NPDES > Details

Wastewater discharges that eventually end up discharged to surface waters will likely require a permit under the National Pollutant Discharge Elimination System (NPDES) section of the Clean Water Act. Since it is much more likely that laboratory sinks and drains discharge to a POTW or institution operated wastewater treatment plant, this section focuses on these requirements.

The United States Environmental Protection Agency (EPA) regulates the discharge of water from facilities through provisions of the Clean Water Act. Activities performed in laboratory facilities potentially subject to the Clean Water Act primarily relate to the discharge of pollutants to a sewer system or local publicly owned treatment works (POTW). Very few laboratories discharge wastewater to directly to surface waters or septic systems because such practices are prohibited by local laws and regulations.

National Pretreatment Standards have been established by the EPA that prohibit the discharge of certain listed pollutants to a sewer system or POTW. The standards are listed under 40 CFR 403.5 and include the following specific pollutants:

• Flammable or explosive pollutants with a flash point of < 140° F.
• Discharges with a pH of < 5.0, unless specifically permitted by the POTW. (Many local POTWs also prohibit discharges with a pH of > 12.0)
• Pollutants that may obstruct flow, such as solids or highly viscous fluids.
• Pollutants capable of releasing harmful gases, such as cyanide or chlorine, which could harm employees at the POTW.
• Pollutants that could impose a high biological oxygen demand (BOD) that might interfere with the operation of the POTW.
• Petroleum and non-biodegradable oils.
• Wastewater hot enough to inhibit biological activity at the POTW, typically > 104° F.

In addition to the requirements noted above, many states, local POTWs and onsite treatment works set their own limits for what may be disposed of down a laboratory sink or drain. Limits are typically set for certain metals, BOD, pH, and organic pollutants. Diluting solutions with additional water to meet the limits is strictly prohibited. Local POTWs and agencies often require facilities that send wastewater for treatment to apply for and adhere to specific permit conditions. Check with you institution’s EH&S department or local regulatory agencies regarding the specific local/state requirements for your lab.

The full text of the National Pretreatment Standards can be found under 40 CFR Part 403 at:

40 CFR 403