Pretreatment standards for existing sources

Pretreatment standards for existing sources. (1) Except as provided in ss. NR 211.13 and 211.14 and sub. (2) , any existing source subject to this subchapter which introduces pollutants into a POTW shall comply with ch. NR 211 and may not discharge process wastewater pollutants into a POTW. (2) A process wastewater impoundment which is designed, constructed, and operated to contain the precipitation from the 25-year, 24-hour rainfall event as established for the impoundment’s location by the national climatic center, national oceanic and atmospheric administration, may discharge a volume of process wastewater equivalent to the volume of precipitation which falls within the impoundment in excess of the precipitation attributable to the 25-year, 24-hour rainfall event, when such an event occurs.