DRYING AS A URINE DEWATERING METHOD / Torkning som metod för att avvattna urin
One strategy to increase the amount of nutrients recycled is to handle urine separately and use it as a fertiliser. However, an extended use of urine separation toilets will result in considerable volumes to be handled. The amount of urine solution could be reduced by using drying techniques. However, the possibilities of dewatering urine by drying are limited by the risk of nitrogen losses through evaporation of ammonia. Two different strategies to prevent ammonia evaporation have been tested in laboratory. The first strategy is based on addition of acid to fresh urine in order to prevent the decomposition of urea into ammonium. The second Strategy is based on acidification of stored urine with a high fraction of ammoniacal nitrogen. The added compounds were supposed to form salts with ammonium, i.e. ammonium sulphate. The experiments show that there is potential in both methods, i.e. ammonia evaporation could be avoided by addition of acid. However, the amount of acid necessary is about 10 times higher if ammonia evaporation is to be prevented by acidification of stored urine.