Fate of organic contaminants in electrochemical nitrogen recovery from urine

Abstract

This study compared the fate of pharmaceuticals and disinfection byproducts across three electrochemical nitrogen recovery processes treating urine: electrochemical stripping (ECS), electrodialysis (ED), and bipolar electrodialysis (BPED). ECS achieved greater TAN recovery efficiencies than ED and BPED and was the only process that recovered a urine-derived ammonium sulfate product rather than a mixed concentrate (containing TAN, sodium, and potassium). Enrichment and removal ratios based on target pharmaceutical quantification and suspect screening were used to evaluate the fate of organic compounds relative to nitrogen recovery. These metrics suggested that ECS prevented organic contamination of the product more effectively than the other two processes and that both ECS and BPED achieved greater organic removal than ED. No disinfection byproducts were detected in the product for any process, but formation in other chambers may require mitigation. Our findings inform pre-and post-treatment for electrochemical nitrogen recovery, as well as modifications to reactor configuration and operating conditions. With future work using suspect screening and identification of additional compounds to build greater mechanistic understanding of compound fate and characterize the toxicity of contaminants detected in treated urine and recovered products, our work will advance electrochemical technologies that recover high-purity, safely applied products and enable a circular nitrogen economy.