35 Ill. Adm. Code 302.212
Total Ammonia Nitrogen
Section 302
Section 302.212Â Total
Ammonia Nitrogen
a)Â Â Â Â Â Â Â Â Total ammonia nitrogen (as N) must in no case exceed 15 mg/L.
b)Â Â Â Â Â Â Â Â The total ammonia nitrogen (as N) acute, chronic, and
sub-chronic standards are determined by the equations given in subsections
(b)(1) and (b)(2). Attainment of each standard must be determined by
subsections (c) and (d) in mg/L.
1)Â Â Â Â Â Â Â Â The acute standard (AS) is calculated using the following
equation:
AS
=
0.411
+
58.4
1
+ 10
7.204-pH
1
+ 10
pH-7.204
2)Â Â Â Â Â Â Â Â The chronic standard (CS) is calculated using the following
equations:
A)Â Â Â Â Â Â Â During the Early Life Stage Present period, as defined in
subsection (e):
i)         When the water temperature is less than or equal to 14.51 °C:
CS
=
{
0.0577
+
2.487
}
(2.85)
1
+ 10
7.688-pH
1
+ 10
pH-7.688
ii)        When the water temperature is above 14.51 °C:
CS
=
{
0.0577
+
2.487
}
(1.45*10
0.028*(25-T)
)
1 + 10
7.688-pH
1 + 10
pH-7.688
Where T = Water Temperature, degrees Celsius
B)Â Â Â Â Â Â Â During the Early Life Stage Absent period, as defined in
subsection (e):
i)Â Â Â Â Â Â Â Â Â When
the water temperature is less than or equal to 7 °C:
CS
=
{
0.0577
+
2.487
}
(1.45*10
0.504
)
1
+ 10
7.688-pH
1
+ 10
pH-7.688
ii)Â Â Â Â Â Â Â Â When
the water temperature is greater than 7 °C:
CS
=
{
0.0577
+
2.487
}
(1.45*10
0.028*(25-T)
)
1 + 10
7.688-pH
1 + 10
pH-7.688
Where T = Water Temperature, degrees Celsius
3)Â Â Â Â Â Â Â Â The sub-chronic standard is equal to 2.5 times the chronic
standard.
c)Â Â Â Â Â Â Â Â Attainment of the Total Ammonia Nitrogen Water Quality Standards
1)Â Â Â Â Â Â Â Â The acute standard of total ammonia nitrogen (in mg/L) must
not be exceeded at any time except in those waters for which the Agency has
approved a ZID under Section 302.102.
2)Â Â Â Â Â Â Â Â The 30-day average concentration of total ammonia nitrogen (in
mg/L must not exceed the chronic standard (CS) except in those waters in which
mixing is allowed under Section 302.102. Attainment of the chronic standard
(CS) is evaluated under subsection (d) by averaging at least four samples
collected at weekly intervals or at other sampling intervals that statistically
represent a 30-day sampling period. The samples must be collected in a manner
that assures a representative sampling period.
3)Â Â Â Â Â Â Â Â The 4-day average concentration of total ammonia nitrogen (in
mg/L) must not exceed the sub-chronic standard except in those waters in which
mixing is allowed under Section 302.102. Attainment of the sub-chronic
standard is evaluated under subsection (d) by averaging daily sample results
collected over four consecutive days within the 30-day averaging period. The
samples must be collected in a manner that assures a representative sampling
period.
d)Â Â Â Â Â Â Â Â The water quality standard for each water body must be
calculated based on the temperature and pH of the water body measured at the
time of each ammonia sample. The concentration of total ammonia in each sample
must be divided by the calculated water quality standard for the sample to
determine a quotient. The water quality standard is attained if the mean of
the sample quotients is less than or equal to one for the duration of the
averaging period.
e)Â Â Â Â Â Â Â Â The Early Life Stage Present period occurs from March through
October. In addition, during any other period when early life stages are
present, and where the water quality standard does not provide adequate
protection for these organisms, the water body must meet the Early Life Stage
Present water quality standard. All other periods are subject to the Early
Life Stage Absent period.
BOARD NOTE:Â Acute and chronic standard concentrations for total ammonia
nitrogen (in mg/L) for different combinations of pH and temperature are shown
in Appendix C.