Novel Approach for Fresh Urine Stabilization during Collection and Storage

Abstract

Waterless urinals are critical in urine diversion systems aimed at nutrient recovery for a circular economy. However, the existence of urease can trigger urea hydrolysis, causing mineral precipitation in waterless urinals and pipes, which leads to nitrogen loss and unpleasant odors. This research focuses on creating a urine stabilization product (USP) by combining camphor, ketone, and citric acid in specific ratios to prevent urea hydrolysis in waterless urinals. The effectiveness of the USP was evaluated using pH, urea, phosphate, and ammonium data in real urine samples. The results showed that the USP inhibited 70% of urea hydrolysis and reduced the pH. The introduction of camphor was found to decrease the diversity of the microbial community, while the Kathon preservative serves as the key active ingredient, significantly affecting urea hydrolysis rates during storage. The developed USP demonstrated a rate of inhibition of the total biomass in urine of ∼80%, with only slight bacterial regrowth over 9 days. Practically, the USP is expected to treat ≤300 L of urine, which is roughly equivalent to 2000 instances of urination. To the best of our knowledge, this study is the first to develop a slow-release USP specifically designed to inhibit urea hydrolysis in waterless urinals.