A toilet that eliminates its own waste
Scion has built a prototype toilet with attached waste treatment system that eliminates waste on the spot. Based on using circular bioeconomy design principles, the toilet uses wet-oxidation technology developed initially for the pulp and paper industry to destroy the solid components of toilet waste and kill disease-causing microorganisms.
This toilet technology could be used to replace unsafe sanitation practices such as pit latrines in developing countries. The technology could also be common place in future circular cities. As disastervulnerable, centralised infrastructure ages, new decentralised waste treatment systems could be installed in apartments or city blocks.
This research is part of the Reinvent the Toilet Challenge supported by the Bill and Melinda Gates Foundation. Their aim is to create a toilet that is safe for humans and the environment, is sustainable, cheap to use (less than US$0.05 per user per day) and works ‘off the grid’.
Our wet-oxidation technology shows promise and has been selected to advance to a new phase of work ‘Generation 2 Reinvented Toilet.’ Scion will join an international team to investigate the most promising technologies developed so far.
The wet-oxidation method we have incorporated into our toilet grew from expertise established in treating waste water for the pulp and paper industry. Wet oxidation is a hydrothermal treatment process that uses oxygen, heat and pressure to breakdown materials. We can destroy toilet waste solids and completely kill pathogens by treating organic and inorganic components at temperatures between 150 to 374°C and pressures between 0.5-20 MPa.
Nutrient recovery and effluent processing that meets ISO 30500 standards for air emission, liquid and solids output and odours, will be part of the total system including wet-oxidation and final treatment. The final step is the filtration stage before wastewater discharge. This filtration step removes any remaining solids and nutrients.
The options being investigated for the total system include membranes, microbial fuel cells and purple phototrophic bacteria for nutrient recovery.
Scion has been developing these technologies for three years through the Reinvent the Toilet Challenge. The Challenge was started by the Bill & Melinda Gates Foundation in 2011. Their aim is to remove the barriers to safe sanitation by funding scientists to create a toilet that is safe for humans and the environment, is sustainable, cheap to use (less than US$0.05 per user per day) and works ‘off the grid’. The next phase (Generation 2) of research will be led by Georgia Institute of Technology, and Scion will join with engineers and researchers from UK, Switzerland and throughout the USA.