Struvite (often called MAP for magnesium ammonium phosphate: MgNH4PO4·6H2O) is a safe, bio-available fertilizer, which can be precipitated from urine by adding magnesium. STUN developed a low-cost process to produce struvite. Conventional phosphate fertilizers are produced from phosphate rocks, a non-renewable resource. Alternative phosphate sources are necessary for a secure food production in the future.
Drip irrigation cum urine fertilization = fertigation
When urine is applied to the field using a bucket or similar, ammonium is lost. To prevent this, urine or struvite process effluent can be applied with drip irrigation; the liquid flows through a set of hoses, no nutrients are lost on the way.
With a drip irrigation system, a maximum of water reaches the crops directly: you save time and water used for irrigation. From time to time, you may add urine to your irrigation system to provide your crops with nutrients.
Urine can be used to fertilize aquatic plants, such as Azolla or Lemna (Duckweed). These plants are rich in proteins and can be used as animal feed. The plants recover nutrients from the urine or struvite process effluent.
Ammonium in wastewater (e.g. urine) has a negative impact on streams, lakes and groundwater. Biological processes can be used to transform ammonia into less harmful nitrate or to remove ammonia completely.
To completely remove nitrogen from urine, either organic substrate has to be added or specialized bacteria - anaerobic ammonium oxidizers - have to be added (anammox process).
STUN developed a rotating biological contactor (RBC), which can be used for the biological treatment of domestic wastewater, urine or struvite production effluent.
Microbiological risk assessment in urine treatment
In certain conditions, urine may be contaminated by bacteria or viruses. To minimize the risks for urine harvestors and urine managers, microbiological studies examined the pathway of pathogens through the process.