546 

§ 133.102 40 CFR Ch. I (7–1–06 Edition) 

(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 (§133.105), if: 

(1) The BOD5 and SS effluent concentrations consistently achievable 

through proper operation and maintenance (§133.101(f)) of the treatment 

works exceed the minimum level of the 

effluent quality set forth in §§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 §§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] 

§ 133.102 Secondary treatment. 

The following paragraphs describe 

the minimum level of effluent quality 

attainable by secondary treatment in 

terms of the parameters—BOD5, SS and 

pH. All requirements for each parameter shall be achieved except as provided for in §§133.103 and 133.105. 

(a) BOD5. 

(1) The 30-day average shall not exceed 30 mg/l. 

(2) The 7-day average shall not exceed 

45 mg/l. 

(3) The 30-day average percent removal shall not be less than 85 percent. 

(4) At the option of the NPDES permitting authority, in lieu of the parameter BOD5 and the levels of the effluent quality specified in paragraphs 

(a)(1), (a)(2) and (a)(3), the parameter 

CBOD5 may be substituted with the following levels of the CBOD5 effluent 

quality provided: 

(i) The 30-day average shall not exceed 25 mg/l. 

(ii) The 7-day average shall not exceed 40 mg/l. 

(iii) The 30-day average percent removal shall not be less than 85 percent. 

(b) SS. (1) The 30-day average shall 

not exceed 30 mg/l. 

(2) The 7-day average shall not exceed 

45 mg/l. 

(3) The 30-day average percent removal shall not be less than 85 percent. 

(c) pH. The effluent values for pH 

shall be maintained within the limits 

547 

Environmental Protection Agency § 133.103 

of 6.0 to 9.0 unless the publicly owned 

treatment works demonstrates that: (1) 

Inorganic chemicals are not added to 

the waste stream as part of the treatment process; and (2) contributions 

from industrial sources do not cause 

the pH of the effluent to be less than 

6.0 or greater than 9.0. 

[49 FR 37006, Sept. 20, 1984; 49 FR 40405, Oct. 

16, 1984] 

§ 133.103 Special considerations. 

(a) Combined sewers. Treatment 

works subject to this part may not be 

capable of meeting the percentage removal requirements established under 

§§133.102(a)(3) and 133.102(b)(3), or 

§§133.105(a)(3) and 133.105(b)(3) during 

wet weather where the treatment 

works receive flows from combined 

sewers (i.e., sewers which are designed 

to transport both storm water and sanitary sewage). For such treatment 

works, the decision must be made on a 

case-by-case basis as to whether any 

attainable percentage removal level 

can be defined, and if so, what the level 

should be. 

(b) Industrial wastes. For certain industrial categories, the discharge to 

navigable waters of BOD5 and SS permitted under sections 301(b)(1)(A)(i), 

(b)(2)(E) or 306 of the Act may be less 

stringent than the values given in 

§§133.102(a)(1), 

133.102(a)(4)(i), 133.102(b)(1), 

133.105(a)(1), 133.105(b)(1) and 

133.105(e)(1)(i). In cases when wastes 

would be introduced from such an industrial category into a publicly owned 

treatment works, the values for BOD5

and SS in §§133.102(a)(1), 133.102(a)(4)(i), 

133.102(b)(1), 133.105(a)(1), 133.105(b)(1), 

and 133.105(e)(1)(i) may be adjusted upwards provided that: (1) The permitted 

discharge of such pollutants, attributable to the industrial category, 

would not be greater than that which 

would be permitted under sections 

301(b)(1)(A)(i), 301(b)(2)(E) or 306 of the 

Act if such industrial category were to 

discharge directly into the navigable 

waters, and (2) the flow or loading of 

such pollutants introduced by the industrial category exceeds 10 percent of 

the design flow or loading of the publicly owned treatment works. When 

such an adjustment is made, the values 

for BOD5 or SS in §§133.102(a)(2), 

133.102(a)(4)(ii), §133.102(b)(2), 

133.105(a)(2), 133.105(b)(2), and 

133.105(e)(1)(ii) should be adjusted proportionately. 

(c) Waste stabilization ponds. The Regional Administrator, or, if appropriate, State Director subject to EPA 

approval, is authorized to adjust the 

minimum levels of effluent quality set 

forth in §133.105 (b)(1), (b)(2), and (b)(3) 

for treatment works subject to this 

part, to conform to the SS concentrations achievable with waste stabilization ponds, provided that: (1) Waste 

stablization ponds are the principal 

process used for secondary treatment; 

and (2) operation and maintenance data 

indicate that the SS values specified in 

§133.105 (b)(1), (b)(2), and (b)(3) cannot 

be achieved. The term ‘‘SS concentrations achievable with waste stabilization ponds’’ means a SS value, determined by the Regional Administrator, 

or, if appropriate, State Director subject to EPA approval, which is equal to 

the effluent concentration achieved 90 

percent of the time within a State or 

appropriate contiguous geographical 

area by waste stabilization ponds that 

are achieving the levels of effluent 

quality for BOD5 specified in 

§133.105(a)(1). [cf. 43 FR 55279]. 

(d) Less concentrated influent wastewater for separate sewers. The Regional 

Administrator or, if appropriate, State 

Director is authorized to substitute either a lower percent removal requirement or a mass loading limit for the 

percent removal requirements set forth 

in §§133.102(a)(3), 133.102(a)(4)(iii), 

133.102(b)(3), 102.105(a)(3), 133.105(b)(3) 

and 133.105(e)(1)(iii) provided that the 

permittee satisfactorily demonstrates 

that: (1) The treatment works is consistently meeting, or will consistently 

meet, its permit effluent concentration 

limits but its percent removal requirements cannot be met due to less concentrated influent wastewater, (2) to 

meet the percent removal requirements, the treatment works would 

have to achieve significantly more 

stringent limitations than would otherwise be required by the concentration-based standards, and (3) the less 

concentrated influent wastewater is 

not the result of excessive I/I. The determination of whether the less concentrated wastewater is the result of