Date of Award
Master of Science (MS)
Karl G. Linden
Urine-diverting toilets are a common method to collect human waste and recover valuable nutrients. While researchers have investigated methods to recover nutrients from urine, most of these methods utilize stored urine that is held in large storage tanks and has undergone the conversion of nitrogen to ammonia (ureolysis), causing spontaneous precipitation of some phosphate and release of odorous NH3. Continuous-flow applications with fresh and stored urine can decrease the need for urine storage and supplement nutrient recovery technologies. Two experimental designs were used to analyze continuous-flow applications for urine management: (1) an engineered ureolysis biological filter and (2) solid media phosphate recovery filter. Two biological filters were fed fresh urine, and bacteria producing urease encouraged ureolysis. Maximum ureolysis rates were 66.9 kg N/m3/day for the column filled with biofilm carriers sampled from a wastewater treatment plant (“activated”) and 7.52 kg N/m3/day for the column filled with fresh carriers (“urine-only”). Urea decay demonstrated a first-order rate constant of 0.036 min-1 in the activated column. While increasing urine concentration had little effect on overall ureolysis rate in the columns, it increased solids build-up in the columns. Based on these data, biological filters can be designed for flow rate, cross-sectional area, and total volume to control the amount of ammonia entering nutrient recovery schemes for various process requirements. Additionally, DNA sequencing of microbial communities over time displayed a decrease incommunity diversity in the activated column, with Proteobacteria dominating in themature column, specifically Rhizobiales, Burkholderiales, and Pseudomadales. Solid phosphate recovery experiments packed columns with various magnesiumcontaining media and pumped ureolyzed urine through them. In a test with 1 liter of urine, magnesium sulfate and compost mixture captured 0.17 moles phosphorus per mole of magnesium initially present in the media; magnesium-rich soil captured 0.12 moles P per mole Mg; and dolomite stone captured 0.027 moles P per mole Mg. Due to leaching of magnesium from the solid phase into the liquid effluent, a sharp decrease in phosphorus recovery occurred after ~3 hours for magnesium sulfate and 5 minutes for soil.
Neethling, Jeanette Erika, "Continuous Flow Applications for Managing Source-Separated Urine Nutrient Recovery" (2016). Civil Engineering Graduate Theses & Dissertations. 145.