and Flowing
Waters, with Particular Reference to Nitrogen and Phosphorus as
Factors in Eutrophication (6)
Eutrophication (15)
I wish here to say "thank you" for the helpful assistance of Dr.
G. A. Rohlich, formerly Director,* and staff of the Water Resources
Center, Unversity of Wisconsin, at Madison, and Dr. J. R. Vallentyne,
Scientific Leader, Eutrophication Section, Freshwater Institute,
Winnipeg, Canada. The following colleagues in the National Environmental
Research Center, Corvallis, were most helpful, also, in providing
pertinent data, ideas, and continuing counsel in connection with this
document: Mr. Daniel F. Krawczyk, Chief, Consolidated Laboratory
Services; Mr. Thomas E. Maloney, Chief, Dr. Kenneth W. Malueg, Chief,
Lake Restoration Section, and Dr. Charles F. Powers, Chief, Technology
Development Section, of the National Eutrophication Research Program;
and Dr. L. P. Seyb, Assistant Director, Pacific Northwest Water
Laboratory.
*Presently, he is C. W. Cook Professor of Environmental Engineering,
University of Texas, Austin.
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SECTION III
CAUSES OF EUTROPHICATION
This section explores the questions of how and why lakes and other waters
become eutrophic. It is generally believed that lakes originally
are o1iqotrophic--low in nutrients, relatively deep, with low productivity
and ample oxygen in the deep water (hypolimnion). As time passes,
the lake is enriched, productivity increases, hypolimnetic dissolved
oxygen is reduced by decay and mineralization processes, and the lake
basin begins to fill. It is becoming a eutrophic lake. Ultimately,
eutrophication leads to the lake's extinction. Lakes in the midpoint
of these changes are mesotrophic. Graphic representation of this
concept is shown in Fig. 1 (15).
.s?
<
zS
P 8
£*£
NATURAL EUTROPHICATION
EXTINCTION-
o M o /^AQUATIC
u /WEED GROWTH
OVER LARGE
AREA OF LAKE
OF THERMOCLINE
AGE OF LAKE
Fig. 1 Progressive Changes in Natural Eutrophication
From Lee (15)
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Ample scientific evidence supports this concept. The earliest known
documentation of eutrophication symptoms dates to Biblical days and
mention of the red coloring of the Nile (Exodus 7:20-21), no doubt
caused by algae. Evidence has been found (16) of man-induced
eutrophication as early as 191 B. C. in Lake Monterosi during the
building of the Via Cassia by the Romans. Paleolimnological
investigations of lake sediments (17) also retrace the process
of eutrophication through the years. Man's influence seems to be
expanding ever since these early times in the expression of
accelerated eutrophication.
The most significant single factor in stimulating eutrophication is
nutrient input from the lake's drainage basin. If basin land is
fertile, the lake water very probably will be fertile. If the
basin is large in relation to lake volume, opportunities for
nutrient input from cities, farms, and other sources are multiplied.
Lakes that have a small or infertile drainage basin, such as
Crater Lake with only 163 square miles, receive little input in
contrast with others, such as Upper Klamath Lake, Oregon, with
3,810 square miles, of which some are cultivated.
Thus, fertility obviously has a quantitative aspect. It has a
qualitative aspect, also, because the potential of a lake to grow
plants depends on the right mix of needed chemical elements. The
following table (Table 1) gives the principal elemental composition
of some freshwater algae. While at least implying the proportionate
nutrient needs, it may not reflect exactly the relative concentrations
required in lake water.
Table 1,
El ement
Carbon
Oxygen
Hydrogen
Nitrogen
Phosphorus
Sulfur
Magnesium
Potassium
Iron
Manganese
Calcium
Strontium
Copper
Zinc
Silicon
Elemental Composition of Freshwater Algae
Percent dry wt.
49.51
17.40
6.57
1.39
1.35
0.42
0.26
0.04
0.02
0.02
0.006
0.0004
0.0008
0.0004
1.00
70.17 (18)
33.20 (18)
10.20 (18)
10.98 (18)
2.76 (19)
0.77 (19)
1.51 (20)
1.44 (20)
3.45 (19)
2.60 (19)
0.40 (19)
0.051(19)
0.034(19)
0.009(19)
50.00 (21)
8
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In addition to these elements, extremely minute amounts of others,
such as molybdenum, cobalt, sodium, boron, and vanadium are required
in the nutrition of some algae. Vitamin B,2> thiamine, and biotin
are important, also.
A lake's algal production rate is governed by the simultaneous operation
of a number of controlling factors. Nutrient availability is but
a single, though exceedingly important requirement. The historical
performances of numerous lakes verify that the extent of production
generally is related directly to nutrient abundance (5, 22). This
relationship can be demonstrated easily with laboratory algal assays,
giving knowledge to affirm that nutrient-rich lakes are expected to
produce large algal crops. It also helps explain why the total of
human activities that increase nutrient levels in various ways so
strikingly accelerate eutrophication. The following table (Table
2) expresses this principle by showing approximate photosynthetic
rates of free-floating algae (phytoplankton) that occur in response
to increasing nutrient supplies that become available as lakes shift
from oligotrophy to eutrophy.
Table 2.* Photosynthetic Rates of Phytoplankton
in Oligotrophic and Eutrophic Lakes
01 i go trophic** Eutrophic
Natural** Polluted**
Mean rates in ?
growing season 30 - 100 300 - 1,000 1,500 - 3,000 mg C/m /day***
Annual rates 7-25 75 - 250 350 - 700 g C/m2/year***
*Modified from Vollenweider (6).
** Oligotrophic = poor in nutrients; natural = rich in nutrients; polluted =
very rich in nutrients.
*** If these values of carbon fixed per square meter per day or year
(representing photosynthetic rate) are multiplied by 2, they approximate
the algal weight.
Another expression of a lake's response to increasing fertility is the
maximum plankton density or standing cron attained during the year:
ultra-oligotrophic lakes, less than 1 cm /m ; highly eutrophic lakes,
more or less exceeding a value of 10 cm /m ; and mesotrophic lakes,
between these two limits (6).
Major controlling factors in addition to nutrient supplies include
lake morphology, geography, climate, and temperature. Mean depth
is the most significant dimension (23), and large, deep lakes are
more resistant to eutrophying influences than small, shallow ones.
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Availability of light energy to trigger photosynthesis is another
principal factor influencing biological production. Effectiveness
of incoming light depends on: (a) the extent to which algal cells
are kept suspended in the surface-lighted layer by turbulence, and
(b) the depth of the layer in which light is sufficient for effective
photosynthesis. If the volume of the lake participating in photosynthesis
is large in relation to total volume, as in shallow lakes, the lake
will tend toward eutrophic characteristics.
In addition, the greater the length of the shoreline, generally the
greater the productivity. This is because of greater contact of water
with land, more bays and coves, more shallow water area for weed growth,
greater diversification of bottom and margin conditions, less exposed
shoal water, and greater extension of photosynthesis to the bottom.
This latter point is particularly important because the closer and
more permanent the association of the photosynthetic and decomposition
zones, the greater the productivity.
Summer temperature distribution in a lake is determined largely by
configuration of the lake basin and its depth, latitude, and degree
of protection from wind. Shallow lakes with gently sloping basins
resist stratification throughout the summer, while deep lakes with
more precipitous topography tend to stratify into an upper epilimnion,
a well-developed thermocline, and a lower hypo!imm"on. Then the thermocline
acts as a barrier to movement of nutrients from the hypolimnion and
sediment into the photosynthetic zone. This happens even though considerable
sedimented phosphorus may dissolve in the hypolimnion at times when
oxygen is depleted.
10
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SECTION IV
SIGNIFICANCE OF PHOSPHORUS
Ample and increasing nutrients have been identified as a major factor
in fostering eutrophication. There are five important points related
to nutrients: (a) a variety is needed, (b) as nutrients increase,
production rate and algal crop size usually increase, (c) accelerated
eutrophication and increasing nitrogen and phosphorus concentrations
commonly proceed together, (d) oligotrophic lakes usually are phosphorus
limited, and (e) as accelerated eutrophication proceeds, the nitrogen/
phosphorus ratio commonly diminishes with the result that phosphorus
is no longer limiting. The qualitative and quantitative aspects represented
by points a and b have already been discussed.
Studies of eutrophication in numerous lakes around the world have
contributed to better understanding of how nutrients are involved. In
analyzing the roles of nitrogen and phosphorus, recognized as key nutrients
in the process, Vollenweider (6) has drawn upon data for numerous lakes,
especially those in Europe. In this context, he explored the significance
of nitrogen and phosphorus from two points of view: (a) concentrations
available for algal use at a given point in the annual cycle and (b)
rates of supply. He (6) commented on concentration as follows: "Looking
upon the results of these analyses as a whole, it can be said that the
critical levels suggested by Sawyer [24] for the permissible nitrogen and
phosphorus concentrations [less than 10 yg/1 inorganic phosphorus and less
than 300 yg/1 inorganic nitrogen] are borne out, by and large, by conditions
existing in the lakes of Central Europe. Of the two, phosphorus is the
more critical "
As shown in Table 3 below, phosphorus and nitrogen levels found in
the Great Lakes substantially agree with these stated critical levels
in relation to their trophic states:
Table 3.
Nitrogen and Phosphorus Concentrations
in the Great Lakes
Oligotrophic
Lake Superior
Lake Huron
Oligo-mesotrophic
Lake Michigan
Lake Erie
Eutrophic
Lake Erie
Western Basin
Central Basin
Lake Ontario
Total P, yg/1
5 (25), 9 (27)
10 (25), 13 (27)
13 (25), 7-21 (28)
20 (26), 10 (27)
61 (25)
50 (26), 93 (27
30 (26), 16 (27
75 (25), 13 (27)
Total N, yg/1
2-71 (27)
340 (27)
60*(27)
420 (27), 470 (26)
710 (27), 740 (26)
430 (27), 470 (26)
60*(27)
*NH3-N only
11
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Using nutrient input data for 30 lakes in Europe and North America,
Vollenweider (6) also analyzed for trophic state of lakes in relation
to nutrient loading rate. It was concluded that rates are more significant
than maximum concentrations that may occur. Similar analyses have
been made by NERP* for several lakes in the United States. While
both the European and American data are somewhat limited, the following
points are significant. First, a commonly occurring feature of oligotrophic
lakes, such as Lake Tahoe and Waldo Lake, is a total phosphorus loading
less £han 0.2 g/m /yr, and total nitrogen loading, probably less than
5 g/m /yr. Second, fairly serious eutrophication, as in Zlirichsee
(6), Lake Erie and other lakes, is to be expected with a total phosphorus
loading greater than 1 g/m /yr and nitrogen loading of 10 g/m /yr.
Third, the specific critical loading level that separates oligotrophic
and eutrophic waters is probably around 0.2-0.5 g total P/m /yr and
5-10 g total N/m /yr. Fourth, no simple relationship can be expected
among nutrient loading, nutrient concentration, and production because
of a variety of other influencing factors such as depth, extent of
shoreline, flow-through, and detention time as pointed out on page
9. Nevertheless, the following table (Table 4) provides tentative
practical guidelines that are worthy of control consideration.
Table 4.** Permissible Loading Levels for
Total Nitrogen and Total Phosphorus
p
(g/m year)
Permissible load- Dangerous loading
ing, up to: in excess of:
Mean depth
up to:
5 m
10 m
50 m
100 m
150 ra
200 m
N
1.0
1.5
4.0
6.0
7.5
9.0
P
0.07
0.10
0.25
0.40
0.50
0.60
N
2.0
3.0
8.0
12.0
15.0
18.0
P
0.13
0.20
0.50
0.80
1.00
1.20
** Modified from Vollenweider (6)
Not many United States lakes can be checked against this table because
nutrient budgets have not been established. But, certainly, for the
following examples, loading, lake status, and lake vulnerability are
in agreement with it:
* National Eutrophication Research Program, EPA, National Environmental
Research Center, Corvallis, Oregon.
12
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Oligotrophic lakes
Waldo Lake, Oregon (29) - mean depth, 35.7 meters
Estimated input: P 0.0026 g/m /yr
N 0.19 g/nr/yr
Lake Tahoe, Calif.-Nev. (30) - raean depth, 249 meters
Estimated input: P 0.04 g/m£/yr
N 0.23 g/m /yr
Oligo-mesotrophic lakes
Lake Michigan (31) - mean depth, 76.0 meters
Estimated input: P 0.13 g/ig /yr
N 1.3 g/m /yr
Eutrophic lakes
Shagawa Lake, Minn. (29) - mean depth, 6.7 meters
Input: P 0.93 g/m /yr
N 7.3 g/m /yr
Lake Erie, 1967 (26)2 - mean depth, 17.7 meters
Input: P 1.6 g/m?/yr
N 6.8 g/m /yr
Lake Ontario, 1967 (26) - mean depth, 84 meters
Input: P 0.65 g/m /yr
N 8.3 g/mVyr
Algae, like many other microorganisms, have a similar elemental composition.
While differing somewhat among species, mixed algal populations contain
carbon, nitrogen, and phosphorus in a weight ratio approximating 41
carbon, 7.2 nitrogen, and 1 phosphorus.* While perhaps not exact
for all algae, this ratio suggests the pattern of nutrient requirements
and availability ratios in the environment that one would expect to
be near ideal. Further, in keeping with Liebig's Law of the Minimum
(32), the essential nutrient present in least supply relative to need
will limit growth and thus determine size of the algal crop.**
This means that if the environment offers 82 weight units of carbon,
14.4 of nitrogen, but only 1 of phosphorus, growth will be limited
by a deficiency of phosphorus because there is only half as much as
needed. Adding phosphorus in abundance at this point via sewage or
otherwise will destroy its growth-regulating function. This, unfortunately,
is what is now taking place at many localities in this country. This
*This equals an atomic ratio of 106 C, 16 N, and 1 P (34).
**In nature the circumstances may be somewhat more complex in detail
because alga populations are mixtures of species with differing
nutrient requirements and differing demands at different times.
13
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mechanism is an important key in the eutrophication problem and prospects
for control.
A related concern is a resulting gradual decrease in the nitrogen/
phosphorus ratio in many lakes as they receive sewage or other high
phosphorus-bearing pollutants. Oligotrophic lakes commonly have
N/P weight ratios of 15 or more and then are usually phosphorus limited,
but, with accelerated eutrophication, the ratios decrease progressively.
At some points in Western Lake Erie, the weights ratio shifted from
15 to 5 in 14 years as NCU-N increased 50 percent and PCL-P percent
(33). However, for the laKe as a whole, the 1967 ratio was still near
15 (26). In Lake Ontario the 1967 ratio was 30. In eutrophic Upper
Klamath Lake the ratio is 5.6 (by weight) whereas in Oregon's ultra-
oligotrophic Waldo Lake it is 75. Lake Tahoe is an exception in
remaining oligotrophic, with an estimated ratio of 7 or less; it is
also nitrogen limited (30).
Such undesirable shifts in nitrogen/phosphorus ratios usually result
from sewage pollution and other human activities that increase nitrogen
and phosphorus inputs at differing rates. Where sewage pollution
is substantial, sewage, with its nitrogen/phosphorus weight ratio
of about 2-3 (36), adds phosphorus at a proportionately much greater
rate than nitrogen. As a result, the added phosphorus, reaching an
excess and no longer limiting, triggers a new productive response.
This actively proceeds until exhaustion of nitrogen, some other nutrient,
or other environmental shift impedes continued production. In this
process, lake status shifts in the direction of eutrophication. The
greater the increase in phosphorus, the greater the shift is likely
to be. Documented case histories for many lakes, including Lake Washington
at Seattle (7, 37), Zurichsee in Switzerland (5, 38), lakes in Germany
(39), and Lake Pure in Denmark, bear this out (22). It is therefore
characteristic of sewage-polluted eutrophying lakes that phosphorus
concentrations increase considerably with continuing phosphorus pollution,
Fig. 2.
Similarly important is the fact that in numerous lakes that have been
studied, when overall production is low, as in oligotrophic ones,
phosphorus concentrations typically are low (less than 5-20 yg/1).
In such lakes the usual factor limiting production is lack of phosphorus
(6). This fact was also expressed by Thomas (5) on the basis of studies
on 40 European lakes: "It is certain, moreover, that oligotrophic
lakes on which man has had little or no influence all have phosphate
as the limiting factor." Lund (35) also found that the addition of
10 ug PO.-P/l alone to Lake Buttermere (England) led to a massive
development of diatoms and a reduction of soluble silica content in
the water — showing that phosphorus had been limiting.
Vallentyne (40) recently summarized the reported experience in fish
pond fertilization. In short, it shows that addition of phosphate
alone or inorganic fertilizer containing phosphate stimulates
14
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450 r
4O5 -
360 -
315 -
270 -
-•225 -
O)
180 -
O
Q.
135 -
194O
Maumee Bay, Lake Erie
'(eutrophic) 33
Greifensee
(highly eutrophjc) 5
Zurichsee
(eutrophic) 5
Lake Washington
/(eutrophic
I improving to
I oligotrophic)47
__- >.
Bodensee (oligo-mesotrophic)5
195O
YEAR
1960 1970
^) First diversion of sewage.
(3) Diversion 97% complete
Fig. 2 Increasing Phosphorus Concentrations
in Phosphorus-Polluted Lakes
15
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increased production of algae that form the base of fish food supplies.
The significance from a practical viewpoint is that fertilizing with
phosphate increased yields of fish of from 50 to 500 percent or more.
The significance to eutrophication is that when increased algal production
is desired for economic reasons, often the way to attain it is to
add phosphorus.
Nine Oregon lakes were selected to give test waters for algal assays
in a desired range of natural quality (29). In high quality waters
from oligotrophic and mesotrophic lakes, maximum yields of algal cells
were directly related to phosphorus concentrations, but not to carbon
or nitrogen (Fig. 3). Additions of carbon, nitrogen, and phosphorus
were also made to these waters singly and together, and the resulting
algal response determined. In waters from oligotrophic and mesotrophic
lakes, phosphorus added alone consistently resulted in a significant
increase in maximum yields of algal cells.
Numerous other algal assays by this laboratory and others (41, 42)
have shown that municipal sewage, even after secondary treatment,
significantly stimulates algal growth when added to natural waters.
When such sewage is chemically treated to remove phosphorus, it no
longer stimulates algal growth. Moreover, when the original phosphorus
level is restored by adding phosphorus to the effluent, its ability
to stimulate algal growth at about its original level also is restored.
To emphasize this point, following are data (29) showing the effects
on algal growth of restoring phosphorus (as KoHPO*) to tertiary sewage
effluents. These data (Table 5) show the increase in algal biomass
resulting after 14 days incubation from adding back 0.02, 0.04, and
0.06 mg P/l to tertiary treated effluent.
Table 5. Algal Stimulation by Tertiary Effluent
Containing Restored Phosphorus
Relative fluores-
cence units, show-
P-conc. . Dry wt of ing cone, of
(mg/1) p_H Cells/ml algal cells mg/1 chlorophyll a
0 7.6 3,718 0.078 30
.02 7.6 213,136 7.250 5040
.04 7.7 348,196 11.500 5000
.06 7.7 643,645 18.300 5700
Laboratory assays such as these show: (a) the growth-stimulating
capability of sewage, (b) the significance of phosphorus in the stimula-
tion, and (c) verify that the important nutrient removal by advanced
waste treatment is actually phosphorus.
16
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10-
(D
o
-------
Biological tests, such as algal assays, were used (5, 41, 43) to determine
experimentally which of the two factors, nitrogen or phosphorus, is
usually limiting in several Swiss lakes. The objective was to facilitate
selection of appropriate remedial measures. The results led to the
following views: (a) there is no reason to suppose that any substance
other than nitrogen and phosphorus need be considered, (b) where nitrogen
becomes a minimum substance in summer, it is no doubt possible to
achieve partial success in combating eutrophication possible to achieve
partial success in combating eutrophication by reducing the nitrogen
income, and (c) even in this case the best remedy is to cut down the
influx of phosphorus compounds as far as possible.
A recent study was made of 55 North Florida lakes and their water-
sheds. The results showed that here, too, while trophic state was
largely dependent on gross supplies of nitrogen and phosphorus, phosphorus
loading was the more limiting factor (44). The significance of phosphorus
is shown for eutrophic Lake Minnetonka in Minnesota, also, where sewage
is a major source of phosphorus input. A close relationship was found
between concentrations of total phosphorus and chlorophyll in surface
waters at eleven observation points during the midsummer peak of algal
densities (45). Findings are shown in Table 6 and Fig. 4.
Table 6.* Mean Concentration (ug/1) of Chlorophyll a_ and
Phosphorus in Surface Waters at 11 Localities
in Lake Minnetonka during July and August, 1968
and 1969.
Chlorophyll Total phosphorus
Locality concentration concentration
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Tanager Lake
Hal stead Bay
West Arm
Cooks Bay
Gale Island
Browns Bay
Wayzata Bay
Crane Island
Crystal Bay
Carman Bay
North Arm
91
56
50
40
38
33
31
25
25
12
13
200
119
90
68
53
52
52
43
42
37
40
*Modified from Megard (45).
18
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50
150
200
100
p-g/1
TOTAL PHOSPHORUS
Fig. 4 The Relationship between Photosynthesis at
Optimal Illumination and Concentrations of
Total Phosphorus in Surface Samples from
11 Localities in Lake Minnetonka. Modified
from Megard (45).
It is obvious that phosphorus plays a significant role in the overall
process of eutrophi cation. Phosphorus compounds also play important
roles in all phases of algal metabolism—building blocks in the eutrophication
process. Many of them are concerned with energy transforming reactions.
One of the most important is photosynthesis, in which light energy
is used to convert inorganic phosphate to adenosine triphosphate (ATP).
ATP is a carrier of energy-rich phosphate and serves as a driving
force for many other metabolic reactions.
Because phosphorus in natural environments is mainly as ortho-
phosphate, it is generally felt that algae take up phosphorus from
the water in that form. It has been shown, also, that at least some algae
have the necessary extracellular enzymes to convert more complex phos-
phate compounds to orthophosphate to facilitate absorption. Much of
the phosphorus incorporated into algal cells occurs as polyphosphates,
which apparently accumulate and act as reserves of high-energy phosphate.
Thus, the algae are capable of "luxury uptake" of phosphorus and can
assimilate in excess of their normal metabolic requirements. Uptake
depends not only on phosphorus concentrations in the surrounding water,
but also on other factors such as light, hydrogen-ion concentration,
19
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and other compounds that are present. Recent studies have shown that
the efficiency and rate of uptake are favorably affected by inorganic
salts in natural waters (46).
It is not known if "luxury uptake" is a universal capability of
algae or exists in only a limited number of species. In any event,
laboratory observations have shown that as a result of such uptake
some algae are able to continue through several reproductive generations
without added phosphorus input. In doing so, the store of phosphorus
is subdivided into the increasing number of algal daughter cells. While
this is an interesting phenomenon, it has no real or lasting impact on
eutrophication because: (a) maximum standing crop—the crux of bad
conditions—must still depend on total supply of usable phosphorus available
at the moment in cells or in the water, and (b) luxury uptake, with or
without reproduction, must cause a proportion at least of phosphorus-laden
defunct cells to settle out and take phosphorus to the bottom (see 45).
Many of the enzymes and coenzymes involved in algal metabolism contain
phosphorus, also. For example, respiratory oxidation of glucose to
carbon dioxide and water leads to the generation of an energy-rich
form of phosphate. Thus, of the total of 680,000 calories liberated
in the oxidation of one mol of glucose, as much as 290,000 calories
may be stored in the form of phosphate bond energy.
20
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SECTION V
SOURCES OF PHOSPHORUS
Because of the key role of phosphorus in eutrophication, coupled with
the present unfavorable prospect of effectively controlling any other
nutrient, only phosphorus inputs are emphasized.
All phosphorus inputs are additive and contribute ultimately to phosphorus
availability and use by algae in lakes. Therefore, all sources and
their inputs must be assessed for amount and seriously considered
for control regardless of apparent magnitude. In focusing on major
point source inputs, such as municipal sewage and its added detergent
phosphorus, too often other potentially significant inputs have been
largely ignored. Therefore, summary information on some nine input
sources is given, arranged more or less in ascending order of importance.
In considering sources of nutrients, it is logical to think of "natural"
ones as opposed to "sources affected by human activities." Among
natural sources that help establish long-term baseline eutrophication,
we are concerned on a national scale with several: (a) tributary
drainage of land areas of great variety ranging from mountain slopes
to level plains, from wooded lands to range!and and prairie; (b) soil
erosion, both waterborne and airborne; (c) biological sources, such
as excreted droppings from waterfowl, other birds, animals, leaf fall,
and nitrogen fixation; and (d) the input from rain, snow, and dust.
Precipitation
While only scanty information is available on significance of the
atmosphere and rainfall, there have been observations at widely scattered
points in the United States and Europe. It seems apparent that phosphorus
inputs, although typically small, are sometimes sufficient to warrant
consideration in ^utrophication. In general, they range from about
0.015 to 0.06 g/m /yr (6, 48). Reported concentrations vary from
as little as 0.3 to as much as 130 ug/1. At Con/all is, Oregon,
concentrations have been found to range from 2-33 yg/1 (29). In Oregon
snowfall amounts are similar, but in France as much as 800 ug/1 has
been found (6). When viewed in context of a troubled lake, precipitation
may contribute up to 2 percent of the input, as estimated for Lake
Mendota, Wisconsin (15).
Biological Sources
Lakes on flyways used heavily by waterfowl receive nutrients from
their droppings. Domestic birds, such as the famous Long Island duckling,
excrete about 954 g nitrogen and 408 g phosphorus per bird per year
(49). Estimates of nutrient input to lakes by wild ducks have been
21
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based on half this value. Inputs estimated for Upper Klamath Lake
from transient waterfowl were considered negligible when related to
the total nutrient budget (50). In some waters, however, such as
Lake Darling in the Upper Souris drainage in North Dakota, waterfowl
may be a major phosphorus source.
There are several other biological phosphorus sources to be noted.
Among them are fall-in of leaves, pollen, spores, and insects*.
Nitrogen additions may come from fixation by blue-green algae, bacteria,
and stream bank red alder (Alnus rubra). Quantitative measurements
of such sources appear to have been made only rarely in the context
of nutrient budgets of lakes (51).
Gasoline
It is estimated that 2.5 million pounds of phosphorus are consumed
annually in the United States in gasoline used by motor vehicles.
It is not known how or in what amounts the phosphorus in burned gasoline
reaches the Nation's surface waters. In any event, the amount obviously
must be less than 2.5 million pounds as based on the following information
and assumptions (29):
Concentrations found in highest of five gasolines purchased in
May 1971 in Corvallis, Oregon, area: 12.6 mg P/l (0.1 Ib P/1000 gals)
Assume: 100 million motor vehicles in the United States. Each
vehicle consumes 1000 gals/yr. Twenty-five percent of
vehicles use phosphorus-containing gasoline.
If the resulting 2.5 million pounds of phosphorus is washed from
the air by rainfall evenly over the 3.6 million sq mi of the United
States, and if average United States rainfall were 24 in./yr, it is
calculated that the concentration of such phosphorus would not exceed
0.0002 mg/1. Actual conditions obviously would give higher localized
concentrations.
Boats and Ships
The problem of pollution from watercraft is widespread, because
such craft frequent all navigable water areas of the Nation, including
many susceptible to eutrophication because they already receive nutrients
from a variety of sources. Congregations of pleasurecraft for extended
periods can contribute untreated wastes equivalent to the sewage dis-
charge from a small city. Regardless of watercraft size, untreated
sewage generally is discharged directly from watercraft today just as
it always has been. New treatment devices that comminute and chlorinate
onboard wastes will have little or no beneficial effect in decreasing
nutrient pollution or preventing eutrophication.
22
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Undisturbed Lands
In looking at tributary drainage from undisturbed lands, it soon
becomes apparent that little nutrient information is available; also,
tha-t nitrogen and phosphorus contributions per unit area of watershed
vary considerably. Such variations are influenced by land slope, soil
character, underlying geology, plant cover, amount and nature of precipi-
tation, and many other factors (53). Assessment of natural wooded environ-
ments on the west side slopes of the Upper Klamath Lake Basin show annual
runoffs of 89 g of nitrogen and 21 g of phosphorus per acre (54). Other
sources give woodland contributions of 0.57-1.3 kg nitrogen and 44.5-348
g phosphorus per acre. European figures for Lower Alpine regions are
similar at 526 g nitrogen and 105 g phosphorus per acre. Reported runoffs
from grassland are similar.
Urban Land
For some time storm water runoff from urban areas has been viewed
as a potential pollutant because of the dejecta accumulated in community
living—residues from vehicle wear and drippage, garbage from careless
handling, pet animal droppings, fertilizing lawns and gardens, and
erosion silt (48). Several studies have shown that street runoff is far
from clean and contains various pollutional components including
considerable phosphorus.
A 1959-1960 study (55) showed that samples of storm water from
Seattle street gutters contained up to 0.78 mg/1 soluble phosphorus, and
up to 1.4 mg/1 total phosphorus. The highest concentrations usually were
found when antecedent rainfall had been low. Storm water runoff in the
Cincinnati area contained an average concentration of 0.36 mg/1 PO/.-P (48).
In another study (56) the maximum total phosphorus concentration observed
in separate storm water at Ann Arbor, Michigan, was 5.3 mg/1. The maximum
concentration from a combined system at Detroit was 14.1 mg/1. Dilution
of 36 to 1400 times would be required for these runoffs to attain a
tolerable target level of 0.01 mg/1.
In 1960, the Nation's urban land had a total area of about 25,544
sq mi and contained a population of about 85,800,000--somewhat more than
half of the United States population (57). For that time the phosphorus
contribution from such land to storm or combined sewers with a 30-inch
annual rainfall would vary from 11-170 million pounds per year based on
an estimated total phosphorus concentration of 0.1-1.5 mg/1.
Industry
We know little about industries as nutrient sources except that
there are some, depending on process and raw materials, that can shed
phosphorus in their wastes. But there is no real knowledge, even today
on a national scale, as to how many factories are involved or how much
23
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these input quantities may be. It is known, however, that important
users of phosphorus were as shown below (Table 7). Some information in
this regard is available for German industries also and is given (Table 8)
U. S. data (62) show that combined phosphorus loads generated by fruit
and vegetable processing amounts to roughly 10 million pounds per
year. Some 50-60 percent is discharged to municipal sewers and the
remainder goes to industrial waste treatment plants or directly to
receiving streams.
Table 7. Commercial Phosphorus Consumption in the
United States (million pounds)
Fertilizers
Built detergents
Animal feeds
Water softening
Pharmaceuticals, foods
Surface treatment of metals
Plasticizers, gasoline
additives and insecticides
Other
1958 (58)
1980
376
238
57
37
31
20
91
1965 (59)
3098 (60)
—
207
__
—
--
23
843
1968
7320 (60)
506*
__
--
--
--
__
--
Total 2830
*Based on 4 percent increase from the 486.8 million pounds reported for
1967 (61).
Table 8.* Phosphorus Concentrations in
German Industrial Wastes
Phosphorus
Type of waste mg/1
Beet sugar factories:
Wash water 2.6 - 13
Press water 31 - 274
Potato starch 27 - 80.5
Dairy 0.9 - 1.3
Malt-house 13
Brewery 20.2
Slaughter-house 8.2
Rendering plant 43.7
Flax retting 26.1
Starch 76.5
Dairy 8.7
*Modified from Vollenweider (6).
24
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Agricultural Lands
It has been pointed out that eutrophication due to man's activities
is as old as history. In 1825 the blue-green alga, Oscillatoria rubescens,
believed by some to be an early sign of eutrophication, first appeared
in Lake Murten in Switzerland (63). This was believed to have been
stimulated by nutrient runoff from newly tilled lands.
In looking at the impact of agriculture, it is not necessary to review
the many complex interrelationships examined recently in great detail
by Vollenweider (6). Related to them are: soil types, leaching
characteristics, slopes, fertilization practices, animal populations,
manure compositions, feedlot practices, and silo drainage. It is
enough to say that, in general, agricultural lands yield more nitrogen
and phosphorus in runoff than undisturbed and natural lands. The
Williamson and Sprague Rivers in the Upper Klamath Lake Basin drain
lands that are devoted 90 percent to production of forage and feed
grains and 10 percent to grazing (50). Runoff losses of nitrogen
and phosphorus are twice as great as for nearby nonagricultural lands.
In other areas of the United States, orchards have been found to yield
four times as much phosphorus and 30 times as much nitrogen as grass
and woodland (54). Losses from grain-crop areas were found to be
even greater.
In some irrigated areas in the watershed of Upper Klamath Lake, annual
nitrogen losses to irrigation drain-water are as great as 0.1 to 11
kg/acre and phosphorus losses range from 0.2 to 4.0 kg/acre (29).
The significance of agricultural drainage depends on how much nutrient
finally reaches the responsive waters, regardless of the hydro!ogic
pathway.
In some farming areas, nutrient losses from barnyards, manure spreading
(53), and feedlots are special points of concern. It has been estimated
that animals currently under confined feeding in the United States
yield pollutional wastes equal to sewage from 850 million people (64).
When considering, in addition, the frequent and unfortunate practice
of feeding livestock on hillsides adjacent to streams, the avenues
for nutrient input are quite wide open.
In addition to runoff of dissolved nutrients, unmeasured quantities
are carried along with erosion sediments. As the Mississippi River
drains the "Great Breadbasket" of the United States, it alone carries
nearly 450 million metric tons of sediment to the Gulf annually (65).
But elsewhere other drainages enter lakes and reservoirs, filling
up the bottom and yielding nutrients into solution. Human activities
such as construction of highways, urban complexes, forest roads, logging,
overgrazing, and poor farming practices, greatly increase the erosion
input.
25
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Municipal Sewage
Accelerated eutrophication in many lakes in the United States, Europe,
and elsewhere has been stimulated by and appeared concurrently with
increasing inputs of municipal sewage. That sewage plays a major
role in this resource destruction has been known for many years. Noted
examples of such impact are the lakes at Madison, Wisconsin, Ziirichsee
in Switzerland, Lake Washington at Seattle, Lake Erie, and the Potomac
Estuary (66). These bodies of water exemplify the situation in which
sewage was, and in some cases still is, the major point source of
phosphorus. It is important, therefore, to examine this source in
some detail.
Sewage derives nutrients, including phosphorus, from several sources.
As expected, the amounts of phosphorus remaining after partial removals
through treatment in the sewerage system are carried along with the
sewage when discharged to the environment. It is estimated (29) that
in 1968 the United States sewered population of 137 million people
discharged 376 million pounds of phosphorus to receiving waters (Table
9). This is potentially controllable phosphorus and corresponds to
2.74 Ibs P/capita/yr. Of the some 3.5 pounds of phosphorus per person
per year discharged in raw wastewater (i.e., before treatment), 1.2
pounds come from human excretion and 2.3 from other sources (67).
Therefore, with an average 22 percent reduction through sewage treatment
as shown in Table 10, a total of 129 million pounds originating in
human excretion reaches the water system annually (0.94 Ib P/capita)
and a total of 247 million pounds in sewage from other sources (1.8
Ibs P/capita).
Table 9. Estimated Quantity of Phosphorus Discharged
to Receiving Waters in the U. S. in 1968
from the Sewered Population
Amount of phosphorus
Source of phosphorus as P (million pounds)
Human excretion
Soft drinks 2.5
Beer 2.5
Other 124.
Detergents 222.*
Other sources 25.
Total 376^
*Based on 104 percent of the 213 million pounds reported for 1967 (61).
26
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Table 10.* Estimated Phosphorus Removals by
Municipal Sewage Treatment in 1968
Type of treatment Efficiency Pounds of
and population of P discharged
served <68) removal (67) (3.5 Ibs P/capita/yr) (67)
1. No treatment — 210 x 106
60 x 10 (uncontrolled)
2. Raw sewage 0 21 x 10
6 x 108
3. Primary-intermediate 10% 135 x 10
43 x 10
4. Activated.sludge 40% 86 x 106
41 x 10D
5. Trickling.filter 25% 74 x 106
28 x 10°
6. Miscellaneous 10% 60 x 106
*From Barth (67).
One of the metabolic sources of phosphorus in sewage is soft drink
consumption; another is beer. A recent report (69) shows that almost
300 units of soft drinks are consumed annually per capita in the United
States. Of this amount, 65 percent are cola drinks. Analyses of various
soft drinks obtained^* the Corvallis, Oregon, area in May 1971 showed
the following phosphorus content (29):
Seven brands of cola drinks 112-240, av. 161 mg/1 ortho-P
Five brands of non-cola drinks - 0.11-3.54, av. 2.4 mg/1 ortho-P
Because cola drinks contain an average of 161 mg P/l, represent
65 percent of the soft drinks consumed in the United States, and because
other soft drinks with one exception contain relatively small amounts,
the phosphorus contribution to the environment is estimated only for
cola drinks. On this basis 3.2 million pounds of phosphorus were
contained in the cola drinks consumed by the 137 million sewered population
assuming a 12 oz per soft drink unit. If one allows 22 percent removal
by various waste treatments, this yields 2.5 million pounds of phosphorus
reaching the water systems in the United States in 1968.
Similar contribution of phosphorus through consumption of beer is
estimated to have been 2.5 million pounds in 1968 (29). This is based
on the following 1968 information (70):
27
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U. S. population over age 18 129 million
Per capita annual U. S. consumption
of beer by over 18 group 25.88 gallons
Analyses of four samples of beer including a bottle and can of each
of two nationally marketed brands purchased in the Corvallis, Oregon,
area in May 1971 showed the following phosphorus content (29):
Ortho P - mg/1
Brand A (bottle) 155
Brand B (can) 190
Brand B (bottle) 146
Brand B (can) 137
Average 157
With the above information and assuming 69.6 percent of the over 18
population connected to sewers and 22 percent of the sewered phosphorus
removed by treatment, then 2.5 million pounds of the phosphorus in beer
reached United States water systems in 1968.
Other estimates (57) based on nutrient removals by waste treatment
suggest annual sewage discharges to surface waters of 200-550 million
pounds of phosphorus and 1.1-1.6 billion pounds of nitrogen. Assuming
these estimates are reasonable (our own estimate [29] of 376 million
pounds of phosphorus is within this range), it appears the expected
nitrogen/phosphorus ratios are in the range of 3 to 6. This is in general
agreement with specific observations (71) that under optimal operating
conditions, the effluent from an activated sludge plant had 17.1 mg/1
total nitrogen and 7.3 mg/1 total phosphorus, giving a nitrogen/phosphorus
ratio of 2 to 3.
The phosphorus content of domestic sewage is about 3 to 4 times the
level found before the advent of synthetic detergents (72) at about 1945.
Sawyer (73) estimated the 1950 detergent industry contribution at about
1.6 Ib P/capita/yr. A 1955 estimate (74) is 1.9 Ibs P/capita/yr. A
Task Force estimate for 1958 (57) gives 2.1 pounds. These estimates of
increasing amounts apparently relate to increased popularity of detergent
use. This is evident from the progressively increasing production from
1945 to recent times (Table 11). Phosphorus consumption in detergent
formulations is second only to consumption in fertilizer (57).
The laundry soaps of yesteryear were manufactured from fatty acids
and saponified rosin and then fortified with silicates of soda, soda
ash, at times with borax, and/or up to five percent trisodium phosphate
as a replacement for soda ash and borax (78). Today's marketed deter-
gent contains the constituents shown in Table 12 (79). The major ingre-
dient noted is sodium tripolyphosphate. Data on the levels of sodium
28
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tripolyphosphate as found in analyses conducted by and for the Federal
Water Quality Administration are presented in Table 13 (80). For house-
hold detergents amounts range from 18.6 to less than 0.25 percent.
Table 11.* Detergent History
Production of Production of P
synthetic detergents for detergents
Year millions of pounds millions of pounds
1945
1950
1955
1960
1965
1968
83
1030
2330
3330
4160
4730
130 (est.)
380
500
630 (est.)
*From (76,77)
While a national average appears unavailable, a recent source (75)
estimates that approximately 50 percent of the municipal phosphate
discharges in Canada to lakes Erie and Ontario is from detergents. In
the United States the corresponding figure is 70 percent. Based on
these values, it is estimated that detergent phosphorus accounts for
40 percent of the total input to the two lakes. If these figures are
essentially correct, detergents obviously then are a substantial source
of phosphorus and can be a significant contributor to eutrophication.
Where phosphorus is present in large amounts, algal and plant growth
will increase until another nutrient will eventually become growth-
limiting. Since nitrogen is usually the second most important growth-
limiting nutrient, agricultural run-off, which is often particularly
high in nitrate-nitrogen, would further enhance the eutrophying
effects of detergent phosphorus.
29
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Table 12.* Synthetic Detergent Formulas
Heavy duty Light duty Light duty Detergent
product powders liquids laundry
US - Canada All countries All countries bars
Active ingredient
(e.g., alkylbenzene
sulfonate, fatty
alcohol sulfate) 14-20%
Foam Booster
(e.g., lauryl alcohol
cocomonoethanolamide) 1.5-2%
Sodium
tripolyphosphate 40-60%
Anti-soil redeposi-
tion agent (e.g.,
sodium carboxy
methyl cellulose)
Anti-corrosion agent
(e.g., sodium silicate)
Optical brightener
Enzymes
Moisture
Ethanol or
sodium xylene
sulfonate
Sodium bicarbonate
Sodium carbonate
Filler (e.g., sodium
sulfate) 0.32%
0.5-0.9%
5-7%
0.30-0.75%
0.20-0.75%
6-12%
25-32%
30-37%
5-12%
2-15%
0.02-0.08%
1-4%
6-9%
60-68%
20-25%
15-25%
0.3-0.5%
3-8%
0.05-0.25%
3-8%
15-20%
15-30%
*From Si 1 vis (79).
30
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Table 13.* Concentration of Phosphorus in Detergent
Formulation as Percent Phosphorus**
(1% = 10,000 nig/kg)
% P
Pre Soak
Biz
Enzyme Brion
Amway Trizyme
Axion
Laundry Detergents
Blue Rain Drops
Salvo
Tide
Amway SA-8
Cold Water Surf
Drive
Oxydol
Bold
Cold Water All (powder)
Ajax Laundry
Cold Power
Punch
Dreft
Rinso with Chlorine Bleach
Gain
Duz
Bestline B-7
Bonus
Breeze
Cheer
Fab
White King with Borax
Royalite
Instant Fel Soap
Wisk (liquid)
* From Eiserer (80).
** The P values of this table
•i r\ •H'lft v*f±~Fr*Y*£Mr\f+r\
Laundry Detergents (cont.)
18.6 "
18.0
18.0
15.9
15.9
14.3
12.6
12.4
12.2
12.0
11.8
11.5
11.5
11.3
11.3
11.2
10.6
10.3
10.0
9.7
9.6
9.5
9.4
9.2
8.8
8.8
5.5
4.2
3.6
Par Plus
Addit Liquid
Ivory Liquid
Lux Liquid
White King Soap
Cold Water All (liqui
Automatic Dishwasher
Amway
Cascade
All
Calgonite
Electrosol
Household Cleaners
Ajax All Purpose
Mr. Clean
Whistle
Pinesol
Miscellaneous
Snowy Bleach
Bora teem
Downy
were calculated from the NacP
0
1.1
0.6
0.5
0.5
.25
d) .25
Detergents
15.1
13.8
13.6
12.5
8.8
7.2
6.8
0.8
.25
9.2
.25
.25
3°10 values
31
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SECTION VI
CONTROL OF EUTROPHICATION
Intense reflection on possible approaches to restore lakes or control
eutrophication yields only five major possibilities. The first includes
efforts to limit fertility in water, a necessary first step in every
problem lake; and second, to improve the food web so that a harvestable
and valuable crop such as fish, could be produced with a concomitant removal
of nutrients; third, to stimulate diseases and parasites among the
unwanted plants to keep them under control; fourth, to recycle nutrient
laden waters to agricultural and forested areas for fertilization and
to prevent re-entry of the nutrients to surface waters; and fifth, to
use toxic chemicals to kill aquatic vegetation. These options are
in decreasing order of choice. Some are now only ideas.
For many years eutrophication control efforts have emphasized obliterating
the most onerous symptoms of the process—excessive algae, waterweeds,
and fill-in. Since 1903 (82) copper sulfate and more recently developed
algicides have been used to treat lakes for temporary relief from
algal blooms. Sodium arsenite served a similar purpose to control
unwanted waterweeds but has been largely replaced by other aquatic
herbicides. Fill-in from accumulated silt input, settling algal remains,
and centripetal growth of encroaching floating bog has been attacked
by dredging in efforts at lake rejuvenation. Because these and several
other mechanical approaches do not really seek to correct the root
causes of the problem, the results usually are short-lived and futile
as a true solution.
Without question, the soundest preventive and restorative approach
that seeks to correct the root cause is to curb nutrient input. Every
nutrient source is important and eventually must be examined for control
possibilities, but first attention must be directed to sources for
which there is now control capability. The major nutrient control
procedure available and practical in the United States at this time
is treatment of sewage or other wastes to strip them of their nutrient
content. Naturally, the question arises as to what nutrient or nutrients
should be removed. The answer can be derived in rational fashion.
In studying Table 1, obviously, one could consider carbon, nitrogen,
phosphorus, micronutrients, or any other elements as potential targets
for control. In keeping with Liebig's Law, theoretically it would
be possible to limit production if any one or more nutrients could
be reduced to critical levels. As already pointed out, such conditions
commonly prevail naturally in oligotrophic lakes where there may be
limitations of phosphorus, sometimes nitrogen, and less commonly carbon
and lesser nutrients—iron (83), molybdenum (84), silica (85) and
others (86).
33
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Based on this fundamental knowledge, coupled with conclusions from
the long period of scientific study and experience with lakes and
the findings from laboratory and specific lake studies in the countries
most concerned with eutrophication, two principal remedial approaches
have emerged. In the first, sewage is collected and directed away
from lakes to less susceptible waters as in: (a) Madison, Wisconsin,
lakes (81); (b) Lake Washington, in Seattle (37); (c) Zurichsee and
Hallwillerzee, in Switzerland (5); (d) Tegernzee and Schlierzee, in
Germany (39); Zellersee, in Austria (5); and (e) Annecy and Nantua
Lakes, in France (87). This approach has proved effective but,
unfortunately, cannot be used in many locations that lack favorable
watercourses to receive diverted sewage flows.
In the second, the objective is to curtail input of one selected
nutrient, namely phosphorus, through advanced waste treatment processes
and through limiting phosphorus contributions to sewage via synthetic
detergents. The logic of curtailing phosphorus input through advanced
treatment has been widely accepted—even by many persons who take an
opposite view on the necessity to eliminate phosphorus from detergents.
Many actions to control eutrophication, already underway, are based on
this waste treatment approach. Examples are: (a) abatement programs
for all of the Great Lakes except Lake Huron; (b) Upper St. Lawrence
River; (c) Potomac River and estuary; (d) state legislation passed
or under consideration to set municipal waste effluent standards for
phosphorus; and (e) city, state, and federal legislation passed or
under consideration to regulate phosphorus content of detergents primarily
so as to decrease quantities in sewage that must be removed by treatment.
In spite of the logic, need and scientific base for those actions,
intense efforts have sought to focus attention on other nutrients and
lead the emphasis away from phosphorus. During the last two years, or
a little longer, a campaign has been waged by a small group to establish
a position that "We (U.S. and Canada through the International Joint
Commission) Hung Phosphates (by advocating elimination of phosphorus from
detergents) Without a Fair Trial" (88). The crux of this accusation
seems to be nurtured by three papers that emphasize the role of carbon
in algal nutrition and in lakes (89, 90, 91). The position is taken
that carbon and not nitrogen or phosphorus is the "key" nutrient in
eutrophication. This, in turn, forms the basis to advocate that control
efforts be focused on carbon and not on phosphorus.
This issue, in part referred to as the "Lange-Kuentzel-Kerr" thesis,
has been debated thoroughly and repeatedly within the scientific community
and has been found scientifically inadequate as a basis for eutrophication
control (92). The most recent debate was a Symposium on Nutrients and
Eutrophication, "The Limiting Nutrient Controversy," sponsored by the
American Society of Limnology and Oceanography, held at Gull Lake, Michigan,
on February 10-12, 1971. The proceedings are in press, but a summary state-
ment prepared at close of the meeting (93) says, "...one generalization
seemed to emerge—that the efforts to remove phosphorus from influents to
34
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lake ecosystems is not a waste of time and money It was generally
agreed by the participants that the only realistic option for controlling
or reversing cultural eutrophication in lakes is to remove phosphorus
from the influent waters."
Because some of the stimulated confusion still persists, several
pertinent points are offered:
1. The "Lange-Kuentzel-Kerr" thesis is not accepted by numerous
scientists throughout the world who have given their professional
attention to this problem for many years.
2. The considered conclusion of such scientists holds that nitrogen
and phosphorus universally are the most significant nutrients in eutro-
phication, with phosphorus typically the limiting nutrient in oligotrophic
lakes.
3. Recent algal assays have shown the importance of phosphorus in
relation to carbon and nitrogen (29). When carbon, nitrogen, and phos-
phorus were added singly and in combination to water from lakes of nine
different levels of fertility, maximum standing crops of an introduced
test alga were directly proportional only to phosphorus, and had no
obvious correlation with carbon or nitrogen.
4. At Lake Washington, in 1957, sewage effluents contributed 56
percent of total phosphorus and 12 percent of nitrogen inputs. Following
progressive diversions begun in 1963 to control eutrophication (see Fig.
2), phosphate decreased 72 percent by 1969 and algae (as shown by
chlorophyll) followed the same pattern, decreasing about 80 percent.
Concurrently, nitrate decreased by only 20 percent or less, and free C02
fluctuated around 75 percent of the original level, neither showing a
positive relationship to algal production. This performance is considered
a valid basis to predict improvement in similar lakes through phosphorus
limitation (37).
5. A recent paper discussing nutrient control policies in Canada
points out that the total pollutant BOD input to Lake Erie has a carbon
equivalent of 75,000 tons (75). In contrast, the lake's bicarbonates
(with 20-25 ppm C) equal 10-12.5 million tons of available carbon, or
about 150 times the amount from an entire year's input of sewage. At
peak of the growing season, the biomass of 4.9 million tons contains
1.8 million tons of carbon, a value far exceeding the amount potentially
controllable in pollutant inputs. Obviously, also, the carbon available
in bicarbonates—not to even mention the additional free C02 from the
atmosphere and from microbiological decomposition of organics--far exceeds
the demands of algal production. The ratio of carbon in bicarbonates
to the lake's total phosphorus is 800:1. If the carbon/phosphorus ratio
35
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in algae is about 40 (see page 14), then there is 20 times more
bicarbonate carbon available than required to completely deplete the
water of phosphorus. Similarly, Lake Erie has a six-fold surplus of
nitrogen, assuming a nitrogen/phosphorus ratio of 7. These calcu-
lations show that in Lake Erie, as in many other lakes, it is
phosphorus and not carbon that is the growth limiting element.
6. Experimental efforts by Morton (94) to limit algal growth
by carbon dioxide control were not successful in waters open to the
atmosphere. He found that the atmosphere supplied adequate C0? to
water depths of 5.5 feet to support algal production of 2 mg/l/d,
even without turbulent mixing.
7. Vallentyne (40) presented many of the arguments against
the "Lange-Kuentzel-Kerr" thesis. The reader is referred to his
entire paper, but following is one of the most significant aspects
that can be derived from his statement.
As shown in Table 14, of all nutrient elements known to be growth-
controlling in lakes, only phosphorus is also controllable by man.
Carbon is too ubiquitous and is not controllable and nitrogen only
partly so. There are several reasons why nitrogen is only partly
controllable. In its various forms, as nitrate, ammonia, and organic,
it enters lakes from natural and cultural sources much more readily
than phosphorus. Avenues of entry are surface and subsurface soil
drainage, rain, snow, dust, and fixation of atmospheric nitrogen by
some blue-green algae and other microorganisms. While sewage sources
may contribute high percentages to total phosphorus inputs, sewage
provides lower percentages of total nitrogen inputs--56 percent vs.
12 percent for Lake Washington. These differences reflect the difficulty
in effectively controlling nitrogen.
Table 14.* Comparison of Various Plant Nutrients in Respect to
(A) Whether They are Ever Growth-Controlling in Lakes
and (B) Whether They are Controllable by Man. Elements
Listed in Order of Increasing Atomic Weight. Note
that Phosphorus is the Only Element Meeting Both
Requirements.
Nutrient
A
B
Nutrient
A
B
Hydrogen
Boron
Carbon
Nitrogen
Oxygen
Sodium
Magnesium
Aluminum
Silicon
Phosphorus
Sulphur
no
no
rarely
yes
no
no
no
no
yes**
yes
rarely
no
no
no
partly
no
no
no
no
no
yes
no
Chlorine
Potassium
Calcium
Manganese
Iron
Cobalt
Copper
Zinc
Molybdenum
Iodine
no
no
no
sometimes
sometimes
rarely
no
no
sometimes
no
no
no
no
no
no
no
no
no
no
no
* From Vallentyne (40)
**Diatoms only
36
-------
On the other hand, it is safe to assume that human activities that
contribute phosphorus are the only significant cause of declining
nitrogen/phosphorus ratios. Therefore, this growing imbalance can be
corrected only by appropriate adjustment in human affairs. It is
recognized that all phosphorus inputs cannot be eliminated. Those that
can be controlled should be brought under control as soon as possible.
Once the major inputs are effectively controlled, the naturally occurring
concentrations of calcium, aluminum, iron, and biological systems will-
serve as phosphorus sinks, and hydro!ogic flow-through will help decrease
fertility.
37
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SECTION VII
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27. Potos, Chris. Region V, Environmental Protection Agency. Personal
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28. Risley, C., and F. D. Fuller. 1965. Chemical characteristics of
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30. McGauhey, P. H., et al. 1963. Comprehensive Study on Protection
of Water Resources of Lake Tahoe Basin Through Controlled Waste
Disposal. Prepared for Lake Tahoe Area Council. 157 p.
31. Based on 1971 data, Region V, EPA, Chicago.
32. Liebig, J. 1841. Complete Works on Chemistry. Philadelphia, T.B.
Peterson.
33. Verduin, J. 1966. Eutrophication and Agriculture in the United
States. In: Agriculture and the Quality of Our Environment.
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36. Dean, R. D. Environmental Protection Agency, Robert A. Taft
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37. Edmondson, W. T. 1970. Phosphorus, nitrogen, and algae in Lake
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41. Shapiro, J., and R. Ribeiro. 1965. Algal growth and sewage effluent
in the Potomac Estuary. Journal WPCF 37: 1034-1043.
42. Fitzgerald, G. P. Water Resources Center, Univ. of Wise, Madison.
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43. Rodhe, W. 1948. Environmental Requirements of Freshwater Plankton
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44. Shannon, E. E. and P. Brezonik. 1971. The dependence of lake
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54. Bartsch, A. F. 1970. Accelerated eutrophication of lakes in the
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67. Barth, E. J. Environmental Protection Agency, Robert A. Taft
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45
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SELECTED WA TER
RESOURCES ABSTRACTS
INPUT TRANSACTION FORM
3. A ccession No.
w
4. Title 5 Report Date
ROLE OF PHOSPHORUS IN EUTROPHICATION
6.
7. Author(s)
Bartsch, A. F.
9. Organization
National E
Protection Agency, Corvallis, Oregon
National Environmental Research Center, Environmental 1L ContTactlGiantIi°-
8. Performing Organization
Report No.
10. Project No.
12. Sponsoring Organization NERC-Corvallis, EPA
^5. Supplementary Notes
Environmental Protection Agency report
number EPA-R3-72-001, August 1972.
13. Type of Report and
Period Covered
16. Abstract
The process of eutrophication is a natural one, often accelerated greatly by man's
activities that contribute nutrients. The key nutrient is phosphorus. Although there is
no simple relationship, it is clear that increasing phosphorus content frequently leads
to accelerated eutrophication. Of all important nutrients, phosphorus is most control-
lable.
Sources of phosphorus include runoff from undisturbed agricultural and urban lands;
waste from watercraft; industrial and domestic wastes; biological sources; and precipita-
tion. Also, the most important single source is municipal sewage, fortunately, the most
potentially controllable of all inputs.
Control efforts follow five basic directions: Limiting fertility; improving food webs;
stimulating plant diseases and parasites; recycling nutrient-laden water to agricultural
and forest lands; and using toxic chemicals to kill vegetation. Limitation of nutrients
is the most desirable approach, particularly through curtailing phosphorus inputs.
17a. Descriptors
Eutrophication, nutrients, algal blooms, primary productivity, trophic levels
17b. Identifiers
*Phosphorus, detergents
17 c. CO WRR Field & Croup
18. Availability 19. Security Class.
(Report)
20. Security Class.
(Page)
Abstractor \ Institution
21. No. of Send To:
Pages
77
**•
WAT ER R ESOURCES SCI ENTI FIC I NFORM ATION CENT ER
U.S. DEPARTMENT OF THE INTERIOR
WASHINGTON. D. C. 20240
WRSIC102(REV JUNEI971) G p 0 913.26t
-• U. S. GOVERNMENT PRINTING OFFICE ; I 972 — 51 "4- 11(6 (39)
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