Permits shall impose the following technology-based effluent limitations, unless more stringent water quality-based effluent limitations are required for these pollutants:

1. (1) Municipal and domestic wastewater treatment plants shall be limited by application of monthly average concentrations, weekly average concentrations, daily maximum amounts, and daily maximum concentrations of the five day, 20°C biochemical or carbonaceous biochemical oxygen demand (BOD5 or CBOD5) and suspended solids. In some cases, the daily maximum amount may be replaced by a minimum daily percent removal requirement. Limitations on chlorine residual may be required to prevent harmful amounts of chlorine discharge to the receiving waters. In addition, where harmful materials are acquired in a collection system, effluent limitations applicable to the treatment system will be required for such parameters. The Commissioner may adjust these effluent limitations in accordance with 40 C.F.R. § 133.103(b) (2021).

   1. (a) Conventional secondary treatment plants. Parameter Monthly Weekly Daily Maximum Monthly Average Average (mg/l) Average % (mg/l) (mg/l) Removal BOD5 or CBOD5 30/25 40/35 45/40 85 TSS 30 40 45 85 The concentration of settleable solids shall not exceed 1.0 ml/l as measured by the standard one-hour Imhoff cone test.
   2. (b) Domestic waste stabilization lagoons. Parameter Monthly Weekly Daily Maximum Monthly Average Average (mg/l) Average % (mg/l) (mg/l) Removal BOD5 /CBOD5 45/40 50/45 65/60 65 TSS 100 110 120 n/a

2. (2) Industrial discharges.

   1. (a) For industrial discharges with applicable federal effluent limitations guidelines, technology-based effluent limitations and standards in accordance with those guidelines shall be applied.
   2. (b) For industrial discharges without applicable federal effluent limitations guidelines, best professional judgment should be employed to establish appropriate effluent limitations and standards.
   3. (c) A combination of the limitations derived from subparagraphs (2)(a) and (b) of this rule may be established in a permit, as applicable. ELIMINATION SYSTEM (NPDES) PERMITS

Authority: T.C.A. §§ 4-5-201, et seq., and 69-3-101, et seq. Administrative History: Original rule filed November 20, 2013; effective February 18, 2014. Amendments filed February 14, 2022; effective May 15, 2022.