FVVPCA criteria is a dissolved oxygen concentration above ve ppm thatmay
.
drop to four ppm for only short periods of time. Cold—water sh like salmon
_
and trout require even more oxygen: The FWPCA criteria is seven ppm,and
,
may not drop below ve for more than six hours at a time; in the hypohm Ï
nion—the lower, colder layer of water where trout live—the dissolved oxygen
concentration should neVer drop below six ppm [9].
_
Seconda1y Treatment and BCD. In order not to overburden nature’s
î
ability to consume organic matter (and to prevent oxygen depletion), second—
a1y
waste treatmentmay be provided. Secondary treatment, in effect,
natural processes. Sewage is incubated in large tanks where bacteria
_
lowed to consume approximately 75—90 percent of the organic matter before :
the efuent is released. The stream will presumably be able to
’
remaining 10—25 percent of the organic substances without becoming devad
of oxygen.
To determine what eect séwage efuent from secondary treatment
plants will have on the oxygen concentration of the receiving stream, samtary
engineers determine the efuent’s BCD—its biological (or biochemical)oxygen demand. The BOD is the oxygen required by bacteria to
ganic wastes. Samples of treated sewage efuent are incubated in
asks for ve days at 20°C. The difference between the amounts of àssolved
;
oxygen present at the beginning and at the end of these incubation period$(m
î
the amount of oxygen lost) is the BCD. From this test it is then possible tode
»
termine whether organic wastes will reduce the oxygen in a stream
)
_
;
lev'el critical to sustain aquatic life.
Ï
_“
The convenience of the BOD measurement has made it
f,;
waste treatment effectiveness and even general water quahty
'
summarizing the EPA Water Quality report:
*
?_
"
OXygen demand (BOD5) is probably the inost
Ïl
strength of organic wastes; . . . it isthe
.
in almost shorthand fashion, the general quality ofWäteh
'
“
J‘
sanitary engineers, if not ecolôgists, as a
0thel‘pameters in broad descriptions of waste Characteristics or
. ? quality £OfitS well established position as the prime
_
" '
Of_WaSte‘_strength,-BOD reduction is the standard indicatorof waste
‘
nlntfyil@i
1nœntrnntnnenrhercauon about BOD was so@dédinarev1ewme
paredf0ïïeFWPCA,predecessorof‘the Water Quality Ofce.
_ _ ”
E W- KIre“CŒûûrm—mted
*"
,.
,
‘
;
* ‘,
_
.
The
and
‘
of BDD :;redœtiônsÿifather,‘ithan
JsdlÏids
sômeth‘ingÿ‘zèïï“'f"
:”
else
-ÎïzThe‘îsimplèïtnùthis ihsi.neays hifiyn
…
Streeter
there;
still..Îsbf
‘:‘ŸÏÏ
kn°“’ns Âin
andsomfmY zj ; l‘
.
fa°t°rs that
[
nnnn nny frnhtwnhnttdiluuii
:
128
0vçrfed
;
ii”
h\
‘
…“ w \” î‘i l
Will
H… “… l‘
H \ l
,
.
drop to four ppm for only short periods of time. Cold—water sh like salmon
_
and trout require even more oxygen: The FWPCA criteria is seven ppm,and
,
may not drop below ve for more than six hours at a time; in the hypohm Ï
nion—the lower, colder layer of water where trout live—the dissolved oxygen
concentration should neVer drop below six ppm [9].
_
Seconda1y Treatment and BCD. In order not to overburden nature’s
î
ability to consume organic matter (and to prevent oxygen depletion), second—
a1y
waste treatmentmay be provided. Secondary treatment, in effect,
natural processes. Sewage is incubated in large tanks where bacteria
_
lowed to consume approximately 75—90 percent of the organic matter before :
the efuent is released. The stream will presumably be able to
’
remaining 10—25 percent of the organic substances without becoming devad
of oxygen.
To determine what eect séwage efuent from secondary treatment
plants will have on the oxygen concentration of the receiving stream, samtary
engineers determine the efuent’s BCD—its biological (or biochemical)oxygen demand. The BOD is the oxygen required by bacteria to
ganic wastes. Samples of treated sewage efuent are incubated in
asks for ve days at 20°C. The difference between the amounts of àssolved
;
oxygen present at the beginning and at the end of these incubation period$(m
î
the amount of oxygen lost) is the BCD. From this test it is then possible tode
»
termine whether organic wastes will reduce the oxygen in a stream
)
_
;
lev'el critical to sustain aquatic life.
Ï
_“
The convenience of the BOD measurement has made it
f,;
waste treatment effectiveness and even general water quahty
'
summarizing the EPA Water Quality report:
*
?_
"
OXygen demand (BOD5) is probably the inost
Ïl
strength of organic wastes; . . . it isthe
.
in almost shorthand fashion, the general quality ofWäteh
'
“
J‘
sanitary engineers, if not ecolôgists, as a
0thel‘pameters in broad descriptions of waste Characteristics or
. ? quality £OfitS well established position as the prime
_
" '
Of_WaSte‘_strength,-BOD reduction is the standard indicatorof waste
‘
nlntfyil@i
1nœntrnntnnenrhercauon about BOD was so@dédinarev1ewme
paredf0ïïeFWPCA,predecessorof‘the Water Quality Ofce.
_ _ ”
E W- KIre“CŒûûrm—mted
*"
,.
,
‘
;
* ‘,
_
.
The
and
‘
of BDD :;redœtiônsÿifather,‘ithan
JsdlÏids
sômeth‘ingÿ‘zèïï“'f"
:”
else
-ÎïzThe‘îsimplèïtnùthis ihsi.neays hifiyn
…
Streeter
there;
still..Îsbf
‘:‘ŸÏÏ
kn°“’ns Âin
andsomfmY zj ; l‘
.
fa°t°rs that
[
nnnn nny frnhtwnhnttdiluuii
:
128
0vçrfed
;
ii”
h\
‘
…“ w \” î‘i l
Will
H… “… l‘
H \ l
,