15A NCAC 08G .0302      CLASSIFICATION OF BIOLOGICAL WATER POLLUTION CONTROL TREATMENT SYSTEMS

(a)  The following discharging systems shall be assigned a classification of Grade I Biological Water Pollution Control System unless the permitted design flow, or operational complexity of the system requires a higher classification:

(1)           septic tank/ media filter systems;

(2)           biological lagoon systems; and

(3)           constructed wetlands and associated appurtenances.

(b)  Systems that utilize an activated sludge or submerged fixed growth process with a permitted flow less than or equal to 0.5 million gallons per day (mgd) shall be assigned the classification of Grade II Biological Water Pollution Control System.

(c)  Systems utilizing an activated sludge or submerged fixed growth process with permitted flows of greater than 0.5 through 2.5 mgd shall be assigned the classification of Grade III Biological Water Pollution Control System.

(d)  Systems utilizing an activated sludge or submerged fixed growth process with a permitted flow greater than 2.5 mgd shall be assigned a classification of Grade IV Biological Water Pollution Control System.

(e)  Any system receiving a classification of Grade II Biological Water Pollution Control System that is required to comply with a permit limit for Total Nitrogen or Total Phosphorus shall be assigned the classification of Grade III Biological Water Pollution Control System.

(f)  Any system receiving a classification of Grade III Biological Water Pollution Control System that is required to comply with a permit limit for Total Nitrogen or Total Phosphorus shall be assigned the classification of Grade IV Biological Water Pollution Control System.

History Note:        Authority G.S. 90A-37;

Eff. April 1, 1999;

Amended Eff. December 1, 2006;

Readopted Eff. September 1, 2018.