Separately collected urine has become recognized as a promising source of nitrogen, phosphorus, and potassium, which are key fertilizer ingredients.. Urine contains the majority of these macronutrients (80% N, 50% P, 70% K) and comprises only 1% of wastewater volume, but also contains high concentrations of hydrophilic organic compounds, including pharmaceuticals and exogenous metabolites, which preferentially partition (on average 65%) into urine. Because creating urine-derived fertilizers cycles both nutrients and other urine constituents; it is therefore critical to effectively remove pharmaceutical compounds from urine-derived fertilizers. Ideally, urine treatment would selectively concentrate nutrients and minimize or destroy contaminants. A major knowledge gap in the literature is the relative fates of nutrients and pharmaceuticals, which can be expressed as a nutrient/pharmaceutical enrichment ratio.  The goal of this study was to apply suspect screening to compare the fate of a broad suite of urine pharmaceuticals through several urine treatment processes for real urine. To achieve this goal, we characterized the suite of organic compounds present in urine, and focused on xenophobic compounds likely to be pharmaceuticals and their metabolites. We also included target analyses with a limited set of compounds to benchmark our suspect screening workflow. To provide mechanistic insights on pharmaceutical transformation, we correlated several physicochemical properties of compounds with their fold changes during urine treatment processes. Finally, we considered the implications of this approach to characterizing pharmaceuticals during urine treatment, including identifying indicator compounds and considering toxicity. By applying suspect screening to various unit treatment processes, this study illustrates a systematic approach to benchmarking urine treatment processes in terms of their nutrient concentration and pharmaceutical mitigation. This approach can also be used to engineer urine treatment trains that extract maximal value and remove sufficient pharmaceuticals for use of urine-derived products and environmental discharge of effluent.

Suspect screening to determining pharmaceutical fate in urine-derived fertilizers

2019 Fall National Meeting

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