NR 110.24(1) (1) Design report. A design report shall be submitted in accordance with s. NR 110.15 (1).

NR 110.24(2) (2) Basis of design.

NR 110.24(2)(a) (a) Number of cells. A minimum of 2 treatment cells shall be provided for aerated lagoons and stabilization ponds. Where a controlled discharge is required, additional effluent storage cells shall be provided.

NR 110.24(2)(a)1. 1. For aerated lagoons designed to treat domestic wastewater only, the hydraulic detention time of each cell shall be based on the following formula:

Where:

T = detention time, days

E = BOD removal efficiency, percent

K = Reaction coefficient (log base e), days-1

NR 110.24(2)(a)1.a. a. For domestic wastewater K = 0.5 at 20°C.

NR 110.24(2)(a)1.b. b. The reaction coefficient (K) must be adjusted for temperature according to the formula:

KT = K20QT-20

Where:

KT = Corrected reaction coefficient

K20 = 0.5

Q = 1.07

T = Low design temperature, °C

NR 110.24(2)(a)2. 2. The appropriate summertime and wintertime reaction coefficients for aerated lagoons designed to treat combined domestic and industrial wastewater shall be determined from laboratory or pilot studies, or from operating data of existing full scale aerated lagoons which are treating similar wastewater. The reaction coefficients developed shall be used to calculate the required detention time.

NR 110.24(2)(a)3. 3. In addition to the treatment volume calculated in subd. 1. or 2., quiescent settling zone or cell shall be provided for aerated lagoon systems. Minimum settling time shall be 6 days for surface water discharge, and 3 days for land disposal discharge.

NR 110.24(2)(a)4. 4. Aerated lagoons designed to treat combined domestic and industrial wastewater shall be provided with the means to recirculate final lagoon effluent to the first treatment cell.

NR 110.24(2)(b) (b) Stabilization ponds.

NR 110.24(2)(b)1. 1. Stabilization ponds may be used to treat domestic wastewater. Combined domestic and industrial wastewater may be treated in stabilization ponds only if the treatability of the industrial wastewater is demonstrated through pilot testing.

NR 110.24(2)(b)2. 2. The BOD5 loading to any one stabilization pond may not exceed 23 kilograms per hectare (20 pounds per acre) per day.

NR 110.24(2)(b)3. 3. A minimum hydraulic detention time of 150 days at the average design flow shall be provided in the entire stabilization pond system. In accordance with s. NR 210.06 (3) (h), a stabilization pond system which discharges to surface water, and has a hydraulic detention time of 180 days or longer at average design flow, does not require disinfection except in extenuating circumstances.

NR 110.24(3) (3) Design requirements.

NR 110.24(3)(a) (a) Location. Lagoon systems shall be located in compliance with s. NR 110.15 (3) (b) and (c).

NR 110.24(3)(b) (b) Separation from groundwater.

NR 110.24(3)(b)1. 1. For all lagoons not sealed with a synthetic liner, a minimum separation distance of 1.25 meters (4 feet) shall be maintained between the bottom of lagoons and the highest recorded or indicated seasonal groundwater table elevation.

NR 110.24(3)(b)2. 2. For all lagoons sealed with a synthetic liner, a minimum separation distance of 60 centimeters (2 feet) shall be maintained between the bottom of the lagoon and the highest recorded or indicated seasonal groundwater table elevation.