Human urine contains hormones such as contraceptive pill oestrogen, medicine residues (including antibiotics) and the nutrients phosphorus, nitrogen and potassium, which wastewater treatment plants largely fail to capture. Flowing into rivers and seas, the nutrients then upset the natural balance: they foster algae blooms, which during its decomposition deplete the affected body of water from oxygen, eventually killing its biodiversity. Indeed, according to Professor Tove Larsen of the Swiss Federal Institute of Aquatic Science and Technology (Eawag):
“Wastewater management is vital if we are to prevent catastrophic damage to the world’s rivers and oceans.”
If the nutrients could be separated out, they could be used to create valuable fertilisers but, historically, efforts to remove these pollutants have been expensive, energy intensive and of limited success. Some years ago, a company called Vuna, a spinoff of the Eawag, did devise a process which both filters out medicinal residues and nutrients, and turns the nutrients into a fertiliser licensed by the Swiss Federal Office for Agriculture. However, this system can process only urine: once mixed with faeces and grey water, it is too late.