Medically-derived 131I in municipal sewage effluent

Area of Science:

• Environmental Science
• Radiochemistry
• Environmental Engineering

Background:

• Thyroid cancer treatments utilize Iodine-131 (131I), a radioactive isotope.
• Radioactive isotopes in medical effluent pose environmental challenges.
• Wastewater treatment plants (WPCPs) receive and process medical waste.

Purpose of the Study:

• To quantify Iodine-131 concentrations in sewage effluent from a WPCP serving a cancer treatment facility.
• To determine the sewage half-life (T(s)) of 131I in the studied WPCP.
• To understand the fate of 131I within the wastewater treatment process.

Main Methods:

• Collected sewage effluent samples from the Stony Brook Water Pollution Control Plant (WPCP).
• Measured 131I concentrations using appropriate detection methods.
• Analyzed time-series data following patient treatments to calculate the mean sewage half-life (T(s)).

Main Results:

• Detected 131I concentrations in sewage effluent ranging from 1.8 ± 0.3 to 227 ± 2 Bq L(-1).
• Determined the mean sewage half-life (T(s)) of iodine to be 3 days at this WPCP.
• Observed that most 131I exits the WPCP via sewage effluent, not sludge, due to activated sludge processes.

Conclusions:

• Wastewater effluent from cancer treatment facilities is a continuous source of 131I discharge.
• The prolonged retention of 131I in WPCPs, longer than hydraulic retention time, is influenced by treatment processes like activated sludge.
• 131I in effluent can serve as a valuable tracer for sewage-derived materials in aquatic environments and aids in understanding its behavior.