J
The most visible evidence of this shortsightedness is the buildup of heavy
algal scums that stain nearshore waters in US. streams and lakes, Lake Michigan included. The algae proliferate by consuming nutrients, including the
phosphates and nitrates man generously supplies. One of the largest sources
of this supply of algal food is in the discharge of secondary sewage treatment
plants. In nature, inorganic nutrients produced by bacteria are intricately bal—
anced by a number of factors. The secondary sewage treatment plant, on the
other hand, releases nutrients in uncontrolled amounts that feed the algae and
consequently produce the condition known as eutrophication that reduces the
water’s dissolved oxygen content.
The visible decline of Lake Michigan due to eutrophication was compared with the condition of Lake Erie by A. F. Bartsch of the Federal Water
Pollution Control Administration (now the Federal Water Quality Ofce) at
the February 1, 1968 session of the Lake Michigan conferences:
Lake Erie at some point in the past. With increasing time, nutrient levels will
increase until finally the entire lake becomes involved. With certain reserva—
tions, Lake Erie can be viewed as & prototype and a preview of what can hap—
pen
in Lake Michigan if nutrient—bearing waste input continues unabated.
Data available since 1968 show that the waste input has indeed con—
tinued. In a series of reports to the Lake Michigan conferences, james C.
Vaughn, Engineer of Water Purication at Chicago’s Department of Water
and Sewers, traced the steady buildup of phosphate concentrations in Lake
Michigan water near the Chicago shoreline and in open water along the 11—
linois shoreline. Four—month average concentrations of phosphates in mixed
offshore and shore water at the Chicago South Water Filtration Plant in—
creased from a 1966 range of .024—.042 to a 1971 range of 061—086 milli—
grams of total phosphates per
liter of water.° In other words, the quarterly
average concentrations rose, with some uctuations, to values in 1971 that
were two to three times those in 1966.
The annual average
for total phosphates in 1969 was .05 mg/l; in 1970,
the average was .06 mg/l, three times the permissible annual average value
set by the Illinois Pollution Control Board. The control board value, an an—
nual average of .02 mg/l of phosphates of water, is considered to be the level
above which excessive algal growth will be likely.
Reports from Mr. Vaughn demonstrate a similar trend in open water. In
1970, annual averages along a 12—mile stretch of water from Çhicago up
to
Waukegan exceeded .09 mg/l of phosphates at four of ten sample points one
to ve miles from shore. These averages, then, were more than four times the
permissible level set by the Illinois Pollution Control Board. In fact, the 1970
average was below that value at only one of the ten test points, and that one
was ve miles offshore. In 1971, the permissible value was exceeded at 20 of
21 sample points.
°Coneentrations of contaminants in water and Public Health standards for permissible concentrations are
usually given in milligrams per liter (mg/1), but are sometimes expressed in parts per million (ppm). Since
pure water weighs one thousand grams per liter, or one million milligrams, one mg/l is comparable to one
ppm.
Problems Accumulote
19
The most visible evidence of this shortsightedness is the buildup of heavy
algal scums that stain nearshore waters in US. streams and lakes, Lake Michigan included. The algae proliferate by consuming nutrients, including the
phosphates and nitrates man generously supplies. One of the largest sources
of this supply of algal food is in the discharge of secondary sewage treatment
plants. In nature, inorganic nutrients produced by bacteria are intricately bal—
anced by a number of factors. The secondary sewage treatment plant, on the
other hand, releases nutrients in uncontrolled amounts that feed the algae and
consequently produce the condition known as eutrophication that reduces the
water’s dissolved oxygen content.
The visible decline of Lake Michigan due to eutrophication was compared with the condition of Lake Erie by A. F. Bartsch of the Federal Water
Pollution Control Administration (now the Federal Water Quality Ofce) at
the February 1, 1968 session of the Lake Michigan conferences:
Lake Erie at some point in the past. With increasing time, nutrient levels will
increase until finally the entire lake becomes involved. With certain reserva—
tions, Lake Erie can be viewed as & prototype and a preview of what can hap—
pen
in Lake Michigan if nutrient—bearing waste input continues unabated.
Data available since 1968 show that the waste input has indeed con—
tinued. In a series of reports to the Lake Michigan conferences, james C.
Vaughn, Engineer of Water Purication at Chicago’s Department of Water
and Sewers, traced the steady buildup of phosphate concentrations in Lake
Michigan water near the Chicago shoreline and in open water along the 11—
linois shoreline. Four—month average concentrations of phosphates in mixed
offshore and shore water at the Chicago South Water Filtration Plant in—
creased from a 1966 range of .024—.042 to a 1971 range of 061—086 milli—
grams of total phosphates per
liter of water.° In other words, the quarterly
average concentrations rose, with some uctuations, to values in 1971 that
were two to three times those in 1966.
The annual average
for total phosphates in 1969 was .05 mg/l; in 1970,
the average was .06 mg/l, three times the permissible annual average value
set by the Illinois Pollution Control Board. The control board value, an an—
nual average of .02 mg/l of phosphates of water, is considered to be the level
above which excessive algal growth will be likely.
Reports from Mr. Vaughn demonstrate a similar trend in open water. In
1970, annual averages along a 12—mile stretch of water from Çhicago up
to
Waukegan exceeded .09 mg/l of phosphates at four of ten sample points one
to ve miles from shore. These averages, then, were more than four times the
permissible level set by the Illinois Pollution Control Board. In fact, the 1970
average was below that value at only one of the ten test points, and that one
was ve miles offshore. In 1971, the permissible value was exceeded at 20 of
21 sample points.
°Coneentrations of contaminants in water and Public Health standards for permissible concentrations are
usually given in milligrams per liter (mg/1), but are sometimes expressed in parts per million (ppm). Since
pure water weighs one thousand grams per liter, or one million milligrams, one mg/l is comparable to one
ppm.
Problems Accumulote
19