31. Urine separation & water recycling

Urine separation & water recycling

21ST CENTURY

(picture © Eawag / Switzerland. Photographer: Lucky Lugogwana)

The Blue Diversion Autarky system, here being tested in Durban, South Africa, provides an effective way of locally recycling water in areas without affordable, safe water supplies and sewerage systems; it requires minimal energy input and only occasional refilling with water. It also yields nitrogen-based fertiliser.

(Picture: © Eawag / Switzerland. Photographer: Kai Udert)

This urinal and urine-separating toilet pan are shown connected to the Blue Diversion Autarky system during the Reinvented Toilet Exhibition in Beijing in November 2018, part of the Bill & Melinda Gates Foundation Reinvent the Toilet Challenge. The system was developed as a response to the problem faced by the billions of people worldwide who don’t have access to safe, hygienic sanitation.

Urine-separating toilets divert the flow of the two types of human waste – liquid urine and solid faeces – enabling them to be retrieved and treated separately. Nitrogen and phosphates found mainly in urine can be retrieved and used as fertiliser.

The Blue Diversion Autarky system processes liquid waste (urine and water from hand-washing) through its ‘Water Wall’, which comprises a a bioreactor and ultrafiltration membrane that undertakes the core treatment. The resulting liquid is then passed through an activated carbon filter to be ‘polished’ and disinfected, removing remaining microorganisms leaving the water ready to be used again for hand-washing and flushing. Together, these processes remove most pathogens and odours.

A faeces-treatment module has also been developed, using high temperature and pressure to mineralise the solid waste and separate water. Both sets of treatment systems are due to undergo large-scale field testing.

Each toilet flush uses several litres of water – which adds up to large volumes for whole households. Finding ways to recycle this water, as well as reducing the quantity needed for flushing, is increasingly important across the world. Local on-site treatment of human waste can also be hugely useful in places where adequate piped sewerage or waste collection systems aren’t available.