Investigation of N-Nitrosodimethylamine (NDMA) Fate and Transport
Year Released: 2006
Funding Partners: Bureau of Reclamation, California State Water Resources Control Board, Santa Clara Valley Water District, Orange County Water District, West Basin Municipal Water District, Los Angeles County Sanitation District, Irvine Ranch Water District, National Water Research Institute, Water Replenishment District of Southern California
Total Investment: $546,000 (Cash)
Principal Investigator: David Sedlak, University of California, Berkeley
N-Nitrosodimethylamine (NDMA) is a potent carcinogen that has been detected in effluent from conventional and advanced wastewater treatment systems. The presence of NDMA in systems where indirect potable water reuse is practiced is a concern. NDMA precursors are a concern because they can produce NDMA when chloramines are used for disinfection. Prior to this project, little was known about the potential for loss of NDMA and NDMA precursors under conditions experienced in water reuse programs.
Goals and Objectives
The project assesses the fate and transport of NDMA and NDMA precursors in soil, groundwater and surface waters.
The project includes a review of available data from NDMA contaminated sites to identify environmental variables that influence NDMA transport and transformation. The project also includes experimental studies to assess the potential for biotransformation and field studies to assess volatilization and transport of NDMA in irrigated soil plots and soil columns.
Findings and Conclusions
Results of these experiments indicated that nearly all of the NDMA was removed as water passed through the unsaturated zone through processes including volatilization and biodegradation. Complementary experiments with intact soil cores suggested that the loss of NDMA was mainly attributable to volatilization.
NDMA in wastewater effluent may be removed through several processes in systems used for water reuse. In landscape irrigation systems, NDMA readily volatilizes from soil after application with nearly complete removal within several hours under conditions typically used for turfgrass. NDMA also can undergo photolysis and biotransformation. Photolysis is potentially important in surface waters (e.g., effluent-impacted rivers) whereas biotransformation is potentially important in groundwater systems. The rate of biotransformation in groundwater systems may be affected by the amount of labile organic carbon. Thus, soil aquifer treatment systems or systems in which surface water is blended with highly treated effluent may exhibit more biotransformation than what is typically observed at hazardous waste sites where NDMA is typically released in water that contains little additional labile organic carbon.
NDMA precursors, which are mainly derived from wastewater effluent, are highly resistant to biotransformation. The NDMA precursors are partially removed in saturated soil columns, indicating that they exhibit some affinity for soil surfaces.