74:52:06:01Definitions.

The following definitions are applicable to secondary treatment standards: (1) "Seven-day average," the arithmetic mean of pollutant parameter values of samples collected in a period of seven consecutive days; (2) "30-day average," the arithmetic mean of pollutant parameter values of samples collected in a period of 30 consecutive days; (3) "BOD5," the five-day measure of the pollutant parameter biochemical oxygen demand; (4) "CBOD5," the five-day measure of the pollutant parameter carbonaceous biochemical oxygen demand; (5) "Effluent concentrations consistently achievable through proper operation and maintenance," for a given pollutant parameter, the 95th percentile value for the 30-day average effluent quality achieved by a treatment works in a period of at least two years, excluding values attributable to upsets, bypasses, operational errors, or other unusual conditions, and a seven-day average value equal to 1.5 times this value; (6) "mg/L," milligrams per liter; (7) "Percent removal," a percentage expression of the removal efficiency across a treatment plant for a given pollutant parameter, as determined from the 30-day average values of the raw wastewater influent pollutant concentrations to the facility and the 30-day average values of the effluent pollutant concentrations; (8) "TSS," total suspended solids; and (9) "Significantly more stringent limitations," BOD5 and TSS limitations necessary to meet the percent removal requirements of at least five mg/L more stringent than the otherwise applicable concentration-based limitations.

Source: 14 SDR 86, effective December 24, 1987; 19 SDR 122, effective February 21, 1993; transferred from § 74:03:22:01, July 1, 1996.