Study Of Nutrients Recovery From Source-separated Human Urine By Evaporation And Crystallization

Human urine is considered a high quality liquid fertilizer,which is rich in cropgrowth requirements nutrients. In traditional drainage patterns, About87%of thenitrogen,50%of the phosphorus and54%of the potassium from domestic wastewaterreside in urine，but accounts for less than one percent of the waste water volume.Based on ecological sanitation concept, the Source-separated urine and urine processingis not only simplify sewage treatment process, but also reduce its operating costs、improve its treatment effect, which is also a effective way to achieve the furtherutilization of urine. In this study, a series of experimental were investigated forseparating nutrients from urine by evaporation and crystallization. In this study, a seriesof experimental were investigated for separating nutrients from urine by evaporationand crystallization.The effects of temperature and storage on urea hydrolysis in fresh urine and staleurine were studied. Results showed that the number and activity of bacteria were themost important factors to the urea hydrolysis. Urine in open box at room temperaturewas hydrolyzed easier than in a closed box with freezing or warming, which attribute tothe higher activity of bacteria and higher amounts of bacteria in air. The urea hydrolysisof fresh urine could be completed50%in20days, but the90%mixed-stored urinehydrolyzed only in two days. The hydrolysis rate of the stale urine was much higherthan fresh urine because the count of microbes increased by the new mixed urine.The level of ammonia is very high in hydrolyzed urine but ammonia volatilizationmay occur during storage. The evaporation characteristics of ammonia wereinvestigated at three different temperatures and six different pH to avoid ammonia losses. The results showed that, pH is the key factors influencing the degree ofammonia volatilization in the urine, and temperature affects the speed of nitrogenvolatilization, just have little impact on the extent of the nitrogen loss. Specifically, atpH <4, the loss rate of ammonia was lower than5%when the volume reduced to evenlower than1/5of the initial volume of urine.After evaporation and crystallization,37.2g crystals separated out from1L urineat pH4. It contributes15.8%of N,4.75%of P, and5.77%of K. XRD analysis foundthat the main elements are ammonium salt-NH4Cl, accounts for about80%, NaCl, KClis about15%and4%respectively. The author also research with soil as the carrier ofnutrients to analyse the feasibility of soil fertilizer by experiment. After10timesrepetitions absorption studies, the nitrogen content in the soil is no longer increased,nitrogen content of soil eventually reach185mgN/g, its total nutrition content of T (N,P2O5and K2O)%is26.4%. According to organic standards (GB15063-2009),,soilfertilizer by this way is a kind of high nitrogen and NPK proportion balanced compoundfertilizer.