Nitrosamine precursor removal by BAC: A case study of adsorption versus biotreatment

Biological activated carbon (BAC) can effectively remove nitrosamine (NA) precursors. However, the relative significance of adsorption and biotreatment in the NA removal process remains unclear. In this study, organic matter in the influent of a pilot-scale BAC plant was separated into four fractions that were adsorbable, biodegradable, or both. Bench-scale tests showed that 70% of the N-nitrosodimethylamine formation potential was biodegradable and 42% was adsorbable. In addition, 45% of the N-nitro sodiethylamine formation potential was biodegradable and 59% was adsorbable. Biological treatment included two consecutive actions: biosorption, which was quick and accounted for 10% of the removal of NA formation potential, and biodegradation, which accounted for 70% of the removal of NA formation potential but took up to seven days to maximize. Activated carbon adsorption during bench-scale tests was capable of effectively removing NA formation potential in 7 h, but its performance was impaired in pilot-scale tests because of declining adsorption capacity after extended operation and shorter contact time in the BAC filter.