Wis. Admin. Code Department of Natural Resources NR 110.20

Current through October 28, 2024

Section NR 110.20 - Rotating biological contactors

(1) GENERAL.

(a)Applicability. Rotating biological contactors may be used when the wastewater is amenable to biological treatment. This treatment process may be used for carbonaceous or nitrogenous oxygen demand reduction, or both.

(b)Manufacturer's warranty. Manufacturers of rotating biological contactor equipment shall guarantee the rotating shafts, and media against failure during the initial 5 years of operation for all proposed rotating biological contactor treatment systems. The guarantee shall include equipment replacement and installation costs.

(2) DESIGN CONSIDERATIONS.

(a)Design report. A design report for rotating biological contactors shall be submitted in accordance with s. NR 110.15(1).

(b)Design parameters. The design of rotating biological contactors shall consider:

1. Design flow rate;

2. Influent carbonaceous and nitrogenous biochemical oxygen demand;

3. Rotational velocity;

4. Wastewater temperature; and

5. Percent influent biochemical oxygen demand which is soluble.

(3) DESIGN FEATURES.

(a)Primary treatment. Rotating biological contactors shall be preceded by primary treatment.

(b)Contact tanks.

1. Contact tanks shall be sized to maintain a maximum hydraulic detention time of 100 minutes.

2. Tanks shall contain positive liquid level control so that the rotating biological contactors will remain approximately 40% submerged.

3. Contact tanks and rotating shafts shall be enclosed. The enclosure shall be ventilated.

4. Removable baffles shall be provided between contact stages.

(c)Equalization. Equalization facilities shall be provided ahead of rotating biological contactors if the ratio of maximum hourly design flow to average design flow exceeds 2.5:1.

(d)High density media. High density shafts may not be used in the first 2 stages of any rotating biological treatment unit or system.

(e)Rotational speed.

1. Contactors shall be equipped with drive units which will allow variable rotational speed.

2. Maximum rotational speed shall be limited to a peripheral velocity of 49 centimeters per second (1.6 feet per second).

(f)Load monitoring. Each rotating biological shaft shall be equipped with a load monitoring device.

Wis. Admin. Code Department of Natural Resources NR 110.20

Cr. Register, November, 1974, No. 227, eff. 12-1-74; r. and recr. Register, February, 1983, No. 326, eff. 3-1-83.