Section 418.12 - Effluent limitations guidelines representing the degree of effluent reduction attainable by the application of the best practicable control technology currently availableExcept as provided in §§ 125.30 through 125.32 , any existing point source subject to this subpart shall achieve the following effluent limitations representing the degree of effluent reduction attainable by the application of the best practicable control technology currently available (BPT):
(a) Subject to the provisions of paragraphs (b) and (c) of this section, the following limitations establish the quantity or quality of pollutants or pollutant properties, controlled by this section, which may be discharged by a point source subject to the provisions of this subpart after application of the best practicable control technology currently available: There shall be no discharge of process wastewater pollutants to navigable waters.(b) Process wastewater pollutants from a calcium sulfate storage pile runoff facility operated separately or in combination with a water recirculation system designed, constructed and operated to maintain a surge capacity equal to the runoff from the 10-year, 24-hour rainfall event may be discharged, after treatment to the standards set forth in paragraph (c) of this section, whenever chronic or catastrophic precipitation events cause the water level to rise into the surge capacity. Process wastewater must be treated and discharged whenever the water level equals or exceeds the mid point of the surge capacity.(c) The concentration of pollutants discharged in process wastewater pursuant to the limitations of paragraph (b) shall not exceed the values listed in the following table: | Effluent characteristic | Effluent limitations (mg/l) |
| Maximum for any 1 day | Average of daily values for 30 consecutive days shall not exceed- |
| Total phosphorus (as P) | 105 | 35 |
| Fluoride | 75 | 25 |
| TSS | 150 | 50 |
The total suspended solid limitation set forth in this paragraph shall be waived for process wastewater from a calcium sulfate storage pile runoff facility, operated separately or in combination with a water recirculation system, which is chemically treated and then clarified or settled to meet the other pollutant limitations set forth in this paragraph.
(d) The concentration of pollutants discharged in contaminated non-process wastewater shall not exceed the values listed in the following table: | Effluent characteristic | Effluent limitations (mg/l) |
| Maximum for any 1 day | Average of daily values for 30 consecutive days shall not exceed- |
| Total phosphorus (as P) | 105 | 35 |
| Fluoride | 75 | 25 |
39 FR 12836, Apr. 8, 1974, as amended at 41 FR 20584, May 19, 1976; 42 FR 16141, Mar. 25, 1977; 60 FR 33956, June 29, 1995