Can we extract organic micropollutants residues from concentrated liquid urine to produce a clean fertiliser product

Abstract

Human urine is a waste stream which is high in N, P & K nutrients that shows promise to produce a fertiliser product, whilst reducing the nutrient load on wastewater treatment plants. However, hydrophilic organic micropollutants are excreted in urine. The proposal of stricter wastewater directives by the European Commission in October 2022 proposed greater regulation on the treatment of wastewater, particularly the removal of pharmaceuticals, which pose ecological risks. This study investigates solvent extraction as a method to remove organic micropollutants (OMPs) from source-separated urine while preserving nitrogen for fertiliser use. Through experimentation with various solvents, including methanol and acetonitrile, the study evaluates their efficacy in OMP removal. Methanol demonstrated high removal rates of OMPs (67-95%) but also significantly removed urea nitrogen, posing a challenge for fertiliser quality. Acetonitrile, while less effective, showed potential for further refinement. Principal Component Analysis (PCA) aided solvent selection based on properties, facilitating the identification of effective solvents. The study underscores the need for solvent extraction optimization to achieve efficient OMP removal while maintaining fertiliser quality, offering insights for future wastewater treatment strategies.