Bench-scale column evaluation of factors associated with changes in N-nitrosodimethylamine (NDMA) precursor concentrations during drinking water biofiltration

Production of N-Nitrosodimethylamine Precursors by Biofilters Is Highly Dynamic and Affected by Filter Media Type and Backwashing Conditions

“…Nevertheless, even if nitrification activity in GAC biofilters is stimulated by chloraminated backwash, the role of nitrification and nitrifying microorganisms in NDMA precursor production remains unclear. Although Zeng and Mitch observed that exudates from nitrifying biofilms can serve as NDMA precursors, our results from lab-scale testing suggested that increasing ammonia loading had no effect on NDMA production by biofilters.…”

“…Pilot-scale biofilters were operated to test the effects of biofilter design and operating conditions on NDMA precursor production, complimenting controlled bench-scale experiments published previously. 20 The lime-softened river water feed to pilot-scale filters generally contained substantial concentrations of NDMA precursors as well as substances that could be transformed into precursors in the biofilters or that stimulated precursor production by the biofilter biomass. The effect of biofilters on NDMA precursor concentrations was highly dynamic, varying throughout the year and even throughout a 72-h filter run.…”

“…To assess the roles of water quality and microbial community composition on NDMA precursor change across biofilters, our research team performed a series of bench-scale column tests. 20 Several round-robin type experiments were conducted in which biofilter media from multiple facilities were sampled, characterized, and distributed to each facility and then tested in parallel using the water at each facility. The results of this investigation demonstrated that the water source was the key factor in determining the quantity of NDMA precursors produced across the biofilters.…”

Metformin Contamination in Global Waters: Biotic and Abiotic Transformation, Byproduct Generation and Toxicity, and Evaluation as a Pharmaceutical Indicator

“…Apart from biodegradation and chlorination, ozonation of metformin can generate carcinogens such as UDMH and NDMA, which have been frequently detected at concentrations ranging from several to tens of ng/L in water systems worldwide . However, metformin is not considered the major source of UDMH and NDMA in waters because these TPs can also be generated from numerous other chemicals including DMA and quaternary amines or tertiary amine-containing pharmaceuticals with dimethylamine functional groups. , Thus, the occurrence of NDMA and UDMH as metformin TPs is not discussed herein, nor is that of DMA, BGN, biuret, guanidine, and DMG because of their numerous other sources …”

“…40 However, metformin is not considered the major source of UDMH and NDMA in waters because these TPs can also be generated from numerous other chemicals including DMA and quaternary amines or tertiary amine-containing pharmaceuticals with dimethylamine functional groups. 82,83 Thus, the occurrence of NDMA and UDMH as metformin TPs is not discussed herein, nor is that of DMA, BGN, biuret, guanidine, and DMG because of their numerous other sources. 84 Notably, although 32 organic TPs of metformin have been identified, only a few (GU, MBG and NCDC) have quantitative data.…”