Section 92a.47. Sewage permit

(a) Sewage, except that discharged from a CSO that is in compliance with subsection (b), or as provided for in subsections (f)—(i), shall be given a minimum of secondary treatment. Secondary treatment for sewage is that treatment that includes significant biological treatment and accomplishes the following:

(1) Monthly average discharge limitation for BOD₅ and TSS may not exceed 30 milligrams per liter. If CBOD₅ is specified instead of BOD₅ the limitation may not exceed 25 milligrams per liter.

(2) Weekly average discharge limitation for BOD₅ and TSS may not exceed 45 milligrams per liter for POTW facilities. If CBOD₅ is specified instead of BOD₅ the limitation may not exceed 40 milligrams per liter.

(3) On a concentration basis, the monthly average percent removal of BOD₅ or CBOD₅, and TSS, must be at least 85% for POTW facilities.

(4) From May through September, a monthly average discharge limitation for fecal coliform of 200/100 mL as a geometric mean and an instantaneous maximum effluent limitation not greater than 1,000/100 mL.

(5) From October through April, a monthly average discharge limitation for fecal coliform of 2,000/100 mL as a geometric mean and an instantaneous maximum effluent limitation not greater than 10,000/100 mL.

(6) Provision for the disposal or beneficial use of sludge in accordance with applicable Department regulations.

(7) Compliance with § 95.2(1) and (2) (relating to effluent standards for industrial waste).

(8) Compliance with § 92a.48 (b) (relating to industrial waste permit) if chlorine is used.

(b) Dischargers of sewage from a CSO shall implement, as approved by the Department, nine minimum controls (NMCs) and a long-term control plan (LTCP) to minimize or eliminate the CSO discharge impact on the water quality of the receiving surface water.

(c) Discharges from an SSO are prohibited.

(d) When pollutants contributed by indirect dischargers result in interference or pass through, and a violation is likely to recur, a permittee shall develop and implement specific local limits for indirect dischargers and other users, as appropriate, that together with appropriate sewerage facility or operational changes, are necessary to ensure renewed or continued compliance with the plant’s NPDES permit or sludge use or disposal practices.

(e) POTWs that serve indirect dischargers shall give notice to the Department in accordance with 40 CFR 122.42(b) (relating to additional conditions applicable to specific categories of NPDES permits (applicable to State NPDES programs, see § 123.25)).

(f) POTWs with effluent limits that are less stringent than those specified in subsection (a)(1) and (2) in effect on October 9, 2010, shall meet the requirements of subsection (a)(1) and (2) when a new or amended water quality management permit authorizing an increase in the design flow of the facility is issued under the provisions of Chapter 91 (relating to general provisions).

(g) POTWs subject to this section may not be capable of meeting the percentage removal requirements established under subsection (a)(3) during wet weather, where the treatment works receive flows from combined sewers (that is, sewers which are designed to transport both storm water and sanitary sewage). For those 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.

(h) POTWs subject to this section may not be capable of meeting the percentage removal requirements established under subsection (a)(3) during dry weather, where the treatment works receive flows from combined sewers. The Department may substitute less stringent removal requirements than that specified in subsection (a)(3) for any POTW with less concentrated influent wastewater for combined sewers during dry weather. The Department may substitute either a lower percent removal requirement or a mass loading limit for the percent removal requirements specified in subsection (a)(3) provided that the permittee satisfactorily demonstrates all of the following:

(1) The treatment works is consistently meeting, or will consistently meet, its permit effluent concentration limits, but the 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 effluent concentrations than would otherwise be required by the concentration-based standards.

(3) The less concentrated influent wastewater does not result from either excessive infiltration or clear water indirect dischargers during dry weather periods. The determination of whether the less concentrated wastewater results from excessive infiltration is discussed in 40 CFR 35.2005(b)(28) (relating to definitions), plus the additional criterion that either 40 gallons per capita per day or 1,500 gallons per inch diameter per mile of sewer may be used as the threshold value for that portion of the dry weather base flow attributed to infiltration. If the less concentrated influent wastewater is the result of clear water indirect dischargers, the treatment works must control these discharges pursuant to 40 CFR Part 403 (relating to general pretreatment regulations for existing and new sources of pollution).

(i) The Department may substitute less stringent removal requirements than that specified in subsection (a)(3) for any POTW with less concentrated influent wastewater for separate sewers, provided that the permittee satisfactorily demonstrates all of the following:

(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.

(3) The less concentrated influent wastewater is not the result of excessive inflow/infiltration. The determination of whether the less concentrated wastewater is the result of excessive inflow/infiltration will be based on the definition of excessive inflow/infiltration in 40 CFR 35.2005(b)(16), plus the additional criterion that inflow is nonexcessive if the total flow to the POTW (that is, wastewater plus inflow plus infiltration) is less than 275 gallons per capita per day.