TENORM: Wastewater Treatment Residuals
Water and wastes which have been discharged from schools, residences and businesses flow through municipal sewer systems and are treated at wastewater treatment plants, also referred to as publicly owned treatment works (POTWs). The most frequently-occurring natural radionuclidesradionuclideRadioactive forms of elements are called radionuclides. Radium-226, Cesium-137, and Strontium-90 are examples of radionuclides. (and their decay products) found in wastewater treatment residuals include:
Unlike TENORM, man-made radioactivity discharged from research, medical and industrial facilities are regulated under the Atomic Energy Act.
Over time, as large volumes of sewage and wastes are collected, naturally occurring and man-made radionuclides can accumulate in municipal sewer systems and POTW equipment. POTWs process these materials and generate solid wastes (e.g. incinerated ash), sludges (also known as biosolids) and liquid wastes. Some drinking water treatment residuals are disposed through municipal sewer systems and become commingled with the wastewater treatment residuals.
Ultimately, wastewater treatment residuals are either disposed in landfills or land-applied as a soil amendment.
In 2016, EPA established pretreatment standards under 40 CFR 435 Subpart C. These standards prohibit discharges of wastewater pollutants from onshore unconventional oil and gas (UOG) extraction facilities to publicly owned treatment works.
A multi-year study conducted by EPA and other federal agencies who are members of the Interagency Steering Committee on Radiation Standards (ISCORS) Exit provided detailed information on radionuclides in POTWs. The study, published in 2005, was conducted in several phases:
Sewage Sludge POTW Pilot Survey
ISCORS established a subcommittee to examine radiation found in sewage sludge and the ash from its incineration. The subcommittee's first project was to conduct a pilot survey to determine the levels of radioactivity at nine POTWs.
Sewage Sludge POTW National Survey
Following completion of the pilot study, ISCORS undertook a nationwide survey. Three reports based on this work describe the national-level findings. View the ISCORS Study of Wastewater Treatment Plant TENORM reports.