Struvite recovery from urine (Nepal)

Human urine is considered as a main contributor of nutrients in domestic wastewater with 85 percent of total nitrogen, 50 percent of the total phosphorus, and 55 percent of total potassium by mass though it consists only 1 percent of raw wastewater volume. These nutrients can be retrieved in the form of struvite which otherwise mix in water resources creating eutrophication and algal blooms and also load wastewater treatment plant. It is estimated that the use of struvite as agricultural fertilizer from urine can replace 20-25 percent of commercial fertilizers. The use of wood ash as a magnesium source in struvite precipitation is one of the major purposes of the study. Chemical analysis indicated less concentration of Mg in wood ash requiring high amount for struvite formation. The physicochemical parameters (pH, temperature, electrical conductivity, TSD and phosphate concentration) of the urine were monitored over the storage period of 25 days which play important role in struvite precipitation. The quantity of struvite formed was comparatively more in 1.5:1 molar ratio than the optimum ratio 1:1 (Mg:PO4). Based on the result, it was concluded that urine treatment using commercial magnesium source or wood ash from the standpoint of struvite as agricultural fertilizer alone was not economically beneficial; however, considering the use of effluent and the environmental benefit of waste treatment, the whole process may be considered beneficial.