Electrochemical treatment of human urine for its storage and reuse as flush water.

We proposed the electrochemical treatment of human urine to enable its storage without the accompanying unpleasant odor. This urine can then be reused as flush water in toilets as a means to tackle water shortage problems. In laboratory-scale experiments, the time-dependent variation in the pH of human urine, after the addition of urease, could be suppressed by chlorine produced via the electrochemical treatment of diluted human urine. Ureolysis was quantified by pH increase within 100 h. This suppression occurred as a result of an irreversible change in the conformation of urease that resulted in its inactivation at an oxidation-reduction potential (ORP) of ca. 240 mV or above. Due to the electrochemical inactivation of urease during the entire storage period of urine, the hydrolysis of urea in urine, which results in the production of the unpleasant odor due to ammonia formation, can be avoided. Thus, the treatment enables the storage of urine for its reuse as flush water in toilets.