Epsilon Archive for Student Projects

Abstract

This thesis investigated the suitability of using MgO to alkalize source-separated fresh human urine at the toilet so that enzymatic ureolysis can be prevented and the urine can be transported and dried off-site without the loss of nitrogen as ammonia. This was assessed by determining the solubility of MgO in urine and the MgO consumption for saturating urine, and evaluating the changes in physicochemical properties of urine when it is saturated with MgO. The effect on MgO solubility of phosphates and organics present in urine and of concentrating urine were also investigated by performing experiments on synthetic, dephosphatized synthetic urine and concentrated fresh urine. Results showed that the solubility of MgO in fresh urine varies between 0.3 and 0.6 g L-1 and ~1 g MgO L-1 is consumed to saturate fresh human urine and increase its pH >10. The solubility of MgO in different types of urine varied as fresh urine > synthetic urine > dephosphatized synthetic urine. Concentrating urine increased the solubility of MgO in it. When MgO-saturated fresh urine was subjected to urease contamination, there was no urea degradation, indicating that MgO saturation is sufficient for inactivation of urease in urine. Based on results obtained in the laboratory, as a prestep to alkaline urine dehydration, a prototype “on-site urine alkalizer” was built and tested. The prototype successfully alkalised 15 L of urine periodically added over a week’s time. For a family of four, 2 kg MgO. year-1 and 5 SEK. year-1 is required to alkalize fresh urine excreted by the family. Therefore, this thesis concluded that the use of MgO for alkalising urine is promising.