Background
By design, publicly owned treatment works (POTWs), or local sewage treatment plants, can treat household sewage and other degradable wastes. However, many upstream commercial and industrial users also discharge their wastes, including some toxic pollutants, to POTWs. If the operations at the POTW cannot treat these influents, they may “pass through” the treatment processes and enter the receiving body of water. This causes pollution and may compromise the permit under which the POTW operates. Wastes can also compromise the operations of the treatment facility, causing further harm.
POTWs must have National Pollutant Discharge Elimination System (NPDES) permits from the state or federal Environmental Protection Agency (EPA) under the Clean Water Act (CWA). Under these permits, POTWs must issue sewer use ordinances (local limits). Large POTWs (greater than 5 million gallons per day) must identify significant industrial users and those facilities that must perform pretreatment.
Key Concepts
Publicly Owned Treatment Works (POTWs)
A POTW is a local sewage treatment plant. A village, town, city, county, state, or other authority usually operates the POTW. Even though this is a unit of local government, the CWA grants it authority to regulate all users, including federal and state institutions.
Significant Industrial User
These are users that contribute large volume discharges to the POTW. Discharges that are larger than 25,000 gallons per day, 5% of the POTW capacity, or otherwise designated are “significant industrial users.” Colleges and universities that meet these criteria are significant industrial users, regardless of the connotation of “industrial.”
Sewer Use Ordinance (Local Limits)
This is a document that outlines the limits or restrictions of discharges to the POTW. Although there are often additional local restrictions, the CWA requires all POTWs, regardless of size, to restrict
- flammables or explosives,
- corrosives that could cause structural damage,
- solid or viscous materials that could obstruct flows,
- materials that could interfere with POTW operations,
- extremely hot materials,
- petroleum, nonbiodegradable cutting oil or mineral oil, and
- materials that can affect health or safety of POTW workers.
Categorical Pretreatment Standards
These are the standards that apply to certain industrial facilities. The standards may apply when a particular operation on a campus is primarily commercial.
Does this apply to my campus?
Yes. Any campus facility with releases to a local POTW must comply with the limits of all applicable sewer use ordinances. All wastewater discharges are regulated by these local limits, including sewage and those from laboratories, art studios, photographic and X-ray sources, cafeterias, HVAC systems, etc. The POTW may require your campus to sample effluents, obtain a permit, and/or submit reports about use of the sewer.
What do I have to do?
Thoroughly review your POTW’s sewer use ordinances to understand limitations, then communicate the restrictions to campus users. Next, determine all sewer discharges and ensure that they are within local limits. Also, determine whether your drains flow to sanitary sewer or storm drains. Testing might be required.
Some POTWs have strict reporting requirements for hazardous materials discharges that the sewer use ordinance allows. Confirm that all sewer discharges from laboratory, arts, maintenance, and operations meet both the sewer use ordinance and any reporting requirements.
Campuses should assess operations to determine applicability of categorical pretreatment standards. These rules may apply to commercial or semicommercial research and development operations or contracted manufacturing facilities.
Although other environmental regulations have specific exemptions that allow for releases of certain wastes to the POTW, the sewer use ordinances still take precedence.