Anna Pedersen

The Big Blue

Sustainable and financially profitable sanitation

Three years ago, an off-grid closed-system toilet known as the Blue Diversion won an award in the Bill & Melinda Gates Foundation's "Reinventing the Toilet"-challenge. It has also won the title of Most Innovative Project presented by the International Water Association and the project is currently shortlisted for the "Designs of the Year 2015"-awards presented by the Design Museum in London.
So, what makes this toilet so special? Well, for one, the water it flushes with is subsequently used in its hand-washing sink. Also, it comes with with a fully-equipped community-scale business plan.


Blue Diversion Toilet - Eawag

Worldwide, 2.7 billion people currently rely on on-site sanitation technologies. Meanwhile, some 2.5 billion people lack access to safe and clean sanitation facilities. The Blue Diversion is a squatting toilet adresses these challenges while also introducing an obtainable and local businessplan that can provide jobs and steady incomes for the area.

Here's how the Blue Diversion works ...
Feces, urine, and flush water are separated right below the toilet bowl. The water, because it's used more to rinse out the bowl than to actually transport the waste, isn't as contaminated as what goes down a regular toilet's pipes. It's still fairly disgusting, though, so it's pumped into a filtration system in the back wall of the setup.

Here, it is passed through a bioreactor that neutralizes organic matter and ammonia, along with an ultrafiltration membrane that blocks pathogenic organisms such as bacteria and viruses. Any remaining trace amounts of organic matter and ammonia are then neutralized by an electrolysis unit, which also adds chlorine to disinfect the water.
From there, the water runs down to be used in the sink, in the shower head-like washer, or to rinse out the bowl once again. According to Eawag, the main developer of the Blue Diversion toilet, the same water is good for about 50 uses per day. The power for pumps, electronics and the electrolysis unit is provided by a top-mounted photovoltaic(solar powered) panel.

A team from Eawag (the Swiss Federal Institute of Aquatic Science and Technology) partnered with Austrian design firm EOOS, and the Blue Diversion Toilet was born. The single unit separates undiluted urine, feces, and water into separate containers below the pan. The water that is used for flushing is then filtered through a self-cleaning multi-barrier treatment system to make it safe and clean for washing. The same water can be used around 50 times a day, and power for the pumps and electronics within the toilet is provided by photovoltaic panels atop the unit.

The urine and feces from the tanks is collected twice a week by a service person who safely transports the sealed waste containers to a community-scale resource recovery plant. Here, the feces are safely treated and composted, while the nutrients from the urine are extracted through partial nutrification and distillation to create “marketable urine-based fertilizer". In other words, the urine treatment is quite similar to that of our friends at de Ceuvel.

The team from Eawag is currently working on developing a sit-down version as well as one that will have onsite resource recovery, dubbed the Autarky Toilet. They are also seeking support to begin large-scale production of the toilets, which they hope to market for around $500.