NR 106.32(3)(c)5.5. The department may adjust Qs from the values in subd. 1. where natural receiving water flow is significantly altered by flow regulation.

NR 106.32(3)(d)(d) Effluent flows (Qe). Effluent flows used in the calculation of ammonia limits shall be determined using the procedures in s. NR 106.06 (4) (d).

NR 106.32(3)(e)(e) Background concentrations of ammonia (Cs). Background ammonia concentrations used in the calculation of ammonia limits shall be determined using the procedures in s. NR 106.06 (4) (e).

NR 106.32(4)(4) Values for parameters which affect the limit. Effluent limitations for ammonia shall be based upon the effects of pH and temperature on the toxicity of ammonia. The department shall determine the value of the pH and temperature on a case-by-case basis as follows:

NR 106.32(4)(a)(a) Receiving water.

NR 106.32(4)(a)1.1. The geometric mean of temperature and the arithmetic mean for pH in the receiving water shall be used to establish the chronic toxicity criteria for purposes of determining the effluent limitation for ammonia. Representative seasonal values of pH and temperature may be used. The pH and temperature determined under this subdivision may be modified to account for the mixture of the receiving and effluent flows when either of the following conditions occur:

NR 106.32(4)(a)1.a.a. Whenever the value of the pH and temperature of the effluent as determined in par. (b) is significantly greater than or less than the value in the receiving water.

NR 106.32(4)(a)1.b.b. Whenever, as a result of demonstrated or measured physical, chemical or biological reactions, the value of the pH and temperature, after mixing of the receiving water and the effluent, is significantly different than the respective background value of the pH and temperature in the receiving water.

NR 106.32(4)(a)2.2. If information on the pH and temperature of the receiving water is not available, information on the quality of similar water bodies in the area and best professional judgment of the department may be used.

NR 106.32(4)(b)(b) Effluent.

NR 106.32(4)(b)1.1. The daily maximum effluent pH shall be used to calculate the daily maximum ammonia limit based on acute toxicity criteria and in any calculations under par. (a).

NR 106.32(4)(c)(c) A permittee may conduct an investigation to demonstrate that alternate values for the pH and temperature determined under pars. (a) and (b) should be used. The investigation shall be based on site-specific conditions and shall address all of the following: critical loading conditions; buffering capacity of the stream; whether pH changes persist long enough to allow decay of ammonia to non-toxic levels; the effect of seasonal variations; maintaining the pH at the edge of the chronic mixing zone within the range of 6.0 to 9.0; and separate analyses for chronic mixing zone and an acute zone of initial dilution.

NR 106.32(4)(d)(d) Real-time data. Effluent limitations may be established based on real-time effluent and stream data provided the permittee demonstrates that the real-time data can be collected, and the discharge can be controlled to attain the effluent limitations. Adjustment of effluent pH may be an appropriate modification for compliance with real-time daily maximum limits. Real-time stream data may not be used to calculate ammonia limits if the department determines that the discharge may affect the existence of any endangered or threatened species listed under ch. NR 27.

NR 106.32(5)(a)(a) Limitations based on acute toxicity criteria. Effluent limitations for ammonia that are established in permits based on the acute toxicity criteria in ch. NR 105 shall be expressed only as concentrations.

NR 106.32(5)(b)(b) Limitations based on chronic toxicity criteria. Effluent limitations for ammonia that are established in permits based on the chronic toxicity criteria in ch. NR 105 shall be expressed as concentrations, except mass limits may also be included in a permit if there is more than one discharger of ammonia at a location or where the discharge is to an exceptional resource water designated under s. NR 102.11 or outstanding resource water designated under s. NR 102.10. If mass limits are determined to be necessary by the department, they shall be calculated using the procedure in s. NR 106.07 (2).

NR 106.32(5)(c)(c) Maximum and average ammonia limitations. Effluent limitations based on acute toxicity criteria shall be expressed in permits as daily maximum limitations. Effluent limitations based on 4-day chronic toxicity criteria shall be expressed in permits as weekly average limitations. Effluent limitations based on 30-day chronic toxicity criteria shall be expressed in permits as monthly average limitations.

NR 106.32(5)(d)(d) Monitoring frequency. The department shall determine on a case-by-case basis the monitoring frequency for ammonia to be required in a permit.

NR 106.32 HistoryHistory: CR 03-050: cr. Register February 2004 No. 578, eff. 3-1-04; CR 15-085: am. (2) (b) (intro.), 2., cr. (2) (e), am. (3) (a) 4. a. Register August 2016 No. 728, eff. 9-1-16.

NR 106.33(1)(a)(a) For a permitted discharge that is not already subject to an ammonia water quality-based effluent limitation, the procedures specified in s. NR 106.05 shall be used to determine if water quality-based effluent limitations for ammonia are necessary in a reissued permit. When application of the procedures in s. NR 106.05 results in a determination that ammonia effluent limits are not necessary in a permit, the permit holder shall continue to be operated in a manner that optimizes the removal of ammonia within the design capabilities of the wastewater treatment plant. The department may require that the permittee monitor ammonia at a frequency established on a case-by-case basis in its permit for the purpose of determining representative discharge levels.

NR 106.33(1)(b)(b) If a permittee is subject to an ammonia limitation in an existing permit, the limitation shall be included in any reissued permit. Ammonia limitations shall be included in the permit if the permitted facility will be providing treatment for ammonia discharges.

NR 106.33(2)(2) Permit limitations for continuous POTWs. The procedures for expressing limitations in permits in this subsection apply to continuous discharges subject to ch. NR 210 when there is reasonable potential under s. NR 106.05 to exceed an ammonia limitation. Both a weekly average and monthly average permit limitations shall be included in a permit for ammonia whenever any water quality-based effluent limitation for ammonia is determined necessary under sub. (1). A daily maximum limitation shall be included in permits in addition to weekly average and monthly average limitations if necessary under sub. (1). The department shall use all of the following procedures to include weekly average and monthly average limitations in permits:

NR 106.33(2)(a)(a) If a daily maximum limitation is the only ammonia limitation determined necessary under sub. (1), a weekly average limitation shall be set equal to the WQBEL based on the 4-day chronic toxicity criteria calculated under s. NR 106.32 (3) or the daily maximum limitation, whichever is more restrictive.

NR 106.33(2)(b)(b) If a weekly average ammonia limitation is determined necessary under sub. (1), and a monthly average limitation is not already determined necessary, a monthly average limitation shall be set equal to the WQBEL based on the 30-day chronic toxicity criteria calculated under s. NR 106.32 (3) or the weekly average limitation, whichever is more restrictive, except as provided under par. (c).

NR 106.33(2)(c)(c) The department may on a case-by-case basis use an alternative methodology for calculating monthly average limitations whenever historical flow data or real time data are used to calculate weekly average limitations under s. NR 106.32 (3) (c) 2. and these limitations are determined to be necessary under sub. (1).