[Code of Federal Regulations]
[Title 40, Volume 18]
[Revised as of July 1, 2002]
From the U.S. Government Printing Office via GPO Access
[CITE: 40CFR133.101]

[Page 490]
 
                   TITLE 40--PROTECTION OF ENVIRONMENT
 
         CHAPTER I--ENVIRONMENTAL PROTECTION AGENCY (CONTINUED)
 
PART 133--SECONDARY TREATMENT REGULATION--Table of Contents
 
Sec. 133.101  Definitions.

    Terms used in this part are defined as follows:
    (a) 7-day average. The arithmetic mean of pollutant parameter values 
for samples collected in a period of 7 consecutive days.
    (b) 30-day average. The arithmetic mean of pollutant parameter 
values of samples collected in a period of 30 consecutive days.
    (c) Act. The Clean Water Act (33 U.S.C. 1251 et seq., as amended).
    (d) BOD. The five day measure of the pollutant parameter biochemical 
oxygen demand (BOD).
    (e) CBOD5. The five day measure of the pollutant 
parameter carbonaceous biochemical oxygen demand (CBOD5).
    (f) Effluent concentrations consistently achievable through proper 
operation and maintenance. (1) 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 (2) a 7-day average value equal to 1.5 times the value 
derived under paragraph (f)(1) of this section.
    (g) Facilities eligible for treatment equivalent to secondary 
treatment. Treatment works shall be eligible for consideration for 
effluent limitations described for treatment equivalent to secondary 
treatment (Sec. 133.105), if:
    (1) The BOD5 and SS effluent concentrations consistently 
achievable through proper operation and maintenance (Sec. 133.101(f)) of 
the treatment works exceed the minimum level of the effluent quality set 
forth in Secs. 133.102(a) and 133.102(b),
    (2) A trickling filter or waste stabilization pond is used as the 
principal process, and
    (3) The treatment works provide significant biological treatment of 
municipal wastewater.
    (h) mg/l. Milligrams per liter.
    (i) NPDES. National Pollutant Discharge Elimination System.
    (j) 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 for a given time period.
    (k) Significant biological treatment. The use of an aerobic or 
anaerobic biological treatment process in a treatment works to 
consistently achieve a 30-day average of a least 65 percent removal of 
BOD5.
    (l) SS. The pollutant parameter total suspended solids.
    (m) Significantly more stringent limitation means BOD5 
and SS limitations necessary to meet the percent removal requirements of 
at least 5 mg/l more stringent than the otherwise applicable 
concentration-based limitations (e.g., less than 25 mg/l in the case of 
the secondary treatment limits for BOD5 and SS), or the 
percent removal limitations in Secs. 133.102 and 133.105, if such limits 
would, by themselves, force significant construction or other 
significant capital expenditure.
    (n) State Director means the chief administrative officer of any 
State or interstate agency operating an ``approved program,'' or the 
delegated representative of the State Director.

[49 FR 37006, Sept. 20, 1984; 49 FR 40405, Oct. 16, 1984, as amended at 
50 FR 23387, June 3, 1985]