Wastewater Discharge Monitoring and the Clean Water Act

Wastewater Discharge Monitoring and the Clean Water Act

It’s been 46 years since the Clean Water Act (CWA) was established by Congress in 1972.  The CWA, the primary federal law governing water pollution, regulates the wastewater discharge of pollutants into the waters of the United States and also establishes water quality standards for the country’s surface waters.  The launch of the CWA made it illegal to discharge into navigable waters any pollutant without a permit.  The National Pollutant Discharge Elimination System (NPDES) was created as the permitting tool for regulating discharges. 

Companies with an NPDES permit are required to perform routine monitoring. NPDES compliance monitoring is typically implemented at the state level with the exception of four individual states that are overseen by the U.S. EPA (Massachusetts, New Hampshire, Idaho, and New Mexico).   Permits are issued to industrial and municipal facilities with a point source discharging into a navigable water. Point sources include discharge pipes or ditches.  There are five different classifications of discharges for the CWA program:

  • Pretreatment: Some examples include industrial and commercial facilities, like manufacturing facilities, dry cleaners, and painting operations.
  • Stormwater: Industrial facilities, construction sites, and municipal systems.
  • Municipal Wastewater Overflows and Stormwater Management: Examples include Publicly Owned Treatment Works (POTWs).
  • Discharges from Concentrated Animal Feeding Operations (CAFOs): One example is a cattle farm.
  • Biosolids: Sewage sludge from wastewater treatment plants.

Monitoring is required for compliance with an NPDES permit.  Monitoring frequency and analytical testing requirements are detailed in a facility-specific permit.  Sample collection and laboratory testing must be performed following the NPDES permit specifications and CWA requirements. In addition, laboratory test methods must be performed following the guidelines established in 40 CFR Part 136.  There are specific test methods listed in 40 CFR Part 136 that apply to wastewater, stormwater, and surface water.  

A facility with an NPDES permit typically self-reports its compliance monitoring results to the state environmental regulatory agency using a Discharge Monitoring Report (DMR) format.  As an example, NPDES permit holders in Michigan self-report compliance monitoring results to the Michigan Department of Environmental Quality using an electronic DMR format.  Reporting is due to the MDEQ no later than the 20th day of the month following each month of authorized discharge.

Merit Laboratories, providing laboratory testing to support NPDES wastewater monitoring requirements, is certified for CWA wastewater methods by the National Environmental Laboratory Accreditation Program (NELAP).  Merit has been supporting NPDES monitoring programs for over 30 years and is experienced in assisting companies with analytical testing for both compliance monitoring and permit renewals. Please contact Merit to learn more about how we can support your wastewater testing needs.