Section 304.125  pH

a)         Except as provided below a person must not cause or allow the negative logarithm of the hydrogen ion concentration (pH) in any effluent to be more or less respectively than the maximum and minimum values for pH range indicated in the following table:

b)         The pH limitation is not subject to the averaging rule contained in Section 304.104(a).

c)         Effluents that are monitored to provide a permanent, continuous pH record may be outside of the listed range for a total of not more than fifteen minutes in any day provided the excursion is accidental and less than one pH unit above or below the listed range.

d)         The pH 9 maximum limitation may be exceeded if the elevated pH level:

1)         is caused entirely by algae in treatment lagoons, in which case there is no upper pH limit; or

2)         is caused by the addition of alkali in the wastewater treatment process to cause precipitation of barium, cadmium, chromium, copper, lead, manganese, zinc, or other materials requiring such elevated pH for treatment, in which case the upper limit is pH 10 and subsection (c) does not apply to the upper limit.

e)         The burden of proving that subsection (c) or (d) applies is upon the discharger.

(Source:  Amended at 47 Ill. Reg. 4601, effective March 23, 2023)