Since urine normally has high concentrations of urea, it is often considered as a valuable resource for nitrogen recovery. However, urea in stored urine undergoes catalytic hydrolysis by urease to ammonia and carbon dioxide. As ammonia in urine reacts with water to produce hydroxide, pH in stored urine rises leading in many cases to the formation of struvite, which in turn causes blockages in pipes. This sequence of reactions lowers the efficiency of nitrogen recovery. Urine is also the major carrier of excreted pharmaceuticals and their metabolites. Herein, we examine 23 pharmaceuticals and metabolites, which are commonly detected in human urine, and study their interaction with urease. We observed that 1,2,4-benzenetriol, hydroquinone, catechol, and disulfiram inhibited urease. Given this inhibitory effect, 94% of urea in stored human urine was stabilized for one month by catechol. The inhibitory effect of catechol and disulfiram on urease was relatively constant over a broad concentration range of phosphate concentrations and salinity. Furthermore, higher pH values in stored urine appeared to enhance the inhibition of urease by disulfiram. Inhibition of urease in five different water sources was also explored to examine the impact of variations in urine discharge water on urea hydrolysis. Reaction mechanisms of urease inhibition by polyphenolics and disulfiram were proposed.

Human urine stablization by pharmaceuticals and their metabolites

ACS Spring 2022

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