PUBLIC HEALTH BULLffTDT
No. 203
A STUDY OF THE POLLUTION
AND NATURAL PURIFICATION
OF THE UPPER MISSISSIPPI
RIVER
SURVEYS AND LABORATORY STUDIES
U. S. TREASURY DEPARTMENT
PUBLIC HEALTH SERVICE
WASHINGTON
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U. S. TREASURY DEPARTMENT
PUBLIC HEALTH SERVICE
Public Health Bulletin No. 203
December, 1932
A STUDY OF THE POLLUTION
AND NATURAL PURIFICATION
OF THE UPPER MISSISSIPPI
RIVER
SURVEYS AND LABORATORY STUDIES
By
H. R. CROHURST
Sanitary Engineer
PREPARED BY DIRECTION OF THE SURGEON GENERAL
UNITED STATES
GOVERNMENT PRINTING OFFICE
WASHINGTON : 1932
For sale by the Superintendent of Documents, Washington, D. C. ------- Price 10 rents
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CONTENTS
Page
Introduction XI
Section I. Features of the upper Mississippi River and its watershed 1
General features 1
Geology and glacial history 1
Present drainage system 2
Topography 3
Present river channel 3
Precipitation on the watershed 5
Variations in stream flow 7
Section II. Hydrometric measurements 13
Purpose of hydrometric studies 13
Data from which calculations were made 13
Maps 13
River gages ._ 14
Rating stations 16
Methods of calculating discharge 16
Discharges from rated tributaries 16
Rates of discharge at sampling stations 18
Time of flow calculations 21
Section III. Population and sources of pollution on the upper Mississippi
River watershed 25
Presentation of data 25
Population 26
Sewerage and sewage treatment 28
Sewerage 29
Sewered population 30
Sewage treatment . 32
Pollution due to industrial wastes 32
Section IV. Methods of procedure in field and laboratory studies 36
Selection of sampling points 36
Description of Mississippi River sampling stations 37
Description of tributary sampling stations 39
Collection of water samples 40
Delivery of water samples 40
Chemical methods 41
Turbidity 41
Alkalinity 41
Dissolved oxygen 41
Biochemical oxygen demand 42
Bacteriological methods 42
Culture media 42
Sterilization of bottles 43
Plate counts 43
Determination of B. coli 44
ill
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IV CONTENTS
Page
Section V. Results of chemica' analyses 45
Presentation of data 45
Discussion 53
Alkalinity 53
Turbidity 55
Hydrogen-ion concentration (pH) 57
Dissolved oxygen 58
Monthly and seasonal changes in concentration 58
Quantitative changes in dissolved oxygen 63
Biochemical oxygen demand 65
Monthly and seasonal changes in oxygen demand 65
Quantitative changes in oxygen demand 68
Oxygen balance 70
Seasonal changes in the ratio between dissolved oxygen and
oxygen demand 70
Per capita changes in oxygen balance within the metropolitan area- 72
Rates of decrease in oxygen balance below the zone of pollution. 73
Secondary increase in oxygen balance below Lake Pepin 74
Section VI. Bacteriological studies 75
Presentation of data 75
Bacterial pollution of upper Mississippi River 90
Seasonal changes in bacterial concentration 91
Quantitative changes in bacteria 94
Relation of bacterial pollution to the contributing sewered population. 96
Comparison of bacterial pollution from different metropolitan areas. 97
Rates of bacterial purification 99
Methods of making calculations 99
Comparisons between summer and winter rates of bacterial puri-
fication in the upper Mississippi River 103
Comparison between rates of bacte ial purification in the Ohio,
Illinois, and upper Mississippi Rivers 104
Section VII. General summary 110
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LIST OF TABLES
SECTION I
No_ Page
1. Average monthly and annual precipitation, in inches, on the upper
Mississippi River watershed and its major subdivisions 5
2. Average monthly precipitation, in inches, on the upper Mississippi
River watershed and its major subdivisions, during the period
June, 1926, to August, 1927 5
3. Average monthly discharge, in second-feet, of the Mississippi River
as measured at St. Paul, Minn., during the period January, 1922,
to September, 1927, inclusive 8
4. Ratio of the average monthly discharge, in second-feet, of the Missis-
sippi River at Elk River, Minn., to that of the Minnesota River at
Mankato, Minn., during the period October, 1925, to September,
1927, inclusive 10
5. Distance, in miles, along the channel of the Mississippi River from the
Camden Avenue bridge, Minneapolis, to designated points below.- 12
SECTION II
6. Relation of various datum planes of the Mississippi River Valley 14
7. Summary and description of Mississippi River prisms 15
8. Data relative to watershed areas, above and below gaging stations, on
the principal tributaries of the upper Mississippi River 17
9. Monthly average rates of discharge, in second-feet, of the tributaries
of the upper Mississippi River at their mouths 17
10. Estimated normal monthly discharge, in second-feet per square mile,
from 7,040 square miles of watershed on the upper Mississippi
River, between the Elk River, Mankato, and St. Paul gaging stations,
June 1, 1926, to August 31, 1927 18
11. Monthly average rates of discharge, in second-feet, of the upper Mis-
sissippi River at sampling stations and above and below the mouths
of tributaries 20
12. Monthly mean time of flow, in hours, of the Mississippi River between
consecutive sampling stations and the mouths of tributaries, from
St. Paul to Winona, Minn., during the summer and winter months. _ 24
13. Cumulative monthly mean time of flow, in hours, of the Mississippi
River from Station No. 5, St. Paul, to consecutive sampling stations
and the mouths of tributaries, during the summer and winter months. 24
SECTION III
14. Total, urban, and rural population on the Mississippi River watershed,
above Winona, Minn., by tributary areas, in 1910 and 1920, and the
estimated population on January 1, 1927 27
15. Estimated total, urban, and rural population, as of January 1, 1927,
above sampling stations on the upper Mississippi River 27
16. Estimated total, urban, and rural population, as of January 1, 1927, on
the Mississippi River watershed, above Winona, Minn., arranged by
States 28
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VI LIST OF TABLES
No. Page *
17. Percentage of the population classed as rural, on the tributaries of the
upper Mississippi River and on the main stream, above Minneapolis.
Population estimates as of January 1, 1927 28 *
18. Summary of sewered population and sewage treatment data on the
Mississippi River watershed above Winona, Minn., by watershed
divisions 29
19. Estimated population discharging untreated sewage, by 50-mile zones,
above sampling stations on the upper Mississippi River 30
20. Distribution of the estimated population discharging untreated sewage,
on the upper Mississippi watershed, by tributary areas 31
21. Summary of the actual sewered population on the upper Mississippi
River, between sampling stations within the metropolitan area of
Minneapolis and St. Paul, with estimates of population equivalent
to industrial wastes 34
SECTION V
22. Summary of monthly average results of chemical analyses for each
sampling station on the upper Mississippi River, arranged by months. 45
23. Summary of average monthly and seasonal alkalinity, in parts per
million, at sampling stations on the upper Mississippi River, June,
1926, to August, 1927, inclusive 54
24. Summary of average monthly and seasonal turbidity, in parts per
million, at sampling stations of the upper Mississippi River, June,
1926, to August, 1927, inclusive 56
25. Summary of average monthly and seasonal initial dissolved oxygen,
in parts per million, at sampling stations on the upper Mississippi
River, June, 1926, to August, 1927, inclusive 59
26. Summary of monthly and seasonal averages of initial dissolved oxygen,
expressed as the percentage of saturation, at sampling stations on the
upper Mississippi River, June, 1926, to August, 1927, inclusive 60
27. Seasonal averages of dissolved oxygen, in terms of kilograms per day,
at sampling stations on the upper Mississippi River 63
28. Summary of average monthly and seasonal 5-day biochemical oxygen
demand determinations, in parts per million, at 20° C., at sampling
stations on the upper Mississippi River, June, 1926, to August, 1927,
inclusive 66
29. Seasonal averages of 5-day biochemical oxygen demand at 20° C.,
expressed as kilograms, at sampling stations on the upper Missis-
sippi River 69
30. Seasonal ratios of the dissolved oxygen to the 5-day biochemical oxygen
demand at 20° C., at main river and tributary sampling stations on
the upper Mississippi River 71
31. Seasonal and yearly averages of the changes in oxygen balance,
expressed as kilograms, between designated main river sampling
stations on the upper Mississippi River 72
SECTION VI
32. Summary of bacteriological observations, by stations, in terms of bac-
teria per cubic centimeter and bacterial "quantity units" (bacteria
per cubic centimeter x discharge in thousands of second-feet)
arranged as monthly means and seasonal averages, at each sampling
station 76
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LIST OF TABLES VII
•No. Page
33. Summary of bacteriological observations, by months, in terms of
bacteria per cubic centimeter and bacterial "quantity units" (bac-
teria per cubic centimeter x discharge in thousands of second-feet)
arranged as monthly means for all sampling stations 83
34. Summary of bacteriological observations at all sampling stations, in
terms of quantity units, seasonal averages of agar counts, and B.
coli , 88
35. Summary of average yearly numbers of bacteria, per cubic centimeter,
at sampling stations on the upper Mississippi River, during the 12-
month period, July, 1926, to June, 1927, inclusive 90
36. Summary of seasonal averages of bacteria, per cubic centimeter, at
sampling stations on the upper Mississippi River 92
37. Bacterial pollution of the upper Mississippi River, in terms of quan-
tity units, contributed by the sewered population of the Minnea-
polis and St. Paul metropolitan area 97
38 Bacterial pollution of the upper Mississippi River, expressed as quan-
tity units per capita per day, contributed by the sewered population
of the Minneapolis-St. Paul metropolitan area 97
39. Seasonal changes in numbers of bacteria added to streams by sewered
populations 98
40. Bacterial pollution of the upper Mississippi River at Hastings, Minn.,
Station No. 7, with estimates of the pollution contributed below
Hastings by sewered communities and tributary inflow, in terms of
quantity units 100
41. Calculation of the percentage of bacteria remaining in the upper
Mississippi River at sampling stations below Hastings, Minn.,
Station No. 7, during the winter period of ice cover, based on the
37° C. agar plate counts 101
42. Bacteria remaining at sampling stations on the upper Mississippi
River, below Hastings, Minn., Station No. 7, corrected for tributary
inflow and cities, expressed in percentages of the maximum and with
times of flow below this maximum 103
43. Comparison between the initial numbers of bacteria, per cubic centi-
meter, in the Ohio, Illinois, and upper Mississippi Rivers, during
the summer and winter periods 108
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LIST OF FIGURES
SECTION I
No. Page
1. Map of the Mississippi River watershed above Winona, Minn., show-
ing the location of communities having sewerage systems and sewage
treatment works 2
2. Profile of the Mississippi River from Lake Itasca to the Minnesota-
Iowa State line 4
3. Mean monthly precipitation on the upper Mississippi River watershed,
by tributaries, and the actual monthly precipitation during June,
1926-August, 1927 6
4. Mean monthly stream flow, in second-feet, at gaging stations on the
upper Mississippi River watershed, by tributaries, and the actual
monthly stream flow during June, 1926-August, 1927 9
5. Map of the Mississippi River between Minneapolis and Winona,
Minn., showing the location of sampling points 11
SECTION V
6. Variation in monthly averages of dissolved oxygen, in percentage of
saturation, at sampling stations No. 1-7-11 and 14 61
7. Changes in seasonal averages of dissolved oxygen, in terms of kilo-
grams per day, at sampling stations on the upper Mississippi River_ _ 64
8. Variation in monthly averages of 5-day biochemical oxygen demand,
in parts per million at 20° C., at sampling stations No. 1-7-11 and
14 67
SECTION VI
9. Rates of bacterial purification in the upper Mississippi River, in rela-
tion to times of flow from Station No. 7, Hastings, Minn., during
the summer and winter periods 102
10. Comparison of summer rates of bacterial purification in the Ohio,
Illinois, and upper Mississippi Rivers, in relation to times of flow
from the zone of maximum pollution 105
11. Comparison of winter rates of bacterial purification in the Ohio, Illi-
nois, and upper Mississippi Rivers, in relation to times of flow from
the zone of maximum pollution 106
IX
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INTRODUCTION
The deficiency in rainfall on the upper Mississippi River basin,
beginning about 1922, depleted reservoir and ground-water storage to
such an extent that in the summer of 1925 the flow in the river
through Minneapolis and St. Paul became insufficient to properly
dilute the sewage and industrial wastes discharged from the Twin
City metropolitan area without creating objectionable conditions in
the river.
Numerous complaints, brought to the attention of the Minnesota
and Wisconsin State Legislatures in the summer of 1925, resulted in
each legislative body appointing an interim committee with instruc-
tions to study conditions in the river through Minneapolis and St.
Paul, and in the St. Croix and Mississippi Rivers, which form the
boundary between Minnesota and Wisconsin, and to submit recom-
mendations to the 1927 State legislatures on methods of improving
the condition of these waters. A joint interim committee, including
three members from each of the State committees, was then organ-
ized to study, without duplication of effort, conditions in the water-
courses and to present a concordant report of the steps necessary by
each State to remedy conditions. This joint committee, at a meet-
ing held in October, 1925, decided, inasmuch as the problem was one
involving an interstate stream, to request the United States Publis
Health Service to assist them in the study. Pursuant to this deci-
sion, a request was transmitted to the Surgeon General of the Public
Health Service, who detailed an officer to confer with the committee
and to make a preliminary report.
At a subsequent meeting a joint report was presented to the com-
mittee by sanitary engineers representing the Minnesota and Wis-
consin State health organizations and the United States Public
Health Service outlining the kind and extent of the survey deemed
necessary, the lands of data to be collected, and the cost of such an
investigation, to cover a period of approximately one year.
The funds necessary for making the required study were made
available from allotments already appropriated by the State legisla-
tures to the Minnesota Game and Fish Commission and the Wiscon-
sin Conservation Commission, under whose supervision such studies
would ordinarily be made. Additional funds, appropriated for a less
extensive study of the river by the cities of Minneapolis and St.
Paul, were also made available for the general and more extensive
study of the problem. The Public Health Service furnished the
XI
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XII INTRODUCTION
necessary laboratory equipment and supplies to operate a chemical
and bacteriological laboratory and detailed tlie writer of this report
to have general supervision of the investigation.
The data were collected, therefore, primarily to determine sanitary
conditions in the river due to the discharge of untreated sewage and
industrial wastes from the Twin City metropolitan area, especially
during periods of low water; the distance downstream that the ef-
fects of pollution were noticeable; and the probable further effect of
increasing sewage loads. An attempt was also made to estimate
from the data obtained the effect to be anticipated from the dis-
charge of sewage and industrial wastes from St. Paul and South St.
Paul into a pool to be created by the construction of a second navi-
gation dam near Hastings.
The investigation was made during the 15-month period June,
1926, to August, 1927, inclusive, and covered approximately 137
miles of river channel from above Minneapolis to above Winona,
Minn. During the study samples of river water were collected for
chemical and bacteriological analysis at regular intervals from
sampling points established on the main stream and on tributaries
near their mouths. At the same time information was secured rela-
tive to existing sources of pollution on the watershed and the neces-
sary hydrometric data were obtained.
The data collected during the summer and fall of 1926, when
extremely low flows were recorded in the Mississippi River through
the Twin Cities and when conditions in the river became extremely
objectionable, were made the subject of a preliminary report to the
joint interim committee in January, 1927. This report was used as
the basis of the committee's recommendations to the 1927 State
legislatures. As a result of the preliminary report, the Minnesota
Legislature created the Metropolitan Drainage Commission of Min-
neapolis and St. Paul to study methods of collecting and treat'ug
the sewage from the Twin City metropolitan area and to recommend
methods for financing such construction as was deemed necessary.
In January, 1928, after the close of the investigation, all the data
collected were summarized in tabulated form in a second report which
was submitted through the Surgeon General of the Public Health
Service to the State health authorities and the Drainage Commission
for their immediate use.
In the present report the data collected during the investigation
have been reassembled and retabulated, and an endeavor made to
analyze them from the standpoint of a study of stream pollution and
natural-stream purification, similar to previous studies of the Illinois
and Ohio Rivers made by the United States Public Health Service.
In such a presentation of the data it was necessary to estimate
rates of stream discharge; times of flow; sewered population; pollu-
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INTRODUCTION XIII
tion due to industrial wastes; the per capita contributions of bacteria
and oxygen demand to the stream, from the chemical and bacteriolo-
, gical results above and below the sewer outlets; and rates of puri-
fication taking place in the stream, as shown by the satisfaction of
oxygen demand and decrease in bacteria, in a relatively long section
of the river free from additional pollution, in which times of flow
could be calculated.
While the data were collected for studies other than those of natural
stream-purification phenomena, one section of the river offered an
opportunity to estimate the rates of purification taking place in the
upper Mississippi River, for a comparison with the rates observed
during studies of the Ohio and Illinois Rivers.
The present report, therefore, contains data relative to the physical
features of the upper Mississippi River watershed and the river
channel; summaries of total and sewered population, with estimates
of sewered population equivalent to the industrial waste pollution;
estimates of discharge and times of flow; and a summary of the
chemical and bacteriological findings at various points on the sec-
tion of the river under investigation. These data are presented in
a series of basic tabulations, condensed to the form of monthly
averages, with a discussion of the salient features of each.
Such success as was attained by the investigation was made pos-
sible by the assistance of the various State and municipal legislative
bodies, by many local organizations, and by numerous individuals.
Acknowledgment is due the Joint Interim Committee of the Minne-
sota and Wisconsin State Legislatures, through whose efforts the
appropriations were obtained from their respective States to assist
in conducting the investigation; to the City Councils of Minneapolis
and St. Paul for the appropriation of additional funds used during
the study; to the State health organizations of Minnesota and Wis-
consin, from whose records was obtained much valuable information
pertinent to the investigation; to the Minnesota Game and Fish
Commission and the Wisconsin Conservation Commission, through
whose organizations the funds appropriated by the States were
disbursed; and to the Minnesota Drainage Commission and the
Wisconsin Railroad Commission, who assisted, in cooperation with
the United States Geological Survey, in the collection of the hydro-
metric data.
Individual acknowledgments are made to Mr. H. A. Whittaker,
director, division of sanitation, State Department of Health of Min-
nesota; to Mr. N. W. Elsburg and Mr. George M. Sheppard, city
engineers of Minneapolis and St. Paul, respectively, for supplying
much valuable data used in the preparation of this report; to Mr.
J. A. Childs, chief engineer, Metropolitan Drainage Commission of
Minneapolis and St. Paul, for information collected subsequent to
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XIV INTRODUCTION
the present investigation which has been used in the final report;
and to Mr. H. A. Bailey, chemist and bacteriologist in immediate
charge of the special field laboratory throughout the entire period
of the survey.
During the progress of the field work and in the preparation of the
basic data contained in this report the personnel of the United States
Public Health Service stream pollution investigations organization
has rendered much assistance. Special acknowledgments are due to
Bacteriologist C. T. Butterfield for establishing the field laboratory
at Minneapolis and inaugurating the bacteriological technique used
throughout the investigation, and to Chemist E. J. Theriault for
assistance and advice relative to the chemical technique used during
the studies. Consultant W. H. Frost, of the Public Health Service,
in charge of stream pollution investigations at the time the study of
the upper Mississippi River was made, has reviewed the manuscript
of the report and offered many valuable suggestions which have con-
tributed to its final form of presentation.
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SECTION I
FEATURES OF THE UPPER MISSISSIPPI RIVER AND ITS
WATERSHED
GENERAL FEATURES
The Mississippi River system above the Minnesota-Iowa State
line drains portions of the States of Minnesota, Wisconsin, South
Dakota, Iowa, and a few square miles in the State of Michigan. The
source of the river is in Lake Itasca, in southeastern Clearwater
County, Minn., 2,550 miles from the mouth of the Mississippi at the
Gulf of Mexico. From its source the river flows northerly for a short
distance, then easterly and southerly to the mouth of the Crow Wing
River; and after covering a distance of 350 miles is then only about 75
miles from its source. From the Crow Wing River to the Gulf of
Mexico the course of the Mississippi is quite consistently toward the
south or southeast.
GEOLOGY AND GLACIAL HISTORY
The extensive mantle of glacial deposits covering the entire water-
shed gives evidence of several invasions of the ice sheet from the
north at widely separated times and from different directions. The
earlier invasions brought down from Manitoba the limestones which
are found imbedded in the lower part of the drift, while later ice
movements, from the northeast, brought down the stony red drift
from the Superior Basin as far as Mille Lacs Lake and Saint Paul.
The older drift deposits were eroded by the early drainage systems,
which became so extensive that very few lakes and undrained basins
remained upon them. The younger drift deposits still retain their
lakes and poorly drained areas, which the present river systems have
not yet reached. The younger drift formation, on the upper part of
the main river basin, accounts for the numerous lakes and swampy
areas on this part of the watershed, while to the west, on the Minne-
sota River Basin, and to the south, which is of the older drift forma-
tion, not covered by the later ice invasion, lakes and swampy areas
are almost entirely lacking.
The drift sheet covering the watershed varies in thickness from 100
to 300 feet, forming an undulating plain with comparatively slight
irregularities which form long low swells and hollows, with no outlets,
giving rise to the lakes and swamps. The bulk of the drift is composed
of blue till, a compressed mixture of sand, clay, and gravel; but to the
1
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2 l_ POLLUTION AND PURIFICATION OF UPPEE MISSISSIPPI EIVEB
eastward this is replaced by the red till. In the southwestern part of
the basin, in Minnesota, the till is covered by a layer of loam, sep-
arated from it by a distinct line of demarcation. Along the valleys of
the Mississippi and most of the larger tributaries flowing southerly
there are deposits of a mixture of stratified sand and gravel covered
with fine sand. The same formation is also found in isolated plains
in some of the counties. Extensive lenticular beds of stratified gravel
and sand constitute a large portion of the till in the rolling or broken
tracts, including the Leaf Hills in the northwestern section of the
basin and the Coteau des Prairies in the southwestern part.
PRESENT DKAINAGE SYSTEM
The outline of the watershed of the Mississippi Kiver and its
tributaries above Winona, Minn., as shown in Figure 1, is somewhat
leaf-shaped, due to extensions of the main stream in the central part
of the watershed and to the headwaters of the Minnesota and Chip-
pewa Eivers on the west and east, respectively. The main stream
divides the watershed about equally and forms the central vein of
the leaf. The maximum length of the watershed from north to south
is 250 miles, and from east to west 280 miles. The drainage area of
the stream above Winona is estimated at 59,230 square miles, of
which 15,020 square miles, or 25 per cent, lie within the State of Wis-
consin; 1,870 square miles, equal to about 3 per cent, in the State of
South Dakota; and 400 square miles, or somewhat less than 1 per
cent, in the State of Iowa. The remainder of the watershed, amount-
ing to 41,940 square miles, or 71 per cent of the total area above
Winona, is within the State of Minnesota.
In the northern portion of the watershed there are many lakes,
the more important of which are Bemidji, Cass, Winnibigoshish, and
Leech. From its source to the Falls of St. Anthony, in Minneapolis,
the channel of the Mississippi River is narrow in places, forming rap-
ids along its course, and is broad in others, where the current becomes
sluggish. At the Falls of St. Anthony the river drops 70 feet within
half a mile as it passes from between its relatively low banks to flow
between bluffs of lime and sandstone which continue for a considerable
distance downstream, increasing in height to 500 feet as the river bed
sinks below the general prairie level.
The Minnesota Kiver enters the Mississippi about 8 miles below
the Falls of St. Anthony, and the width of the main stream then averages
about a thousand feet, with fertile flats between the river and the foot
of the bluffs. The larger tributaries of the upper Mississippi River
are the St. Croix, Chippewa, and Black Rivers entering from Wis-
consin, and the Minnesota, Cannon, Zumbro and Root Rivers enter-
ing from Minnesota. Sand carried by the Chippewa River has been
deposited in the main stream, forming a dam across the Mississippi
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FEATURES OF THE UPPER MISSISSIPPI KIVER 6
River. The body of water created above this obstruction is knovra as
Lake Pepin. This lake is approximately 22 miles in length, has an
„ average width of about 2 miles and a maximum width of nearly 3
miles. The water surface at normal river stage is estimated at about
40 square miles. The upper end of the lake is comparatively shallow,
the depth increasing to a maximum of nearly 60 feet just above the
outlet. The average depth throughout the lake is probably about
30 feet.
The total distance from the source of the river to the point where
it leaves the State of Minnesota, at the Minnesota-Iowa State line,
is 660 miles. The St. Croix River and the main channel of the Mis-
sissippi River below the mouth of the St. Croix form the boundary
line between the States of Minnesota and Wisconsin.
TOPOGRAPHY
The topography of the upper Mississippi Basin is flat or slightly
rolling over a large portion of the central area, with more abrupt
slopes toward the watershed divide. The surface elevation is 620
feet above sea level where the Mississippi River leaves the southeast-
ern corner of Minnesota, and reaches a maximum of about 1,750 in
the Leaf Hills near the headwaters. Other areas of over 1,500 feet
elevation are found in the rocky ranges in the northeast section and
in the plateau southwest from Coteau des Prairies.
PRESENT RIVER CHANNEL
The course of the main river channel from its source to the Minne-
sota-Iowa State line is shown in Figure 1. Figure 2, a profile of the
river at low-water stages, shows river distances below its source and
the elevation of the water surface at various points.
During the first 30 miles of flow, to Lake Bemidji, the fall of the
Mississippi River is quite rapid, averaging over 4 feet per mile. In
the next 290 miles, from Bemidji to Brainerd, the slope is flatter,
averaging about 0.5 foot per mile. From Brainerd to Minneapolis,
a distance of about 150 miles, there is a continuous and rapid descent
of the stream, amounting to 430 feet, or 2.9 feet per mile. Below
Minneapolis to the Iowa State line the slope again becomes more
gradual, amounting to 113 feet in 175 miles, an average of about 0.6
foot per mile. The fall along the river has been utilized for power
development by the construction of dams in the vicinity of Bemidji,
Brainerd, Little Falls, St. Cloud, at the Falls of St. Anthony, and just
above the mouth of the Minnesota River in Minneapolis.
The Mississippi River has been made navigable as far as the Falls
of St. Anthony by the construction of many wing dams to confine the
low-water flows to a well-defined navigation channel, and by a lock-
and-dam, operated by the Federal Government, on the main stream
129540—32 2
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POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
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FEATURES OF THE UPPER MISSISSIPPI RIVER
just above the mouth of the Minnesota River, which forms a pool
extending upstream to the head of navigation. An additional dam
is to be constructed by the Federal Government just above Hastings,
which will form a second pool extending to the foot of the present
dam. Sufficient depth is to be provided to eliminate to a large extent
regulation of summer flows by the reservoir system on the headwaters
of the Mississippi, now operated by the Engineer Corps of the United
States Army.
PRECIPITATION ON THE WATERSHED
Records of precipitation are available at 66 stations on the upper
Mississippi River watershed, above Winona, at which observations
have been made for 12 years or longer. These records have been
summarized in Table 1 to show the average monthly and annual
precipitation on the entire watershed, above Winona, and its major
subdivisions. The actual monthly precipitation on the watershed
and its major subdivisions for the period of the investigation, June,
1926, to August, 1927, inclusive, is indicated in Table 2. The data
of these tables have been brought together, graphically, in Figure 3,
which shows the relation between the actual monthly precipitation
during the months of the investigation and the mean monthly precipi-
tation as determined from the entire record at the various stations.
TABLE 1.-—Average monthly and annual precipitation, in inches, on the upper
Mississippi River watershed and its major subdivisions
Watershed
Mississippi River above Minne-
St. Croix River
Zumbro River
Mississippi River above Winona —
"5
umber
stations
A
•M
18
9
fi
13
5
66
*B £
03
ja ^
Cue i~,
>-i s
12-50
12-47
16-66
12-36
15-37
12-39
12-56
b
03
3
S
^
:> H7
80
95
84
1 13
98
.85
3
tH
,0
f*
n m
80
CO
87
1 00
95
.83
1
^
1 111
i sn
1 35
1 36
1 57
1 43
1.29
I
,
^
3 55
3 3fi
3 87
3 44
4 in
3 51
3 63
s
3 31
3 ?1
3 ?7
3 37
3 (W
3 21
3 32
1
"a
m
•f 73
? 78
3 n9
3 M
3 59
3 48
3.02
fe
A
O
1 c?
1 77
? 37
? ?n
9 84
H 91
2.12
ovembe
^
1 03
1 09
1 40
1 17
1 69
1 4?
1.28
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3 23
2.90
3.50
2.57
4.84
3.12
3.43
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4.09
4 23
4.66
2.86
5.22
3.65
4.35
September
5.74
6 11
5.51
7.56
7 29
6.49
6.26
October
2.21
1 29
3.00
1.70
2.86
1.95
2.21
November
1.30
1.30
2.01
1 82
3.00
2.18
1.84
December
0.72
1.17
1.46
1.73
1.64
1.66
1.22
1927
n
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0.62
.59
.56
.73
.65
.59
.62
February
0.67
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.88
.39
.66
.39
.63
March
1.34
1.84
1.76
2.15
2.34
1.85
1.78
o,
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2.05
3.49
2.11
2.98
1.49
2.50
2.43
I
3.26
3.47
3.22
3.53
3 96
4.36
3.57
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3 57
3.48
3 63
3.84
3.27
3 40
3.42
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1 64
4 69
2 04
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-------
6
POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
ft
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ON ON THE UPPER MI
HE ACTUAL MONTHLY
AUGUST, 1927.
HLY PRECIPITATI
BUTARIES,AND T
*JG JUNE, 1926,
FIGURE NO. 3. MEAN MONT
RIVER WATERSHED, BY TRI
PRECIPITATION DURIt
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-------
FEATURES OF THE UPPER MISSISSIPPI RIVER
The annual average precipitation on the upper Mississippi River
watershed is about 27 inches, of which from 2 to 4 inches is in the
form of snow and remains on the watershed during the winter period.
June is the month of highest precipitation, with an average of 4.4
inches. Precipitation in the form of snow during the months of
December, January, and February is quite uniform and averages
0.84 inch per month during these three months.
The geographical distribution of the monthly and annual precipi-
tation shows an increase from the northwest to the southeast, the
precipitation being from one-quarter to one-third greater at stations
along the eastern border of the watershed than at those along the
western border.
During the period of the investigation the actual precipitation on
the entire watershed was about normal during the summer of 1926,
the winter of 1926 and 1927, and the spring of 1927. It was below
normal in the summer of 1927, and above normal in the fall of 1926.
While the precipitation of the summer of 1926 was of average amount,
.it came at the close of an extended dry period and was utilized to
increase reservoir and ground-water storage, producing but little
effect on stream flow. The precipitation in the fall period was above
the average, due to the high September rainfall, and stream flows
approached the normal for that season. The summer precipitation,
in 1927, was below the average and less than that of the preceding
summer; but as a result of the high fall and normal winter precipi-
tation, it produced higher stream flows than those recorded during
the preceding summer.
VABIATIONS IN STREAM FLOW
The mean monthly discharge of the Mississippi River at St. Paul,
Minn., is approximately 10,000 second-feet, while its maximum
monthly discharge, observed in April, 1897, has been estimated at
60,000 second-feet. The lowest discharge usually occurs in the
winter months, when the precipitation, in the form of snow, is held
on the upper watershed; and monthly averages of less than 2,500
second-feet are frequent in winter. The low winter flows are followed
by a spring peak in April, May, or early June, when the snow leaves
the basin, after which the discharge diminishes quite consistently
through the summer. Average monthly flows of less than 5,000
second-feet have occurred, during the months of July, August, or
September, in 9 of the 28 years from 1900 to 1927. The minimum
monthly average discharge for a summer month was recorded in July,
1926, as 2,590 second-feet. From April, 1922, when the average
monthly discharge was 34,100 second-feet as measured at the St. Paul
gaging station, the flow of the river was consistently low until April,
1927, when the discharge reached 27,000 second-feet.
-------
8
POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
The average monthly flows at the St. Paul gaging station for the
period January, 1922, to September, 1927, inclusive, are summarized
in Table 3.
TABLE 3.—Average monthly discharge, in second-feet, of the
measured at St. Paul, Minn., during the period January,
1927, inclusive
River, as
'-September,
Month
January
February. ._ ._ _.
April
May
July.
September
December . . - _
Average. .
1922
2,850
3,050
12,500
34,100
15,300
7,420
5,020
4,200
4,030
3 760
4,560
2,950
8,310
1923
2,630
2.500
3 370
7,570
9,030
5,300
5,720
3 640
3,860
4 060
3,170
2,560
4,450
1924
2,120
2,380
2 680
5,480
5,770
4 830
4,860
6 880
5,920
6 630
4 040
2,190
4,480
1925
1,650
1,700
5 240
6,060
5,320
10 400
8,650
3 820
4,400
4 370
2,990
2,470
4,750
1926
1,880
1,680
5 620
7,150
3,650
2 850
2,590
2 810
8 630
9 970
5 150
3,770
4,650
1927
2,950
2,850
18 900
27,000
19,700
16 000
7,090
5 440
6,210
Figure 4 shows the average monthly discharge of the Mississippi
River at St. Paul and the discharge at gaging stations on the larger
tributaries during the period from June, 1926, to August, 1927,
inclusive, as compared with the mean monthly discharge during the
entire period for which discharge records are available at each of the
gaging stations.
It will be observed that the investigation of the pollution in the
Mississippi River was conducted during a period which included
months of extremely low summer flow in 1926; a fall-and-winter
period of nearly average stream-flow conditions; a spring period with
flows somewhat above the average; and a second summer period in
1927, in which the flow was again below the average but in excess of
that of the preceding summer. The Chippewa River was an excep-
tion, the flow being above the average during the period from August,
1926, to March, 1927, inclusive, and then below the average for the
remainder of the period of the investigation.
A marked difference exists between the yield of the Mississippi
River Basin above the mouth of the Minnesota River and that of the
Minnesota River Basin. Table 4 gives a comparison, for the period
from October, 1925, to September, 1927, between the average monthly
discharge from 14,600 square miles of watershed above Elk River,
Minn., on the upper Mississippi River, and the discharge from 14,900
square miles of watershed on the Minnesota River above Mankato.
The monthly discharge of the Mississippi River, as indicated by the
table, varies from 0.93 to 19.2 times that of the Minnesota River.
During this period the average monthly flow in the Mississippi River
was nearly six times that in the Minnesota River from the same
watershed area.
-------
FEATURES OF THE UPPER MISSISSIPPI RIVER
\T GAGING
IBUTARIES,
\UGUST, 1927.
DW, SECOND FEET,.
WATERSHED, BY TR
NG JUNE, 1926,- ;
FIGURE NO. 4. MEAN MONTHLY STREAM FLC
STATIONS ON THE UPPER MISSISSIPPI RIVER 1
AND THE ACTUAL MONTHLY STREAM FLOW DURI
ISSISSIPPI RIVER-ST. ANTHONY FALLS MISSISSIPPI RIVER f
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-------
10
POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
TABLE 4.—Ratio of the average monthly discharge, in second-feet, of the Mississippi
River at Elk River, Minn., to that of the Minnesota River at Mankato, Minn.,
during the period October, 19%5-September, 19S7, inclusive
Month
1925
October
November
December
1926
January..
February
March
April
May
June
July
August
September .
Mississip-
pi River
at Elk
River,
Minn.,
watershed
14,600
square
miles
2 990
2,140
1,650
1,060
947
3,900
3,820
2,230
2,160
2,150
2 050
5,110
Minne-
sota Kiver
at Man-
kato,
Minn.,
watershed
14,900
square
miles
345
305
315
i 247
2 2, f>30
1.150
551
296
132
236
1,510
Ratio of
the dis-
charge,
Missis-
sippi
River to
Minne-
sota River
8.7
7.0
4.9
4.3
1.5
3.3
4.1
7.3
16.3
8.7
3.4
Month
1926
October
November
December
1927
January .
February .
April...
June
July
September
Mississip-
pi River
at Elk
River,
Minn.,
watershed
14,fiOO
square
miles
5,750
3,170
2,210
1 900
1,790
7,840
13, 600
9,490
6,320
4,920
5 380
6,320
Minne-
sota River
at Man-
kato,
Minn.,
watershed
14,900
square
miles
1,720
799
3 668
1 8, 430
7,790
5 420
4,570
1,190
470
329
Ratio of
the dis-
charge,
Missis-
sippi
River to
Minne-
sota River
3.3
4.0
3.3
.93
1.7
1.8
1.4
4.1
11 5
19.2
1 January 1 to 11, inclusive.
1 March 16 to 31, inclusive.
3 December 1 to 12, inclusive.
* March 7 to 31, inclusive.
The increased yield of the upper Mississippi River is due in part to
the numerous lakes and extensive swampy areas on this portion of the
watershed, which act as a natural reservoir for steadying the flow of
the river. Lakes and swampy areas are almost entirely lacking on
the Minnesota River Basin. Of greater importance than the natural
regulation of the upper Mississippi River is the regulation by an
artificial reservoir system constructed and operated to increase water
depths in the navigable channel between St. Paul and Lake Pepin.
This system, started in 1884, now consists of six reservoirs, with a
combined available capacity, between high and low water stages, of
nearly 94,000,000,000 cubic feet. They are operated to maintain, in so
far as possible, a depth of 6 feet in the navigable portion of the Missis-
sippi River below Minneapolis, comparable with a gage reading of
about 1.5 feet above low water at St. Paul. Daring the winter, or
nonnavigable season, the reservoirs are drawn down to make avail-
able, on about the first of April, a storage capacity of 40,000,000,000
cubic feet, in which to store the excess water during the spring period
of high run-off. If the preceding year was dry and the storage
depleted, only the normal minimum winter flow, as determined prior
to the construction of the storage reservoirs, is allowed to pass down
the river, the remainder going to storage. If the preceding naviga-
tion season did not draw heavily upon the stored water, the winter
flow in the river is increased by a sufficient amount to make available
the required storage capacity on April 1. During the navigation
season the stored water is held until the St. Paul gage reaches a stage
-------
FEATURES OF THE UPPER MISSISSIPPI RIVER
11
of about 1.5 feet, after which water is drawn from storage in an
attempt to hold the river at this reading on the gage.
For the purpose of designating sampling stations and other points
of reference along that portion of the Mississippi River channel under
examination, all such points have been referred to their distance
MINNESOTA
FIGURE NO. 5.
MAP OF
MISSISSIPPI RIVER
MINNEAPOLIS TO W1NONA
SHOWING LOCATION OF
SAMPLING POINTS
SCALE. IN wibes
O 5 10 15 2O 25 SO 35
below the Camden Avenue bridge in Minneapolis, the location of the
uppermost sampling station on the river which is above all sources of
pollution from the city of Minneapolis. The locations of the more
important points along the river between Minneapolis and Winona
are summarized in Table 5 and shown in Figure 5.
-------
12
POLLUTION AND PURIFICATION OP UPPEE MISSISSIPPI EIVER
TABLE 5.—Distance, in miles, along the channel of the Mississippi River from the
Camden Avenue Bridge, Minneapolis, to designated points below
Points below Camden Avenue Bridge
Camden Avenue Bridge, Minneapolis
Plvmouth Avenue Bridge, Minneapolis - . .
Hennepin Avenue Bridge, Minneapolis
Falls of St. Anthony, Minneapolis
Washington Avenue Bridge, Minneapolis _ —
Franklin AvAnnp. "Rrirlgp., Minneapolis L
Marshall Avenue Bridge, Minneapolis
Intercity Bridge, Minneapolis-St. Paul
Government lock and dam. .
Mouth of Minnehaha Creek „
Mouth of Minnesota River, Fort Snelling
Roberts Street Bridge, St. Paul
South St. Paul Stockyard district
Newport, Minn - _
St. Paul Park, Minn ...
Hastings Bridge , - - -._
Mouth of St. Croix River
Preseott, Wis
Mouth of Cannon River
Red Wing Bridge
Upper end of Lake Pepin - - . -
Maiden Rock, Wis
Frontenac, Minn .
Stockholm, Wis
Lake City, Minn ... -
Pepin Village, Wis
Ontlpf of T.plre Pppin
Mouth of Chippewa River —
Wabasha, Minn
Alma, Wis
Mouth of Zurnbro River
Mouth of Whitewater River
Minneiska, Minn—
Fountain City, Wis
Sam-
pling
point
1
2
3
4
5
6
7
8
10
g
11
12
13
14
Miles
below
Camden
Avenue
Bridge,
Minne-
apolis
0
3.1
3.8
4 6
5.5
6.6
8.1
10 1
10 5
11.0
12 9
19.2
24.7
27.6
23 2
28.7
45.0
47.4
47.5
66.1
68 3
73.3
79 8
80.8
85 7
87.2
92 7
95.1
96.2
96 7
99.7
107.6
109.9
117 8
118. 0
129 5
136 8
Remarks
Minneapolis water works intake.
Lower dam.
Head of pool, Minneapolis; limit of
navigation.
End of pool, Minneapolis.
Watershed area, 192 square miles.
Watershed area, 16,750 square miles.
Population, 6,860.
Population, 453.
Population, 363.
Population, 900.
Population, 4,571.
Watershed area, 7,610 square miles.
Population, 892.
Watershed area, 1,520 square miles.
Population, 8,637.
Population, 293.
Population, 207.
Population, 2,846.
Population, 555.
Watershed area, 9,600 square miles.
Population, 2,249.
Population, 970.
Watershed area, 1,420 square miles.
Population, 208.
Population, 880.
Population, 19,143
-------
SECTION II
HYDROMETRIC MEASUREMENTS
PURPOSE OF HYDROMETRIC STUDIES
The collection of certain hydrometric data was necessary in order
to interpret the results of the chemical and bacteriological analyses;
to determine the effect of pollution in the river below the metropolitan
area; and to estimate rates of natural purification taking place in the
stream.
The hydrometric data have been reduced to the following basic
tabulations, which give:
(a) Estimates of the monthly mean discharge at sampling points
at the mouth of each of the larger tributaries.
(6) Estimates of the monthly mean discharge at sampling points
on the main river.
(c) Estimates of monthly mean times of flow between certain
sampling points on the main river, during low-water stages, when the
available data would permit of such calculations with a reasonable
degree of accuracy.
DATA FROM WHICH CALCULATIONS WERE MADE
The hydrometric calculations and related data were compiled from
maps of the entire watershed of the Mississippi River above Winona,
Minn.; from large-scale maps of the river channel on which soundings
were given; and from river gage heights and discharge estimates made
by the United States Geological Survey working in cooperation with
the Minnesota Drainage Commission and the Wisconsin Railroad
Commission.
MAPS
A map of the entire drainage basin of the Mississippi River, above
the Minnesota-Iowa State line, on a scale of 1:500,000, prepared by
the United States Geological Survey, was used to compute drainage
areas above gaging stations and sampling points on the main river
and its tributaries. Larger-scale maps of the river channel in the
section under investigation were also available from which measure-
ments of cross sectional areas were obtained. The maps of the
Mississippi River Commission, on a scale of 1:20,000, made in 1897,
showed the river channel and soundings taken at intervals of about
800 feet, together with the topography to the top of the bluffs on
13
-------
14
POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
either side of the stream. Later surveys, made in 1921, 1925, and
1926 by the Engineer Corps of the United States Army, on a scale of
1 inch to 400 feet, showed low-water soundings taken about every
200 feet, but indicated practically none of the topography above the
elevation of the water surface on the days soundings were made.
Elevations on the Missipissippi River Commission maps are referred
to the Memphis datum, while those of the Army Engineer Corps are
referred to the Cairo datum. Weather Bureau gage elevations are
above mean sea level.
The relation between the various datum planes, to which elevations
on the upper Mississippi Valley are referred, is given in Table 6.
TABLE 6.—Relation of various datum planes of the Mississippi River Valley
Datura
Cairo , -
Memphis
Quiflevel . .
Sandy Hook _
Elevation in feet above —
Cairo
0.00
13.13
21.26
21.31
Memphis
-13. 13
0.00
8.13
8.18
Gulf
level
-21. 26
-8.13
0.00
0.05
Sandy
Hook
-21. 31
-8.18
-0.05
0.00
NOTE.—From Appendix A, Public Health Bulletin No. 171.
KIVER GAGES
River gages, from which daily water-surface elevations were
obtained when the river was not frozen, were maintained by the
United States Weather Bureau at four points on the section of the
upper Mississippi River under investigation. Gages of the Army
Engineer Corps were read less frequently or were used only for ref-
erence during the course of river surveys. Gages on the larger tribu-
taries, maintained by the United States Geological Survey in coopera-
tion with the States of Minnesota and Wisconsin, were usually read
daily.
Data relative to river gages, watershed areas, and the various
prisms through which discharge estimates and times of flow have
been made are summarized in Table 7.
-------
HYDKOMETRIC MEASUREMENTS
15
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-------
16 POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
EATING STATIONS
Rating stations for estimating the discharge of the Mississippi
River were located on the main stream at Elk River and St. Paul,
Minn., and were maintained under the supervision of the United
States Geological Survey. In addition to these estimates of discharge,
the St. Anthony Falls Water Power Co. made calculations of the flow
of the main river at Minneapolis as the water passed the Falls of St.
Anthony, where it was distributed for power purposes; and another
estimate of discharge was made at the Government lock and dam a
short distance above the mouth of the Minnesota River, by the
Ford Motor Co., lessee of the power developed at this point. The
discharge of the Mississippi River at Elk River was calculated from
gage heights read twice daily; at St. Paul from continuous gage
readings, and at St. Anthony Falls and at the Government lock and
dam from power-house records.
Rating stations previously established on tributaries by the Geo-
logical Survey were located on the Minnesota River at Mankato, on
the St. Croix River at St. Croix Falls, and at two points on the
Chippewa River, one at Chippewa Falls, Wis., and the other on the
Red Cedar River, at Menomonie, Wis., a tributary of the Chippewa
River. Rating stations had previously been established by the
United States Geological Survey, but later discontinued, on the
Cannon and Zumbro Rivers. These stations were reopened, under the
direction of the Minnesota Drainage Commission, during the summer
and fall of 1926, and then again discontinued.
Discharge of tributary streams was calculated from continuous-gage
readings at Mankato, Chippewa Falls, and Menomonie; from power-
house records at St. Croix Falls; and from gage readings taken twice
daily at Welch and Zumbro Falls, on the Cannon and Zumbro Rivers,
respectively. During times of ice cover, the relationship between gage
reading and discharge was affected and the estimates of run-off were
less reliable.
METHODS OF CALCULATING DISCHARGE
DISCHARGES FROM RATED TRIBUTARIES
Daily rates of discharge of tributaries have been supplied by the
United States Geological Survey from the gage height-discharge cor-
relations determined by current-meter readings at the rating sections,
or from the quantity of water passing the wheels or flowing over the
dams in the case of power stations. In most instances rating stations
on tributaries were located at considerable distances above their
mouths. The run-off from tributaries below rating sections was
assumed to be proportional to that above the section. The discharge
at the mouth was calculated by multiplying the discharge at the
-------
HYDROMETRIC MEASUREMENTS
17
rating section by a factor obtained by dividing the total watershed
area, by the area above the point where the measurements were made.
The factors so determined for the five larger tributaries of the
Mississippi River are given in Table 8.
TABLE 8.—Data relative to watershed areas, above and below gaging stations, on the
principal tributaries of the upper Mississippi River
Tributary
tw»
St. Croix River
Ohippewa River-
Area of
water-
shed in
square
miles
16 750
7,610
1,520
9,600
1,420
Area of
water-
shed
above the
rating
station
14 900
6,190
1,390
7,460
1,140
Station
of con-
fluence
with Mis-
sissippi
12 9
47.4
66.1
96.2
109.9
Location of gaging station
St. Crok Falls. .
Welch
Chippewa Falls and Menomonie—
Zumbro Falls..
Ratio of
total
water-
shed to
that
above
rating
station
1 12
1 23
1.09
1.29
1 25
The monthly average rates of discharge, expressed in cubic feet per
second (second-feet), at the mouths of the tributaries on the upper
Mississippi River watershed, calculated from the factors of Table 8,
are given in Table 9. The discharge from the Cannon and Zumbro
Rivers, after the rating stations were closed on the first of November,
1926, until the end of the investigation, was assumed to be the same
per square mile of watershed as the run-off from the Minnesota River
above Mankato, the nearest rated tributary.
TABLE 9.—Monthly average rates of discharge, in second-feet, of the tributaries oj
the upper Mississippi River at their mouths
Month
1920
June .- -
July - - -
November - _--.._.
1927
January. --------
March- . --
April
May.- ,- .
July
August. ... - - -
Minnesota
River
400
213
375
2,040
2,380
1,110
830
625
610
9,120
9,270
6,680
5,910
1,450
369
St. Croix
River
2,900
2,100
2,520
4,800
6,050
4,300
2,940
2,420
2,260
12,600
15,400
7,700
6,700
4,650
2,470
Cannon
River
134
95
97
293
276
256
214
126
132
570
1,220
1,030
1,100
212
46
Chippewa
River
5,500
3,600
9,500
23,400
12,600
15,500
6,840
6,500
7,130
24,500
11,100
13,500
7,500
7,260
4,170
Zumbro
River
272
154
163
454
474
238
200
118
124
530
1,130
965
1,030
197
43
AVERAGES
Yearly
Summer 1926
Summer 1927. .
Winter
Fall - -
Spring- _ -.
3,260
329
2,680
688
1,840
8,360
5,820
2,510
4,610
2,540
5,050
11,900
450
109
453
157
275
940
11,810
6,200
6,310
6,820
17,200
16,400
465
196
423
147
389
875
Yearly average=July, 1926 to June, 1927, inclusive.
Summer average=June, July, August.
Winter average=December, January, February.
Fall average™September, October, November.
Spring average = March, April, May.
-------
18 POLLUTION AND PURIFICATION OF UPPEK MISSISSIPPI EIVER
EATKS OF DISCHARGE AT SAMPLING STATIONS
In calculating the discharge at sampling stations below St. Paul,
it was necessary to extend the discharge measurements from the
St. Paul rating station, with modifications, downstream to Winona,
as no other rating section had been established on the Mississippi
River in the section under investigation.
The flow of the Mississippi River below St. Paul during the sum-
mer months is controlled for navigation purposes by the storage
reservoirs already referred to, near the headwaters of the stream.
In order to eliminate the effects of increased flow due to the oper-
ation of the reservoir system, the normal run-off from the watershed
was estimated by deducting from the discharge at St. Paul the
combined discharges of the Mississippi River at Elk River and the
Minnesota River at Mankato, and determining the yield, per square
mile, of the 7,040 square miles of watershed between these points.
As an example, the average discharge of the Mississippi River at
St. Paul during the month of July, 1926, was 2,590 second-feet from
36,570 square miles. During the same month the average discharge
of the Mississippi River at Elk River was 2,150 second-feet from
14,630 square miles of watershed, and of the Minnesota River at
Mankato 132 second-feet from 14,900 square miles of drainage area.
The normal discharge from the 7,040 square miles of watershed below
Elk River and Mankato and above St. Paul for this month was,
therefore, assumed to be 308 second-feet, or 0.044 second-foot per-
square mile of watershed. The estimated normal yield per square
mile of watershed for the other months of the investigation is tabu-
lated in Table 10. The figures were assumed to represent the yield
of the watershed adjacent to the river, between the mouths of tribu-
taries, from St. Paul to Winona.
TABLE 10.—Estimated normal monthly discharge, in second-feet per square mile,
from 7,040 square miles of watershed on the upper Mississippi River, between the
Elk River, Mankato, and St. Paul gaging stations, June 1, 19S6, to August 31,
1927.
Month
1926
July
August
September
October
November
December .
Total yield
in second-
feet from
7,040 square
miles
394
308
524
2,010
2 500
1,181
990
Yield, cubic
feet per
second, per
square mile
0 056
044
.075
.286
.355
.168
.141
Month
1927
March
April
May
June
July
Total yield
in second-
feet from
7,040 square
miles
580
610
2,630
5,610
4,790
5,110
980
211
Yield, cubic
feet per
second, per
square mile
0 083
.087
.374
.798
.680
.725
.139
.030
-------
HYDROMETRIC MEASUREMENTS 19
The total area of the Mississippi River watershed, above Winona,
has been estimated from the Geological Survey maps as 59,230 square
miles. Of this area, 52,750 square miles, or about 89 per cent of the
area of the watershed, is above the rating station at St. Paul or above
those on tributaries. By extending the rates of run-off from the
rating stations on tributaries, to their mouths, as already explained,
this area is increased to 56,720 square miles, or to about 96 per cent
of the total area of the watershed, leaving 2,510 square miles of water-
shed area directly tributary to the main stream, to which the calcu-
lated yields of Table 10 were applied.
The monthly average rates of discharge, in second-feet, of the upper
Mississippi Eiver at the various sampling stations, and above and
.below the mouths of the larger tributaries, are summarized in Table 11.
129540—32 3
-------
20 POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
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-------
HYDROMETRIC MEASUREMENTS 21
TIME OF FLOW CALCULATIONS
Computations of times of flow in the section of the river under in-
vestigation were limited by the hydrometric data available and by the
character of the surveys giving soundings in the river channel. Eates
of discharge at St. Paul, with correction for stream control, were
extended downstream to Winona and are, in the absence of a lower
rating station upon which to check results, undoubtedly subject to
considerable error. During December, January, and February when
the river was frozen, gage readings were discontinued at many of the
main river gages. At the St. Paul rating section increased velocities
usually prevent the river from freezing, and daily gage readings were
obtained throughout the year, but the relationship between gage height
and discharge was affected by the ice cover above and below the sta-
tion. Winter estimates of stream discharge are, therefore, subject to
considerable error. The estimation of water slope, in the various
prisms along the river, was limited to gage readings, when available,
at St. Paul, Red Wing, Reads, and Winona. The water-surface slope
between successive gages was assumed as uniform, which probably
was not altogether true. Surveys of the river between Minneapolis
and Winona, with soundings, were made on four occasions by the
Engineer Corps of the United States Army. The survey of 30 years
ago, made in 1897, for the Mississippi River Commission, was the
most extensive and shows the topography between the top of the
bluffs on either side of the river, the river channel, and the soundings
as of that date. The construction of the Federal lock and dam at
Minneapolis, about 1914, and the improvement in the low-water
channel below St. Paul by the construction of many more wing dams
and cut-off walls, together with frequent dredging operations, has
probably altered channel conditions and water slopes to such an ex-
tent that the older survey is of little value in calculating cross-sec-
tional areas at the present time. Later surveys of the river were made
in 1921, between St. Paul and the mouth of the St. Croix River;
in 1926 between the St. Croix River and the upper end of Lake Pepin;
and in 1925 between the outlet of Lake Pepin and Winona. These
recent surveys, made primarily for the purpose of obtaining depths
in the navigation channel under low-water conditions, show soundings,
usually from bank to bank or in the channel between wing dams, at
low river stages, with no attempt to indicate probable cross-sectional
areas as the river approaches flood stages. At times of low water the
wing dams and cut-off walls confine the flow to a definite channel,
but with increasing stages the dams become submerged and the water
spreads out over the flood plain to the foot of the bluffs, making com-
putation of the cross-sectional areas exceedingly difficult. Further
difficulties arise in attempting to estimate the effect on the mean
-------
22 POLLUTION AND PUEIPICATION OF UPPER MISSISSIPPI RIVER
velocity of flow through a prism, due to the submergence of the wing"
dams, which act as baffles, of varying height, above the bottom of the
river. Because of the limitations in the data, estimates of times of ..
flow were confined to that section of the Mississippi River below
Roberts Street, St. Paul, Station No. 5, where data from recent
surveys were obtainable and were made only for the summer and
winter periods, when river stages were more nearly comparable to
those at the time soundings were taken in the river.
Estimates of times of flow though the various prisms into which
the river was divided, Table 7, were based on the following funda-
mental relationship: Q, the discharge in second-feet, is equal to V,
the velocity of flow in feet per second, times A, the cross-sectional
area in square feet.
By dividing the estimated mean discharge through the prism by its
mean cross-sectional area, the estimated velocity of flow from the
upper to the lower limit was obtained. The time of flow was then
computed from the length of the section and the mean velocity of
flow. To determine the mean areas of wetted cross section in the
selected prisms with respect to the reference gage, the following
procedure was employed.
Large-scale maps, supplied by the U. S. Army Engineer Corps,
gave water-surface elevations at the reference gages on the days
that soundings were made in the river. From the soundings, three
to four or more representative cross sections along the river, per mile
of channel, were plotted to scale on cross section paper.
The slope of the water surface was assumed to be uniform between
reference gages. Water-surface elevations at the selected cioss
sections were calculated for the days on which soundings were taken,
and then indicated on the plots of representative river sections.
A correlation of gage heights, at reference gages, above and below
those of the dates on which soundings were made, indicated changes
in water slopes with changing river stages. Elevations at the
selected sections were then calculated and plotted on the cross-
sectional areas for several corresponding changes at the reference
gages.
Planimeter measurements were made of the areas below water-
surface elevations, on the cross-sectional plots, corresponding to
known readings on the reference gages. These areas were weighted
by the distance to the next section above and gave a relationship
between reference gage readings and mean cross sectional areas of the
prism.
-------
HYDROMETRIC MEASUREMENTS 23
" At reference gages below St. Paul an approximate relationship
was first established between reference-gage readings and corre-
sponding volumes of flow, which was used with the reference gage
reading, mean cross-sectional area relationship to estimate velocity
of flow through the various prisms between reference gages.
Prisms were selected so that all main tributaries entered at the
upper end. The increase in flow between the upper and lower end
of a prism, from the area immediately adjacent to the river, was
assumed to enter uniformly along the prism and the mean volume of
flow was assumed as that catering the prism, to which was added
one-half of the increase between the upper and lower limits.
The mean velocity of flow through the various prisms was next
computed from the mean discharge and the mean cross-sectional area,
at corresponding gage heights, and the time of flow by dividing the
length of the prism by the mean velocity of flow through it. Curves
showing the relation between gage height and mean cross-sectional
area and gage height and mean time of flow were then constructed
from these data.
Times of flow between points of the main river, from St. Paul to
the head of Lake Pepin, and from the outlet of the lake to Winona,
were calculated by the above method. In Lake Pepin, for which no
recent survey was available, the older maps of the Mississippi River
Commission were used, and the volume in the lake calculated from 5-
foot contours, below the reference gage at the outlet. Monthly mean
times of flow through the lake were assumed as the mean capacity,
during the month, divided by the monthly mean discharge at the out-
let of the lake.
In Tables 12 and 13 there are assembled, where the data would
permit of calculation, the monthly mean times of flow, during the
summer and winter periods, through designated prisms on the
Mississippi River, between St. Paul and Winona. The data of Table
12 show the time of flow through each of the designated prisms, that
of Table 13 the cumulative time of flow, for the same months, to
successive sampling stations below Station No. 5 at St. Paul.
-------
24
8
'C
s
S
15
rf£
POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
Mean time of flow, in hours
Ml
Oi
1
1*
January
11
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gs
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Station No 5 and Station No. 6 .,. .
Station No. 6 and Station No. 7
Station No. 7 and St. Croix River _
St. Croix River and Cannon River _ _.
c
1C
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Station No. 6, Invergrove Bridge .- ... __
Mouth of St. Croix River
-HrfOt^tO
Station No. 9, Red Wing _.
Tipper end of Lake Pepm ---
Outlet of Lake Pepin
i
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Js
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-------
SECTION III
POPULATION AND SOURCES OF POLLUTION ON THE UPPER
MISSISSIPPI RIVER WATERSHED
PRESENTATION OF DATA
The pollution of a river system at any given point along its course
depends upon the amount and composition of all the wastes dis-
charged into it above the point, the volume of the water into which
they are diffused, and the direction and extent of the changes which
the wastes have undergone between the point of entry and the
point of observation.
Polluting material enters a watercourse with the surface run-off
which carries portions of the eroded land surface and wastes of
various kinds resulting from the activities of the rural population
on the basin; as wastes from the more highly developed centers of
population, collected in artificial sewerage systems, either of the
combined or separate type; and as the wastes from industrial and
manufacturing processes. In highly developed industrial centers the
pollution contributed by these manufacturing wastes may be far
in excess of that contributed as domestic sewage. In terms of
polluting effect, the wastes contributed as domestic sewage from
different communities are generally proportionate to the respective
number of persons contributing to the sewers. The contributions
from different communities may, therefore, be summed up and
compared in terms of sewered population. It is also possible, to
a limited extent, to summarize the wastes from certain industrial
processes in terms of sewered population which would contribute
equivalent pollution, in the form of domestic sewage, and then to
obtain a rough quantitative estimate of the combined domestic
and industrial waste pollution from a series of urban communities.
The amount and character of the wastes derived from unsewered
rural areas vary to such an extent with the topography, character
of the surface formations, extent of agricultural operations, distri-
bution of rainfall, and other indeterminate factors that they can
not be estimated with any degree of accuracy or in any significant
quantitative terms.
Sources of pollution on the upper Mississippi River are, therefore,
presented as estimates of population; total, urban and rural, on the
watershed and its various subdivisions; summaries of the sewered
population contributing to the various watercourses; and as estimates
of the industrial waste pollution in terms of equivalent sewered
population.
25
-------
26 POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
POPULATION
Statistics of population used in this study were derived from the
Federal census enumerations of 1910 and 1920, redistributed accord-
ing to drainage areas, and extended to the year 1927 by assuming
an arithmetical rate of increase since 1910.
As tabulated in the census reports, the populations of the States
are distributed primarily by counties, and the population of each
county further distributed according to the civil subdivisions which
are included within the county area. Within the State of Minnesota
these minor civil divisions consist of organized and unorganized
townships, villages, and cities. In Wisconsin the county area is
divided into minor civil divisions consisting of "towns," which are
the equivalent of townships in most other States, cities, and un-
incorporated villages.
In the classification of the Census Bureau the population resident
in incorporated places having 2,500 or more inhabitants is classed
as "urban," and the remainder of the population, residing in the
county and in incorporated places of less than 2,500 inhabitants, is
classed as "rural." This classification has been followed in the-
present report.
In order to regroup the population according to drainage areas,
each watershed was outlined on State maps on which were indicated
the boundaries of the civil divisions of the population enumerations
of the census. Watershed boundaries were adjusted in accordance
with topographic maps of the United States Geological Survey where
available, or, in their absence, from maps of the State Drainage or
Conservation Commissions.
Counties lying wholly within a single watershed required only
simple summation of the populations, classified as rural and urban,,
respectively. In apportioning the population of counties inter-
sected by the watershed boundary, the proportion of the county
area lying within the watershed was first determined by planimeter
measurement. The population of all incorporated places was next
deducted from the total county population, and the remainder
prorated, allocating to the watershed a fraction of this population
proportionate to the fraction of the county area included in the
watershed as indicated by planimeter measurement. The prorated
population added to the population of all incorporated places of
less than 2,500 inhabitants within the watershed, as shown from
the maps, gave the total rural population. The urban population
was the sum of all incorporated places of 2,500 or more inhabitants
lying in that portion of the county included in the watershed.
In the densely populated areas, in the vicinity of Minneapolis and
St. Paul, population estimates were made with somewhat greater
precision by using city maps, on which ward boundaries were indi-
-------
POPULATION AND SOURCES OF POLLUTION
27
cated, or maps showing sewerage districts for which population
estimates were available.
The Mississippi River investigation was conducted during the
period from June 1, 1926, to August 31, 1927; and since January 1,
1927, represented approximately the mid-point of the study, estimates
of population on the entire watershed above Winona, Minn., and on
the various major subdivisions, as well as above sampling points,
were made for 1910 and 1920 and these estimates extended to Jan-
uary 1, 1927.
Statistics of population for the upper Mississippi River Basin,
above Winona, are summarized in Tables 14 and 15. Table 14 shows
the total, urban, and rural populations in 1910 and 1920 and the esti-
mated populations as of January 1, 1927, by major subdivisions and
for the entire watershed. The estimated populations on January 1,
1927, have been rearranged in Table 15 to show the total, urban, and
rural populations above the various sampling stations on the main
river and its tributaries.
TABLE 14.—Total, urban, and rural population on the Mississippi River water-
shed above Winona, Minn., by tributary areas, in 1910 and 1920, and the esti-
mated population on January 1,
Watershed
Mississippi above
Minneapolis
Minnesota River..
St. Croix River. ._
Cannon River
Chippewa River. _
Zumbro River
Mississippi, di-
rect, Minneapo-
lis to Winona
Total
Area,
square
miles
19,440
16, 750
7,610
1,520
9,000
1,420
2,890
59,230
Population in 1910
Total
345,528
404, 460
128, 632
54, 868
181, 382
43, 783
642, 793
1, SOI, 446
Urban
56, 939
47, 43S
14, 461
17, 924
43, 206
7,844
544, 850
732, 663
Rural
288, 589
357, 021
114, 171
36,944
138, 176
35, 939
97,943
1, 068, 783
Population in 1920
Total
404, 528
438, 879
148, 137
57, 978
211, 545
50, 429
749, 762
2, 061, 258
Urban
70, 219
60,384
13, 042
22,364
48, 431
13, 722
649,460
877, 622
Rural
334, 309
378, 495
135, 095
35, 614
163, 114
36, 707
100, 302
1, 183, 636
Population Jan. 1, 1927
Total
442,327
463, 65S
162, 181
60, 218
233,263
55, 215
831, 384
2, 248, 247
Urban
79, 780
69, 705
12, 021
25, 561
52, 193
17,954
724, 878
982, 092
Rural
362, 547
393, 954
150, 160
34, 657
181, 070
37, 261
106,506
1, 266, 155
TABLE 15.—Estimated total, urban, and rural population, as of January 1, 1927,
above sampling stations on the upper Mississippi River
Population above points on the Mississippi River and
tributaries
Above Minneapolis:
Station No. 2-..
Above lock and dam, Minneapolis, Station No. 3
Minnesota River watershed above station No 4
Above St Paul, Station No 5
Above Hastings, Station No. 7 _ _ __
Mississippi River above the mouth of Cannon River
Cannon River watershed above Station No. 10
Chippewa River watershed above Station No 12 -- .
Mississippi River above the Zumbro River
Water-
shed
area,
square
miles
19, 440
19,490
19,580
19, 780
16, 750
36, 570
36, 680
36, 820
7,610
44, 850
1,820
46, 950
9,600
57, 000
1,420
59,230
Population Jan. 1, 1927
Total
442, 327
505, 933
922, 376
954, 136
463, 659
1,417,795
1, 650, 586
1,661,672
162, 181
1, 835, 923
60, 218
1, 924, 680
233,263
2, 173, 023
55, 215
2, 248, 247
Urban
79, 780
136, 653
649, 391
566, 813
69, 705
636, 518
858, 395
863, 389
12, 021
875, 410
25, 561
911, 945
52, 193
964, 138
17,954
982, 092
Rural
362, 547
369, 280
372,985
387, 323
393, 954
781, 277
792, 191
798,283
150, 160
960, 513
34, 657
1, 012, 735
181, 070
1, 208, 885
37, 261
1, 266, 155
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28 POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
The distribution, by States, of the estimated total, urban, and rural
populations on the watershed, as of January 1, 1927, is indicated in
the following tabulation, Table 16.
TABLE 16.—Estimated total, urban, and rural population, as of January 1, 1927,
on the Mississippi River watershed, above Winona, Minn., arranged by States
State
South Dakota..
Total
Total pop-
ulation
1, 856 819
353, 678
28, 729
9,021
2, 248, 247
Urban pop-
ulation
923, 840
58, 262
982, 092
Rural pop-
ulation
932, 979
295, 426
28, 729
9,021
1, 266, 155
The estimated total population on the upper Mississippi River
watershed, above Winona, on January 1, 1927, was 2,248,247, of
which 1,266,155, or 56 per cent, was classed as rural, and 982,092,
or 44 per cent, as urban. Of the total population on the watershed,
approximately 82 per cent was within the State of Minnesota and 16
per cent in the State of Wisconsin. The urban population of the
watershed, 982,092, was divided between the States of Minnesota and
Wisconsin, 94 per cent residing in the former and only 6 per cent
within the latter. Within the metropolitan area of the Twin Cities,
in Minnesota, there was an urban population of 708,910, equivalent
to approximately 72 per cent of the total urban population on the
entire watershed.
The population on the watershed of the mam river, above Minne-
apolis, and on the tributaries, was largely rural in character, as indi-
cated in the following tabulation, which shows the percentage of
watershed population classed as rural, on the larger tributaries.
TABLE 17.—Percentage of the population classed as rural on the tributaries of the
upper Mississippi River and on the main stream, above Minneapolis. Popula-
tion estimates as of January 1, 1927
Watershed
St Croix River
Per cent
of water-
shed pop-
ulation
classed
as rural
82
85
93
Watershed
Per cent
of water-
shed pop-
ulation
classed
as rural
57
78
67
With the exception of Minneapolis and St. Paul, there were but
19 communities on the upper Mississippi River watershed, above
Winona, with populations of 5,000 or over. Of these, 16 were in
Minnesota and 3 in Wisconsin. Five communities in Minnesota
and one in Wisconsin had populations in excess of 10,000.
SEWERAGE AND SEWAGE TREATMENT
Sewerage systems had been installed in approximately 182 commu-
nities on the Mississippi River watershed above Winona. Data
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POPULATION AND SOUBCES OF POLLUTION
29
'relative to the population contributing to sewerage systems, methods
of sewage treatment, and industrial-waste pollution were secured by
. visits to the communities comprising the metropolitan area of the
Twin Cities and to those located directly on the main stream, between
the metropolitan district and Winona. Information for the remain-
ing places, comprising a large number of small communities, scattered
over the entire watershed, was obtained by circular letter addressed
to the health officer, mayor, or other local official, supplemented by
data from the records of the State health organizations.
SEWERAGE
Table 18 presents in summarized form the data collected rela-
tive to the number of sewered communities on the entire watershed,
above Winona, and by tributary areas; the total population residing
in these communities; the population actually contributing sewage;
the number and types of sewage-treatment plants; and the popula-
tion contributing to each type of treatment plant.
TABLE 18.—Summary of sewered population and sewage-treatment data on the
Mississippi River watershed above Winona, Minn., by watershed divisions
Watershed
St. Croix River
Vermillion River - -
Cannon River -
Chippewa River
Buffalo River
Mississippi River, directly, Minneapolis to
Winona
Total
Watershed
St. Croix River
Cannon River -
Isabelle Creek
Zumbro River
Buffalo River
Mississippi River, directly, Minneapolis to
Winona _
Total .
Number
of sewered
commu-
ities
58
58
21
1
4
1
20
9
1
1
8
182
Per cent
of popu-
lation in
sewered
commu-
nities con-
tributing
sewage
03.5
61.7
62.2
85 5
82 4
74.7
63. 3
09 5
58.1
87 3
97.2
85 7
Number of sewage-
treatment plants
Primary
treatment
only
22
25
3
1
0
0
3
4
0
1
0
59
Population
contribut-
ing untreat-
ed sewage
49, 810
46, 480
IB, 910
22, 150
40, 430
2,440
1,000
696, 360
875,580
Primary
and sec-
ondary
treatment
2
1
0
0
0
1
1
2
0
0
0
7
Population
contiibut-
ing sewage
after pri-
mary treat-
ment
24, 920
28, 300
2,440
1 500
1,850
2,430
1 300
62, 740
Total pop-
ulation of
sewered
communi-
ties Jan. 1,
1927
120, 880
121,590
31, 270
1,760
26,830
1,070
68, 050
25, 620
1,720
1, -190
717, 100
1, 117, 380
Population
contribut-
ing sewage
after pn-
mary and
secondary
treatment
2,040
360
800
800
12, 960
16,960
Estimated
actual
sewered
popula-
tion
76, 770
75, 140
19, 350
1,500
22, 150
800
43, 080
17, 830
1,000
1,300
696, 360
955, 280
Estimated
population
discharg-
ing the
equiva-
lent of un-
treated
sewage *
66, 930
65, 440
18,540
1,000
22, 150
200
41, 860
7,300
1,000
900
696, 360
921, 680
i Based on 33H per cent reduction for primary treatment and 75 per cent reduction for primary and
secondary treatment.
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30
POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVEE
SEWERED POPULATION
In order to estimate the population discharging the equivalent of
untreated sewage, it was assumed that primary treatment, consisting
in most cases of sedimentation in septic or Imhoff tanks, would
reduce the sewage load by about one-third, and that primary and
secondary treatment would cause a reduction of 75 per cent in the
sewage load. The last column of Table 18 indicates, therefore, for
various subdivisions of the watershed, the estimated population
discharging the equivalent of untreated sewage.
The data of Table 18 have been rearranged in Table 19 to show the
population discharging the equivalent of untreated sewage, by 50-
mile zones, above each of the sampling stations on the main stream
and its larger tributaries.
TABLE 19.—Estimated population discharging untreated sewage, by 50-mile zones,
above sampling stations on the upper Mississippi River
Sampling station
1
2
3
Minnesota River
5 . .
6
7 .
St. Croix River
9
Cannon River
11-
Zumbro River
14
Sampling station
1
2
3 -
6
6
7 ...
St. Croix River
9 .
Cannon River
11
Chippewa River -
14
50-mile zone
0-50
3,420
54, 890
462, 910
3,100
598, 160
684, 580
682, 080
10, 690
286, 870
6,650
13,400
3,500
1,680
50-100
22, 510
22, 610
19, 770
5,430
21, 770
21, 270
7,230
3,230
437, 310
15,500
708, 660
28, 610
6,780
38, 690
100-150
19, 140
16, 640
9,870
17, 150
26, 800
27, 020
41,460
2,320
24, 860
18, 920
6,800
520
725, 810
150-200
6,550
8,720
18, 230
10, 200
28, 630
26, 580
23, 810
2,300
28, 170
42, 190
2,950
24, 630
200-250
2,200
2,530
3,330
10, 700
17, 230
17, 440
17,900
31, 430
26,500
46, 300
50-mile zone
300-350
7 230
7,230
7,230
6,820
11, 850
12, 420
15, 020
12,290
11,820
15, 470
350-400
1,950
3,330
5,030
9,880
13, 850
14, 770
13,220
40CM50
4,800
4,800
4 800
4,800
100
450
3,330
10, 130
15, 020
450-500
4,700
4,800
4,800
450
6,730
500-550
4,800
300
550-600
4,700
250-300
1,080
1,080
1,080
11,090
14,290
15, 310
11,820
15, 730
17,900
29,130
Total
popula-
tion dis-
charging
untreated
sewage
66, 930
118,400
527, 220
65, 440
726, 860
814,450
814, 450
18,540
858, 340
22, 150
869, 540
41,860
7,300
921,680
The estimated total sewered population on the upper Mississippi
watershed, above Winona, is 955,280, equivalent to about 86 per
cent of the total population in all the sewered communities. Omitting
the sewered population of Minneapolis and St. Paul, which is equiva-
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POPULATION AND SOURCES OF POLLUTION 31
lent to about 94 per cent of the total population within these two cities,
about 68 per cent of the remaining urban population on the watershed
contributes to sewerage systems. Similar calculations for the Ohio
River drainage area, made in 1915, indicated a sewered population
equivalent to about 72 per cent of the entire urban population; and
on the Illinois River basin, in 1922, excluding the urban population
of Chicago, which was practically 100 per cent sewered, the sewered
population on the remainder of the watershed was 76 per cent of the
total urban population.
Of the estimated total population of 921,680 discharging untreated
sewage on the Mississippi watershed above Winona, 868,490, or
about 94 per cent, are within the State of Minnesota and 53,190, or
about 6 per cent, within the State of Wisconsin. The distribution
of the population discharging untreated sewage by various subdivisions
of the watershed is shown in Table 20.
TABLE 20.—Distribution of the estimated population discharging untreated sewage,
on the upper Mississippi River watershed, by tributary areas
St. Croix River
Camion River
Zurabro River
Mississippi River,
Watershed division
above Minneapolis _ - -
below metropolitan area . .-
Estimated
population
discharg-
ing un-
treated
sewage
66, 930
65 440
682 060
18 540
22, 150
41 860
7 300
17,400
921 680
Per cent
of total
popula-
tion dis-
charging
untreated
sewage
7 3
7 1
74 0
2 0
2 4
4 6
g
1.9
100 0
It will be observed from Table 20 that 74 per cent of the total esti-
mated population discharging untreated sewage on the entire water-
shed contributes to the Mississippi River within the metropolitan
area of the Twin Cities in Minnesota. Sewage from this area is dis-
charged from about 75 main sewer outlets, located on both sides of
the river along a distance of 25 miles.
At the time of the investigation practically all of the sewage from
Minneapolis, and some from St. Paul, entered the main river above
the Government lock and dam. Sedimentation of sewage solids
took place in the pool behind the dam, forming sludge deposits along
the sides and bottom. Decreased rates of stream flow combined
with high water temperatures, in the summer months, produced
septic conditions in this pool the effects of which were noticeable
downstream as far as Hastings.
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32 POLLUTION AND PURIFICATION OP UPPER MISSISSIPPI RIVER
SEWAGE TREATMENT
Of the 182 sewered communities on the Mississippi River water-
shed above Winona, 66 treated their sewage before discharging it
into the various watercourses. In 59 communities, in which the esti-
mated total sewered population was 62,740, or 6.6 per cent of the total
sewered population on the entire watershed, treatment consisted of
sedimentation in various types of tanks. In the remaining seven
communities, with an estimated sewered population of 16,960, or 1.8
per cent of the total sewered population on the entire watershed, the
sewage received more or less complete treatement in primary and
secondary sewage treatment works. In the communities having
primary treatment works, the population contributing the equivalent
of untreated sewage was assumed as two-thirds of the actual sewered
population, and in communities having both primary and secondary
treatment, as one-quarter of the actual sewered population. On this
basis sewage treatment on the upper Mississippi River basin caused a
reduction in pollution equivalent to the sewage from a population of
33,600 persons.
At the close of the field work of this investigation studies were in
progress toward the collection and disposal of the sewage from the
metropolitan area of the Twin Cities, to improve conditions in the
Mississippi River through and below this area.
POLLUTION DUB TO INDUSTRIAL WASTES
In the questionnaire sent to local government officials concerning
sewerage, sewered population, and sewage treatment, there was in-
cluded a request for information relative to the number and types of
manufacturing establishments discharging industrial wastes into the
watercourses. Through these inquiries, a total of 107 possible waste-
producing industries were reported on the watershed, outside of the
metropolitan district. Included in this number were 68 creameries;
18 canning plants and a beet-sugar factory, operating only a portion
of the year; 6 slaughtering and rendering establishments; 7 pulp
and paper mills; 4 poultry-dressing establishments; a malting plant;
a vinegar factory; and a woolen mill. This list, undoubtedly in-
complete, indicated in a general way that the predominating types
of industry on the watershed were those engaged in the production
of milk products, canned goods, and paper. The data further indi-
cated, from the distribution of the plants on the watershed, that the
Chippewa River received the largest amounts of industrial-waste
pollution, there having been reported on this watershed 6 pulp and
paper mills, 12 canning plants, 2 milk condenseries, and 11 butter
and cheese factories.
-------
POPULATION AND SOURCES OP POLLUTION 33
During the year 1928 the Minnesota State Department of Health
made a study of the sewage and industrial waste pollution of the
. tributaries of the Mississippi Biver in Minnesota. By taking into
consideration the reduction in the strength of part of the sewage by
treatment and the increase in strength due to industrial wastes a
population estimate was derived which indicated the number of
persons on each watershed that would produce, in terms of domestic
sewage, pollution equivalent to that of the domestic sewage and the
industrial wastes reaching the stream. These population estimates,
designated as the total sewered population equivalents, were 150,000
on the Mississippi River watershed above Minneapolis, 100,000 on
the Minnesota River watershed, 22,800 on the Cannon River water-
shed, and 20,000 on the Zumbro River watershed. If from these
figures there is deducted the estimated population on the same water-
sheds discharging the equivalent of untreated sewage as given in
Table 20, a rough approximation is obtained of the population neces-
sary to produce, in terms of domestic sewage, pollution equivalent
to that of the industrial wastes. The population equivalent to the
discharge of industrial wastes derived in this manner was 83,070 on
the Mississippi River watershed above Minneapolis, 34,560 on the
Minnesota River watershed, 650 on the Cannon River watershed, and
12,700 on the Zumbro River watershed. In other words, the pollu-
tion from industrial wastes on the Mississippi River watershed above
Minneapolis and on the Zumbro River watershed appeared to be
greater than the pollution by domestic sewage, on the Minnesota
River watershed the pollution by industrial wastes was about half
the pollution by domestic sewage, and the pollution of the Cannon
River by industrial wastes seemed to be of no great significance.
In the absence of detailed information as to the points of discharge
of the various polluting wastes entering the tributaries and the nature
and extent of the changes taking place in the streams, the chemical
and bacteriological samples collected at the mouths of the tributaries
were assumed to be indicative of the final effects of all the pollution
entering above the sampling point, after the operation of such natural
purification agencies as existed between the source of pollution and
the mouth.
The Metropolitan Drainage Commission of Minneapolis and
St. Paul, in its investigation of methods of collecting and treating
the sewage from this area, has made extensive measurements of the
flow from nearly all of the 75 or more larger sewer outlets into the
river and has collected many composite samples of sewage and indus-
trial wastes, from the same outlets, for chemical analysis. The flow
data and the 5-day biochemical oxygen demand determinations were
utilized to estimate the total daily oxygen requirements, in pounds.
-------
34
POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
of the combined sewage and industrial wastes from each of the sewer
outlets.
Assuming that the 5-day biochemical oxygen demand of domestic
sewage is 0.163 pound per capita per day ' the total oxygen require-
ments of the combined sewage and industrial wastes from each sewer
outlet were converted into terms of a sewered population which
would contribute pollution, in the form of domestic sewage, equivalent
to that of the sewage and industrial wastes. This calculated popula-
tion was designated as the total sewered population equivalent.
The actual sewered population contributing to each outlet was
next estimated from the population of the sewer district and the
extent of the sewerage system, and this figure checked roughly by
measuring the volume of flow and collecting samples for analysis on
Sundays when industrial plants were not in operation. By deducting
the estimated actual sewered population from the total sewered popu-
lation equivalent, there remained the number of persons necessary to
produce pollution, in terms of domestic sewage, equivalent to the
industrial-waste pollution. This population was designated as the
sewered population equivalent to industrial wastes.
Estimates of the actual sewered population, sewered population
equivalent to industrial wastes, and the total sewered population
equivalent, as determined for each of the sewer districts, have been
supplied through the courtesy of the chief engineer of the Metro-
politan Drainage Commission. These data have been summarized
in Table 21 and show the distribution of these populations between
the various sampling stations within the metropolitan area.
TABLE 21.—Summary of the actual sewered population on the upper Mississippi
River, between sampling stations within the metropolitan area of Minneapolis and
St. Paul, with estimates of population equivalent to industrial wastes
Mississippi River between —
Station No. 1 and Station No. 2_
Station No. 2 and Station No. 3 .. ._
Station No 3 and Station No 5
Station No. 5 and Station No. 6_ -
Actual sew-
ered popu-
lation
(1)
51, 460
408, 820
134 200
87 610
682 090
Total sew-
ered popu-
lation
equivalent
(2)
51, 460
606, 360
198 545
450 125
1 306 490
Population
equivalent
to indus-
trial wastes
C2)-(l)
197, 640
64 345
362 515
624 400
Table 21 indicates that the total population, equivalent to all the
organic industrial wastes, in the metropolitan area is 624,400, or
approximately 92 per cent, of the actual sewered population; that is,
industrial wastes are responsible for nearly as much pollution as that
attributed to domestic sewage. Ratios of industrial waste to sewage
' The Oxygen Demand of Polluted Waters. E. J. Theriault. Public Health Bulletin No. 173, page 54.
-------
POPULATION AND SOURCES OF POLLUTION 35
pollution, similarly calculated during the study of the Ohio River, for
the metropolitan areas of Pittsburgh, Pa.; Wheeling, W. Va.; Cin-
cinnati, Ohio; and Louisville, Ky., ranged from 48 to 59 per cent.
The pollution of the Illinois River by industrial wastes from Chicago
was estimated as being about 52 per cent of the pollution from domes-
tic sewage.
Nearly two-thirds of the industrial-waste pollution of the Missis-
sippi River within the metropolitan area of Minneapolis and St. Paul
is attributable to the discharge of untreated wastes from the large
packing establishments in South St. Paul. Deducting the population
represented by these wastes, the pollution of the river from the remain-
ing more diversified industrial establishments within the metropolitan
area is equivalent to about 44 per cent of the pollution by domestic
sewage, a figure more nearly comparable to those derived for the
other metropolitan areas.
129540—32 4
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SECTION IV
METHODS OF PROCEDURE IN FIELD AND LABORATORY
STUDIES
The investigation of the upper Mississippi River was made pri-
marily at the request of the States of Minnesota and Wisconsin and
the cities of Minneapolis and St. Paul, to determine (a) the extent of
pollution in the river through these cities; (b) the condition of the
boundary waters between the States below the junction of the St.
Croix River; (c) the probability of future recurrences of the objec-
tionable conditions which existed in the river from Minneapolis to
Hastings, in the summer months of 1925 and 1926, during the low
stream flows of these years; and (d) to obtain data as to the necessity
for sewage-treatment works in Minneapolis and St. Paul to relieve
the sewage load in the river.
The collection of data was, therefore, planned with these main pur-
poses in view, keeping in mind at the same time the possibility of
locating sampling points and collecting other necessary data to make
the investigation profitable for a more general study of stream pollu-
tion and natural stream purification, to compare the results with those
obtained in similar studies which had previously been made by the
United States Public Health Service on the Ohio and Illinois Rivers.
SELECTION OF SAMPLING POINTS
Sampling stations were located at accessible points which were
indicative of conditions at the more important points along the river.
Selection of sampling points was limited, to a certain extent, by ex-
press service for the shipment of samples from points below South St.
Paul. It was necessary to collect samples early in the day, between
4 and 7 a. m., and from points accessible by automobile from the
larger communities. Accordingly sampling stations were located in
the vicinity of Hastings, Red Wing, Wabasha, and Winona, Minn.
These communities were located near the entrance of tributaries so
that, in most instances, one sample collector could collect two sam-
ples—one from the main river, above the local sewer outlets, and above
the entrance of a tributary, showing the condition of the main stream
before the admixture of tributary water; and another from the tribu-
tary, indicating the condition of the inflowing water in relation to that
of the main stream. It was found impracticable to collect samples
below the confluence of tributaries to indicate conditions after the
mixing of the two waters.
36
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PROCEDURE IN FIELD AND LABORATORY STUDIES 37
Six sampling stations were selected along the river within the metro-
politan area and indicated the condition of the river as it entered the
district; the effect of the sewage of Minneapolis and some from St.
Paul in the pool above the Government lock and dam; the condition
of the Minnesota River, at its mouth, entering the main stream be-
tween Minneapolis and St. Paul; the condition of the river at St.
Paul; and the effect of all the sewage and industrial wastes as the river
left the metropolitan area. Sampling points below the metropolitan
area indicated successive changes in the condition of the river as a
result of the inflow of tributaries and natural purification in the pas-
sage downstream.
Sampling stations were numbered, in order of their location, down-
stream from Station No. 1, at the Camden Avenue bridge in Minne-
apolis, to Winona. Fourteen regular stations were maintained on the
Mississippi River and the more important tributaries during the
period of the investigation. The following summary shows the loca-
tion of the sampling points selected on the main river and its tribu-
taries and gives, for each station, information as to the character of
the river channel, conditions of flow, and other related data.
DESCRIPTION OF MISSISSIPPI RIVER SAMPLING STATIONS
STATION NO. 1
Camden Avenue Bridge, Minneapolis.—Located just below the city waterworks
intake. Width of river section about 800 feet; depth over 15 feet at low water.
River flows between banks with very little change in the width of cross section at
high water. Main channel was between the central bridge abutments, with per-
ceptible current. The sampling point was above all of the Minneapolis sewer
outlets and samples represented the water entering the metropolitan area. Sam-
ples taken from the bridge during open-water conditions; from the waterworks
intake well, located just above the bridge, during periods of ice cover on the river.
STATION NO. 2
Plymouth Avenue Bridge, Minneapolis.—Located 3 miles below Station No.
1 and about a mile above the Falls of St. Anthony. Width of section about 1,000
feet; maximum depth at low water 10 feet. Very little change in river section
during periods of high water. Island at east end of the bridge divided the river,
but the main channel was between the central bridge abutments where the current
was usually fairly rapid. At the Falls of St. Anthony the water dropped about
70 feet over the falls or through the turbines to the pool formed by the lock and
dam at sampling station No. 3. Samples from this station were discontinued
during periods of ice cover.
STATION NO. 3
Government lock and dam, Minneapolis.—Sampling station located just below
the Intercity bridge between Minneapolis and St. Paul at the dam, 7.5 miles
below Station No. 2. Width of river section 1,000 feet under all conditions of
discharge. Depth of water at the dam about 30 feet. The pool formed by the
dam extended upstream for about 5 miles to the head of navigation on the Missis-
sippi River at the Washington Avenue bridge, Minneapolis. The capacity of the
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38 POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
pool was estimated at 340,000,000 cubic feet. The flow through the pool was
sluggish. Most of the sewage of Minneapolis, and some from St. Paul, entered
the pool above the dam. Bottom and sides were covered with sewage material
and the pool became septic during low summer stream flows and high water tem-
peratures. Samples were collected at the east end of the dam, in the channel
leading to the turbines. Below the sampling point the water dropped 30 feet
over the dam or through the turbines and flowed 2.4 miles to the mouth of the
Minnesota River.
STATION NO. 5
Roberts Street Bridge, St. Paul.—Located 6.3 miles below the entrance of the
Minnesota River and 8.7 miles below Station No. 3. Bank-to-bank width of the
section 800 feet. The low-water flow was restricted to a navigation channel about
200 feet wide with a depth of 16 feet. Current through the section usually swift.
Sewage from a part of St. Paul entered the river above this station.
STATION NO. 6
Invergrove Bridge.—Located 9 miles below Station No. 5 and about 3.5 miles
below the stockyard sewer outlets at South St. Paul and vicinity. Low-water
bank-to-bank section about 950 feet. Main flow was confined to a navigation
channel about 200 feet wide with a depth of 7 feet. From Station No. 5 the river
was confined to a navigation channel during periods of low stream flow by about
85 wing dams. Samples were indicative of the condition of the water as it left
the metropolitan area of the Twin Cities.
STATION NO. 7
Hastings, Minn —Located about 1,000 feet above the highway bridge over the
river, and above the Hastings sewer outlets. This station was 16.8 miles below
Station No. 6. Width of the low-water section, 500 feet; maximum depth, 15
feet. The flood plain of the Mississippi River reached a width of a mile just above
the station. During periods of high water, considerable ponding and backwater
occurred on the flood plain. Between this station and the one above, there were
about 160 wing dams, confining the water to a navigation channel during low
river stages. The St. Croix River entered 2.4 miles below the station.
STATION NO. 9
Red Wing, Minn.—Located about 1,000 feet above the highway bridge over
the Mississippi River at Red Wing, 23.3 miles below Station No. 7. Width of
low-water section, 800 feet; maximum depth, over 15 feet. The flood plain of the
main river reached a width of 4.5 miles between bluffs above the station and con-
tained many sloughs, pools, and swampy areas. At high water ponding occurred
above the sampling point. From the station next above there were 125 wing
dams to assist navigation during periods of low stream flow. The St. Croix River
entered 20.9 miles and the Cannon River 2.2 miles above the station. About 5
miles below the station the river entered Lake Pepin.
STATION NO. 11
Outlet of Lake Pepin at Reads, Minn.—Located 0.3 mile above the mouth of
the Chippewa River and 26.8 miles below Station No. 9. Lake Pepin is formed by
an expansion of the main channel due to sand deposits brought down by the
Chippewa River. The lake has a length of about 22 miles and a maximum depth
of 56 feet, average depth probably about 30 feet. The lake occupies the entire
flood plain between bluffs and has a maximum width of about 3 miles. Width at
the sampling section, 2,000 feet. Current usually swift, making sampling difficult
at the station and at Station No. 12 on the Chippewa River.
-------
PEOCEDURE IN FIELD AND LABORATORY STUDIES 39
STATION NO. 14
Winona, Minn.—Located 1,500 feet above the highway bridge over the Missis-
sippi River at Winona and above the local sewer outlets. The station was 41.7
miles below Station No. 11, at the outlet of Lake Pepin, 41.4 miles below the mouth
of the Chippewa River and 27 miles below the mouth of the Zumbro River.
Width of low-water section, 800 feet; maximum depth, 13 feet. The channel
above the section winds across the flood plain, which had a maximum width of
5 miles and on which there were numerous sloughs, ponds, and swampy areas.
About 400 wing dams had been constructed between Stations No. 11 and 14.
DESCRIPTION OF TRIBUTARY SAMPLING STATIONS
STATION NO. 4
Minnesota River at its mouth.—Located opposite Fort Snelling just above Pike
Island. Width of low-water section, 500 feet; depth about 30 feet. The
flow in the lower stretches of the river was very sluggish. Sampling at this station
irregular during periods of ice cover. The Minnesota River entered between
Stations No. 3 and 5 on the main river.
STATION NO. 8
St. Croix River at its mouth.—Located opposite Prescott, Wis., below the high-
way bridge. The sampling point was in the restricted section of the sand bar at
the outlet of Lake St. Croix, an expansion of the lower portion of the main channel
which extended upstream a distance of some 20 miles and which had a depth of
nearly 50 feet in its lower section. The current through the sampling section was
usually swift. The St. Croix River entered the Mississippi River 2.4 miles
below Station No. 7 at Hastings.
STATION NO. 10
Cannon River near its mouth.—Located at the bridge over Highway No. 3,
about 6 miles from Red Wing. Width of section 200 feet with a fairly rapid cur-
rent. The sampling station was above the point where the Cannon River starts
meandering and dividing on the flood plain of the Mississippi River and was
above backwater from the main river. The Cannon River entered the Missis-
sippi River 2.2 miles above Station No. 9 at Red Wing.
STATION NO. 12
Chippewa River at its mouth.—Located on the Wisconsin side of the river
opposite Reads. The river entered through a restricted artificial channel con-
structed to increase its velocity and prevent the deposition of sand in the main
river. The sampling section had a width of 500 feet. Current usually swift
through the section. With the river in flood there was considerable backing up
of water from the Chippewa River through Station No. 11 into Lake Pepin.
Samples discontinued during the winter months on account of the inaccessibility
of the station. The mouth of the river was 0.3 mile below Station No. 11 at the
outlet of Lake Pepin.
STATION NO. 13
Zumbro River at Kellogg, Minn.—Located at the bridge over the river on High-
way No, 3. Low-water section width 100 feet. Sampling station above the point
where the Zumbro River entered the flood plain of the Mississippi River and
began to divide and meander across it to the main river channel. The Zumbro
River entered the Mississippi River 27 miles above Station No. 14 at Winona.
-------
40 POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
COLLECTION OF WATER SAMPLES
Samples from all of the stations selected were taken at a single
point, located in the center of the channel, at mid-depth. During the
first summer and fall of the investigation, samples were taken from
all the stations five times each week, i. e., each day from Monday to
Friday, inclusive; and during the winter and second summer, three
times a week, on Monday, Wednesday, and Friday.
Samples were obtained in a special galvanized-iron collector 2 used
during the Illinois River investigation and patterned after one previ-
ously used by the Sanitary District of Chicago. This type of col-
lector permitted the filling, simultaneously, of two bottles for the dis-
solved-oxygen determinations and one for the bacteriological
analysis.
Samples for the oxygen determinations were taken in 350 c c
bottles, which were filled through tubes in the cover of the sample
collector, extending to the bottom of the sample bottles. The first
water entering these bottles overflowed into the collector and several
changes of water took place before the sample was obtained. Bac-
teriological bottles of 250 c c capacity were filled through a sterile
glass tube, placed in the top of the collector before each sample was
taken. Air bubbles were excluded from the oxygen samples, but an
air space was purposely left in the bacteriological sample bottles.
Temperature readings, made on the larger volume of water in the
collector, were recorded as the temperature of the sample at the time
of collection. Immediately after collecting each set of samples, the
following information was noted on a label which was attached to
each bottle: Date of collection, time of day, sampling-station
number, temperature of the water, and name of the sample collector.
DELIVERY OF WATER SAMPLES
The laboratory for the examination of all water samples was
located in space made available by the division of sanitation of the
Minnesota State Department of Health on the campus of the Uni-
versity of Minnesota, in Minneapolis. All examinations were made
under comparable conditions with the single exception that there
were considerable differences in the time between the collection of
the samples from different stations and their arrival at the laboratory.
Samples from Stations Nos. 1 to 6, inclusive, located on the highly
polluted section of the river, were transported by automobile and
delivered immediately to the laboratory for examination, the maxi-
mum time between collection and arrival for analysis not exceeding
2.5 hours. All down-river samples arrived in Minneapolis on the
same train and reached the laboratory about noon on the day of
1 Diagram in Public Health Bulletin No. 171, page 58.
-------
PROCEDURE IN FIELD AND LABORATORY STUDIES 41
sampling. The time between collection and arrival at the laboratory
depended chiefly on the distance of the sampling station from the
shipping point. For Stations Nos. 7 to 13, inclusive, this period
varied from 4 to 7 hours, while for Station No. 14, the farthest away
from Minneapolis, it was between 7 and 9 hours. Samples from
Stations Nos. 7 and 8 were collected by the same sample collector,
using a boat, and were shipped from Hastings. Samples at Stations
Nos. 9 and 10 were also collected by one sample collector, using an
automobile, from Red Wing for the Cannon River sample. Three
samples were shipped from Wabasha, two collected by boat, from
Reads, at Stations Nos. 11 and 12, and one from the Zumbro River at
Kellogg; all three of these being brought to Wabasha by automobile.
The sample at Station No. 14 was collected from a boat and shipped
from Winona.
Samples were shipped in special metal-lined shipping cases, with
an inner circular compartment, ia which the sample bottles were sup-
ported by a perforated metal disk, with space for eight bottles.
During the summer months, the space beneath and around the
sample bottles shipped by express was packed with ice.
CHEMICAL METHODS
Routine chemical analyses made on each sample as received at the
laboratory comprised the determination of turbidity, alkalinity, dis-
solved oxygen present upon arrival at the laboratory, and the 5-day
biochemical oxygen demand at 20° C. For a period of five months,
hydrogen-ion concentration determinations were made on all samples.
TURBIDITY
Turbidities of less than 25 parts per million were read from bottle
standards of standard silica suspension, while turbidities in excess of
25 parts per million were determined by the standard candle tur-
bidimeter. The excess water from the bacteriological samples was
used for turbidity readings and for alkalinity determinations.
ALKALINITY
Alkalinity, using methyl orange as an indicator, was determined on
a portion of the water from each sampling station.
DISSOLVED OXYGEN
The dissolved oxygen present in all samples was determined imme-
diately upon arrival at the laboratory. To eliminate the interference
of any nitrites that might be present in the samples, the permanganate
modification of the Winkler method for the determination of dis-
solved oxygen was adopted as routine procedure.
-------
42 POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
BIOCHEMICAL OXYGEN DEMAND
The difference between the amount of dissolved oxygen originally
present in the sample and the amount remaining at the end of five
days' incubation at 20° C. was taken as the measure of the 5-day
biochemical oxygen demand. The high organic content of the water
from several of the sampling stations necessitated dilution, before
incubation, to prevent the depletion of the oxygen. The dilution
water used was made up of 75 per cent distilled water and 25 per cent
Minneapolis tap water, stored two weeks before use. During periods
of cold weather, samples arrived at the laboratory supersaturated
with oxygen. These samples were warmed to 20° C. and shaken
until the oxygen content was reduced to about 9 parts per million or
less, after which the initial dissolved oxygen, prior to incubation,
was determined.
The laboratory procedure for the dissolved oxygen and the bio-
chemical oxygen demand determinations was inaugurated by Bac-
teriologist C. T. Butterfield, of the United States Public Health
Service, at the beginning of the investigation, and verified by Chemist
E. J. Theriault during the progress of the laboratory work. The
technique used was similar to that employed during the Illinois
Kiver study and is outlined by Chemist E. J. Theriault in Public
Health Bulletin No. 151.3
BACTERIOLOGICAL METHODS
Routine bacteriological examination of samples consisted in deter-
mining the number of colonies per cubic centimeter of sample, develop-
ing on standard agar plates in 24 hours at 37° C. and in 48 hours at
20° C., and an estimate of the number of B. coli present in the sample
as indicated by the results of fermentation tests, using standard
lactose bouillon.
CULTURE MEDIA
The culture media used throughout the investigation of the upper
Mississippi River were prepared from dehydrated stock, a quantity
of each kind of stock sufficient to last through the entire period of the
survey having been purchased prior to starting the work. It was
specified that each land of dehydrated stock should be from, or pre-
pared as, a single lot, in order to eliminate any variations that might
occur in the manufacture of the media when prepared in separate
lots. For routine examinations three kinds of culture media were
used—nutrient agar, Endo's agar, and lactose broth. All media
were prepared and sterilized in accordance with the instructions of
the manufacturer, to insure the proper final hydrogen-ion concen-
>The Determination of Dissolved Oxygen by the Winkler Method. E. J. Theriault, Public Health
Bulletin No. 181, Washington, D. C.
-------
PROCEDURE IN FIELD AND LABORATORY STUDIES 43
tration. Sterility controls were made, on the media used each day,
and of the water used for dilution. The media used were comparable
. to those utilized in the previous studies of the Ohio and Illinois
Rivers, with the exception that agar instead of gelatin was used to
determine the 20° C. plate count.
STERILIZATION OF BOTTLES
Wide-mouthed ground-glass stoppered bottles were used in col-
lecting the bacteriological samples. The stopper and bottle neck
were covered with paper, tied in place, and the entire bottle pro-
tected by wrapping in heavy paper. The bottles thus prepared were
sterilized, by baking in hot air for two hours, after the temperature
had reached 170° C. At the time of sample collection and during
shipment, adequate precautions were taken to prevent contamination.
PLATE COUNTS
The methods employed in making plate counts on agar at the
two incubation temperatures were substantially those of Standard
Methods, 1925 edition. In planting samples, amounts of 1.0 or 0.1
cubic centimeter of the water were added directly to the plates from
calibrated pipettes. Amounts smaller than 0.1 cubic centimeter
were measured by diluting 1 cubic centimeter of the sample in 99
cubic centimeters of sterile dilution water, so that 1.0 and 0.1 cubic
centimeter of the mixture represented 0.01 and 0.001 cubic centi-
meter of the mixture represented 0.01 and 0.001 cubic centimeter,
respectively, of the original sample. For further dilution, when
required, 1 cubic centimeter from the first dilution bottle was added
to a second, containing 99 cubic centimeters.
Three agar plates were prepared for incubation at each of the two
incubation temperatures. Two of the three plates were planted as
duplicates, with a sufficient amount of the sample to give ordinarily
between 25 (unless the total count from 1 cubic centimeter of the
undiluted sample was less than that number) and 400 colonies per
plate, preferably not more than 200. The third plate of the series
was inoculated with one-tenth or ten times the amount of the dupli-
cates, depending on whether it was more probable that too many or
too few colonies, respectively, would develop on the two duplicate
plates. One set of agar plates was incubated at 20° C. for 48 hours,
and the other at 37° C. for 24 hours. The glass-covered plates were
inverted in the 37° C. incubator during the period of incubation.
The colonies developing at the end of incubation were counted with
a standard reading lens in a special illuminated counting device.
The rules adopted in counting the series of three plates and recording
results were as follows:
(a) When duplicate plates of the series gave more than 25 and less
than 400 colonies per plate and the third plate less than 25 or more
-------
44 POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
than 400 colonies, the third plate was disregarded in the average.
If, however, the number of colonies on the third plate fell between the
number of those on the duplicate plates it was included in the average.
(b) When duplicate plates fell outside of the allowable range of
25 to 400 colonies, the third plate was considered as the representative
count.
(c) When one duplicate plate gave an obviously incorrect result it
was disregarded in determining the average result.
DETERMINATION OF B. COLI
The partially confirmed test was employed in the estimation of
the number of B. coli present in the samples. Three or more gradu-
ated portions of each sample were planted, the amounts being
selected so that the largest would show gas production and the
smallest none. Lactose-broth medium, in Durham fermentation
tubes, was used to record gas production, the amount of the medium
being at least three times that of the volume of water planted and
more often ten or more times. Fermentation tubes were incubated
at 37° C. for 48 hours, and gas production was recorded at the end of
24 and 48 hours.
At the end of 48 hours' incubation an Endo plate was streaked
from the tube, showing gas, which had been inoculated with the
least amount of the sample, unless this was a doubtful tube which had
shown no gas at the end of 24 hours, in which case an additional
Endo plate was made from the positive tube containing the next
larger portion of the sample. Endo plates were incubated for from
18 to 24 hours at 37° C.; and, if typical lactose-fermenting colonies
developed, the partially confirmed test was considered completed.
From Endo plates showing no typical colonies at the end of 24 hours
a colony most nearly resembling the B. coli group was picked, and
a lactose-broth tube inoculated with the culture. At the same time a
second Endo plate was made from the original broth tube and the
plate incubated as before. If the atypical colony from the first
Endo plate produced gas in amounts equivalent to 10 per cent or
more at the end of 24 or 48 hours, or if the second Endo plate from
the original tube showed colonies typical of the group at the end of
48 hours, the partially confirmed test was considered completed.
In estimating the numbers of B. coli present in the samples, the
methods prescribed in the 1925 edition of Standard Methods, of the
American Public Health Association, were used. Since the media
and methods used were the same as during previous studies, the
results of the upper Mississippi River survey are fully comparable
with those obtained in the Ohio and Illinois River studies.
-------
SECTION V
RESULTS OF CHEMICAL ANALYSES
PRESENTATION OF DATA
Chemical examinations of the water from the sampling stations
were made to determine the effect of the gross pollution entering the
river through the metropolitan area of the Twin Cities and the
subsequent changes taking place in the river below the zone of
pollution due to the inflow of tributaries and to processes of natural
stream purification.
During the course of the investigation a total of 2,732 water
samples, from the 14 regular sampling stations, were analyzed in the
field laboratory at Minneapolis. The results of the chemical deter-
minations, together with data relative to water temperatures and
rates of stream discharge, are presented in Table 22 as monthly
averages of the daily observations. The results are summarized by
sampling stations and give the averages of the various determinations
for each month and season.
TABLE 22.—Summary of monthly average results of chemical analyses for each
sampling station on the upper Mississippi River, arranged by months
STATION No. 1.—MISSISSIPPI RIVER AT CAMDEN AVENUE BRIDGE, MINNEAPOLIS
Month
1926
July
August.,
October
December
m 1927
February
March
April ...
May ,_ -.
June
July
August--
Dis-
charge,
second-
feet
2,430
2,360
2,410
6,480
7,460
3,980
2,890
2,300
2,210
9,640
17,400
12, 800
9,810
5,590
5,100
Water
tempera-
ture.
°C.
18.3
23.0
21.9
16.4
9.5
1.4
0
0
0
1.0
7.2
12.8
18.6
22 4
19.9
Constituents in parts per million
Alka-
linity
169
155
141
139
142
143
193
198
197
136
117
136
153
162
155
Turbid-
ity
9
5
5
6
4
2
3
2
2
26
16
21
19
11
6
Initial
dissolved
oxygen
8.05
6.13
6.59
7.96
9.23
12.62
8.79
7.19
5.68
10.63
10.55
9.25
7.75
6.58
6.89
5-day
oxygen
demand
at 20° C.
1.50
1.06
1.03
1.23
1.47
1.96
1.12
1.11
1.09
2.79
2.13
2 09
1.87
1.13
.84
Initial
dissolved
oxygen,
per cent
satura-
tion
84.9
70.7
74 4
80.7
80.5
89.8
60.1
49 1
38.9
74 7
87.1
86.7
82.3
75 2
75.0
(p#)
Hydro-
gen-ion
concen-
tration
7.7
7.8
8 0
8.1
8.0
AVERAGES
Summer, 1926
Fall
Winter
Spring -
Summer. 1927
Yearly
2,400
5,970
2,470
13, 280
6,830
6,650
21.1
9 1
0
7.0
20 3
9 3
155
141
196
130
157
154
6
4
2
21
12
9
6.62
9 94
7.22
10.14
7 07
8.53
1.20
1 55
1.11
2.34
1.28
1.58
78.7
83 7
49.4
82.8
77 5
73.0
7.8
8 0
45
-------
46
POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
TABLE 22.—Summary of monthly average results of chemical analyses for each
sampling station on the upper Mississippi River, arranged by months—Continued
STATION No. 2.—MISSISSIPPI
RIVEB AT PLYMOUTH
MINNEAPOLIS
AVENUE BRIDGE,
Month
1826
July
August
October
December
1927
January
March
May
June
July
August
Dis-
charge,
second-
feet
2,430
2,360
2,410
6,500
7,480
3,990
2,890
2,300
2,210
9,060
17,500
12,800
9,850
5,590
5,100
Water
tempera-
ture,
°C.
18.1
23.4
22.0
16.1
9.5
1.4
0
0
0
2.2
7.2
12.8
18.6
22.4
19.9
Constituents in parts per million
Alka-
linity
169
155
141
137
142
142
175
201
204
109
117
134
152
159
156
Turbid-
ity
10
6
7
5
4
3
2
6
9
25
15
20
18
11
6
Initial
dissolved
oxygen
7.25
5.42
6.08
7.65
9.21
12.59
11.82
6.52
4.44
12.24
10.73
9.26
7.74
6.19
6.68
5-day
oxygen
demand
at 20° C.
1.39
1.28
1.13
1.19
1.47
1.84
1.37
4.20
4.35
2.76
2.09
1.84
1.97
1.09
.88
Initial
dissolved
oxygen,
per cent
satura-
tion
76.1
62.9
68.9
77.1
80 3
89.5
80.8
44.5
30.4
88.9
88.7
86.7
82 2
70.8
72.9
(PH)
Hydro-
gen-ion
concen-
tration
7.7
7.8
8.0
8.0
8.1
AVERAGES
Summer, 1926
Fall
Winter
Spring
Summer, 1927
Yearly
2,400
5 990
2 470
13, 320
6 850
6, 660
21.2
9 0
0
7.4
20 3
9 4
155
140
193
120
156
151
8
4
6
20
12
10
6.25
9 82
7.59
10.74
6.87
8.64
1.27
1.50
3.31
2.23
1 31
2. 12
69.3
82 3
51.9
88.1
75.3
73.4
7.8
8.0
STATION No. 3.—MISSISSIPPI RIVER AT GOVERNMENT LOCK AND DAM,
MINNEAPOLIS
Month
1926
June
July—
September
October
1927
January
February
April
May
June.
July -
August..
Dis-
charge,
second-
feet
2,440
2,370
2,420
6,520
7,510
4,000
2,910
2,310
2,220
9,690
17,500
12,900
9,910
5,610
5,090
Water
tempera-
ture.
°C.
19.4
24 3
23.0
16.9
9.8
1.6
0
0
0
1.2
7.4
12.7
18.6
22.9
20 3
Constituents in parts per million
Alka-
linity
174
161
148
140
146
143
194
200
207
139
120
137
156
164
157
Turbid-
ity
21
14
8
8
5
7
8
12
14
22
13
23
17
9
7
Initial
dissolved
oxygen
0.74
.43
.67
5.27
7.92
11.57
9.30
6.74
5.87
11.00
10 66
9.12
6.41
3.77
4.15
5-day
oxygen
demand
at 20° C.
5.84
3.96
3.31
2.90
4.38
6.90
5.56
9 31
10.05
5.33
3.25
3.14
3.13
3.35
3.13
Initial
dissolved
oxygen,
per cent
satura-
tion
8.0
5.1
7.7
54.0
68.8
82 6
63.5
46.1
40.2
77.7
88.3
85.6
67.9
43 4
45.5
(PH)
Hydro-
gen-ion
concen-
tration
7.7
7.8
7.9
7.7
7.7
AVERAGES
PiiTTiTn«r, 1926
Fall
Winter
Spring
Summer, 1927
Yearly
2,410
6,010
2 480
13, 360
6,870
6,690
22.2
9.4
0
7.1
20 6
9.6
161
143
200
132
159
158
14
7
11
19
11
13
0.61
8.25
7 30
10.26
4 78
7.08
4.37
4.73
8.31
3.91
3.20
5.10
6.9
68.5
49.9
83.9
62.3
57.3
7.8
7.8
-------
RESULTS OF CHEMICAL ANALYSES
47
TABLE 22.—Summary of monthly average results of chemical analyses for each
sampling station on the upper Mississippi River, arranged by months—Continued
STATION No. 4.—MINNESOTA RIVER AT FORT SNELLINQ
Month
1926
July
August
October
November
1927
January
February.,
April
May
June
July
August . .
Dis-
charge,
second-
feet
400
213
375
2,040
2,380
1,110
830
625
610
9,120
9,270
6,680
5,910
1,450
369
Water
tempera-
ture,
°C.
19 4
23.7
22.6
17.2
10.1
1.8
0
0
0
2.4
7.9
13.6
18.4
22.7
20.6
Constituents in parts per million
Alka-
linity
244
244
218
182
219
244
298
341
356
150
187
230
223
262
257
Turbid-
ity
89
86
90
81
70
28
14
9
9
218
70
40
176
65
50
Initial
dissolved
oxygen
4.84
S. 75
5.70
6 79
10.06
12.92
9.67
6.72
6.15
10.89
10 34
10.03
7.20
6.92
8.29
5-day
oxygen
demand
at 20° C.
2.62
3.39
3.10
2.88
2 59
5.46
2 86
1 81
2.15
3.38
2.36
2 73
1.94
2.81
3.76
Initial
dissolved
oxygen,
per cent
satura-
tion
52 2
67.1
65.2
70 0
88.9
92.8
66.1
45.9
42.1
79.5
86.8
96.1
76.2
79.4
91.7
Hydro-
gen-ion
concen-
tration
8.6
8.1
8.1
8.1
8.2
AVERAGES
Summer, 1926
Fall
Winter
Spring
Summer, 1927
Yearly _ _
329
1,840
688
8,360
2,580
3,260
21 9
9.7
0
8 0
20 6
9.8
235
215
332
189
247
241
88
60
11
109
97
74
5 43
9.92
7 51
10 42
7.47
8.52
3.04
3.64
2 27
2.82
2.84
2.89
61 5
83 9
51 4
87 5
82 4
73.1
8.1
8.1
STATION No. 5.—MISSISSIPPI RIVER AT ROBERTS STREET BRIDGE, ST. PAUL
Month
1926
.Tnno
July
August, _
September..
October
December-
1927
January
February-
March . -
ApriL
May -
June ... . . ._
July
August _ .
Dis-
charge,
second-
feet
2,850
2,590
2,810
8,630
9,970
5,150
3,770
2,950
2,850
18,900
27,000
19,700
16,000
7,090
5,440
Water
tempera-
ture,
°C.
19.3
23.5
22.1
16.5
10.0
1.4
0
0
0
1.2
7.8
13.3
18.8
22.8
20.7
Constituents in parts per million
Alka-
linity
195
177
160
147
161
169
208
214
223
133
134
160
181
188
172
Turbid-
ity
26
19
14
10
12
9
23
15
17
100
30
30
91
27
11
Initial
dissolved
oxygen
1.53
.54
.87
5.19
8.46
12.09
9.57
6.24
5.77
10.66
10.37
8 68
6 30
4.35
3.77
5- day
oxygen
demand
at 20° C.
8.32
5.25
3.67
3.55
4.03
5.07
9.83
8.38
7.09
4.86
4.82
3 15
2.92
2.81
2.16
Initial
dissolved
oxygen,
per cent
satura-
tion
16.5
6.3
9.9
52.8
74.5
85.9
65.4
42 6
39.4
75.4
86 7
82.3
67.1
50.0
41.8
(PH)
Hydro-
gen-ion
concen
tra-
tion
7.8
7.9
8.0
7.9
7.9
AVERAGES
Summer, 1926
Fall
Winter
Spring _
Summer, 1927
Yearly
2,750
7,920
3,190
21, 870
9,510
10, 030
21 6
9 3
0
7 4
20 8
9 6
177
159
215
142
180
172
20
10
18
53
43
31
0 98
8 58
7 19
9 90
4 81
7 06
5 75
4.22
8 43
4 28
2.63
5 22
10 9
71 1
49 1
81 5
53.0
57 4
7 9
7.9
-------
48
POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
TABLE 22.—Summary of monthly average results of chemical analyses for each
sampling station on the upper Mississippi River, arranged by months—Continued
STATION No. 6.—MISSISSIPPI RIVER AT INVERGKOVE BRIDGE
Month
1926
July
1927
April
May. _. _-
July
August .
Dis-
charge,
second-
feet
2,860
2,600
2,820
8,660
10,000
5,170
3,790
2,960
2,860
18,900
27, 100
19,800
16,100
7,110
5,440
Water
tempera-
ture,
C.
18.9
23.3
21.9
16.4
9.8
1.4
0
0
0
1.2
7.8
13.3
18.8
22.8
20.6
Constituents in parts per million
Alka-
linity
192
175
162
148
165
171
207
223
222
135
139
160
178
188
172
Turbid-
ity
29
24
22
13
13
11
17
14
17
97
29
31
77
30
14
Initial
dissolved
oxygen
1 22
.26
.51
4.99
8.04
11.14
9.03
5 75
5.65
10.26
10.05
8.62
6.16
3 87
2.96
5-day
oxygen
demand
at 20° C.
6.23
5.95
4.04
3.23
4.36
7.74
10.32
9.30
8.45
5.10
3.28
3.65
3.00
3.02
2.28
Initial
dissolved
oxygen,
per cent
satura-
tion
13.0
3 0
5 8
50.6
70.7
79.3
61.7
39.3
38 6
72.4
84.2
81.8
65.6
44.4
32.7
(PH)
Hydro-
gen-ion
concen-
tra-
tion
7.8
7.9
7.9
7.8
7.8
AVERAGES
Fall
Winter
Spring __
Summer, 1927
Yearly ._
2 760
7,940
3,200
21, 930
9,550
10, 060
21 4
9 2
0
7.4
20 7
9.5
176
161
217
145
179
174
25
12
16
52
40
30
0 66
8.06
6.81
9.64
4.33
6.71
5 41
5 11
9.36
4.01
2.77
5.70
7 3
66.9
46.5
79.5
47.6
54.4
7.9
7.8
STATION No. 7.—MISSISSIPPI RIVEB ABOVE HASTINGS, MINN.
Month
1926
July
August - . _
September
October . _
December,
1927
January _. _.
ApriL
June - . ._
July.
August
Dis-
charge,
second-
feet
2,600
2,830
8,700
10,100
5,190
3,810
2,970
2,870
19,000
27,200
19,900
16, 200
7,120
5,450
Water
tempera-
ture,
°C.
23.6
22.4
17.4
11.7
2.8
0
0
0
2.5
7.6
14.5
18.9
23.9
22 2
Constituents in parts per million
Alka-
linity
181
170
151
163
167
212
231
223
136
145
168
185
192
180
Turbid-
ity
20
12
10
8
15
20
18
22
88
28
17
52
30
19
Initial
dissolved
oxygen
0.16
.39
3.36
6.37
9 20
5.41
3.95
4.46
9.02
9.29
7.63
5 70
3.81
3 49
5-day
oxygen
demand
at 20° C.
8.40
4 19
2 74
3.82
6.16
7.72
7.74
8.90
4.26
2.90
2.59
2 87
2.90
3.22
Initial
dissolved
oxygen,
per cent
satura-
tion
1.9
4 4
34.8
68.4
67.8
37.0
27.0
30 5
66.1
77.2
74.5
60.9
44.6
39.7
(PH)
Hydro-
gen-ion
concen-
tra-
tion
7.7
7.8
7.8
7.8
7.8
AVERAGES
Summer, 1926
Tall
Winter -
Spring.
Summer, 1927
Yearly
2,720
8,000
3,220
22,030
9,590
10 110
23 0
10 6
0
8 2
21.7
10 1
176
160
222
150
186
178
16
11
20
44
34
26
0 28
6 31
4 61
8 65
4.33
5 41
6 29
4 24
8 12
3 25
3 00
5 19
3 2
53 7
31 5
72 6
48 4
45 0
7 8
7 8
-------
RESULTS OF CHEMICAL ANALYSES
49
TABLE 22.-—Summary of monthly average results of chemical analyses for each.
sampling station on the upper Mississippi River, arranged by months—Continued
STATION No. 8.—ST. CEOIX RIVER AT PEESCOTT, Wis.
Month
1926
July
September, - - _
October ..
1927
April
June . -_ _-
July
Dis-
oharge,
second-
feet
2,100
2,520
4,800
6,050
4,300
2,940
2,420
2,260
12,600
15,400
7,700
6,700
4,650
2,470
Water
tempera
turo
°C.
22 9
22.7
18.8
13.1
4.1
0
0
0
2 6
7 4
15 0
18.8
24,2
22.7
Constituents in parts per million
Alka-
linity
98
103
97
82
76
95
101
110
96
55
64
76
82
88
Turbid-
ity
12
6
6
5
4
6
6
6
20
6
6
10
6
4
Initial
dissolved
oxygen
8.20
7.10
7.38
7.23
9.55
11.80
9.96
8 62
9.13
9.99
8.72
7.38
6.57
6 14
5-day
oxygen
demand
at 20° C.
1 82
1.31
.81
1.14
1.34
1 45
1.34
1.36
1.71
1 82
1.75
1.00
1.19
1.12
Initial
dissolved
oxygen,
per cent
satura-
tion
94.4
81.4
78.7
68.3
72.8
80.6
68.1
58.9
66.9
82 9
85 9
78 7
77.2
70.4
(PH)
Hydro-
gen-ion
concen-
tra-
tion
7.2
7.3
7.6
7.7
7.7
AVERAGES
Summer, 1926. _._
Fall
Spring
Summer, 1927
2,310
5,050
2,540
11,900
4,610
5,820
22 8
12 0
0
8.3
21 9
10 5
100
85
102
72
82
88
9
5
6
11
7
8
7.65
8 05
10.13
9.28
6.70
8.76
1.57
1.10
1 38
1.76
1.10
1.40
87 9
73 3
69 2
78.6
75.4
76 5
7.3
7 7
STATION No. 9.—MISSISSIPPI RIVEK ABOVE RED WING, MINN.
Month
1926
July .
September ._
November .
1927
July
Dis-
charge,
second-
feet
4,810
5,480
13,900
16,600
9,820
7,020
5,560
5,300
32,400
44, 100
28,900
24,300
12,000
7,980
Water
tempera-
ture,
°c.
22 6
21 4
18 7
20.4
1.0
0
0
0
1.9
7.3
14 8
18.3
22.9
22.3
Constituents in parts per million
Alka-
linity
149
152
136
140
144
192
182
189
150
152
157
168
156
154
Turbid-
ity
15
13
26
13
9
6
6
7
33
15
14
66
22
13
Initial
dissolved
oxygen
2 13
2 25
4.27
6.51
10.10
8 01
7 52
7 71
8.63
10.10
8 17
6.05
4 99
5.17
5-day
oxygen
demand
at 20° C.
2.90
1 68
1.89
2.74
3.71
3.86
3.21
2 62
2 83
2.51
2.69
2 11
2.72
1.97
Initial
dissolved
oxygen,
per cent
satura-
tion
24 4
25.2
45.3
71 5
70 8
54 6
51.4
52.7
62.2
83.6
80.2
63.8
57.5
58.8
(PH)
Hydro-
gen-ion
concen-
tra-
tion
7.8
7.8
7.8
7.8
7.8
AVERAGES
Summer. 1926.. _. ..
Fall
Winter
Summer, 1927
Yearly
5,150
13, 440
5,960
35 130
14, 760
16,500
22 0
13 4
0
8 0
21 2
10 5
150
140
188
153
159
160
14
16
6
21
34
19
2 19
6 96
7 75
8 97
5 40
6 79
2 29
2 78
3 23
2 68
2 27
2 73
24 8
62 5
52 9
75 3
60 0
57 1
7 8
7 8
-------
50
POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
TABLE 22.—Summary of monthly average results of chemical analyses for each
sampling station on the upper Mississippi River, arranged by months—Continued
STATION No. 10.—CANNON RIVEB AT RED WING, MINN.
Month
1926
July
1927
June
July
Dis-
charge,
second-
feet
95
97
293
276
256
214
126
132
570
1,220
1,030
1,100
212
46
Water
tempera-
ture
°C.
20.8
19.7
18.5
20.6
1.6
0
0
0
1.8
7.5
14.7
18.2
22.0
21.7
Constituents in parts per million
Alka-
linity
202
196
196
198
204
240
290
265
155
195
205
194
216
217
Turbid-
ity
10
100
37
6
3
4
6
5
107
14
20
259
19
40
Initial
dissolved
oxygen
7:09
7.43
8.52
9.86
12.68
10.58
10.19
9.48
9.59
10.83
8.76
7.73
7.05
7.99
5-day
oxygen
demand
at 20° C.
1.75
1.35
1.65
1.42
1.57
2.64
1.44
1.73
2.86
2.58
4.21
2.51
1.56
1.69
Initial
dissolved
oxygen,
per cent
satura-
tion
78.5
80.6
90.2
108.5
90.6
72.3
69.7
64.8
68.8
90.2
85.6
81.4
79.8
89.9
(pH)
Hydro-
gen-ion
concen-
tra-
tion
8.0
8.2
8.1
8.2
8.2
AVERAGES
Fall
Winter
Summer 1927
Yearly
96
275
157
940
453
450
20.3
13.6
0
8.0
20.6
10.3
199
199
265
185
209
212
55
15
5
47
96
48
7.26
10.35
10.08
9.73
7.59
9.40
1.55
1.55
1.94
3.22
1.92
2.14
79.6
96.4
68.9
81.5
83.7
81.8
8.1
8.2
STATION No. 11.—MISSISSIPPI RIVER AT OUTLET OF LAKE PEPIN
Month
1926
July
1927
January
April
Dis-
charge,
second-
feet
4,840
5,520
14,100
16,700
9,920
7,100
5,600
5,350
32,500
44,600
29,300
24,700
Water
tempera-
ture
°C.
22.6
22.0
19.3
13.9
3.5
0
0
0
1.4
6.9
13.6
18.1
Constituents in parts per million
Alka-
linity
152
128
121
132
118
150
172
182
161
118
134
149
Turbid-
ity
4
5
4
2
3
3
3
4
21
10
5
9
Initial
dissolved
oxygen
5.84
5.37
6.92
8.89
11.04
10.96
4.39
2.48
4.91
9.82
8.77
8.32
5-day
oxygen
demand
at 20° C.
0.99
.87
.87
1.17
2.57
.87
1.18
1.55
2.56
3.48
4.12
2.28
Initial
dissolved
oxygen,
per cent
satura-
tion
66.8
60.8
74.4
85.5
82.9
74.9
30.1
17.0
34.9
80.4
83.8
87.4
(pH)
Hydro-
gen-ion
concen-
tra-
tion
7.7
7.7
7.9
AVERAGES
Summer 1926
Fall-
Winter
Spring
Summer 1927
Yearly
5 180
13 570
6 020
35 470
24 700
16 700
22.3
12.2
0
7 3
18.1
10.1
140
124
168
138
149
143
5
3
3
12
9
6
5 60
8 95
5 94
7 83
8 32
7 31
0 93
1 54
1 20
3 39
2 28
1 88
63 8
80.9
40 7
66 4
87 4
64 9
7 7
7 9
-------
RESULTS OF CHEMICAL ANALYSES
51
TABLE 22.—Summary of monthly average results of chemical analyses for each
sampling station on the upper Mississippi River, arranged by months—Continued
STATION No. 12.—CHIPPEWA RIVER AT MOTJTH
Month
1926
July
September.- -.
October _
1927
June - -_
Dis-
charge,
second-
feet
3,600
9,500
23,400
12,600
15, 500
7,500
Water
tempera-
ture
°C.
22.6
21.8
18.2
12.6
6.5
19.2
Constituents in parts per million
Alka-
linity
66
59
67
55
47
53
Turbid-
ity
41
10
9
5
3
"
Initial
dissolved
oxygen
6.59
6.26
7.00
8.70
10.71
7.83
5-day
oxygen
demand
at 20° C
2.78
1.68
1.20
1 57
1.60
2.97
Initial
dissolved
oxygen,
per cent
satura-
tion
75.4
70.6
73.7
81.3
86.7
84.2
(pH)
Hydro-
gen-ion
concen-
tra-
tion
7.4
AVERAGES
Summer 1926
Fall
6,550
17,200
7,500
22.2
12.1
19 2
63
56
53
26
6
14
6.43
8.80
7.83
2.23
1.46
2 97
73 0
80.6
84 2
7.4
STATION No. 13.—ZUMBRO RIVER AT KELLOGG, MINN.
Month
1926
July
August
November - ..
1927
January
May
Dis-
charge,
second-
feet
154
163
454
474
238
200
118
124
530
1,130
965
1,030
Water
tempera-
ture
°C.
21.0
19.9
16.9
9.9
2.1
0
0
0
2.4
7.2
13.5
18.3
Constituents in parts per million
Alka-
linity
222
219
186
196
210
246
260
255
170
207
220
211
Turbid-
ity
52
82
289
41
14
22
16
33
178
42
130
196
Initial
dissolved
oxygen
7.70
8.08
8.71
9.85
12.39
12.03
11.61
12.00
11.58
10.65
9.20
8.12
5-day
oxygen
demand
at 20° C.
1.80
2.41
2.05
1.14
1.02
1.31
1.02
1.19
2.75
1.30
1.64
1.97
Initial
dissolved
oxygen,
per cent
satura-
tion
85.7
88.0
89.2
86.8
89.7
82.3
79.5
82.0
84.4
87.9
87.8
85.6
(PH)
Hydro-
gen-ion
concen-
tra-
tion
7.1
8.0
8.1
AVERAGES
Summer 1926
Fall
Winter - - -
Spring
Summer 1927
Yearly
159
389
147
875
1,030
465
20 5
9 6
0
7.7
18.3
9 3
221
197
254
199
211
217
67
115
24
117
196
91
7.89
10.32
11.88
10.48
8.12
10.16
2.11
1.40
1.17
1.90
1.97
1.63
86 9
88.6
81.3
86.7
85.6
85 7
8.0
8.1
129540—32 5
-------
52
POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
TABLE 22.—Summary of monthly average results of chemical anlayses for each
sampling station on the upper Mississippi River, arranged by months—Continued
STATION No. 14.—MISSISSIPPI RIVER ABOVE WINONA
Month
1926
July
August
November .--
1927
April ..
May.__
June
Dis-
charge,
second
feet
8,650
15,300
38,300
30,300
25,900
14,300
12,300
12,700
58,000
57,900
44,600
34,100
Water
tempera-
ture
°C.
22.0
23.3
21.7
13.0
3.2
0
0
0
2.2
7.4
12.0
18.8
Constituents in parts per million
Alka-
linity
139
106
98
127
118
148
156
160
139
123
136
148
Turbid-
ity
26
17
16
5
5
5
4
7
26
8
10
25
Initial
dissolved
oxygen
6 02
5.99
7.30
9.79
11.47
11.44
10.34
10.21
10.17
10.64
8.95
7.11
5-day
oxygen
demand
at 20° C.
3.51
3.49
2.44
1.87
1.83
1.82
1.73
2.43
2.47
2.44
2 06
2.24
Initial
dissolved
oxygen,
per cent
satura-
tion
68.1
69.5
82.2
92.3
85.3
78.3
70.7
69.6
73.8
88.3
82.6
75.8
(PH)
Hydro*
gen-ion
concen-
tra-
tion
7.9
7.8
7.9
AVERAGES
Summer 1926
Fall
Winter
Summer 1927-. - --
12,000
31,500
13 100
53,500
34,100
29 400
22.7
12.6
0
7.2
18.8
10.3
123
114
155
133
148
133
22
9
5
15
25
13
6.00
9.52
10.66
9.92
7.11
9 12
3.50
2.05
1.99
2.32
2.24
2.36
68.8
86.6
72.9
81.6
75.8
78.0
7.9
7.9
Summer averages of 1926, for Stations Nos. 1 to 6, inclusive, based on the months of June, July, and Au-
gust, 1926. Summer average of 1926, for Stations Nos. 7 to 14, inclusive, based on the months of July and
August, 1926. Summer averages of 1927 for Stations Nos. 1 to 10, inclusive, based on the months of June,
July, and August, 1927. Summer averages of 1927, for Stations Nos. 11 to 14, inclusive, based on the month
of June only. Fall averages at all stations based on the months of September, October, and November,
1926. Winter averages at all stations based on the months of December, 1926, January and February, 1927.
Spring averages at all stations based on the months of March, April, and May, 1927. Yearly average at
all stations based on the 12-month period July, 1926, to June, 1927, inclusive.
Seasonal averages in Table 22 are based on a summer period con-
sisting of the months of June, July, and August; a fall period compris-
ing the months of September, October, and November; a winter
period including the months of December, January, and February;
and a spring period consisting of the months of March, April, and
May. Such a grouping gives a comparison between the summer
period of 1926, with exceptionally low stream flow and water tem-
peratures, averaging over 20° C., and the normal winter period of
1926-27, when stream flows were nearly the same as those of the
summer period of 1926, but with water temperatures at 0° C., and the
surface covered with ice. A further comparison has been possible
between a more nearly normal summer period, represented by the
summer of 1927, and a normal winter period. During the fall and
spring periods average water temperatures were nearly the same,
10.5° and 7.4° C., respectively, but the spring run-off, due to melt-
ing ice and snow, was from two to four times that of the fall period at
main river sampling stations.
-------
RESULTS OF CHEMICAL ANALYSES
53
For purposes of comparison there is presented the relation between
the average stream flow in the main river, at the St. Paul gaging sta-
tion, for the seasons covered by the investigation, and the flow on the
day of minimum and maximum discharge, respectively, during each
of the seasonal periods.
Discharge, second-feet, at St. Paul
Season
Summer of 1928
Winter of 1926-27
Fall of 1926
Summer of 1927
Spring of 1927
• Seasonal „£&*,
average discharge
2,750 1,820
3 190 2,340
i 7,920 3,380
9 510 4, 320
21 900 3,800
Day of
maximum
discharge
4,470
4,620
13,100
19,700
33,700
DISCUSSION
ALKALINITY
Alkalinity determinations are summarized in Table 23 to show
monthly and seasonal averages, in parts per million, at each of the
sampling stations.
-------
54 POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
TABLE 23 Summary of average monthly and seasonal alkalinity, in parts per million, at sampling stations on the upper Mississippi River,
June, 1926, to August, 1927, inclusive
JH ^ n
Seasonal averages
Monthly averages
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Zumbro River
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Summer average, 1926, Stations Nos. 1 to 6, inclusive, based on months of June, July, and August.
Summer average, 1926, Stations Nos. 7 to 14, inclusive, based on months of July and August.
Fall average all stations, based on months of September, October, and November.
Winter average, all stations, based on months of December, January, and February.
Spring average, all stations, based on months of March, April, and May.
Summer average, 1927, Stations Nos. 1 to 10, inclusive, based on mouths of June, July, and August.
Summer average, 1927, Stations Nos. 11 to 14, inclusive, based on month of June only.
Yearly average, all stations, b «ed on 12-month period July, 1928, to June, 1927, inclusive.
-------
RESULTS OF CHEMICAL ANALYSES 55
The alkalinity of the tributaries entering from the west, or Minne-
sota, side of the watershed, was approximately three times that of
the tributaries entering from the east, or Wisconsin, side. The yearly
average for the Mississippi River, above Minneapolis, 154 parts per
million, falls about midway between the yearly average of 220 parts
per million for the Minnesota, Cannon, and Zumbro Rivers and that
of 70 parts per million for the St. Croix and Chippewa Rivers.
The higher alkalinity of the Minnesota River caused a temporary
increase in the alkalinity of the main river below its confluence.
At Red Wing, below the entrance of the St. Croix and Cannon Rivers,
and again at Winona, below the Chippewa and Zumbro Rivers, the
alkalinity of the main stream decreased. The final effect of the
inflow of tributaries from the east, with higher rates of discharge but
lower concentration of alkalinity, was a decrease in the concentration
of alkalinity in the Mississippi River between Minneapolis and
Winona amounting on an average to about 20 parts per million.
WTith the exception of the spring period, seasonal averages of alka-
linity show similar decreases, through the section of the river under
observation. The highest concentration of alkalinity occurred during
the winter period and the lowest during the fall and spring periods.
In the two summer periods the concentration was approximately
the same.
TURBIDITY
Average monthly and seasonal turbidities, in parts per million, at
the various sampling stations, are assembled in Table 24.
-------
56 POLLUTION AND PURIFICATION OF TIPPER MISSISSIPPI RIVEK
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-------
RESULTS OF CHEMICAL ANALYSES 57
In the winter and summer months of decreased stream flow, when
the normal turbidity of the river was low, a slight increase in turbidity
was observed between Stations Nos. 1 and 3, due apparently to the
sewage discharged from Minneapolis above the lock and dam. A
similar increase in turbidity was indicated in the river, from Station
No. 5 to Station No. 6, between which the wastes from the stockyards
are discharged. In the months of higher stream flow the normal
turbidity from the watershed greatly exceeded that of the sewage and
the effects of the latter on the river were not noticeable.
Minnesota River turbidities were higher, except in winter, than
those of the main stream. The lower discharge of this river as com-
pared to that in the main stream resulted in but little increase in
turbidity in the Mississippi River below its confluence. The St.
Croix River, entering through Lake St. Croix at its mouth, in which
the normal turbidity was reduced, decreased the concentration of
turbidity in the main river below its confluence and diminished the
effect of the Cannon River, which at times was high in turbidity.
As the water passed through Lake Pepin, the turbidity decreased
during every month of observation and at the outlet was usually less
than that of the water as it entered the metropolitan area. The
indicated reduction in turbidity through Lake Pepin varied from 33
to 85 per cent. Below the lake, turbidities in the main river again
increased with the inflow of the Chippewa and Zumbro Rivers.
The lowest concentration of turbidity was indicated in the winter
period when the watershed was covered with ice and snow and when
surface erosion was reduced to a minimum. Maximum turbidities
resulted from the increased discharge in the spring period as the
accumulation of ice and snow left the watershed. With the excep-
tion of the winter period the actual quantities of turbidity carried by
the stream, calculated from the concentration and the discharge
estimates, increased with increased rates of run-off from the watershed.
HYDEOGEN-ION CONCENTRATION (pH)
The monthly average hydrogen-ion concentration, determined at
the various sampling stations, during the five months' period April to
August, 1927, inclusive, indicated concentrations corresponding to
pH values of between 7.7 and 8.1 at the main river sampling stations.
On the tributary streams, those entering from the west showed
slightly higher concentrations (7.9 to 8.2) than those entering from
the east (7.2 to 7.7).
-------
58 POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
DISSOLVED OXYGEN
Monthly and seasonal changes in concentration
The dissolved-oxygen results of the basic-data table have been
rearranged in Tables 25 and 26 to show monthly and seasonal averages
at each sampling station. In Table 25 the monthly and seasonal
averages of dissolved oxygen are expressed in parts per million, while
Table 26 shows the same averages expressed in terms of the per-
centage of saturation at the mean water temperature during the
month. Figure No. 6 shows graphically the variation in monthly
averages of dissolved oxygen, as per cent of saturation; at Station
No. 1, above pollution from the Twin City metropolitan area; at
Station No. 7, the point usually showing the greatest effects of the
pollution from the sewers above; at Station No. 11, the outlet of Lake
Pepin, at which recovery from the effects of the pollution has to a
large extent taken place; and at Station No. 14, the lowest sampling
station on the river.
-------
KESULTS OF CHEMICAL ANALYSES
59
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60
POLLUTION AND PURIFICATION OP UPPER MISSISSIPPI RIVER
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-------
RESULTS OF CHEMICAL ANALYSES
61
-------
62 POLLUTION AND PUBLICATION OF UPPEB MISSISSIPPI RIVER
The tables and figure indicate a decrease in the dissolved oxygen
in the water as it flowed downstream, from Station No. 1, and
received increasing amounts of sewage and industrial wastes from the
Twin City metropolitan area. Below the sewer outlets, the dissolved-
oxygen increased as a result of reaeration and the inflow of tributaries.
During the winter months, however, reaeration was to a large extent
prevented by the ice cover and the point of minimum dissolved-
oxygen concentration, which usually occurred at Station No. 7, above
Hastings, was further downstream at the outlet of Lake Pepin. The
effect of the ice cover was particularly noticeable in Lake Pepin
between Stations No. 9 and 11 in the winter and early spring.
Two periods of high oxygen concentration were indicated, one in
the spring, another in the fall. The high oxygen concentration in
fall occurred just prior to the formation of the ice cover, when water
temperatures approached freezing but with reaeration still in progress
at the surface when the water was capable of taking up maximum
amounts of oxygen. The high-dissolved oxygen concentration in the
spring occurred under similar conditions immediately after the ice
cover broke up and disappeared. During both periods of low-water
temperatures, biological activities were decreased, less dissolved
oxygen was utilized in such processes, and the greater reaeration
produced an oxygen reserve.
After the winter ice cover formed, preventing reaeration, a decrease
in the oxygen concentration began, which lasted until the ice dis-
appeared in the spring. Station No. 11, at the outlet of Lake Pepin,
represents changes in dissolved-oxygen concentration of the water
following a long period of detention under the ice cover in winter.
In October and November, 1926, with decreasing water tempera-
tures and reaeration proceeding at the surface, the oxygen saturation
percentages were 85.5 and 82.9, respectively. Ice formed on the lake
at the end of November, after which the monthly average oxygen
saturation percentages were: December 74.9; January, 30.1; Febru-
ary, 17; and March 1 to 15, inclusive, 14. Ice left the lake about
the middle of March and the average oxygen saturation during the
latter part of the month was 58 per cent, which increased to an aver-
age of 80 per cent during April.
In addition to the low concentration of oxygen at the end oi
winter, a second period of decreased oxygen concentration occurred
during the summer months when water temperatures were highest,
the solubility of oxygen lowest, and when biological activities were
greatest.
As already indicated by the monthly averages, the lowest dissolved-
oxygen concentration occurred in the summer and winter seasons, with
the highest amounts present in the spring and fall. The concentra-
tion of dissolved oxygen in the larger tributaries of the Mississippi
-------
KESTJLTS OF CHEMICAL ANALYSES
63
River was greater than that of the main stream above their respective
points of confluence. As a result of tributary inflow, and of reaera-
tion, the oxygen concentration of the water at Winona was nearly
as great as that of the water above Minneapolis before receiving the
pollution from the metropolitan area.
Quantitative changes in dissolved oxygen
In Table 27 the seasonal averages of dissolved oxygen, in parts per
million, have b^en converted into the actual quantities of dissolved
oxygen present in the water passing the various sampling stations.
Quantities of dissolved oxygen are expressed in kilograms per day,
and the data of the table are arranged to show the seasonal changes
in the amount of dissolved oxygen, at successive downstream sampling
stations and at the mouths of tributaries. The data of this table are
shown graphically in Figure 7.
TABLE 27.—Seasonal averages of dissolved oxygen, in terms of kilograms per day,
at sampling stations on the upper Mississippi River
Station
1
2 . -
3
Minnesota River -. - -. - '
5
6
St. Oroix River
Cannon River. . .
9
11 . _
Zumbro River.
14
Summer,
1926
40, 760
36, 800
3,630
4,330
6,720
4,680
1 860
43, 010
1,710
27 660
70, 940
101 910
3,070
176, 060
Fall
139, 380
137, 890
114, 430
42, 580
156,310
147, 860
115, 410
98, 190
6,910
217, 720
290, 370
358, 860
9,450
713, 200
Winter
44,500
48, 160
45,460
13, 050
57, 930
55, 050
36, 870
63, 930
3,920
113, 440
94, 460
4,300
343, 360
Spring
330, 300
346, 710
335, 480
214, 110
532, 840
520, 170
470, 320
274, 420
22, 620
784, 930
697, 850
22,090
1,310,820
Summer,
1927
120, 830
118, 340
86, 400
45, 440
124, 260
116, 620
113, 100
77,720
8,470
202, 660
503, 490
143, 880
20, 490
594, 010
Yearly
average
150, 260
154, 360
137, 350
76, 810
208,130
201, 480
174, 810
126, 400
10, 380
313, 650
324, 450
11,180
670, 690
Summer average, 1926, Stations Nos. 1 to 6, inclusive, based on months of June, July, and August.
Summer average, 1926, Stations Nos. 7 to 14, inclusive, based on months of July and August.
Fall average, all stations, based on months of September, October, and November.
Winter average, all stations, based on months of December, January, and February.
Spring average, all stations, based on months of IVtarch, April, and May.
Summer average, 1927, Stations Nos. 1 to 10, inclusive, based on months of June, July, and August.
Summer average, 1927, Stations Nos. 11 to 14, inclusive, based on month of June only.
Yearly average, all stations, based on 12-month period July, 1926, to June, 1927, inclusive.
Table 27 and Figure 7 show a decrease in the amount of dis-
solved oxygen as sewage and industrial wastes are discharged into
the river between Stations Nos. 1 and 6, and a recovery of dissolved
oxygen below the zone of pollution. During the summer of 1926,
when stream flows were exceptionally low, the dissolved oxygen pres-
ent in the water as it entered the metropolitan area was practically
exhausted at the Government lock and dam at Minneapolis, Station
No. 3, and the water remained depleted of oxygen to Station No. 7,
at Hastings. The indicated average daily loss in dissolved oxygen,
as the water passed through the metropolitan district in the summer
of 1926, was 43,200 kilograms.
-------
64 POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
0 x
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-------
RESULTS OF CHEMICAL ANALYSES 65
During a summer of more normal stream discharge, as indicated
by the 1927 data, there was a decrease in dissolved oxygen through
the zone of highest pollution, but the greater amounts present in the
water entering the area were sufficient to maintain a reserve through
and below the zone of pollution. During the winter months of
normal stream flow, when the surface of the water was covered with
ice retarding reaeration, the quantity of dissolved oxygen present in
the water at each sampling station was less than in the normal sum-
mer period of 1927. The data suggest that in polluted streams of
this type, with long periods of ice cover, critical oxygen conditions
may occur at the end of winter, rather than during the summer
months.
The table and figure further indicate the loss in dissolved oxygen
during the winter and early spring months as the water flowed
through Lake Pepin under the ice. In the winter period the esti-
mated time of flow through the lake was between 30 and 40 days.
Water entering the lake in December, under the ice, would, there-
fore, have reached the outlet during January, and, similarly, the in-
flow during January would have appeared at the outlet in February.
Taking into consideration the period of lag in passing through the
lake, the average daily loss in dissolved oxygen during December,
1926, and January, 1927, was 77,500 and 69,900 kilograms, respec-
tively. The data also indicate the smaller contributions of dissolved
oxygen during the critical summer and winter periods, by the Min-
nesota, Cannon, and Zumbro Rivers, entering from the west through
Minnesota, and the much larger contributions of dissolved oxygen by
the St. Croix and Chippewa Rivers, entering from Wisconsin. The
relatively large amounts of dissolved oxygen contributed by the St.
Croix River in the summer and winter periods at the point of lowest
oxygen content in the main stream are an important factor in im-
proving conditions in the main channel between Hastings, Station
No. 7, and Red Wing, Station No. 9.
BIOCHEMICAL OXYGEX DEMAND
Monthly and seasonal changes in oxygen demand concentration
The results of the 5-day biochemical oxygen demand determina-
tions at 20° C. are summarized in Table 28 as monthly and seasonal
averages at successive sampling stations below Station No. 1. The
results at the mouths of tributaries are inserted beneath sampling
stations on the main river below which the respective tributaries
entered. In Figure 8, changes in monthly average demand are indi-
cated graphically at Station No. 1, above the zone of highest pollu-
tion; at Station No. 7, below the zone of greatest sewage contamina-
tion; at Station No. 11, the outlet of Lake Pepin; and at Station
No. 14, the lowest sampling station on the river.
-------
66
POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
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Winter average, all stations, based on
Spring average, all stations, based on
Summer average, 1927, Stations Nos.
Summer average, 1927, Stations Nos.
Yearly average, all stations, based on
-------
RESULTS OF CHEMICAL ANALYSES
67
n monfh/c/ averages of five ofay b/ochetn/ea
//and
on 2O°C, af sam/3//na stations /V
Yar/af/or>
figure /Vo- 8
oxygen demand, parts per
puousap
129540—32 6
-------
68 POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
Table 28 and Figure 8 indicate an increase in the oxygen demand of
the river through the metropolitan area, between Stations Nos. 1 and
7, from above Minneapolis to Hastings, due to the discharge of sewage
and industrial wastes. Below the zone of heavy pollution, between
Hastings, Station No. 7, and Red Wing, Station No. 9, near the upper
end of Lake Pepin, the river receives the inflow of the St. Croix and
Cannon Rivers and but little additional contamination. The data
indicate a reduction in oxygen demand in this part of the stream due
to the dilution by the tributaries, reaeration, and processes of natural
stream purification. In passing through Lake Pepin there was a
further, and usually much greater, reduction in the oxygen demand of
the water. The velocity of flow was diminished in Lake Pepin and a
long period of sedimentation took place at ordinary rates of run-off.
Because of the increased water surface area, reaeration was increased,
except at times of ice cover, and the time interval permitted the
oxidation of organic matter to take place. A marked reduction in
oxygen demand, therefore, was usually observed as the water passed
slowly through the lake. In the spring months of highest stream
flow, when ice and snow were leaving the watershed, times of flow
were decreased, there was a general flushing out of the drainage area
above the lake, and under these conditions there was very little
reduction in the oxygen demand between the inlet and outlet of
Lake Pepin.
Between the outlet of Lake Pepin, Station No. 11, and Winona,
Station No. 14, the Chippewa and Zumbro Rivers enter the main
stream, and in this section of the river there was a frequent and
unexpected increase in the oxygen demand. In general the increases
occurred during the summer and winter months, when stream flows
were the lowest, and the reduction in demand occurred in the spring
months of highest stream flows.
Quantitative changes in oxygen demand
Table 29 gives the seasonal averages of the 5-day biochemical
oxygen demand at 20° C., converted into the actual 5-day oxygen
requirements expressed in terms of kilograms. The data are arranged
as seasonal averages at successive sampling stations below Station
No. 1.
-------
RESULTS OF CHEMICAL ANALYSES
69
TABLK 29.—Seasonal averages of B-day biochemical oxygen demand at 20° C.,
expressed as kilograms, at sampling stations on the upper 'Mississippi River
Station
1 .
2
3
Minnesc
5
6
7
St. Croi
Cannon
9
11
Chippov
Zunibro
14
River.
•a River . - ... _ .
Kiver
Summer
1!!26
7, 050
7,450
25, 840
2, 400
38, 890
36, 490
41,280
8, 730
3150
28, 370
11,750
31,810
820
102, (500
Fail
21, 84']
21,280
64, SiO '
14,780 ,
79, 160
9'., 130
77, 090
13, 510
J,04()
88, 350
46, 800
59, 340
1,400
101,300
Wmt »r
f,, 700
18,970
49, 000
3,930
fiC, 960
74, 160
63, 650
8, 610
800
48,050
17, 210
430 ,
63,840
-pang
74, 080
70, 880
121,710
57, 930
231,970
210, 330
172,610
51, 490
7,440
228, 770
2
-------
70 POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
requirements of both were more nearly the same. During the months
of lowest stream discharge the average time of flow through Lake
Pepin was approximately 40 days, while in the spring period of highest
run-off the time of detention within the lake was reduced to about
10 days. The data suggest that it was the organic matter of the trib-
utary which influenced the increase in oxygen requirements in the
lower section of the stream. The organic matter of the main stream,
after its long period of detention in the lake, must have reached the
second or nitrification stage of the oxidation process at Station No. 11.
The organic matter in the water entering the main river from the
Chippewa River, in which velocities of flow were comparatively high,
was presumably in the first or carbon stage of oxidation, but in its
passage downstream the time interval was such that it had entered
upon the second stage of oxidation at Winona, showing greater
oxygen requirements than at the upper station.
The survey of the industrial-waste pollution of the river system
indicated that the Chippewa River was probably the most highly
polluted tributary of the Mississippi River, receiving manufacturing
wastes from several paper mills, canning plants, and milk-products
establishments. Industrial wastes inhibiting normal bacterial ac-
tivity in the Chippewa River, and subsequent dilution by the main
' stream, may have been a further factor in the increased oxygen require-
ments in the main stream below the confluence of the tributary.
Sufficient data, however, are not available from which to determine
definitely the particular factors responsible for the indicated increase
in oxygen demand in the lower section of the river.
OXYGEN BALANCE
A comparison between the amount of dissolved oxygen in the water
at a sampling station and the oxygen requirements of the same water,
as indicated by the biochemical-oxygen demand, shows the capacity of
the stream at that particular time to care for the pollution previously
discharged into it. Changes in the ratio of available oxygen to the
oxygen required by the stream take place when polluting substances
are added, which decrease the dissolved oxgyen and increase the oxygen
demand, or when processes of natural stream purification are operat-
ing, tending to increase the amount of dissolved oxygen and decrease
the oxygen demand.
SEASONAL CHANGES IN THE RATIO BETWEEN DISSOLVED OXYGEN AND
OXYGEN DEMAND
Table 30 shows for the various sampling stations the seasonal and
yearly average ratios of the quantity of dissolved oxygen to the oxygen
requirements, as indicated by the 5-day demand at 20° C.
-------
RESULTS OF CHEMICAL ANALYSES
71
TABLE 30.—Seasonal ratios of the dissolved oxygen to the 6-day biochemical oxygen
demand at 30° C., at main river and tributary sampling stations on the upper
Mississippi River
Station
1
2
3
Minnesota River
5 ...
6 --
7
St. Croix River
Cannon River
9 ..
11
Zumbro River.
14
Summer,
1926
5 8
4 9
14
1.8
.17
.13
.05
4.9
4 7
08
0 C
3 2
3 7
1 7
Fall ] Winter Spring
64 66 4. 4
6.5 25 4.9
18 93 28
2. 9 33' 37
2. 0 . 87 . 23
16 74 25
1 5 58 2.7
7. 3 • 74 o 3
fi 6 4.9 30
25 24 34
62 55 24
f,.0
P 7 10 0 60
4. 4 j 31 43
Summer,
1927
5. 1
4 8
1 6
3.3
1.9
1.7
1 6
fi.3
3 3
2 5
3 7
2 6
4.1
3.2
Yearly
average
4.9
4.7
2.0
3.5
1.-9
1.8
1.8
6.0
3.5
2.9
3.2
5. b
4.0
Summer average, 1926, Stations Nos. 1 to 6, inclusive, based on months of June, July, and August.
Summer average, 1926, Stations Nos. 7 to 14, inclusive, based on months of July and August.
Fall average, all stations, based on months of September, October, and November.
AVinter average, all stations, based on months of December, January, and February.
Spring average, all stations, based on months of March, April, and May.
Summer average, 1927, Stations Nos. 1 to 10 inclusive, based on months of June, July, and August.
Summer average, 1927, Stations Nos. 11 to 14, inclusive, based on month of June only.
Yearly average, all stations, based on 12-inonth period July, 1926, to June, 1927, inclusive.
Table 30 shows that the dissolved oxygen carried by the tribu-
taries was always in excess of their oxygen requirements, the amount
of dissolved oxygen varying from about twice the required oxygen
in the Minnesota River in summer to ten times the required oxygen
in the Zumbro River in winter.
Yearly average ratios at main river sampling stations indicate a
decrease in ratio due to the pollution from the Twin City Metropolitan
area, between Stations Nos. 1 and 7, and an increase in ratio below the
zone of pollution.
Seasonal averages show the decrease in ratio within the polluted
section of the stream during all seasons. In the summer of 1926
practically no oxygen was present in the stream between Stations
Nos. 3 and 7. The winter ratios, due to the prevention of reaeration,
were lower than during a normal summer period as indicated by the
1927 data. In the spring and fall periods the dissolved oxygen was
always in excess of the oxygen requirements of the main river. In
all but the fall period an increase in ratio was indicated as the water
flowed through Lake Pepin, between Stations Nos. 9 and 11. In
both summer periods and in the fall period a decrease in ratio was
indicated between the outlet of Lake Pepin, Station No. 11, and
Winona, Station No. 14.
The data of Tables 27 and 29 have been combined to show the
relationship between the actual amount of dissolved oxygen and the
oxygen demand, both expressed in terms of kilograms, at designated
sampling points along the main river. From these relationships
calculations have been made to show the changes in the oxygen bal-
ance taking place between designated points along the stream.
-------
72 POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
Corrections have been made for the effect of tributaries within the
sections below their points of entrance. These data are summarized
in Table 31 as seasonal and yearly averages, expressed as kilograms,
to show the decrease in oxygen balance as a result of sewage pollution,
or the increase in balance resulting from processes of natural stream
purification.
TABLE 31.—Seasonal and yearly averages of the changes in oxygen balance, ex-
pressed as kilograms, between designated main river sampling stations on the
upper Mississippi River
STATIONS XO. 1 TO NO. 3
Summer
1 1928
Total change i — 55,920
Per capita change ]- -- -- 1 — 0 OS5
Fall
-67, 9fiO
-0 103
Winter
-42, 800
-o oe4
Spring
-47, 630
-0.072
Summer
1927
-64, 480
-0 09is
Yearly
average
-51, 260
-0 079
STATIONS NO 3 TO NO. 7
Total change —19,140
Per capita change !--- —0030
-39, 060
-0 060
-32, 360
-0 050
-72, 240
-0.111
-20,390
-0.031
-43, 400
-0 067
STATIONS NO. 7 TO NO. 9
Total change . - . +4,430
Kilograms per hour +148
+C, 370
+3f,, 8SO
+ 1,280
+35, 520
+11, S80
+500
-1-21,890
-TATIONS NO. 9 TO NO. 11
Total change
... i +59,!(00
+49
-J- 11 4, 200
+ll,8fiO
+11
-151,600
+ 244,230 +14,510
+335
STATIONS NO. 11 TO NO. 14
—.55 830
— 2 240
+8 810
—47, 900
1 Based on an estimated total equivalent sewered population of 657,820.
- Based on an estimated total equivalent sewered population of 648,670.
PER CAPITA CHANGES IN OXYGEN BALANCE WITHIN THE METROPOLITAN
AREA
In the upper section of the river, between Stations Nos. 1 and 3,
and also between Stations Nos. 3 and 7, the indicated total decrease
in oxygen balance has been calculated in terms of kilograms per
capita per day, by dividing the total decrease in balance by the
estimated total equivalent sewered population between these sampling
points. Assuming that the per capita oxygen demand of domestic
sewage, as represented by the 5-day biochemical oxygen demand at
20° C., is 0.163 pounds, or 0.074 kilograms, the estimates of per
capita decreases in the oxygen balance between stations on the
upper section of the river calculated from the oxygen determinations
should be of about the same order of magnitude as 0.074 kilograms,
-------
RESULTS OF CHEMICAL ANALYSES 73
except in so far as physical conditions in the stream or processes of
natural stream purification not recorded by the chemical analyses
might alter the results.
Between Stations Nos. 1 and 3 the average per capita decrease
in oxygen balance, Table 31, varies between a minimum of 0.064
kilogram in winter to a maximum of 0.103 kilograms in the fall.
This section of the river includes the pool above the Government
lock and dam at Minneapolis, in which considerable deposition of
sludge takes place. It is believed that this pool accounts to some
extent at least for the variation in the calculated daily average per
capita decrease in oxygen balance. In the summer and early fall,
the accumulated sludge increased the draft on the oxygen resources
of the water, while in winter and early spring biological activities
were decreased and the sedimentation of sludge, without subsequent
decomposition, tended to decrease the draft on the oxygen resources
of the water. In all of the calculations certain discrepancies are
introduced, due to the satisfaction of oxygen demand by the dissolved
oxygen introduced by reaeration not always accounted for in the
chemical analyses, and by the organic matter carried in the surface
run-off. Yearly averages have a tendency to balance the seasonal
variations and the calculated amount of 0.079 kilogram per capita
per day, during the period of a year, for the upper section of the
river is in close agreement with the figure of 0.074 kilogram per
capita per day, representative of the pollution contributed by domes-
tic sewage.
Seasonal averages of the daily per capita change in balance between
Stations Nos. 3 and 7 were less in each season, with the exception of
spring, than in the river section immediately above, and in general
were considerably lower than the estimated figure of 0.074 kilogram.
In this section of the river, nearly 35 miles long, increased times of
flow undoubtedly permitted processes of natural stream purification
to operate, reducing the calculated per capita changes. In the sum-
mer and winter months of lowest stream discharge and lengthened
times of flow, allowing greater natural purification to take place, the
indicated per capita contributions were less than during the fall and
spring periods, when times of flow were less.
RATES OF INCREASE IN OXYGEN BALANCE BELOW THE ZONE OF
POLLUTION
Below Station No. 7 changes in oxygen balance, Table 31, are
expressed as the increase or decrease in kilograms; and where times
of flow were available, as rates of change in terms of kilograms per
hour. Insufficient hydrometric data limited such comparisons to
those taking place in the summer and winter seasons and only for
certain stretches of the river.
-------
74 POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
Such data as were available show an increase in balance between
Stations Nos. 7 and 9 in every season, the indicated rate of increase
in winter greatly exceeding that of summer, and the summer rate in
1927 exceeding that of the summer of 1926.
Between Stations Nos. 9 and 11, which includes Lake Pepin, an
increase in balance was shown during the summer, fall, and winter
periods, and a decrease in balance was indicated in the spring period.
When the time factor was considered, however, the rate of change in
this section was very much less than in the more swiftly moving sec-
tion immediately above. Also, in contrast to the section immediately
above, somewhat greater rates of change were indicated in the sum-
mer period rather than in the winter period of ice cover.
RATES OF SECONDARY DECREASE IN OXYGEN BALANCE BELOW LAKE
PEPIN
From Station No. 11, at the outlet of Lake Pepin, to Station No. 14,
at Winona, an increase in balance was shown only in the fall period.
The indicated decrease in balance in the summer of 1926 in the lower
section of the river was practically the same as the decrease in the
upper section between Stations Nos. 1 and 3, which received the sew-
age from a total equivalent sewered population of 657,820. In the
summer of 1927 the indicated decrease in the lower section of the
river was almost 75 per cent of that in the upper section between
Stations Nos. 1 and 3.
-------
SECTION VI
BACTERIOLOGICAL STUDIES
Observations were made of the bacteriological content of the
Mississippi Kiver and its tributaries on samples of water collected
from the 14 regular sampling stations during the 15-month period
June 1, 1926, to August 31, 1927, as follows:
Station number
1 to 6, inclusive .
7 to 14, inclusive
1 to 10, inclusive
11 to 14, inclusive _
Days of sampling each week
5 (Monday-Friday, inclusive) ,
3 (Monday, Wednesday, Friday) -
3 (Monday. Wednesday, Friday) _ ..
Period of sampling
June 1 to Oct. 31, 1926t
July 1 to Oct. 31, 1926.
Nov. 1, 1926, to Aug. 31, 1927
Nov. 1, 1926, to June 30, 1927
Laboratory determinations consisted of plate counts on agar after
an incubation period of 48 hours at 20° C., and of 24 hours at 37° C.
Quantitative estimates of B. coli were obtained from fermentation
tube tests, with lactose broth, in portions of water in geometric series.
PRESENTATION OF DATA
Results of the daily bacteriological examinations are summarized
as monthly arithmetical averages in the basic tabulations, Tables 32
and 33. Table 32 shows at each sampling station for every month of
observation the monthly average bacterial content per cubic centi-
meter determined from the 20° and 37° C. agar-plate counts and the
estimated number of B. coli from the fermentation-tube results.
Included in the table are monthly average rates of stream discharge
and water temperatures. This table, in addition, summarizes the
monthly averages of the bacterial observations at each sampling sta-
tion in terms of "quantity upits" (bacteria per cubic centimeter
multiplied by the stream discharge in thousands of second-feet). For
purposes of comparison, seasonal and yearly averages of bacteria per
cubic centimeter and in terms of quantity units are included.
In Table 33 the same data are grouped by months, to show for
each month at all sampling stations the monthly averages of bacteria
per cubic centimeter and the bacteria in terms of quantity units.
Sampling stations have been arranged in consecutive order passing
downstream, and the results at the mouths of tributaries have been
inserted beneath the main-river sampling stations below their re-
spective points of entrance.
A study of the actual numbers of bacteria present in the water at
the various sampling stations offers a better basis for comparison than
the concentration of bacteria at the several points. For this purpose
a unit designated as the "quantity unit" was adopted during the
75
-------
76
POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
studies of the Ohio and Illinois Rivers. This unit is defined as the '
product of 1 cubic foot discharge per second, and the concentration
of 1,000 bacteria per cubic centimeter. The number of quantity units
in a stream is therefore:
Discharge in second-feet X Bacteria per cubic centimeter
__
This unit is convertible into actual numbers of bacteria per day by
multiplying the bacteria in one quantity unit by 28,317 (cubic centi-
meters per cubic foot) by 86,400 (seconds per day) by 1,000. Hence
one quantity unit equals 2,446,589,000 bacteria per day.
Bacterial concentration as indicated by the basic tabulations varies
considerably from month to month; and it has been found advisable
to still further arrange the bacteriological observations as seasonal
averages, using the same groupings as ia the study of the chemical
results. In Table 34 the bacteriological results from the agar-plate
counts and the B. coli estimates, in terms of quantity units, are
presented as seasonal averages at the various sampling stations in
their order downstream.
TABLE 32.—Summary of bacteriological observations, by stations, in terms of bacteria
per cubic centimeter and bacterial "quantity units" (bacteria per cubic centimeter
X discharge in thousands of second-feet), arranged as monthly means and seasonal
averages at each sampling station
STATION No. 1.—MISSISSIPPI RIVER AT CAMDEN AVENUE BRIDGE, MINNEAPOLIS
Month
1926
June
July
August
September _ . .
October
November
December.. _ .
1927
January. .
February
March
April
May
June.. ...
July
August
Aver-
age
dis-
charge
second-
feet
2,430
2,360
2,410
6,480
7,460
3,980
2,890
2,300
2,210
9,640
17,400
12,800
9,810
5,590
5,100
Total
days
sam-
ples
taken
22
21
22
21
21
14
13
12
11
13
13
11
13
12
18
Water
tem-
pera-
ture,
C .
18.3
23.0
21.9
16 4
9 5
1.4
0
0
0
1.0
7.2
12.8
18 6
22.4
19 9
Bacteria per cubic
centimeter
On agar at—
20° C.
48 hours
6,600
2,500
1,400
1,700
1,100
1,100
600
550
900
6,600
4,300
3,800
3,000
2,500
2,700
37° C.
24 hours
2,900
1,400
950
1,500
1,000
650
225
100
225
800
600
400
600
850
850
B. coli
(esti-
mated)
1
2
4
7
10
25
6
15
15
20
11
14
6
6
5
Quantity units
Bacteria per cubic centimeterX
thousand second-feet
20° C.
agar
16,038
5,900
3,374
11,016
8,206
4,378
1,734
1,265
1,989
63, 624
74, 820
48, 640
29, 430
13, 975
13, 770
37° C.
agar
7,047
3,304
2,290
9,720
7,460
2,587
650
230
497
7,712
10, 440
5,120
5,886
4,752
4,335
B. coll
2
5
10
45
75
100
17
35
33
193
191
179
59
34
25
SEASONAL AVERAGES
Summer, 1926
Fall
Spring
Summer, 1927
Yearly ....
2,400
5,970
2 4^0
13, ihO
6,830
6,650
Co
56
36
43
185
21. 1
9 1
0
7 0
20 3
93
3, 500
1,300
fSO
4,900
2,700
2,300
1,750
1,050
180
GOO
800
700
2
14
12
15
6
11
8.440
7,870
1 660
62, 360
19,060
21, 200
4,210
6,590
460
7,760
4,990
4,660
6
73
28
188
39
79
-------
BACTERIOLOGICAL STUDIES
77
-TABLE 32.—Summary of bacteriological observations, by stations, in terms of bacteria
per cubic centimeter and bacterial "quantity units" (bacteria per cubic centimeter
X discharge in thousands of second-feet), arranged as monthly means and seasonal
averages at each sampling station—Continued
STATION No. 2.—MISSISSIPPI RIVEB AT PLYMOUTH AVENUE BRIDGE,
MINNEAPOLIS
Month
1926
June...
July
August
September
October
November
December
1927
January
February
March
April
May
June
July-..
August
Aver-
age
dis-
charge
second-
feet
2,430
2,360
2,410
6,500
7,480
3,990
2,890
2,300
2,210
9,660
17,500
12,800
9,850
5,590
5,100
Total
days
sam-
ples
taken
22
21
22
21
21
14
2
10
2
6
13
11
13
12
18
Water
tem-
pera-
ture,
° C.
18.1
23 4
22.0
16.1
9.5
1.4
0
0
0
2.2
7.2
12.8
18.6
22.4
19.9
Bacteria per cubic
centimeter
On agar at—
20° C.
48 hours
8,100
9,200
8,400
2,300
1,200
1,700
2,200
3,300
3,700
3,900
3,700
3,400
3,500
3,100
3,300
37° C
24 hours
3,000
6,200
5,300
2,000
1,100
900
900
1,200
1,200
850
550
450
550
950
900
B. coll
(esti-
mated)
11
33
165
10
10
7
10
351
100
6
6
33
8
15
17
Quantity units
Bacteria per cubic centimeterX
thousand second-feet
20° C.
agar
19, 683
21, 712
20, 244
14, 950
8,976
6,783
6,358
7,590
8,177
37, 674
64, 750
43, 520
34. 475
17,329
16, 830
37° C
agar
7,290
14, 632
12, 773
13,000
8,228
3,591
2,601
2,760
2,652
8,211
9,625
5,760
5,418
5,311
4,590
B. coli
27
78
398
65
75
28
29
807
221
58
105
422
79
84
87
SEASONAL AVERAGES
Summer, 1926
Fall...
Winter __
Spring
Summer. 1927 ...
Yearly
2 400
5,990
2,470
13 320
6,850
6 660
65
56
14
30
43
156
21.2
9.0
0
7.4
20.3
9 4
8,600
1,700
3,100
3,700
3,300
3,900
4,800
1,300
1,100
620
800
1,800
70 ! 20 550 ' 11 570
9 1 10,240 8 270
154 ' 7,380 2,670
15 i 48,650 7 870
13 I 22,880 5,110
62 ! 22 930 7 440
16
5
35
19
8
19
STATION No. 3.—MISSISSIPPI RIVER AT GOVERNMENT LOCK AND DAM,
MINNEAPOLIS
Month
1926
June
July
August . . .
September
October.
November . .
1927
January.,.
February
March
May . .
June. .
July
August
Aver-
age
dis-
charge
second -
feet
2,440
2,370
2,420
6,520
7,510
4,000
2,910
2,310
2,220
9,690
17,500
12, 900
9,910
5,610
5,090
Total
days
sam-
ples
taken
22
21
22
21
21
14
14
12
11
13
13
11
13
12
18
Water
tem-
pera-
ture,
° C.
19.4
24.3
23.0
16.9
9.8
1.6
0
0
0
1.2
7.4
32.7
18 6
22.9
20.3
Bacteria per cubic
centimeter
On agar at—
20° C.
48 hours
440,000
750,000
320,000
330, 000
190,000
90,000
60,000
77, 000
64,000
39, 500
35, 500
61,000
150, 000
160, 000
210, 000
37° C.
24 hours
300,000
650,000
380, 000
400,000
230,000
94,000
51,000
70,000
130,000
47,500
42, 000
80,000
130, 000
180, 000
2CO, 000
B. coll
(esti-
mated)
2,000
1,639
1,565
1,640
1,510
672
1,485
591
1,410
149
1,117
225
1,070
2,800
1,695
Quantity units
Bacteria per cubic centimeterX
thousand second-feet
20° C , 37° r
agar , agar
1, 073, 100
1, 777, 500
774, 400
2,151,600
1, 426, 900
360, 000
174, 600
177,870
142, 080
382, 755
621, 250
786, 900
1,486,500
897, 600
1, 068, 000
732,000
1,540,500
919,600
2, 608, 000
1,727,300
376, 000
148, 410
161, 700
288, 600
460, 275
735, 000
1, 032, 000
1, 288, 300
1, 009, 800
1,018,000
B. coli
4,880
3,884
3,787
10, 693
11,340
2,688
4,321
1,365
3,130
1,444
19, 547
2,903
10, 604
15, 708
8,628
SEASONAL AVERAGES
Summer, 1926
Fall..
Spring
Summer, 1927 ..
Yearly
2,410
6,010
2,480
13, 360
6,870
6.690
65
56
37
37
43
186
22.2
9.4
0
7.1
20.6
9.6
500, 000
200, 000
67,000
45, 300
173, 000
181. 000
440, 000
240, 000
84,000
56. 500
170, 000
192, 000
1,735
1,274
1,162
497
1, 855
1.089
1, 208, 500
1,312,830
164, 850
596, 970
1, 151, 000
855. 200
1, 064, 000
1, 570, 430
199, 570
742, 430
1, 105, 370
940. 470
4,184
8,240
2,939
7,965
11,647
6.309
-------
78
POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
TABLE 32.—Summary of bacteriological observations, by stations, in terms of bacteria-
per cubic centimeter and bacterial "quantity units" (bacteria per cubic centimeter
^.discharge in thousands of second-feet), arranged as monthly means and seasonal
averages at each sampling station—Continued
STATION Xo. 4.-—MINNESOTA RIVER AT FORT SNELLING
Month
1926
June __
July
August
September
October
Novembei
December _
1927
January
February
March, ,
April
May
June . _ . _ . _ ,_
July
August.
Aver-
age
dis-
charge,
second-
feet
400
213
375
2, 040
2.380
1,110
830
625
610
9,120
9,270
6, 680
5.910
1,450
369
Total
days
sam-
ples
taken
22
21
22
21
21
14
13
12
5
7
13
11
13
12
18
Water
tem-
pera-
ture-
19.4
23 7
22.6
17.2
10. 1
1 8
0
0
0
2.4
7.9
13.6
18.4
22 7
20.6
Bacteria per cubic
centimeter
On agar at —
20° C.
48 hours
5,900
2,700
2,400
5,800
12,000
8,800
1, 500
500
525
9,100
8,000
6, 400
4,600
4,500
4,700
37° C.
24 hours
4,100
2.100
1,900
5,300
11,500
5,700
550
95
110
2 400
2,600
2,100
2,000
2,200
2,400
B coli
(esti-
mated)
5
3
5
25
20
7
5
12
6
19
29
14
13
20
22
Quantity units
Bacteria per cubic centimeterX
thousand second-feet
20° C.
agar
2,360
575
900
11,832
28, 560
9,768
1,245
313
320
82, 992
74, 160
42, 752
27, 186
6,525
1,734
37° C.
agar
1,640
447
713
10,812
27, 370
6,327
457
59
67
21, 888
24, 102
14, 028
11, 820
3,190
886
B. ooli
o
1
2
51
4*
8
4
S
4
173
269
94
77
29
S
SEASONAL AVERAGES
Summer, 1926.. .._
Fall .. .
Winter
Spring
Summer, 1927
Yearly..
329 65
1. 840 56
688 30
8, 360 31
2, 580 43
3,260 173
21.9
9.7
0
8.0
20 6
9.8
3,700
8,900
840
7,800
4,600
5,200
2,700
7,500
250
2,400
2,200
3,000
4
17
8
21
18
13
1,280
16, 720
630
66, 640
11, 820
23, 380
930
14, 840
190
20, 010
5,300
9,840
3S
5
179
38
62
STATION No. 5.—MISSISSIPPI RIVER AT ROBERTS STREET BRIDGE, ST. PAUL
Month
1926
June
July-
August.. _ .
September
October
November
December .,
1927
January
February .
March..
April.
May _
June
July .
August. .
Aver-
age
dis-
charge,
second-
feet
2,850
2, 590
2,810
S, 630
9,970
5, 150
3,770
2, 950
2,850
18, 900
27, 000
19. 700
16,000
7,090
5,440
Total
days
sam-
ples
taken
20
21
22
21
21
13
14
12
12
13
13
I'J
12
18
Water
tem-
pera-
ture,
19 3
23.5
22. 1
16.5
10 0
1 4
0
0
0
1.2
7 S
1:1 3
18 8
22 8
20.7
Bacteria per cubic
centimeter
On agar at—
20° C.
48 hours
170, 000
550, 000
170,000
190, 000
120, 000
63, 000
83. 000
71, 000
65,000
56,000
36, 500
100, 000
110, 000
68 000
93,000
37° C.
24 hours
95, 000
360, 000
160, 000
190, 000
110,000
64, 000
58,000
72, 000
86, 000
21,500
21, 000
56 000
81. 000
50, 000
80,000
B. coli
(esti-
mated)
1,130
2, 500
2,964
1,596
1,587
2,040
1,485
692
475
294
577
181
633
618
1,050
Quantity units
Bacteria per cubic centimeterX
thousand second-feet
20° C.
agar
484, 500
1, 424, 500
477, 700
1, 639, 700
1, 196, 400
324, 450
312,910
209, 450
185, 250
1, 058, 400
985, 500
1, 970, 000
1, 760, 000
482, 120
505, 920
37° C
agar
270, 750
932, 400
449, 600
1, 639, 700
1,096,700
329, 600
218, 660
212, 400
245, 100
406, 350
567, 000
1, 103, 200
1, 296, 000
354, 500
435, 200
B coli
3,221
6,475
8.329
13, 773
15, 822
10, 506
5,598
2,041
1.354
5,557
15, 579
3, 5ii6
10, 12S
4.382
5,712
SEASONAL AVERAGES
Summer, 1926
Fall
Winter
Spring
Summer, 1927
Yearly
2,750
7 920
3 190
21 870
9,510
10 030
63
55
38
37
43
186
21 6
9.3
0
7 4
20.8
9 6
297, 000
124, 000
73 000
64,000
90,000
135, 000
205, 000
121 000
72 000
33 000
70 000
107 000
2,198
1,741
884
351
767
1 252
795, 570
1 053 520
235 870
1 337 970
916, 010
962 020
550, 920
1 022 000
225 390
692 180
695, 230
708 060
6, 008
13 367
2 998
8 234
6 741
8 227
-------
BACTERIOLOGICAL STUDIES
79
•TABLE 32.—Summary of bacteriological observations, by stations, in terms of bacteria
per cubic centimeter and bacterial "quantity units" (bacteria per cubic centimeter
^.discharge in thousands of second-feet), arranged as monthly means and seasonal
averages at each sampling station—Continued
STATION No. 6.-—MISSISSIPPI RIVER AT INVEKGROVE BRIDGE
Month
1926
July
August
October
November - --
December
1927
January
April
May
July
August .-
Aver-
age
dis-
charge,
second-
feet
2,860
2,600
2,820
8,660
10,000
5,170
3,790
2,960
2,860
18,900
27,100
19, 800
16, 100
7,110
5,440
Total
days
sam-
ples
taken
21
21
22
21
21
13
14
12
12
13
13
11
13
12
18
Water
tem-
pera-
ture,
0 C.
18.9
23.3
21.9
16 4
9.8
1.4
0
0
0
1 2
7.8
13.3
18.8
22.8
20.6
Bacteria per cubic
centimeter
On agar at—
20° C.
48 hours
190, 000
550, 000
430, 000
130, 000
130,000
79,000
64,000
44,000
78,000
54,000
35,500
97,000
72,000
90,000
110,000
37° C.
24 hours
100,000
390, 000
310, 000
130, 000
110,000
74,000
48,000
47,000
90,000
19, 000
19, 500
63,000
50, 000
59, 000
91,000
B. coll
(esti-
mated)
515
1,531
795
1,081
1,253
515
2,870
1,442
700
224
1,055
451
385
625
700
Quantity units
Bacteria per cubic centimeterX
thousand second-feet
20° C.
agar
543, 400
1, 430, 000
1, 212, 600
1, 125, 800
1, 300, 000
408, 4.30
242, 560
130. 240
223, 080
1, 020. 600
962, 050
1, 920, 600
1, 159, 200
639, 900
598, 400
37° C.
agar
286, 000
1, 014, 000
874, 200
1, 125, 800
1, 100, 000
382, 580
181,920
139, 120
257, 400
359, 100
528, 450
1, 247, 400
805, 000
419, 490
495, 040
B. coli
1,473
3,981
2,242
9,361
12,530
2, 663
10, 877
4,268
2,002
4,234
28, 591
8,930
6,199
4,444
3,808
SEASONAL AVERAGES
Summer, 1926
Fall
Winter .
Summer, 1927 .
Yearly
2 760
7 940
3 200
21 930
9 550
10 060
6-4
55
38
37
43
186
21.4
9.2
0
7.4
20.7
9.5
390 000
113,000
62,000
62 200
90,700
147 000
267, 000
105, 000
62,000
33, 800
66, 700
113,000
947
950
1,671
577
570
1 025
1 062,000
944, 740
198, 630
1,301,080
799, 170
927, 930
724 730
869 460
192, 810
71] 650
573, 180
667 910
2,56
8,18
5,71
13,91
4,81
7,99
STATION No. 7.-—MISSISSIPPI RIVER ABOVE HASTINGS, MINN.
Month
1926
July
\ugust
September
October
December
1927
Januarv
February
March
April . _._
Mav
June _
Julv
August
Aver-
age
dis-
charge,
second-
feet
2,600
2,830
8,700
10,100
6,190
3,810
2,970
2,870
19,000
27,200
19,900
16,200
7,120
5, 450
Total
days
sam-
ples
taken
18
22
21
18
13
13
13
12
13
13
11
13
12
11
Water
tem-
pera-
ture,
C.
23 6
22.4
17 4
11 7
2.8
0
0
0
2 5
7.6
14.5
18.9
23 9
22.2
Bacteria per cubic
centimeter
On agar at—
20° C.
48 hours
1,300,000
750, 000
290, 000
130, 000
110,000
35, 500
50,000
130, 000
59,000
130, 000
99.000
83,000
200,000
170, 000
37° C
24 hours
1,200,000
750. 000
320, 000
100,000
63, 000
22, 000
34. 000
54, 000
16,500
25. 000
48,000
43,000
130, 000
1 iO, 000
B. coli
(esti-
mated)
9,950
3,246
520
535
345
385
685
393
841
280
153
272
2^8
229
Quantity units
Bacteria per cubic centimeterX
thousand second-feet
20° C.
agar
3, 380, 000
2, 122, 500
2, 523, 000
1, 313, 000
570, 900
135, 255
148, 500
373, 100
1,121,000
3, 536, 000
1,970,100
1, 344, 600
1,424,000
926, 500
37° C.
agar
3, 120, 000
2, 122, 500
2, 784, 000
1,010,000
326, 970
83, 820
100, 980
154,980
313, 500
680, 000
955, 200
696, 600
925, 600
817,500
B. coli
25, 870
9.186
4,524
5,404
1,791
1,467
2,034
1,128
15, 979
7,616
3,045
4,406
2,051
1,248
SEASONAL AVERAGES
Summer, 1926-
Fall
Winter
* wing
Summer, 1927_
Yearly
2,720
8,000
3,220
22, 030
9,590
10,110
40
52
38
37
36
liO
23.1) j 1,025,000 ! 97.5,000
10.6
0
8. 2
21.7
10.1
ISO, 000
71, SOO
96, 000
151,000
264, 000
161, 000
36, 700
29, 800
108, 000 !
22.3. 000 :
6, 5S8
407
4«8
2, 75i,2r!0
1. 46S, 970
218 050
2, 209, 030
1,231,700
1,1-J7 j 1, 544 830
2,621.250
1, 373, 660
113,260
Wll, 570
813,230
1, 029, 050
17,528
3,906
1,543
8,880
2,568
6,871
-------
80
POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
TABLE 32.—Summary of bacteriological observations, by stations, in terms of bacteria '
per cubic centimeter and bacterial "quantity units" (bacteria per cubic centimeter
X discharge in thousands of second-feet), arranged as monthly means and seasonal
averages at each sampling station—Continued
STATION No. 8.—ST. CROIX RIVER AT PHESCOTT, Wis.
Aaeer" Total
rtf 1 days
MODth seSd' P™"
1926 1
July.
August
September
October - |
November I
December
1927
January
February
March . _
April
May
June. '
August
2, 100 18
2, 520 22
4, 800 18
6, 050 17
4, 300 13
2, 940 6
2, 420 13
2,260 , 12
12,600 1 13
15,400 13
7,700 11
6, 700 13
4, 650 12
2,470 11
Water
tem-
pera-
ture,
22.9
22.7
18.8
13.1
4.1
0
0
0
2.6
7.4
15.0
18.8
24.2
22 7
Bacteria per cubic
centimeter
On agar at—
20° C.
48 hours
90,000
18, 500
0,000
6,100
3,600
250
2,300
6,000
4,100
3,900
5,200
2.600
12,000
37° C.
24 hours
66,000
11,500
5,200
5,000
3,300
375
170
250
500
650
1,800
700
950
3,600
B. coli
(esti-
mated)
159
245
22
11
1
.5
13
1
.4
.1
.4
.3
.3
.3
Quantity units
Bacteria per cubic centimeterX
thousand second-feet
20° C.
agar
189, 000
46, 620
28,800
36, 905
15, 480
605
5,198
75,600
63, 140
30, 030
34,840
12,090
29, 640
37° C.
agar
138, 600
28, 980
24, 960
30, 250
14, 190
1,103
411
565
6,300
10, 010
13, 860
4,690
4,418
8,892
B. coli
334
617
106
67
4
1
31
2
5
2
3
2
1
1
SEASONAL AVERAGES
Summer, 1926
Fall
Winter
Spring
Summer, 1927.. ..
Yearly
STATION"
2,310 40
5, 050 48
2, 540 31
11,900 37
4,610 ' 36
5, 820 169
N"o 9 — Mi
Month enlrge, |J£
.second- tWeb
feet , taKen
1926
July
September !
October. _.
December
1927
January. .
February
March
April. . [
May
June
July..
4.810 19
5,480 i 22
13, 900 21
16.6PO 21
9,820 ; 12
7. 020 6
5. 560 9
5,300 i 11
32,400 • 13
44, 100 13
28,900 I 11
24, 300 13
12,000 , 11
7 980 10
22 8
12.0
0
8.3
21.9
10. S
54,300
5,200
1,300
4,700
6,600
13,000
38,800
4,500
265
980
1,800
8,000
202
11
5
.3
.3
38
117,810
27, 060
2,900
56, 260
25, 520
47, 840
83, 790
23, 130
690
10,060
6,000
22, 830
476
59
11
S
1
98
3SIS8IPPI RIVER ABOVE RED WING, MINN.
Water
tem-
pera-
ture,
0 C.
22 6
21.4
18.7
20.4
1
0
0
0
1.9
7.3
14.8
18.3
22.9
22 3
Bacteria per cubic
centimeter
On agar at—
20° C.
48 hours
72, 000
44, 000
17, 000
48, 500
81, 000
28, 000
36, 500
26, 000
21, 500
11, 000
29,500
16,500
27, 500
27, 500
37° C.
24 hours
53,000
33, 000
15, 000
28,000
34,500
7,200
8,100
11,000
2,000
2,600
8,500
6,200
17, 000
13,000
B. eoli
(esti-
mated)
104
186
52
70
159
40
28
26
13
21
20
38
2R
9
Quantity units
Bacteria per cubic centimeterX
thousand second-feet
20° C.
agar
346, 320
241, 120
236, 300
805, 100
795, 420
196, 560
202, 940
137, 800
696, 600
485, 100
852, 550
400, 950
330, 000
219, 450
37° C.
agar
254, 930
180, 840
208, 500
464, 800
338, 790
50, 544
45, 036
58,300
64,800
114, 660
245, 650
150, 660
204, 000
103. 740
B. coli
500
1,019
723
1,162
1,561
281
156
138
421
926
578
923
312
72
SEASONAL AVERAGES
Summer, 1926
Fall
Winter
Spring . ,
Summer, 1927
Yearly -. -
5, 150 41
13, 440 54
5, 960 26
35, 130 ' 37
14, 760 34
16. 500 : 171
22.0
13.4
0
8.0
21.2
10 5
58, 000
48, 800
30,000
21, 000
24,000
36.000
43, 000
25,800
8,800
4,400
12,000
17.000
145
94
31
18
24
63
293, 720
612, 270
179, 100
678, 080
316, 800
449. 730
217, 890
337, 360
51, 290
141, 700
152, 800
181. 460
760
1,149
192
642
436
699
-------
BACTEEIOLOGICAL STUDIES
81
TABLE 32.—Summary of bacteriological observations, by stations, in terms of bacteria
per cubic centimeter and bacterial "quantity units" (bacteria per cubic centimeter
X discharge in thousands of second-feet), arranged as monthly means and seasonal
averages at each sampling station—Continued
STATION No. 10.—CANNON RIVER AT RED WING, MINN.
Month
1926
July
August .
October
November
December
1927
January
February
March
April.
July
August
Aver-
age
dis-
charge,
second-
feet
95
97
293
276
256
214
126
132
570
1,220
1,030
1, 100
212
46
Total
days
sam-
ples
taken
19
22
20
20
11
6
9
11
13
13
11
13
11
11
Water
tem-
pera-
ture.
•c.
20.8
19.7
18.5
20.6
1.6
0
0
0
1.8
7.5
14.7
18.2
22.0
21.7
Bacteria per cubic
centimeter
On agar at —
20° C.
48 hours
13,000
15,000
6,500
4,000
1,300
1,200
1,800
12,000
13,000
5,000
4,700
8,900
3,900
4,100
37° C.
24 hours
11,000
11,500
5,700
3,800
600
325
500
2,200
1,700
650
700
3,800
1,000
900
B. coli
(esti-
mated)
14
12
22
13
11
10
4
1
2
3
16
14
4
3
Quantity units
Bacteria per cubic centimeterX
thousand second-feet
20° C.
agar
1,235
1,455
1,905
1,104
333
257
227
1,584
7,410
6,100
4,841
9,790
827
189
37° C.
agar
1,045
1,116
1,670
1,049
154
70
63
290
969
793
721
4,180
212
41
B. coli
1
1
6
4
3
2
1
0
1
4
16
15
1
0
SEASONAL AVERAGES
Summer, 1926_.
Fall
Winter . - .
Spring
Summer, 1927
Yearly
96
275
157
940
453
450
41
51
26
37
35
168
20.3
13 6
0
8.0
20 6
10.3
14, 000
3,900
5,000
7,600
5,600
7,200
11, 300
3,400
1,000
1,000
1, 900
3,500
13
15
7
10
1,350
1, 110
690
6,120
3,600
3,020
1,080
960
140
830
1,480
1,010
1
4
1
7
5
5
STATION No. 11.—MISSISSIPPI RIVER AT OUTLET OF LAKE PEPIN
Month
1926
July
September
October
November .
1927
January
March
April -
June .
Aver-
age
dis-
charge,
second-
feet
4,840
5,520
14,100
16,700
9,920
7,100
5,600
5,350
32, 500
44, 600
29, 300
24, 700
Total
days
sam-
ples
taken
21
22
21
19
10
4
5
9
8
10
10
10
Water
tem-
pera-
ture,
0 C.
22.6
22.0
19.3
13.9
3.5
0
0
0
1.4
6.9
13.6
18.1
Bacteria per cubic
centimeter
On agar at —
20° C
48 hours
22,000
7,300
5,400
1,900
750
450
850
2,100
2,900
2,400
2,700
37° C.
24 hours
18,000
7,400
5,400
2,800
325
100
50
75
400
550
400
1,500
B coll
(esti-
mated)
3
1
7
1
1
.4
.3
.2
. 7
.6
2
.3
Quantity units
Bacteria per cubic centimeterX
thousand second-feet
20° C.
agar
106, 480
40, 296
76, 140
31, 730
7,440
2,520
4.548
68, 250
129, 340
70, 320
66, 690
37° C.
agar
87, 120
40, 848
76, 140
46,760
3,224
710
280
401
13,000
24, 530
11, 720
37, 050
B. coll
15
6
99
17
10
3
2
1
23
27
59
7
SEASONAL AVERAGES
Summer, 1926--.
Fall
Winter
Summer, 1927
Yearly
5,180
13, 570
6,020
35, 470
24,700
16, 700
43
50
18
28
10
149
22 3
12.2
0
7 3
18.1
10 1
14,700
2,700
650
2,500
2,700
4,400
12,700
2,800
75
•ISO
1,500
3,100
2
3
.3
1
.3
1
73, 390
38, 440
3, 530
89, 300
66, 690
54, 890
63, 980
42,040
460
16, 420
37, 050
28, 480
11
42
2
36
7
22
-------
82
POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
TABLE 32.—Summary of bacteriological observations, by stations, in terms of bacteria
per cubic centimeter and bacterial "quantity units" (bacteria per cubic centimeter
^.discharge in thousands of second-feet), arranged as monthly means and seasonal
averages at each sampling station—Continued
STATION No. 12.—CHIPPEWA RIVER AT MOUTH
Month
1926
July
September
October
1927
June
Aver-
age
dis-
charge
second-
feet
3,600
9,500
23,400
12,600
15, 500
7,500
Total
days
sam-
ples
taken
21
21
21
15
2
8
Water
tem-
pera-
ture,
0 C.
22.6
21.8
18.2
12.6
6.5
19.2
Bacteria per cubic
centimeter
On agar at—
20° C.
48 hours
27, 000
13,000
6,500
6,300
1,400
6,600
37° C.
24 hours
25,500
12,500
5,200
7,300
900
2,700
B. coh
(esti-
mated)
25
21
23
18
6
7
Quantity units
Bacteria per cubic centimeterX
thousand second-feet
20° C.
agar
97,200
123,500
152, 100
79, 380
21, 700
49,500
37° C.
agar
91,800
118,750
121, 680
91, 980
13, 950
20, 250
B. coh
90
200
538
227
93
53
SEASONAL AVERAGES
Summer, 1926
Fall
Winter
Summer, 1927...
Yearly
6,550
17,200
7,500
42
38
8
22.2
12 4
19.2
20,000
4,700
6,600
19,000
4,500
2,700
23
16
7
110, 350
84, 390
49,500
105, 280 J 145
75,870 I 286
20,250 j 53
STATION No. 13.—ZTJMBBO RIVER AT KELLOGG, MINN.
Month
1926
July
August
October _
November,. .
December
1927
January - -
March
June
Aver-
age
dis-
charge
second-
feet
154
163
454
474
238
200
118
124
530
1,130
965
1,030
Total
days
sam-
ples
taken
21
21
21
21
11
13
13
11
12
12
10
13
Water
tem-
pera-
ture,
°C.
21.0
19.9
16.9
9.9
2.1
0
0
0
2.4
7.2
13.5
18.3
Bacteria per cubic
centimeter
On agar at—
20° C
48 hours
21,500
7,500
17,000
5,300
3,200
1,700
650
1,400
9,100
5,400
5,900
8,700
37° C.
24 hours
17,000
4,900
15,500
6,500
1,700
600
190
1,000
1,600
750
1,700
2,400
B. coli
(esti-
mated)
14
10
173
13
11
2
2
2
4
]
6
14
Quantity units
Bacteria per cubic centimeterX
thousand second-feet
20° C.
agar
3,311
1,223
7,718
2,512
762
340
77
174
4,823
6,102
5,694
8, 961
37° C.
agar
2,618
799
7,037
3,081
405
120
22
124
848
848
1,641
2,472
B. roll
2
2
79
6
3
0
0
0
2
1
6
14
SEASONAL AVERAGES
Summer, 1926
Fall
Winter
Spring,. . „
Summer, 1927
Yearlv..
159
389
147
875
1,030
465
42
53
37
34
13
179
20.5
9 6
0
7 7
18.3
9.3
14, 600
8,500
1,250
6,800
8.700
7,300
11,000
7,900
000
1,350
2,400
4,500
12
66
2
4
14
21
2,270
3,660
200
5,540
8, 960
3.470
1
1,710 i 2
3, 510 ! 29
90 0
1, 110 3
2,470 14
1,670 I 10
-------
BACTERIOLOGICAL STUDIES
83
TABLE 32.—Summary of bacteriological observations, by stations, in terms of bacteria
per cubic centimeter and bacterial "quantity units" (bacteria per cubic centimeter
X discharge in thousands of second-feet), arranged as monthly means and seasonal
averages at each sampling station—Continued
STATION No. 14.—MISSISSIPPI RIVER ABOVE WINONA, MINN.
Month
1926
Julv
August .-
November
1927
January - _
February
March
Aver-
age
dis-
charge
second-
feet
8,650
15, 300
38,300
30,300
25,900
14,300
12,300
12,700
58,000
57,900
44,600
34,100
Total
days
sam-
ples
taken
21
19
16
16
9
10
10
9
13
12
11
13
Water
tem-
pera-
ture.
0 C.
22.0
23.3
21.7
13.0
3.2
0
0
0
2.2
7.4
12 0
18. S
Bacteria per cubic
centimeter
On agar at—
20° C.
48 hours
320,000
240,000
4,600
2,700
2,000
750
1,200
3,200
5.100
2,400
3,400
5,300
37° C.
24 hours
250,000
240,000
5,100
2,500
1,100
325
450
1,000
700
475
550
650
B. coli
(esti-
mated)
118
156
18
7
17
5
3
38
13
14
6
5
Quantity units
Bacteria per cubic centimeterX
thousand second-feet
20° C.
agar
2, 768, 000
3, 672, 000
176, 180
81, 810
51,800
10, 725
14, 760
40,640
295, 800
138, 960
151, 640
180, 730
37° C.
agar
2, 162, 500
3, 672, 000
195, 330
75, 750
28,490
4,648
5,535
12,700
40,600
27, 503
24,530
22, 165
B. coli
1,021
2,387
689
212
440
72
37
483
754
811
268
171
SEASONAL AVERAGES
Summer, 1926
Fall
Winter
Spring - ,
Summer, 1927
Yearly
12,000
31 500
13,100
53. 500
34, 100
29,400
40
41
29
36
13
159
22 7
12 6
0
7.2
18.8
10.3
280,000
3 100
1,720
3,600
5, 300
49,000
245, 000
2 900
590
580
650
42,000
137
14
15
11
5
33
3, 220, 000
103 260
22,040
195, 470
180, 730
631, 920
2, 917 250
99 860
7 630
30,880
22 170
•522 650
1,704
447
197
611
171
612
Summer average, 1926, Stations Nos. 1 to 6, inclusive, based on months of June, July, and August.
Summer average, 1926, Stations Nos. 7 to 14, inclusive, based on months of July and August.
Fall average, all stations, based on months of September, October, and November.
Winter average, all stations, based on months of December, January, and February.
Spring average, all stations, based on mouths of March, April, and May.
Summer average, 1927, Stations Nos. 1 to 10, inclusive, based on months of June, July, and August
Summer average, 1927, Stations Nos. 11 to 14, inclusive, based on month of June only.
Yearly average, all stations, based on 12-month period, July, 1926, to June, 1927, inclusive.
TABLE 33.—Summary of bacteriological observations, by months, in terms of bacteria
per cubic centimeter and bacterial "quantity units" (bacteria per cubic centimeter
^discharge in thousands of second-feet) arranged as monthly means for all
sampling stations
JUNE, 1926
Station
1
2
3
Minnesota River
5
0
Aver-
age
dis-
charge
(sec-
ond
feet)
2,430
2,430
2,440
400
2,850
2, 860
Total
days
sam-
ples
taken
22
22
22
22
20
21
Water
tem-
pera-
ture,
0 C.
18.3
18.1
19.4
19.4
19 3
18 9
Bacteria per cubic
centimeter
On agar at —
20° C.
48 hours
6,600
8,100
440, 000
5,900
170,000
190. 000
37° C.
24 hours
2,900
3,000
300,000
4,100
95, 000
100,000
B. coli
(esti-
mated)
1
11
2,000
5
1,130
515
Quantity units
Bacteria per cubic centimeterX
thousand second-feet
20° C.
agar
16,038
19, 683
1, 073, 600
2,360
484, 500
543, 400
37° C.
agar
7,047
7,290
732,000
1,640
270, 750
286, 000
B. coli
2
27
4,880
2
3,221
1,473
129540—32-
-------
84
POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
TABLE 33.-—Summary of bacteriological observations, by months, in terms of bacteria "
per cubic centimeter and bacterial "quantity units" (bacteria per cubic centimeter
^discharge in thousands of second-feet) arranged as monthly means for all
sampling stations—Continued
JULY, 1926
Station
1
2 .
3
Minnesota River
5
6
7
St. Croix Hiver
Cannon Eiver ...
9
11
Chippewa River
Zumbro River
14
Aver-
age
dis-
charge
(sec
ond
feet)
2,360
2,360
2,370
213
2,590
2,600
2,600
2,100
95
4,810
4,840
3,600
154
8,650
Total
days
sam-
ples
taken
21
21
21
21
21
21
18
18
19
19
21
21
21
21
Water
tem-
pera-
ture,
0 C.
23.0
23.4
24.3
23.7
23.5
23.3
23.6
22.9
20.8
22.6
22.6
22.6
21.0
22.0
Bacteria per cubic
centimeter
On agar at —
20° 0.
48 hours
2,500
9,200
750,000
2,700
560,000
550,000
1,300,000
60,000
13,000
72,000
22,000
27,000
21,500
320,000
37° C.
24 hours
1,400
6,200
650, 000
2,100
360,000
390,000
1,200,000
66,000
11,000
53,000
18,000
25,500
17,000
250, 000
B. coll
(esti-
mated)
2
33
1,639
3
2,500
1,531
9,950
159
14
104
3
25
14
118
Quantity units
Bacteria per cubic centimeterX
thousand second-feet
20° C.
agar
5,900
21,712
1, 777, 500
575
1, 424, 500
1, 430, 000
3, 380, 000
189,000
1,235
346, 320
106,480
97, 200
3,311
2, 768, 000
37° C.
agar
3,304
14, 632
1, 540, 500
447
932, 400
1, 014, 000
3, 120, 000
138, 600
1,045
254, 930
87, 120
91,800
2,618
2, 162, 500
B. coli
5
78
3,884
1
6,475
3,981
25, 870
334
1
500
15
90
2
1,021
AUGUST, 1926
1
2.
3
Minnesota River _ -
5
6
7
St. Croix River
Cannon River
9
11
Chippewa River
Zumbro River
14
2 410
2,410
2,420
375
2,810
2 820
2,830
2,520
97
5 480
5 520
9,500
163
15,300
22
22
22
22
22
22
22
22
22
22
22
21
21
19
21 9
22 0
23.0
22 6
22.1
21 9
22.4
22.7
19.7
21 4
22 0
21 8
19.9
23.3
1,400
8,400
320, 000
2,400
170,000
430, 000
750,000
18,500
15,000
44,000
7,300
13,000
7,500
240,000
950
5,300
380, 000
1,900
100, 000
310, 000
750, 000
11, 500
11,500
33,000
7,400
12,500
4,900
240, 000
4
165
1,565
5
2,964
795
3,246
245
12
186
1
21
10
156
3 374
20,244
774, 400
900
477, 700
1, 212, 600
2, 122, 500
46, 620
1,455
241,120
40, 296
123, 500
1,223
3, 672, 000
2 290
12, 773
919, 600
713
449, 600
874, 200
2,122,500
28,980
1,116
180 840
40, 848
118, 750
799
3, 672, 000
10
398
3,787
2
8,329
2,242
9,186
617
1
1,019
6
200
2
2,387
SEPTEMBER, 1926
1
2
3
Minnesota Hiver
5
6
7_
St. Croix River
Cannon River
9
11
Chippewa River
Zumbro River
14
6 480
6,500
6,520
2,040
8,630
8,660
8,700
4,800
293
13,900
14 100
23,400
454
38,300
21
21
21
21
21
21
21
18
20
21
21
21
21
16
16 4
16.1
16 9
17.2
16 5
16 4
17.4
18.8
18.5
18.7
19 3
18.2
16.9
21 7
1,700
2,300
330, 000
5,800
190,000
130,000
290,000
6,000
6,500
17,000
5,400
6,500
17,000
4,600
1 500
2,000
400 000
5,300
190, 000
130,000
320, 000
5,200
5,700
15,000
5,400
5,200
15,500
5,100
10
1 640
25
1,596
1,081
520
22
22
52
7
23
173
18
11,016
14,950
2 151 600
11,832
1, 639, 700
1, 125, 800
2, 523, 000
28,800
1,905
236, 300
76, 140
152, 100
7,718
176, 180
9,720
13,000
2 608 000
10, 812
1, 639, 700
1, 125, 800
2, 784, 000
24, 960
1,670
208, 500
76, 140
121,680
7,037
195, 330
45
65
10, 693
51
13, 773
9,361
4,524
106
6
723
99
538
79
689
OCTOBER, 1926
1 , ...
2
3
Minnesota River
t
6 .- -
7
St. Croix River
9
11
Chippewa Hiver
Zumbro River
14
7,460
7,480
7,510
2,380
9,970
10,000
10,100
6,050
276
16,600
16,700
12,600
474
30,300
21
21
21
21
21
21
18
17
20
21
19
15
21
16
9.5
9.5
9.8
10 1
10.0
9.8
11.7
13.1
20.6
20.4
13.9
12.6
9.9
13.0
1,100
1,200
190,000
12,000
120,000
130,000
130,000
6,100
4,000
48,500
1,900
6,300
5,300
2,700
1,000
1,100
230,000
11,500
110, 000
110,000
100,000
5,000
3,800
28,000
2,800
7,300
6,600
2,500
10
10
1,510
20
1,587
1,253
535
11
13
70
1
18
13
7
8,206
8,976
1, 426, 900
28, 560
1, 196, 400
1, 300, 000
1, 313, 000
36, 905
1,104
805,100
31, 730
79,380
2,512
81, 810
7,460
8,228
1, 727, 300
27, 370
1, 096, 700
1, 100, 000
1, 010, 000
30,250
1,049
464,800
46. 760
91,980
3,081
75, 750
75
75
11,340
48
15, 822
12, 530
5,404
67
4
1,162
17
227
6
212
-------
BACTEEIOLOGICAL STUDIES
85-
-TABLE 33.—Summary of bacteriological observations, by months, in terms of bacteria
per cubic centimeter and bacterial "quantity units" (bacteria per cubic centimeter
Xdischarge in thousands of second-feet) arranged as monthly means for all
sampling stations—Continued
NOVEMBEE, 1926
Station
1 _
2
3
Minnesota Biver
5
6. .. .
7
9
11
Chippewa Hiver
Zumhro River -
14
Aver-
age
dis-
charge
(sec-
ond
feet)
3,980
3,990
4,000
1,100
5,150
5,170
5,190
4,300
256
9,820
9,920
15,500
238
25,900
Total
days
sam-
ples
taken
14
14
14
14
13
13
13
13
11
12
10
2
11
9
Water
tem-
pera-
ture,
°C.'
1.4
1.4
1.6
1.8
1.4
1.4
2.8
4.1
1.6
1.0
3.5
6 5
2 1
3.2
Bacteria per cubic
centimeter
On agar at —
20° C.
48 hours
1,100
1,700
90,000
8,800
63,000
79,000
110,000
3,600
1,300
81,000
750
1,400
3,200
2,000
37° C.
24 hour?
650
900
94,000
5,700
64,000
74,000
63,000
3,300
600
34, 500
325
900
1,700
1,100
B. coli
(esti-
mated)
25
672
7
2,040
515
345
1
11
159
1
6
11
17
Quantity units
Bacteria per cubic centimeterX
thousand second-feet
20° C.
agar
4,378
6,783
360,000
9,768
324, 450
408, 430
570, 900
15,480
333
795, 420
7.440
21, 700
762
51,800
37° C.
agar
2,587
3,591
376, 000
6,327
329,600
382, 580
326, 970
14, 190
154
338, 790
3,224
13, 950
405
28, 490
B. coli
100
28
2,688
8
10,506
2,663-
1,791
4
3
1,561
10
93
3
440
DECEMBER, 1926
1
2
3
Minnesota Elver
6
Cannon River
9
11 - -
14
2 890
2,890
2 910
830
3 770
3,790
3 810
2,940
214
7,020
7, 100
6 840
200
14,300
13
2
14
13
14
14
13
6
6
6
4
0
13
10
0
0
0
0
0
0
0
0
0
0
0
o
o
0
600
2,200
60 000
1,500
83 000
64,000
35 500
1,200
28 000
1 700
750
^
900
51,000
550
58,000
48,000
22 000
375
325
7,200
100
600
325
6
10
1,485
5
1,485
2,870
383
5
10
40
o
C
1,734
6, 358
174 600
1,245
312 910
242, 560
135 255
257
196 560
340
10, 725
650
2,601
148 410
457
218 660
181, 920
83 820
1 103
70
50 544
710
120
4,648
IT
29
4,321
4
5,598
10, 877
1 467
1
2
281
3
0
72
JANUARY, 1927
1
2
3
Minnesota River
5
6
7
St. Croix River
Cannon River
9
11
Cnippewa Eiver— _
Zumbro River
14
2 300
2,300
2 310
625
2,950
2,960
2 970
2,420
126
5 560
5 600
6,500
118
12,300
12
10
12
12
12
12
13
13
9
9
5
0
13
10
0
0
0
0
0
0
0
0
0
0
0
0
0
0
550
3 300
77 000
500
71 000
44 000
50 000
250
1 800
36 500
450
650
1 200
100
1 200
70 000
95
72,000
47 000
34 000
170
500
8 100
50
190
450
15
35]
591
12
692
1 442
685
13
4
28
3
2
3
1 265
7 590
177 870
313
209 450
130 240
148 500
605
227
202 940
2 520
77
14 760
230
2 760
161 700
59
212 400
139 120
100 980
411
63
45 036
' 280
22
5 535
35
807
1 365
8
2 041
4 268
2 034
31
1
156
2
0
37"
FEBRUARY, 1927
1 .
2
3
Minnesota River
5
6
St. Croix River
9
11
Ctrippewa River
Zumbro River
14
2,210
2,210
2 220
610
2,850
2 860
2 870
2,260
132
5,300
5 350
7,130
124
12 700
11
2
11
5
12
12
12
12
11
11
9
0
11
g
o
o
o
0
o
o
o
0
o
o
o
o
o
o
900
3 700
64 000
'525
65 000
78 000
130 000
2! 300
12 000
26 000
1 400
3*200
225
1 200
130 000
110
86 000
90 000
54 000
250
2 200
11 ooo
75
1 000
1 000
15
100
1 410
6
475
393
1
26
38
1 989
8 177
142* 080
320
185 250
373* 100
5,198
1 584
137 800
174
497
2 652
67
245 100
565
58 300
12 700
33
221
' 4-
1 354'
' 2
0
138
0
483;
-------
'86
POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
TABLE 33.—Summary of bacteriological observations, by months, in terms of bacteria
per cubic centimeter and bacterial "quantity units" (bacteria per cubic centimeter
^discharge in thousands of second-feet) arranged as monthly means for all
sampling stations—Continued
MARCH, 1927
Station
1
2
3
Minnesota River
5
6
St Oroix River
Cannon River
9
11
•Chippewi River
Zuinbro River
14
Aver-
age
dis-
charge
sec-
ond
feet)
9,640
9,660
9,690
9,120
18, 900
18, 900
19, 000
12, 600
570
32, 400
32, 500
24, 500
530
58, 000
Total
days
sam-
ples
taken
13
6
13
7
13
13
13
13
13
13
8
0
12
13
Water
tem-
pera-
ture.
0 C.
1.0
2.2
1.2
2.4
1.2
1.2
2.5
2.6
1.8
1.9
1.4
2.4
2.2
Bacteria per cubic
centimeter
On agar at —
20° C.
48 hours
6,600
3,900
39, 500
9,100
56,000
54, 000
59, 000
6,000
13, 000
21,500
2,100
9,100
5,100
37° C.
24 hours
800
850
47, 500
2,400
21,500
19, 000
16, 500
500
1,700
2,000
400
1,600
700
B. coli
(esti-
mated)
20
6
149
19
294
224
841
.4
2
13
4
13
Quantity units
Bacteria per cubic centimeterX
thousand second-feet
20° C.
agar
63, 624
37, 674
382, 755
82, 992
1, 058, 400
1,020,600
1, 121, 000
75, 600
7,410
696, 600
68, 250
4,823
295, 800
37° C.
agar
7,712
8,211
460, 275
21,888
406, 350
359, 100
313, 500
6,300
969
64, 800
13, 000
848
40, 600
B. coll
193
58
1,444
173
5,557
4,234
15, 979
5
1
421
23
2
754
APRIL, 1927
\
2
3
Minnesota River
5
'6
7
St. Croix River
Cannon River
9
11
Chippewa River
Zumbto River
14
17 400
17 500
17, 700
9,270
27 000
27, 100
27, 200
15, 400
1 220
44 100
44 600
11 100
1 130
57 900
13
13
13
13
13
13
13
13
13
13
10
0
12
12
7 2
7 2
7.4
7.9
7 8
7.8
7.6
7.4
7 5
7.3
6. 9
7 2
7 4
4 300
3 700
35, 500
8,000
36 500
35, 500
130, 000
4,100
5 000
11, 000
2,900
5 400
2 400
600
550
42 000
2,600
21 000
19 500
25,000
650
650
2 600
o50
750
475
11
6
1,117
29
577
1,055
280
.1
3
21
.6
1
14
74 820
64 750
621, 250
74, 160
985 500
962, 050
3, 536, 000
63, 140
6 100
485, 100
129 340
6 102
138 960
10 440
9 625
735 000
24, 102
567 000
528 450
680, 000
10,010
793
114 660
24 530
848
27 503
191
105
19, 547
269
15 579
28 591
7,616
2
4
926
27
1
811
MAY, 1927
1
2
3
Minnesota River
5
£
St. Croix River
Cannon River
9
11
Chippewa River
Zumbi o River
14
12 800
12,800
12 900
6,680
19 700
19, 800
19 900
7,700
1,030
28 900
29 300
13 500
965
44 600
11
11
11
11
11
11
11
11
11
11
10
o
10
11
12.8
12.8
12.7
13.6
13 3
13.3
14 5
15.0
14.7
14 8
13.6
13.5
12 0
3,800
3,400
61,000
6,400
100 000
97, 000
99,000
3,900
4,700
29 500
2 400
5,900
3 400
400
450
80 000
2,100
56 000
63 000
48 000
1,800
700
8 500
400
1 700
550
14
83
225
14
181
451
153
.4
16
20
2
C
48 640
43' 520
786 900
42, 752
1 970 000
1 920 600
1 970 100
30^030
4 841
852 550
70 320
5 694
151 640
5 120
5 760
1 032 000
14, 028
1 103 200
1 247 400
955 200
13, 860
721
245 650
11 799
1 641
24 530
179
422
2 903
94
3 566
8 930
3 045
3
16
578
59
6
268
JUNE, 1927
1
2
_3
Minnesota River
B
(,
^
St. Croix River
Cannon River
9
11
Chippewa River.-_-_
14
9 810
9,850
9 910
5,910
16.000
16,100
16,200
6,700
1,100
24,300
24,700
7,500
1.030
34 100
13
13
13
13
13
13
13
13
13
13
10
8
13
13
18 6
18.6
18 6
18 4
18 8
18.8
18.9
18.8
18.2
18.3
18.1
19 2
18.3
18 8
3 000
3 500
150 000
4,600
110,000
72 000
83 000
5,200
8,900
16 500
2 700
6,600
8 700
5 300
600
550
130 000
2,000
81,000
50 000
43 000
700
3,800
6 200
1 500
2,700
2 400
650
6
8
1 070
13
633
385
272
.3
14
38
3
7
14
5
29 430
334 475
1 486 500
27, 186
1 760,000
1 159 200
1 344 600
34. 840
9,790
400 950
66, 690
49, 500
8 961
ISO' 730
5 886
5 418
1 288 300
11,820
1 296 000
805 000
696 600
4,690
4,180
150 660
37, 050
20, 250
2 472
2° 165
5
7
10 60
7
10 12
6 191
4 40
1
92
5
-------
BACTERIOLOGICAL STUDIES
87
TABLE 33.—Summary of bacteriological observations, by months, in terms of bacteria
per cubic centimeter and bacterial "quantity units" (bacteria per cubic centimeter
^discharge in thousands of second-feet) arranged as monthly means for all
sampling stations—Continued
JULY, 1927
Station
1
2 .. _
3
Minnesota KIVPI
5
6
7
St. Croix River
Cannon F.ivei . . -
9
Aver-
age
dis-
charge
tec-
ond)
feet
5, .590
5,590
5, 610
1.450
7,090
7,110
7,120
4,650
212
12, 000
Total
days
sam-
ples
taken
12
12
12
12
12
12
12
12
11
11
Water
tem-
pera-
ture,
° C.
22 4
22 4
22 9
22 7
22 8
22 8
23.9
24 2
22 0
22 9
Bacteria per cubic
centimeter
On agar at —
20° C.
48 hours
2.500
3,100
160, 000
4,500
68.000
90,000
200, 000
2,600
3,900
27, 500
37° C.
24 hours
850
950
180, 000
2,200
50. 000
59, 000
130, 000
950
1.000
17, 000
B coli
(esti-
mated)
6
15
2,800
20
618
625
288
.3
4
26
Quantity units
Bactena per cubic centimeter X
thousand second-feet
20° C.
agar
13,975
17, 329
897. 600
6,525
482,120
639, 900
1, 424, 000
12,090
827
330,000
37° C.
agar
4,752
5,311
1, 009, 800
3,190
354, 500
419. 490
925, 600
4,418
212
204,000
B. coli
34
84-
15, 70S
29
4, 382
4,051
2,444
1
1
312
AUGUST, 1927
1 - -
2
3
Minnesota River
5 . .
6
7
St. Croix River
9
5, 100
5 100
5 090
369
5,440
5 440
5,450
2,470
46
7,890
18
18
13
18
18
18
11
11
11
10
19.9
19 9
20.3
20 6
20.7
20.6
22 2
22.7
21 7
22 3
2.700
3 300
210 000
4,700
93, 000
110 000
170,000
12, 000
4 100
27, 500
850
900
200 000
2,400
80,000
91 000
150 000
3,600
900
13,000
5
17
1,695
22
1,050
70
229
.3
3
9
13. 770
16 830
1 068 900
1,734
505. 920
598 400
926, 500
29,640
189
219, 450
4 335
4 590
1 018 000
886
435, 200
495 040
817 500
8,892
41
103 740
25
87
S, 628
»
5,712
3,808
1,248
1
0
72
-------
88 POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
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-------
BACTERIOLOGICAL STUDIES
89
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-------
90
POLLUTION AND PURIFICATION OF TIPPER MISSISSIPPI KIVER
BACTERIAL POLLUTION OF THE UPPER MISSISSIPPI RIVER
A broad picture of the bacterial pollution of the upper Mississippi
River, as indicated by the bacterial-plate counts at 20° and 37° C.
and the B. coli estimates, is presented in Table 35, which shows the
yearly average concentration of bacteria per cubic centimeter during
the 12-month period July, 1926, to June, 1927, inclusive, at each
sampling station on the main river and at the mouths of tributaries.
TABLE 35.'—Summary of average yearly numbers of bacteria per cubic centimeter
at sampling stations on the upper Mississippi River during 13-month period,
July, 19%6, to June, 1927, inclusive
MAIN RIVER SAMPLING STATIONS
Sampling station and location
1. Camden Avenue Bridge, Minneapolis
2. Plymouth Avenue Bridge, Minneapolis
3. Government lock and dam. . __
5. Roberts Street Bridge, St. Paul
6. Invergrove Bridge
9. Above Red Win?
11. Outlet Lake Pepin
Average
discharge
(thou-
sand
second-
feet)
6.65
6.66
6.69
10.03
10.06
10.11
16. 50
16.70
29.40
Average yearly bacteria per
cubic centimeter
20° C.
agar
count
2,300
3,900
181, 000
135,000
147, 000
264, 000
36,000
4,400
49,000
37° C.
agar
count
700
1,800
192, 000
107, 000
113, 000
223,000
17,000
3,100
42,000
B. coli
(esti-
mated)
11
62
1,089
1,252
1,025
1,467
63
1
33
TRIBUTARY SAMPLING STATIONS
8 St Croix River at mouth
10. Cannon River at mouth. _
12. Chippewa River at mouth.
13. Zumbro River at mouth
3.26
5 82
.45
11 80
.46
5,200
13 000
7,200
7,300
3,000
8 000
3,500
4,500
13
38
10
21
Yearly averages show that the bacterial concentration of the
tributaries was as low or lower than the bacterial concentration of the
main stream at their respective points of confluence, and, in general,
the effect of tributary inflow was that of dilution. The St. Croix
and Chippewa Rivers, entering from Wisconsin, contributed much
larger quantities of diluting water than the Minnesota, Cannon, and
Zumbro Rivers, entering from the Minnesota section of the watershed.
At the main river sampling stations the yearly averages show three
zones within the section of the river under observation in which bac-
terial variations occurred. Between Stations Nos. 1 and 7, a distance
of 45 miles, the bacterial concentrations showed a progressive increase
due to the discharge of sewage and industrial wastes from the Twin
City metropolitan area. From Station No. 7, at Hastings, to Station
No. 11, at the outlet of Lake Pepin, a distance of 50 miles, in which
the stream received but little additional pollution, there was a marked
reduction in bacterial concentration due to the diluting effect of
-------
BACTERIOLOGICAL STUDIES 91
tributaries and to natural processes of stream purification which oper-
ated during the relatively long period of flow between these points.
In the 42 miles of river between the outlet of Lake Pepin and Winona,
Station No. 14, in which relatively little additional sewage pollution
reached the river, a further reduction in bacterial concentration was
to be expected. Contrary to expectation, however, a considerable
increase in bacterial concentration was noted at the lower sampling
station.
SEASONAL CHANGES IN BACTERIAL CONCENTRATION
Seasonal averages of bacterial concentration have been summarized
in Table 36 for each of the sampling stations on the main river and
its tributaries.
-------
92
POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
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Sampling station and location
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Sammer average, 1926, Stations Nos
Summer average, 1920, Stations Nos
Fall average at all stations based on
Winter average at all stations based
Spring average at all stations based
Summer average, 1927, Stations Nos
Summer average, 1927. Stations No?
-------
BACTERIOLOGICAL STUDIES 93-
Seasonal averages show the same increases in bacterial concentra-
tion in the upper section of the river, but the point of maximum
'pollution occurred at different sampling points between Stations
Nos. 3 and 7. The decrease in bacterial concentration was indicated
in every season between Stations Nos. 7 and 11, as was also the
secondary increase in the lower section of the river, between Stations
Nos. 11 and 14. The greatest increase in bacteria below Lake Pepin
occurred during the winter and the summer period of 1926, when
stream flows were the lowest.
Between Stations Nos. 3 and 7 the Mississippi River received the
inflow of the Minnesota River at a point 2.4 miles below Station
No. 3. The Minnesota River was less heavily polluted than the
main river and tended to reduce the bacterial concentration of the
Mississippi River below its confluence. Because of the manipula-
tion of the storage reservoirs on the headwaters of the main stream,
for navigation purposes below the Twin Cities, the mean monthly
discharge of the Mississippi River, at Minneapolis, varied from three
to seven times that of the Minnesota River. At such times the
effect of the Minnesota River in reducing the bacterial concentration
of the main stream below its confluence was not great. In the
summer months, however, the apparent effect of the Minnesota
River was accentuated by that of natural purification taking place
between Stations Nos. 3 and 5, a distance of 9 miles. The combina-
tion of dilution and natural purification is believed to influence, to a
considerable extent, the change in the location of the point of maxi-
mum bacterial concentration in the upper section of the stream.
In the summer period of 1926 the mean discharge of the Missis-
sippi River was practically the same as that during the winter period
of 1926-27. In the winter months the water temperatures were con-
tinuously at 0° C., a large portion of the water surface was covered
with ice, and surface run-off from the watershed was reduced to a
minimum. In the summer period water temperatures were above
20° C.; water surfaces were exposed, allowing reaeration; and surface
run-off entered the water courses. The seasonal averages for these
two periods show a much lower bacterial concentration at all stations
during the winter, with the point of greatest pollution occurring either
at Station No. 5 or Station No. 6, rather than at Hastings, Station
No. 7.
During the fall period and the summer period of 1927, which more
nearly represents normal summer conditions, the point of maximum
bacterial concentration occurred at Station No. 3, the outlet of the
pool at Minneapolis, followed by a decrease in concentration below
this station and a secondary rise at Station No. 7, Hastings.
-------
94 POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
QUANTITATIVE CHANGES IN BACTERIA
A study of the monthly and seasonal changes in the actual number
of bacteria in a stream furnishes a better basis for comparison than *
the changes in bacterial concentration. In Tables 32 and 33 the
bacterial concentrations at the various sampling stations have been
expressed in terms of quantity units. As already stated, the quan-
tity unit is the product of the number of bacteria per cubic centimeter
as indicated by the plate counts and B. coli estimates and the stream
flow in thousands of second-feet. The quantity unit is proportional
to the actual number of bacteria carried past a given section in the
river during a given period of time and is more convenient to use
than the estimated actual number of organisms present in the stream.
Table 34 summarizes the data of Tables 32 and 33 as seasonal and
yearly averages of the quantity units of bacteria at the various
sampling stations.
Yearly averages of quantity units show the progressive increase in
numbers of bacteria within the zone of pollution between Stations
Nos. 1 and 7; the decrease in numbers from Station No. 7 to Station
No. 11, the outlet of Lake Pepin; and the secondary increase in bac-
teria in the lower section of the river, between Stations Nos. 11 and
14. The smaller number of bacteria contributed by the tributaries,
as compared to those present in the main stream at their points of
confluence, is clearly indicated.
Seasonal averages of quantity units show the same increases in
numbers of bacteria in the upper and lower sections of the river and
the decrease in bacteria within the intermediate zone. During the
winter period, of lowest water temperatures and surface run-off, the
numbers of bacteria present at each sampling point were lower than
in any other season of the year. In general, the greatest numbers of
20° C. organisms in the stream occurred in the spring months of
highest stream flow, when surface run-off was greatest; the largest
numbers of 37° C. organisms in the summer and fall months of 1926,
when stream flows were the lowest; and the greatest number of B. coli
organisms in the spring and fall months.
The table of monthly averages of quantity units indicates greater
numbers of bacteria at Station No. 14, above Winona, than at Station
No. 11, the outlet of Lake Pepin, during every month of the investi-
gation. For a period of six months during the study, comprising the
months of July to November, 1926, inclusive, and the month of June,
1927, complete data were available at the two lower main river sam-
pling stations, Nos. 11 and 14, and at Stations Nos. 12 and 13, on the
Chippewa and Zumbro Rivers, respectively, which enter this section
of the main stream. Of these six months, an increase in quantity
units of bacteria was indicated during July, August, and November,
-------
BACTERIOLOGICAL STUDIES 95
'1926, and in June, 1927. A decrease in quantity units between Sta-
tions Nos. 11 and 14 was indicated in September and October, 1926.
.The greatest increase at Station No. 14, amounting to from 10 to 20
times the quantity units at Station No. 11, occurred in July and Au-
gust, 1926, when the flow in the main stream was only 4,800 and 5,500
second-feet, respectively, and when the inflow of the Chippewa River
was 3,600 and 9,500 second-feet, respectively; or from 75 to over 100'
per cent of that of the main river. During September and October,
when stream flows increased, those in the main channel averaging
14,100 and 16,700 second-feet, respectively, and those in the Chippewa
River 23,400 and 12,600 second-feet, respectively, tributary inflow
again amounting to from 75 to over 100 per cent of the flow in the
main channel, a decrease in quantity units of bacteria at Station No.
14 resulted. In November, stream discharges again decreased; the
flow in the main stream averaged 9,900 second-feet. During this
month another increase in quantity units of bacteria occurred at
Station No. 14, but of lesser magnitude than during July and August.
In June, 1927, main-river flows reached an average of 24,700 second-
feet, but the Chippewa River contributed only 7,500 second-feet, or
about 30 per cent of that of the main river. In this month there was
an increase in the 20° C. and B. coli organisms at Station No. 14,
but a decrease in the 37° C. organisms.
In the months of September and October, when the decrease in
organisms at the lower station was indicated, the sum of the quantity
units of bacteria contributed by the Chippewa and Zumbro Rivers
added to those present at Station No. 11 was greater than the quan-
tity units present at Station No. 14, but the actual decrease in quan-
tity units at the lower station was much less than would be expected
as a result of natural purification processes taking place in the 42
miles of river between Lake Pepin and Winona. As noted in the
discussion of the chemical results, there was also an increase in the
oxygen demand of the river in the lower section between these same
sampling points during every month of observation, which could not
be accounted for by additional pollution reaching the main stream
directly or contributed by the tributaries.
During the course of the Illinois River survey, a similar increase-
in bacteria, not accounted for by additional pollution, was observed
in the main stream below the confluence of the Kankakee River.
The greatest increase in bacteria was observed when the inflow of the
Kankakee River amounted to 10 per cent or more than the flow in.
the main stream. A study of the changes in numbers of bacteria in
stored water samples conducted at the Cincinnati laboratory of the
Public Health Service also gave evidence, in some cases at least, that
if a sample of water reaching a state of bacterial stability was sub-
-------
96 POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVEK
sequently diluted, a further increase in numbers of bacteria might*
occur. During the course of stream-pollution investigations it has
repeatedly been observed that the maximum bacterial effect of the „
sewage entering a stream was not immediately below the sewer out-
lets but at a considerable distance downstream, suggesting that dilu-
tion may be one of the factors influencing changes in bacterial numbers.
One seems forced to the conclusion that under certain conditions it
may be possible, in the absence of additional pollution, to have actual
measurable increases in bacteria between points on a stream due to
an altered relationship between inhibitive or destructive forces and
growth factors.
RELATION OF BACTERIAL POLLUTION TO THE CONTRIBUTING SEWERED
POPULATION
The effect of the bacterial pollution of a stream should be reflected
in the increase in bacteria between sampling points above and below
the sources of pollution. Such an estimate, however, does not take
into consideration any indeterminate increase in bacteria which may
have taken place in the stream, nor any reduction in the number of
bacteria from destructive substances which might reach the stream,
or from processes of natural stream purification. The total change
in bacterial numbers divided by the contributing population above
the point of maximum bacterial pollution should be a measure of the
per capita contribution of bacteria to the river and provide a means
of comparing the intensity of bacterial pollution in various sections
of the same stream or in different streams.
On the upper Mississippi Kiver the difference between the quantity
units of bacteria at the point of maximum bacterial concentration
below the metropolitan area and the sum of the quantity units of
bacteria present at Station No. 1 above all local sources of pollution
and the quantity units contributed by the Minnesota Kiver should
indicate the increase in bacteria in the river due to the pollution from
the Twin City metropolitan area.
Table 37 summarizes the seasonal increases in bacteria in terms of
total bacterial quantity units within the metropolitan area, calculated
from those present at the point of maximum bacterial content and
those present at Stations Nos. 1 and 4. In Table 38 the seasonal
changes in total bacterial quantity units from Table 34 have been
converted into the estimated actual daily per capita contribution
of bacteria, due to the sewered population above the indicated point
of greatest pollution.
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BACTERIOLOGICAL STUDIES
97
. TABLE 37.—Bacterial pollution of the upper Mississippi River, in terms of quantity
units, contributed by the sewered population of the Minneapolis and St. Paul
metropolitan area
Season
Summer. 1926 .--
Fall
Winter
Spring. ._ . -.
Summer 1927
20° C. agar count
Maximum
quantity
units
2, 741, 530
1, 444, 380
233, 580
2, 080, 030
1, 200, 820
Occur
at sta-
tion
No.
7
7
5
7
37° C. agar count
Maximum
quantity
units
2,616,110
1, 503, 840
224, 740
734, 670
1, 100, 380
Occur
at sta-
tion
No.
7
3
5
3
3
B. coli organisms
Maximum
quantity
units
17,520
13,258
5,683
13, 551
11, 608
Occur
at sta-
tion
No.
7
5
6
6
3
TABLE 38.-—Bacterial pollution of the upper Mississippi River, expressed as quan-
tity units per capita per day, contributed by the sewered population of the Minne-
apolis and St. Paul metropolitan area
Season
Summer, 1926
Fall
Winter
Summer, 1927
20° C. agar count
Quantity
units
per
capita
per day
4.02
2.12
39
3 05
1 76
Above
station
No.
7
7
5
7
37° C. agar count
Quantity
units
per
capita
per day
3.83
3.40
38
1.60
1.39
Above
station
No.
7
3
5
3
3
B. coli organisms
Quantity
units
per
capita
per day
0.026
.022
008
.020
.025
Above
station
No.
7
5
6
6
3
The data of Table 38 indicate that the lowest daily per capita
contribution of bacteria to the upper Mississippi River occurred
during the winter period. The contribution of B. coli organisms
was quite consistent during the remaining periods of the year, with
a tendency to be slightly higher in the summer months. The greatest
per capita contribution of 20° and 37° C. organisms occurred in the
summer period of 1926; the lowest in the summer of 1927; with con-
tributions in the spring and fall lying between these extremes.
COMPARISON OF BACTERIAL POLLUTION FROM DIFFERENT METROPOLITAN
AREAS
Table 39 gives, for comparison with the upper Mississippi River
data, estimates of the actual average daily per capita contribution
of bacteria during the summer and winter periods from metropol-
itan areas on the Ohio and Illinois Rivers.
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98
POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
TABLE 39.—Seasonal changes in numbers of bacteria added to streams by sewered •
populations
Community
Minneapolis-St. Paul:
1926 ---
1927
Pittsburgh .. .
Wheeling
Billions of bacteria per capita per diem
Gelatin 20° C.
Winter
9,740
2,130
2,560
7,380
'570
382
Summer
24, 750
15,800
14,100
13,600
1 6, 710
' 2, 938
108
505
Agar37° C.
Winter
1,920
7,650
1,000
907
550
170
Summer
25,400
25,600
18, 300
15,800
6,400
2,690
160
495
B. coh
Winter
39
141
119
193
14
32
Summer
433
231
583
291
43
28
4
24
1 Counts on agar at 20° C., 48 hours, not comparable to gelatin counts.
Variations in the calculated per capita contribution of bacteria
from a sewered population are influenced to a considerable extent by
the amount and character of the industrial wastes reaching the
sewers or watercourse; those having a high bacterial content tending
to increase the number, while wastes germicidal in character cause a
decrease in numbers. Variations also result from the nature and
amount of surface run-off reaching the stream, either directly or
through the sewers; the period of detention within the sewer system,
minor tributaries or the main stream; the physical and biological
condition of the receiving stream; and the relation of the various
sampling points to the location of the sewer outlets. Accurate
measurements of the bacterial content of the river are only possible
when the sewage is discharged into a comparatively narrow zone and
when sampling stations are so spaced along the stream to give the
actual maximum bacteria at all the stations.
The data of Table 39 indicate a much smaller contribution of
bacteria in the winter months as compared to the summer months.
It further indicates that the contribution of bacteria to the upper
Mississippi River, below the Twin City metropolitan area, was less
than the contribution from any of the other metropolitan areas so far
studied, with the exception of the contributions from the Pittsburgh
and Wheeling areas. Within the Pittsburgh area the bacteria con-
tributed to the Ohio River were materially reduced by the presence of
acid iron wastes, causing coagulation and precipitation in the stream
through Pittsburgh. In addition the operation of the navigation
dams below Pittsburgh and Wheeling during periods of low water
increased the times of flow from the sewer outlets to the sampling
points, allowing natural stream-purification processes to take place,
tending toward a reduction in the bacteria contributed by the sewered
population.
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BACTERIOLOGICAL STUDIES 99
Estimates of the average daily per capita contribution of bacteria
within the Twin City metropolitan area are influenced by the pool at
Minneapolis, which increased times of flow and permitted sedimenta-
tion of sewage sludge which caused septic conditions in the pool during
summer; by the discharge of sewage from a large number of outlets
throughout the entire metropolitan area; by the inflow of the Min-
nesota River and by variations in times of flow from the sewer outlets
to the sampling stations below the district. These factors combine to
give an indicated lower per capita bacterial contribution on the upper
Mississippi River than the contributions indicated from some of the
other metropolitan areas, but are not entirely outside the range of '
previous observation and emphasize the fact that different local
conditions may greatly affect the results.
RATES OF BACTERIAL PURIFICATION
Methods of making calculations
In previous studies of the rates of natural stream purification,
which were made from the data secured during the Ohio and Illinois
River investigations, the bacterial decreases in these watercourses
could be described with fair accuracy by relatively smooth curves,
showing the relation between the bacteria remaining in the water at
sampling stations below the points of maximum bacterial concentra-
tion and the time of flow to these stations.
The tables which have been exhibited in the present report show
similar decreases in bacteria in the upper Mississippi River as the
water flows away from the zone of maximum pollution, and they also
have indicated variations in the bacterial decreases during different
seasons of the year. As has been previously noted, the character of
the channel of the upper Mississippi River, the location of sampling
stations, and the data from which to make time of flow estimates were
such that studies of rates of bacterial decrease comparable in signifi-
cance to those made in the Ohio and Illinois Rivers could not be
undertaken. The river section between Hastings, Station No. 7,
and Station No. 11, the outlet of Lake Pepin, did, however, provide
an opportunity to observe rates of bacterial decrease taking place
below the Twin City metropolitan area, and made possible limited
comparisons between the rates observed in the upper Mississippi
River with similar observations in the Ohio and Illinois Rivers.
Table 40 summarizes for the winter and summer periods the
quantity units of bacteria at main-river sampling stations from
Hastings, Station No. 7, to the outlet of Lake Pepin, Station No. 11,
and at the sampling stations at the mouths of tributaries entering this
section of the river. The table also shows the location of the sewered
communities on the river below Station No. 7 and the point of entrance
129540—32 8
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100 POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVEE
of the larger tributaries, together with the estimated times of flow
from Station No. 7 to points downstream during the summer and
winter periods.
TABLE 40.—Bacterial pollution of the upper Mississippi River at Hastings, Minn.,
Station No. 7, with estimates of the pollution contributed below Hastings by sewered
communities and tributary inflow, in terms of quantity units
AVERAGE SUMMER CONDITIONS
Sampling stations on main stream with inter-
vening tributary rivers and sewered cities
(1) Sampling Station No. 7 . _
(2) City of Hastings (2,200). ...
(3) St Croix River
(4) Cannon River
(5) Sampling Station No. 9 _ . . .
(6) Red Wing (10,400)
(7) Sampling Station No 11
Distance
from
Station
No. 7,
miles
0
.2
2.4
21.1
23.3
23 5
50.1
Time of
flow
from
Station
No. 7,
hours
0
.3
4 1
24.8
26 8
27.2
1, 260. 0
Quantity units of bacteria
Agar 20° C.
1,963,000
'6,300
69, 300
930
284,000
1 29, 700
73,400
Agar 37° C.
1, 746, 000
15,600
45,000
600
185, 900
i 26, 600
64,000
B. coli
9,590
130
238
1
476
1 146
10
AVERAGE WINTER CONDITIONS
(1) Sampling Station No. 7 _ ..
<2) City of Hastings (2,200)
(3) St Croix River. ...
(4) Cannon River
(5) Sampling Station No 9
(6) Red Wing (10,400) ._
<7) Sampling Station No. 11
0
2
2.4
21 1
23 3
23 5
50.1
0
4
46
26 6
28 8
29 1
1, 120 0
218, 950
1 704
2,900
690
179 100
1 3, 330
3,530
113, 260
1 836
690
140
51 290
1 3 950
460
1,534
1 18
11
1
192
1 87
2
i Calculated on the assumption that the per capita contribution of bacteria is the same as observed for
Minneapolis and St. Paul.
Summer average based on months of July and August, 1926 and 1927.
Winter average based on months of December, 1926, January and February, 1927.
The estimates of bacterial quantity units and times of flow for the
summer period in Table 40 are averages for the months of July and
August, 1926 and 1927, while the winter period is based on averages
for the months of December, 1926, and January and February, 1927.
In these particular months, bacteriological data were complete at all
of the sampling stations and stream flows were such that times of
flow could be estimated with a reasonable degree of accuracy. The
quantity units of bacteria contributed by the sewered communities
on the river below Station No. 7, as indicated in Table 40, have been
calculated by assuming that in these communities the per capita con-
tribution of bacteria from the sewered population was the same as
observed from Minneapolis and St. Paul. While such an estimate
was exceedingly crude, the attempted correction was of little signifi-
cance, since the total contribution of bacteria by these sewered com-
munities was usually only a fraction of the bacteria carried by the
receiving water.
In estimating the rates of bacterial decrease in sections of the
river where pollution was contributed to the main stream by the
entrance of tributaries or was added from sewered communities the
-------
BACTERIOLOGICAL STUDIES
101
following assumptions were made: (a) Inasmuch as the bacterial
content of the main stream tended to diminish as the water passed
downstream, the pollution, brought in by a tributary or added by the
sewers of a community, was assumed to decrease with the down-
stream flow and at the same rate as the decrease which occurred at the
stations on the main river between which the added pollution entered;
and (b) that the pollution added between stations on the main river
entered immediately below the nearest sampling point.
The detailed method of calculating the rates of bacterial decrease
is best illustrated by the actual computation, Table 41, of the decrease
which took place in the Mississippi River below Station No. 7 during
the winter period, using the bacterial quantity units derived from the
agar-plate counts at 37° C.
TABLE 41.—Calculation of the percentage of bacteria remaining in the upper Mis-
sissippi River at sampling stations 'below Hastings, Minn., Station No. 7, during
the lointer period of ice cover, based on the 37° C. agarplate counts
Station
St.ition No. 7:
\dded bs" Hastings - .-
Added by St. Croix River . -. - ~
Station No. 9. &
Remaining from Station No. 7 - .
Added bv Cannon River __ - - - .-.
^tation No. 11:
Remaining from Station No. 7
Quantity
units
113, 260
836
690
114, 786
51, 150
50, 485
358
307
140
3,950
M, 240
460
420
3
3
1
33
Per cent
of total
quantity
units
98.7
.7
.6
100.0
91.4
.6
.6
.3
7.1
100.0
91.4
.6
.6
.3
7.1
Per cent
remain-
ing from
Station
No. 7
100.0
44.5
.37
Time of
flow,
hours,
below
Station
No. 7
0
28.8
1, 120. 0
Estimates of times of flow and calculations of bacterial decreases,
expressed as the percentage of bacteria remaining in the water at
sampling points below Station No. 7, with corrections for tributary
inflow and contributions by sewered communities, have been made
from the other bacteriological findings during the summer and winter
periods and are summarized in Table 42, the data of which are shown
graphically in Figure 9.
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102 POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVEK
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BACTEEIOLOGICAL STUDIES
103
TABLE 42.—Bacteria remaining at sampling stations on the upper Mississippi
River below Hastings, Minn., Station No. 7, corrected for tributary inflow and
cities, expressed in percentages of the maximum with times of flow below this
maximum
AVERAGE SUMMER CONDITIONS
ximpjing station
-
,(
i: ... . -
Time of
flow in
hours
below
Station
No. 7
0
26.8
1, 260. 0
20° C. agar—
Per cent of
maximum
remaining,
corrected for
additions by
tributaries
and cities
100 0
14.0
3 2
Time of
flow in
hours
below
Station
No. 7
0
26 8
1, 260. 0
37° C. agar—
Per cent of
maximum
remaining,
corrected for
additions by
tributaries
and cities
100.0
10.4
3.1
Time of
flow in
hours
below
Station
No. 7
0
26.8
1, 260. 0
B. coli— Per
cent of maxi-
mum re-
maining,
corrected for
additions by
tributaries
and cities
100 0
4.9
.07
AVERAGE WINTER CONDITIONS
_
9
11
0
28 8
1,120.0
100 0
80 6
1.6
0
28.8
1, 120. 0
100 0
44.5
.37
0
28.8
1, 120. 0
100 0
12 2
.0
Summer average based on the months of July and August, 1926 and 1927.
Winter average based on the months of December, 1926, January and February, 1927.
COMPARISON BETWEEN SUMMER AND WINTER RATES OF BACTERIAL
PURIFICATION IN THE UPPER MISSISSIPPI RIVER
Table 42 and Figure 9 indicate that the summer rates of disap-
pearance of the organisms growing on agar at 20° and 37° C. were
practically the same and that the rate of disappearance of the B. coli
organisms was considerably grea ter than the rate of disappearance of
the 20° and 37° C. organisms. In the winter period organisms of the
B. coli group disappear from the stream at a faster rate than the
37° C. agar organisms, which in turn showed a higher rate of disap-
pearance than the 20° C. organisms. The table and figure further
indicate considerable differences in the rates of bacterial disappearance
in the stream during the summer and winter periods, when the times
of flow in the river were substantially the same. Under average sum-
mer conditions only 14 per cent of the 20° C. organisms which were
present in the water at Station No. 7 remained at Station No. 9 after
approximately 27 hours' flow. In the winter period the mean time of
flow between the same stations was practically the same, 29 hours,
but in this period 81 per cent of the 20° C. organisms present in the
water at Station No. 7 still remained at Station No. 9.
Of the organisms growing at 37° C. and organisms of the B. coli
group which were present at Station No. 7 in the summer period only
10 and 5 per cent, respectively, remained at Station No. 9 after 27
hours' flow. During the winter months, with approximately the
same time of flow between the same points on the river, 45 per cent
of the 37° C. organisms and 12 per cent of the B. coli organisms re-
mained in the water at Station No. 9. The data indicate, therefore,
that in the section of the river between Stations Nos. 7 and 9 the sum-
-------
104 POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVEK
mer rate of disappearance of the 20° C., 37° C., and B. coli organisms
was about 4.3,1.6, and 1.1 times, respectively, the rate of disappearance
in the winter period.
Lake Pepin, in which the average time of flow in both the summer
and winter periods was in excess of 1,000 hours, is located between
Stations Nos. 9 and 11. A still further reduction in bacteria occurred
between these points. The data for this section of the stream appear
to indicate that the winter rate of disappearance of bacteria was
greater than the summer rate, the disappearance of the 20° C., 37° C.,
and B. coli in Avinter being about 7.3, 6.0, and 2.4 times the rate in
summer. However, in the absence of data from additional sampling
stations within the lake itself, it seems reasonable to suppose that a
state of bacterial stability may have been reached in Lake Pepin
during a period of flow considerably less than that indicated by the
time of flow through the entire lake as given in Table No. 42. The
reductions in bacteria as determined at the outlet of the lake indicate
that in summer only 3 per cent or less of the organisms present at
Station No. 7 were still present in the water at the outlet of Lake
Pepin, while in winter the residual bacteria from Station No. 7 were
only 1 % per cent or less.
COMPARISON BETWEEN RATES OF BACTERIAL PURIFICATION IN THE
OHIO, ILLINOIS, AND UPPER MISSISSIPPI RIVERS
Figures 10 and 11 give curves showing a comparison between the
summer and winter rates of bacterial purification in the Ohio, Illinois,
and upper Mississippi Rivers. Curves for the Ohio River show the
indicated decrease in bacteria in the 123 miles of river, from the point
of maximum bacterial concentration below Cincinnati, Ohio, to Louis-
ville, Ky. The Illinois River curves include a section in the upper
portion of the river, 126 miles long, between Lockport and Peoria,
and a section in the lower portion of the stream, 160 miles long, from
Peoria to Kampsville. The data for the upper Mississippi River are
for the 50 miles of river between Hastings, Station No. 7, and the
outlet of Lake Pepin, Station No. 11. Data for the Ohio and Illinois
Rivers were obtained from river sections in which velocities of flow
were comparatively high, while the Mississippi River section includes
Lake Pepin, in which velocities of flow are extremely low, particularly
in the winter and summer periods to which the curves apply. The
data of the Mississippi River are therefore not entirely comparable
to those from the other two rivers.
Rates of purification in Figures 10 and 11 are expressed in terms
of the percentage of bacteria remaining below the point of maximum
bacterial concentration on the Ohio and Illinois Rivers and below
Station No. 7 on the Mississippi River, which is usually the point of
-------
BACTERIOLOGICAL STUDIES
105
s «
£ i
fe
-------
106 POLLUTION AND PUBLICATION OF UPPEK MISSISSIPPI KIVEE
1
kl
11
«.
§
-s-
20'Ca
~
V)
c;
I
Ij
5
1
1
.1
-------
BACTERIOLOGICAL STUDIES 107
maximum pollution, and the corresponding times of flow below the
points of highest pollution.
While the data for the upper Mississippi River are extremely lim-
ited, they do however appear to indicate, as shown in Figure 10, that
the summer rates of bacterial disappearance in the more rapidly mov-
ing section of the river, between Station No. 7 and the inlet to Lake-
Pepin, are in general comparable with the rates observed in the
Ohio and Illinois Rivers.
The summer rate of bacterial disappearance in the upper Missis-
sippi River during the first 30 hours of flow appears to follow some-
what more closely the rates of disappearance in the Illinois rather
than those in the Ohio River. After about 30 hours' flow there is a
marked flattening of the 20° and 37° C. curves for the upper Missis-
sippi River, indicating much lower rates of purification than those
observed in the Ohio and Illinois Rivers. The lower portion of the
Mississippi River curve is based on times of flow through Lake Pepin,
which are extremely uncertain. Had a condition of bacterial stabil-
ity been reached within the lake at any considerable distance above
the outlet, the time factor would have been reduced, and the Missis-
sippi River curves would then approach more closely those of the
Ohio and Illinois Rivers during the later stages of purification. The
flattening of the lower part of the Mississippi River curve of B. coli
disappearance is less marked than in the curves for the agar counts,
indicating rates of B. coli disappearance in the lake more nearly
comparable to those in the Ohio and Illinois Rivers but somewhat
greater than those observed in the lower Illinois River.
Winter curves of bacterial purification, given in Figure 11, show
quite consistent rates of B. coli disappearance in the three river
sections, the indicated rate in the upper section of the Mississippi
River being somewhat higher than in the other rivers. In the winter
period, during the first 20 hours of flow, rates of decrease of the 20° C.
organisms were less in the upper Mississippi River than in the other
river sections. After about 20 hours' flow the rates in the upper
Illinois and Ohio Rivers greatly exceeded the indicated rate in the
upper Mississippi River, which in turn showed a higher rate of reduc-
tion in 20° C. organisms than that observed in the lower Illinois
River. The winter rate of disappearance of the 37° C. organisms was
greatest in the upper Illinois River. During the first 30 hours' flow,
below the point of maximum pollution, the rates of disappearance of
37° C. organisms in the lower Illinois, Ohio, and Mississippi Rivers
were quite consistent. After 30 hours' flow the rates of reduction in
the Ohio and Mississippi Rivers were more nearly comparable and
were greater than the rate in the lower Illinois River.
In the preceding comparisons, defining average rates of bacterial
purification in the Ohio, Illinois, and Mississippi Rivers, the curves
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108 POLLUTION AND PURIFICATION OF UPPER MISSISSIPPI RIVER
were started, in each instance, from the point of maximum bacterial
concentration, no account being taken of the initial numbers of bac-
teria present at the upper station of the river section. In the three •
rivers studied, the greatest bacterial concentration occurred in the
upper Illinois River, and, in the order of decreasing bacterial pollu-
tion, followed the Mississippi, lower Illinois, and Ohio Rivers. Table
43 shows the variation in the average initial number of bacteria per
cubic centimeter at the points of greatest pollution in the Ohio, Illinois,
and Mississippi Rivers in the summer and winter seasons.
TABLE 43.—Comparison between the initial numbers of bacteria, per cubic centi-
meter, in the Ohio, Illinois, and upper Mississippi Rivers during the summer and
winter periods
Kiver
Initial number ot bac-
teria per cubic centi
meter
Summer
period
Winter
period
20° C. COUNT ON AGAR OB GELATIN
Upper Illinois River
Lower Illinois River .. - - _
Ohio River
3, 310, 000
605 000
281,000
84,400
751,000
71 800
29,000
28 600
37° C. AGAR COUNT
Lower Illinois River.
Ohio River - -
3, 420, 000
558,000
254,000
99,300
142,000
36 700
9,440
8,300
B. COLI
Upper Illinois River - ~ _ - _- .
Ohio River
57, 100
3,430
3,730
2,220
3,030
490
180
121
A further comparison between the rates of bacterial decreases in
the three river systems was attempted by adjusting the coordinates
of the lower Illinois, Ohio, and Mississippi Rivers to those of the
upper Illinois River, so that comparisons could be made between the
rates of bacterial disappearance below points of equal bacterial con-
centration, rather than below the same origin of 100 per cent, repre-
senting the point of maximum pollution in each case. The maximum
concentration of bacteria growing on agar at 37° C., on the upper
Illinois River in summer was 3,420,000 bacteria per cubic centimeter,
while the corresponding concentrations on the Mississippi, lower Illi-
nois, and Ohio Rivers were 558,000, 254,000, and 99,300 bacteria per
cubic centimeter, respectively. The concentrations in the Missis-
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BACTERIOLOGICAL STUDIES 109
sippi, lower Illinois, and Ohio Rivers were therefore 16.3, 7.4, and 2.6
per cent, respectively, of the concentration on the upper Illinois
River, as represented by the 37° C. agar count. Therefore, the 100
per cent point of the Mississippi River curve was moved to the 16.3
per cent point on the upper Illinois River curve and proportionate
changes made on the other points of the Mississippi River curve.
In a similar manner the curves of the lower Illinois and Ohio Rivers
were adjusted to the 7.4 and 2.6 per cent points on the upper Illinois
River curve.
In some instances such an adjustment of the curves indicated
somewhat more comparable rates of bacterial decrease in the sections
of the watercourses studied, showing the varying effect of initial den-
sity on the rate of bacterial purification. In other instances the
divergence in the adjusted curves was more pronounced than when
comparisons were made on the basis of maximum concentration On
the whole the coincidence of the adjusted curves was not particularly
striking and leads one to believe that the degree of bacterial pollu-
tion in these streams could in general be more accurately indicated
by a series of curves having the maximum points at a common origin
with respect to time, and at ordinates corresponding to the bacterial
• density at such maximum.
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SECTION VII
GENERAL SUMMARY
Sewage and industrial wastes discharged from the metropolitan
area of Minneapolis and St. Paul create objectionable conditions in
the upper Mississippi River between Minneapolis and Hastings during
the summer months of low stream flow.
The necessity for sewage treatment to improve conditions in the
river through and below the Twin Cities has previously been discussed
in unpublished preliminary reports to local and State authorities and
in the published reports of the Metropolitan Drainage Commission of
Minneapolis and St. Paul created in 1927 to continue observations
along the river and to formulate plans for collecting and treating the
sewage from this district.
In the present report an attempt has been made to analyze the
various data collected during the investigation from the standpoint
of a study; of the factors involved in processes of natural stream
purification. An extensive analysis of the data has not been possible
due to lack of sufficient information from which to estimate times of
flow in the river, because of the physical characteristics of the river
channel affecting uniform conditions of flow and because of the diffi-
culty in determining rates of purification in Lake Pepin, a large body
of water located a comparatively short distance below the metro-
politan area. The data obtained during the Mississippi River
investigation have, however, indicated conditions not encountered
during previous studies of stream pollution and in some instances
have assisted in interpreting data collected during the earlier
investigations.
The point of maximum pollution in the upper Mississippi River
varies to some extent in the different seasons as a result of dilution by
tributary inflow and natural processes of stream purification, but
usually occurs in the vicinity of Hastings, Minn., about 20 miles by
river below the lower sewer outlets of the metropolitan area. During
the summer and winter periods of decreased stream flow Hastings is
approximately 15 hours' flow below the lowest sources of pollution
from the Twin Cities. Thus the results from the upper Mississippi
River are in agreement with observations of previous studies, the
point of maximum pollution occurring in the Ohio River after a flow
of from 10 to 15 hours below the Cincinnati sewers, and in the Illinois
River after a period of flow varying from 10 to 25 hours below the
sources of pollution.
110
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GENERAL SUMMARY 111
The results of the chemical analyses indicate a decrease in dissolved
•oxygen as sewage and industrial wastes enter the river from the
metropolitan area, and an increase in dissolved oxygen below the
zone of pollution due to tributary inflow and to reaeration. In the
winter months of ice cover, reaeration is retarded, the dissolved oxygen
in the water is lower at all points along the river than in other seasons,
and the point of minimum dissolved oxygen content is found at
points farther downstream. Data for the upper Mississippi River
suggest that critical oxygen conditions in polluted streams having a
long period of ice cover may occur toward the end of winter rather
than in the summer months, and that the effects of pollution may be
noticeable in winter at points considerably farther downstream than
in summer.
The oxygen requirements of the upper Mississippi River, indicated
by the 5-day biochemical oxygen demand, increase, as would be
•expected, with the addition of pollution from the Twin City metro-
politan area and are usually greatest at Hastings, about 20 miles
below the lower sewer outlets. The oxygen requirements of the stream
decrease between Hastings and the outlet of Lake Pepin as the organic
matter in the water is oxidized during the long period of flow within
the lake. In the lower section of the river, from the outlet of Lake
Pepin to Winona, which receives but little additional pollution, a
further reduction in the oxygen requirements of the stream would be
-expected. Contrary to expectation, however, an increase in oxygen
requirements is frequently observed in this section of the river.
Increased oxygen requirements occur when times of flow from sources
of pollution 011 the main river are greatest and when the flow of the
'Chippewa River, which enters below Lake Pepin, is as great or greater
than the flow in the main channel. The data suggest that the indi-
•cated increases are due either to the relatively fresh pollution in the
tributary which reaches the transitional period between the first and
second stages of oxidation at the lower station or to changes in the
biological balance of the stream after the industrial waste-polluted
water of the Chippewa River mixes with the water of the main stream.
The oxygen balance in the main river, as represented by the ratio of
the dissolved oxygen to the oxygen demand at various points along
the river, shows a progressive decrease through the metropolitan
area as far downstream as Hastings, due to the added pollution.
In periods of open water the balance begins to increase below Hastings;
but during the season of ice cover when reaeration is retarded,
recovery in oxygen balance begins at points considerably farther
downstream. Below Lake Pepin a secondary decrease in oxygen
balance is indicated, due to the increased oxygen requirements at the
lower station. Changes in the relation between the dissolved oxygen
and the oxygen demand within the pool at Minneapolis during the
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112 POLLUTION AND PURIFICATION OP UPPER MISSISSIPPI RIVEE
summer months show a draft on the oxygen resources of the stream in
excess of that to be expected from the sewered population. Increased
summer drafts result from the sludge accumulated during periods of
low water temperatures, when biological activities are lowest, which
remains to exert its influence in the months of higher water tempera-
tures. The indicated reduction in oxygen balance in the lower
section of the river, in which but little actual sewage pollution is
discharged into the stream, is equivalent to a sewered population
almost as great as that discharging sewage into the pool above the
dam at Minneapolis.
The results of the bacteriological analyses show a progressive
increase in numbers of bacteria from above Minneapolis to Hastings
as increasing amounts of sewage and industrial wastes reach the river.
From Hastings to the outlet of Lake Pepin there is a decrease in
numbers of bacteria, due to the dilution by tributary inflow and to
processes of natural stream purification during the long period of
flow through the lake. In the lower section of the stream, between
the outlet of Lake Pepin and Winona, in which the oxygen demand
increased, there is also at times an unexpected increase in bacteria
not accounted for by additional pollution. An increase in bacteria in
the Illinois River below the Kankakee comparable to that in the
Mississippi River below the Chippewa had previously been observed
during the Illinois River investigation. Laboratory studies have
since indicated the possibility of bacterial increases due to the dis-
turbance of biological conditions as a result of dilution. Increases in
the bacterial content of streams during a considerable time of flow
below the sewer outlets have been consistently indicated in all of the
stream-pollution studies. It does not seem entirely without the
range of possibility that actual measurable increases in bacteria may
occur in a watercourse as a result of changes which influence biological
activities and alter the balance between destructive forces and
growth factors.
The indicated per capita contribution of bacteria from the sewered
population of the Twin City metropolitan area above the point of
maximum pollution on the upper Mississippi River is lower than the
observed per capita contribution of bacteria from metropolitan areas
on the Ohio and Illinois Rivers, with the exception of the contributions
from the Pittsburgh and Wheeling areas on the upper Ohio River.
The lower per capita contribution to the upper Mississippi River,
while not outside the range of previous observations, emphasizes
the fact that local conditions influence results to a considerable
extent. The indicated bacterial purification in the Mississippi
River between the point of maximum bacterial pollution and the
outlet of Lake Pepin varies in the different seasons from 97 to 98.5
per cent during the long period of flow through the lake.
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GENERAL SUMMARY 113
Rates of bacterial decrease were determined in the summer and
winter periods in the upper Mississippi River between Hastings and
, the outlet of Lake Pepin. This river section includes 28 miles of
relatively narrow river channel above Lake Pepin, representing a
time of flow of about 21 hours and 22 miles of lake in which seasonal
times of flow are usually in excess of 1,000 hours. Inaccessibility
of sampling stations along the lake and the difficulty of collecting
representative samples from such a large body of water made the
determination of rates of purification within the lake impracticable.
The rate of disappearance of B. coli organisms between Hastings and
the inlet of Lake Pepin during the summer months is greater than the
rate of disappearance of the 20° and 37° C. agar organisms, which
have rates practically the same. In winter, B. coli is also eliminated
from this section of the river at a rate greater than are the 37° C.
organisms, which in turn have a greater rate of decrease than the
20° C. organisms. A comparison between seasonal rates of bacterial
disappearance indicates that all three types of organisms in the river
above Lake Pepin disappear in summer at rates varying from 1.1 to
4.3 times the winter rates, showing, as in the case of the Ohio and
Illinois Rivers, the effect of seasonal temperatures on rates of natural
stream purification.
Rates of bacterial decrease in the upper Mississippi River are
influenced by conditions in Lake Pepin and are not entirely compa-
rable with the rates of decrease observed in the more rapidly flowing
portions of the Ohio and Illinois Rivers. During a period of about 21
hours' flow in the more swiftly moving section of the river above the
lake rates of bacterial decrease appear to be intermediate between
the rates determined in the upper and lower Illinois River and greater
than the rates observed in the Ohio River. The concentration of
bacteria at the point of maximum bacterial pollution in the upper
Mississippi River is also intermediate between the concentration of
bacteria at the points of greatest pollution in the upper and lower
Illinois River, suggesting that the initial concentration of bacteria
may influence to some extent rates of bacterial disappearance in
streams.
Of special significance in the upper Mississippi River is the effect
of the winter ice cover, which reduces the dissolved oxygen content
of the entire river system, so that critical oxygen conditions are
approached toward the end of the winter period at points further
downstream from the sources of pollution, the reversal of conditions
in the lower section of the river producing an increase in the oxygen
demand and the bacterial concentration in the absence of additional
sewage pollution.
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