_
‘
g
1»
<
—
31
i
,
phate waste, and suggests that the removal of phosphates from detergents
âfï
would decrease the phosphate level from 40 micrograms per liter (ng/l) of
lake water to approximately 20 [Lg/l. Complete removal of phosphates from
5
all sewage would reduce the phosphate concentration level in Lake Erie
to 11.9 pig/l (lower than the 1942 level of 14 png/l) [41].
'
i
The extent to which restrictions on the use of phosphate detergents relieve the inux of phosphate nutrients is illustrated by data supplied to the
Subcommittee on the Environment of the Senate Commerce Committee in
_
October 1971 by Councilman Carl Levin of Detroit. Councilman Levin re—
%
ported on the change in phosphate levels in sewage entering Detroit’s water
…,
-
tereatment facilities after phase I of Detroit’s ban on the sale of detergents
%
»‘
.
containing more than 8.7 percent phosphorus by weight went into effect july
f
_
l, 1971. These gures are listed below:
…
'
Date
Pounds per Day
Ï““.
'
1970
-
;;
July
58,500
August
55,200
‘
'
‘
-
'*
_.
September
_
54,400
‘
1971
,
.
.
july
42,000
,
;,
Ÿ
August
.
'
47,000
…
…
_
:
September
; _.
42,600 ‘
.
It is expected that the changes will be more dramaüc after phase II.of the
phosphate ban begins, when all
in detergents will be eliminated
[42]. In Erie County, New York, the ceiling of 8.7 percent placed on the
phosphate content of detergents in 1971 was reducedto 0.05 ppm in 1972.
This resulted in more than a 60 percent reduction in orthophosphates in six”
treatment plants monitored, m0re than a 45 percent decrease in phosphates
in the streams below these plants,
:a 43 percent improvement in stream
quality in terms of reduced BDD,
and algal blooms [43].
Unfortunately, a…store of phosphates has already built up over a period of
years in the bottom sediments of: Lake Eric, so that sufcient nutrients to per—
petuate
bloom can be"released even if future sewage efuents are rel—
_
atively free—of phosphates. Nutriènts stored in bottom mud are ordinarily pre—
vented…from mixing with the water by a protective layer of insoluble iron
_
saltS,
the water is»depleted of oxygen,
this protective layer ë-di‘s+
__
at
laboratory of the State University
Y0r£k>atæçBuffalo‘revealèdthätÏdu‘ring those periods When the shallow»weStel‘n
the lake frequently becomes
oxygen} as a result of the decay of algae that .havedied
_
Once the hypolimnion becomes.‘aüaer0bicand1e
__
breaks ups
* Ph9—Sphates
in
oxygensïis
__
‘
“
ReversungfheProcessî39 ï ‘
'«
'
‘
g
1»
<
—
31
i
,
phate waste, and suggests that the removal of phosphates from detergents
âfï
would decrease the phosphate level from 40 micrograms per liter (ng/l) of
lake water to approximately 20 [Lg/l. Complete removal of phosphates from
5
all sewage would reduce the phosphate concentration level in Lake Erie
to 11.9 pig/l (lower than the 1942 level of 14 png/l) [41].
'
i
The extent to which restrictions on the use of phosphate detergents relieve the inux of phosphate nutrients is illustrated by data supplied to the
Subcommittee on the Environment of the Senate Commerce Committee in
_
October 1971 by Councilman Carl Levin of Detroit. Councilman Levin re—
%
ported on the change in phosphate levels in sewage entering Detroit’s water
…,
-
tereatment facilities after phase I of Detroit’s ban on the sale of detergents
%
»‘
.
containing more than 8.7 percent phosphorus by weight went into effect july
f
_
l, 1971. These gures are listed below:
…
'
Date
Pounds per Day
Ï““.
'
1970
-
;;
July
58,500
August
55,200
‘
'
‘
-
'*
_.
September
_
54,400
‘
1971
,
.
.
july
42,000
,
;,
Ÿ
August
.
'
47,000
…
…
_
:
September
; _.
42,600 ‘
.
It is expected that the changes will be more dramaüc after phase II.of the
phosphate ban begins, when all
in detergents will be eliminated
[42]. In Erie County, New York, the ceiling of 8.7 percent placed on the
phosphate content of detergents in 1971 was reducedto 0.05 ppm in 1972.
This resulted in more than a 60 percent reduction in orthophosphates in six”
treatment plants monitored, m0re than a 45 percent decrease in phosphates
in the streams below these plants,
:a 43 percent improvement in stream
quality in terms of reduced BDD,
and algal blooms [43].
Unfortunately, a…store of phosphates has already built up over a period of
years in the bottom sediments of: Lake Eric, so that sufcient nutrients to per—
petuate
bloom can be"released even if future sewage efuents are rel—
_
atively free—of phosphates. Nutriènts stored in bottom mud are ordinarily pre—
vented…from mixing with the water by a protective layer of insoluble iron
_
saltS,
the water is»depleted of oxygen,
this protective layer ë-di‘s+
__
at
laboratory of the State University
Y0r£k>atæçBuffalo‘revealèdthätÏdu‘ring those periods When the shallow»weStel‘n
the lake frequently becomes
oxygen} as a result of the decay of algae that .havedied
_
Once the hypolimnion becomes.‘aüaer0bicand1e
__
breaks ups
* Ph9—Sphates
in
oxygensïis
__
‘
“
ReversungfheProcessî39 ï ‘
'«
'