1.5 Classifying Water Pollution Control Systems Under 15A NCAC 08G .0300

1.5 Classifying Water Pollution Control Systems Under 15A NCAC 08G .0300

Unlike the drinking water Board, the WPCSOCC does not use a point sheet. Section .0300 of 15A NCAC 08G classifies each system by the kind of treatment it performs and, for biological and collection systems, by size. The classification then sets the type and grade of the ORC under 08G .0201.

---

Biological water pollution control systems (08G .0302)

The nutrient bump. Paragraphs (e) and (f) are heavily tested: a system that would be Grade II but is required to comply with a permit limit for Total Nitrogen or Total Phosphorus becomes Grade III; a Grade III system with a TN or TP limit becomes Grade IV. A 0.4 MGD oxidation ditch discharging to the Neuse basin with a TN limit is therefore a Grade III system, and its ORC needs a Grade III Biological certificate.

"Submerged fixed growth" is defined in 08G .0102(26) as a biological system treating wastewater by contact with growth fixed to submerged support media, and it expressly includes rotating biological contactors and sequencing batch reactors.

---

Collection systems (08G .0303)

Collection systems conveying wastewater to permitted systems (or tributary to municipalities, regional systems, authorities, public utilities, or Grade II–IV state or federally owned systems) are classified as the lower of:

1. the grade of the biological system the collection system is tributary to, or
2. the grade from the population served:

If population served cannot be determined, equivalent population = design flow ÷ 60 gallons per day per person. A collection system with a 1.8 MGD design flow therefore serves an equivalent population of 30,000 (Grade III) — but if it discharges to a Grade II plant, the lower grade (II) governs.

Any collection system, regardless of ownership, may be classified and required to designate an ORC and Back-up ORC if the Commission determines it is not being operated and maintained in a manner that prevents wastewater from escaping into the environment.

---

Physical/chemical systems (08G .0306)

• Grade I: any system, including groundwater remediation systems, that uses a physical process — electrodialysis, adsorption, absorption, air stripping, gravimetric sedimentation, flotation, or filtration.
• Grade II: any system that uses a chemical process (including systems whose treatment is augmented by physical processes). Reverse osmosis, electrodialysis, and ultrafiltration systems are Grade II.
• A system with a biological component is additionally classified as a biological system, but a physical or chemical process used only to enhance activated sludge or fixed growth does not trigger a separate physical/chemical classification.

---

Surface irrigation, land application, and subsurface systems

• Surface irrigation (.0304): systems using surface irrigation for treatment, reuse, or disposal. A system containing only preliminary processes — septic tanks, media filters, oil/water separators, lagoons, storage basins, screening, or sedimentation — is not subject to the additional operator requirements of .0302 or .0306.
• Land application of residuals (.0305): systems permitted to land-apply residuals produced by a water pollution control system, a water supply treatment facility, or an air pollution control facility, or to land-apply contaminated soils.
• Subsurface (.0307): systems permitted by the EMC that use the soil for subsurface treatment and disposal, plus any subsurface system required to have a certified operator under 15A NCAC 18A .1961. If the subsurface system consists only of septic tanks, pump tanks, siphons or dosing pumps, media filters, grease traps or interceptors, or oil/water separators with subsurface disposal, no additional classification is required.
• Systems not otherwise classified (.0308): the Commission may classify any system receiving wastewater with distinctly different characteristics from domestic wastewater, or using treatment processes different from the conventional processes in .0302 through .0306.

---

When classifications change (08G .0301)

The Commission modifies a classification when design features or inherent operational requirements make operation more or less complex than at permitting, when upgrades or modifications are completed, or when the classification rules themselves change. Two exclusions are worth memorizing: in-plant processes that are an integral part of direct industrial production are not water pollution control systems for classification purposes, and closed-loop recycle systems at sand, gravel, and crushed stone operations are exempt unless the Commission finds they are not being operated in accordance with permit conditions.

[!IMPORTANT] Designation follows classification. Under 08G .0201 the owner of a classified system must designate one ORC holding a valid certificate of the same type and at least the same grade, plus one or more Back-up ORCs holding a certificate of the same type and no more than one grade lower. The only systems excused from naming a Back-up ORC are those whose minimum visitation requirement is twice per year.