Reliable Removal of NDMA to Less Than 0.28 ng/L Under Field Conditions

NDMA is a priority pollutant and byproduct of chloramination and ozonation of wastewater. NDMA water quality objective is 0.69 ng/L and California has a Drinking Water Notification Level of 10 ng/L. Best Available Technology for NDMA removal is UV-peroxide (UV-H2O2) advanced oxidation process. Energy consumption for UV-H2O2 is 5-10 times higher than UV disinfection systems typically used in WRRFs. Removal of NDMA in a pilot-scale biological activated carbon (BAC) filter was monitored over 20 months. Filtered effluent (membrane or sand filtration) was ozonated (dosed at 5 mg/L with 3.5 mg/L peroxide), which resulted in formation of 6 to 21 ng/L of NDMA. Over 99% removal of NDMA was consistently observed during the entire study independent of initial NDMA concentration, upstream filtration type, and bed life. A comparative analysis of NDMA removal results from three independent studies was completed to develop design, operational, and process monitoring guidelines for biofilters.