Urea hydrolysis is a chemical reaction that has many implications for emerging technologies. Water saving and nutrient recovery fixtures such as waterless urinals, urine diverting toilets, and their respective plumbing and storage tanks are experiencing great difficulty due to odor, clogging, and expensive maintenance. Urea hydrolysis, which is catalyzed by the urease enzyme, hydrolyzes urea to produce ammonia and bicarbonates. The result is an elevated pH, odor, and spontaneous precipitation of valuable nutrients in the fixtures, pipes, and storage tanks. Precipitation has caused the technologies to be removed or the installation of flushing mechanisms which eliminates the ability to conserve potable water and recover valuable nutrients. Since urease is the catalyst, if inhibited, the reaction will not occur and the technologies will function correctly. The goals of this research was to (1) provide an improved understanding of urea hydrolysis and its inhibition with respect to engineered systems and (2) to find a chemical addition that inhibits urea hydrolysis at a certain concentration which is affordable, sustainable, and can easily be implemented into the daily maintenance of the emerging technologies. Batch experiments were performed where urea hydrolysis was simulated in both synthetic and real fresh urine by addition of Jack bean urease and tracked though different measurements. Once hydrolysis was able to be measured and understood, different chemicals were added to the batch experiments to inhibit urea hydrolysis and the inhibition was quantified. The results showed that acetic acid, vinegar, and citric acid were all effective at inhibiting urea hydrolysis in both synthetic and real fresh urine at concentrations varying from 32.26 to 161.29 meq/L. Ionic silver and zinc, notable urease inhibitors in previous soil research, were ineffective at inhibition due to the composition of urine which caused precipitation of the silver and zinc.

Urea hydrolysis characterization and inhibition by chemical addition

253rd National Meeting (2017)

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