title: Fate of nitrogen during volume reduction of human urine using an on-site volume reduction system.
abstract: This study was carried to assess the effect of a mixture of salts, urea and creatinine on water evaporation from urine using an on-site volume reduction system in long-term experiments. Subsequently, the fate of nitrogen during volume reduction of urine was also assessed. The water evaporation rate, salt accumulation in the gauze sheet, concentrations of urea and ammonia-N, and pH of urine were measured periodically. Based on the results, a mass balance of nitrogen in concentrated urine was calculated for a moderate evaporating condition. The results revealed that steady-state evaporation was observed throughout the experiment period without any inhibition due to salt accumulation. Salt concentration in the gauze sheet reached steady-state illustrating the possibility of salt falling back to the tank from the sheet. No significant reduction of urea was observed for a moderate evaporating condition, which indicates inhibition of urea hydrolysis by the high concentration of the mixture of salts, urea and creatinine in the urine. In contrast, for a low evaporating condition, the pH of the urine increased to 8.9, which indicates early urea hydrolysis, causing an offensive odour and ammonia loss to the air. In simple storage experiments, a mixture of salts, urea and creatinine amounting to 227-334 g L(-1) in urine inhibited urea hydrolysis, even with faecal contamination, at 25 degrees C, while urine samples containing a mixture of salts, urea and creatinine at less than 227 g L(-1) did not provide strong inhibition of hydrolysis.
authors.affiliation: Environmental Engineering Department, Graduate School of Engineering, Hokkaido University, Kita-13 Nishi-8, Kita-Ku, Sapporo 060--8628, Japan. mohammad_masoom@eng.hokudai.ac.jp
authors.forename: Muhammad Masoom
authors.initials: MM
authors.lastname: Pahore
authors.forename: K
authors.initials: K
authors.lastname: Ushijima
authors.forename: R
authors.initials: R
authors.lastname: Ito
authors.forename: N
authors.initials: N
authors.lastname: Funamizu
mesh_terms: D000641:Ammonia / Q000032:analysis*; D003404:Creatinine / Q000737:chemistry; D006801:Humans; D006868:Hydrolysis; D009584:Nitrogen / Q000032:analysis*; D014508:Urea / Q000032:analysis* / Q000737:chemistry; D014556:Urine / Q000737:chemistry*; D014865:Waste Disposal, Fluid
chemical_list: D000641:Ammonia; D014508:Urea; D003404:Creatinine; D009584:Nitrogen