Common Pollutants Regulated in NPDES Permits
You are probably wondering what types of pollutants permitted facilities are discharging and what effects these pollutants have on water quality. NPDES permits generally regulate three categories of pollutants: conventional pollutants, toxic pollutants, and non-conventional pollutants. This section discusses each of these categories and provides a list of some of the most common pollutants being discharged into Georgia’s waters.
Conventional are those specifically defined in the federal regulations at 40 C.F.R. Sec. 401.16 and are representative of basic sewage components. They are biochemical oxygen demand (BOD), total suspended solids (TSS), fecal coliform bacteria, oil and grease, and pH. These are relatively easy to test for and used for the basic limits in most permits. For example, all sewage treatment plant permits should have limits for all of these, except oil and grease. For industrial permits or sewage plants that need more advanced treatment due to the complexity of the waste make up or due to the size or sensitivity of the receiving stream, additional pollutants or parameters will need to be put in the permit.
Toxic pollutants are those pollutants that are particularly harmful to animals (including humans). Toxic pollutants cause death, disease, behavioral abnormalities, cancer, genetic mutations, physiological malfunctions, or physical deformations in organisms that ingest or absorb them. The quantities and length of exposure necessary to cause these effects can vary widely.
Toxic pollutants are grouped into two categories: organics and metals. Organics include such things as pesticides, solvents, PCBs, and dioxins. Common metals include lead, silver, mercury, copper, chromium, zinc, nickel, and cadmium. Toxicity of heavy metals can kill fish, contaminate their flesh (decreasing their value as a food source), and impair water supplies.
Non-conventional pollutants are those substances that are not classified as conventional pollutants or toxic pollutants but sometimes need to be included in permits due to the nature of the waste and/or to protect the receiving stream. Nutrients such as phosphorus and nitrogen are common non-conventional pollutants.
Examples of common pollutants:
These are just some examples of pollutants that you might see in a permit. Other limits may be placed for color, oil & grease, and many chemicals not listed here.
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