The objectives of this study were to compare the extent of deposition in drain pipes behind different waterless urinal systems and to determine the nature of those deposits. Urinals were removed from the walls of men's restrooms in different buildings on the University of North Carolina at Chapel Hill campus and at the Raleigh-Durham International Airport, and samples of mineral deposits in the drain pipes were collected. Upon analysis of these mineral deposits, it was determined that the deposits are composed primarily of struvite (magnesium ammonium phosphate). This determination was made using x-ray diffraction analysis, and the results were confirmed using scanning electron microscopy. Additionally, a chemical equilibrium model was used to simulate the hydrolysis of urea in the drain lines behind water-free urinals and determine the equilibrium pH of the system as urea hydrolyzes. This model showed that water-free urinal collection systems are oversaturated with respect to struvite, calcite, and calcium hydroxylapatite, indicating that these minerals are likely to deposit in these systems.Master of Science in Environmental Engineerin
