Pembroke sewage sludge contaminated with tritium
SRBT discharges tritium-contaminated water into Pembroke’s sanitary sewer system. Annual discharges during the 2010-2014 period ranged from 7-13 GigaBecquerels (a GigaBecquerel (GBq) is the amount of a radioactive substance that produces one billion radioactive disintegrations every second). CNSC sets a 200 GBq limit for SRBT’s liquid discharges.
The City of Pembroke’s sewage treatment plant receives SRBT’s liquid discharges of tritium. Some of the tritium becomes incorporated in sewage sludge, while the remainder is discharged to the Ottawa River. A recently published study, Measurements and Dose Consequences of Tritium in Municipal Sewage Sludge, found that Pembroke had the highest levels of tritium contamination in sewage sludge of any city studied, at 34 Bq/kg of HTO, and 400 Bq/kg of OBT, or 1800 Bq/kg dry weight (CNSC 2015c). According to this study, “A 38 percent increase was observed in the measured OBT concentration of the 2014 sample compared to the one obtained in 2013.”
The study does not examine the potential for tritium contamination of soil and crop plants if Pembroke sewage sludge were to be spread as biosolids on agricultural land. It says that sewage sludge from Pembroke’s sewage treatment plant “is currently disposed of at the Ottawa Valley Waste Recovery Centre” (CNSC 2015c).