Engineering Minute

Engineering Minute – Wastewater Recycler Increases Ability for Handwashing in Developing Countries

A group of environmental engineers at the Swiss Federal Institute of Technology in Zurich (ETH Zurich) are working on a grid-free wastewater treatment system that will increase the availability of water to wash one's hands in developing countries where clean water is scarce. The team is led by ETH Professor Ebehard Morgenronth, head of Process Engineering at Eawag, and has been working on the system for more than seven years in conjunction with microbiologists, social scientists, urban planners, and industrial engineers. Their efforts are in response to figures put out by WHO showing millions of people die each year due to diseases that could easily be prevented by regular handwashing. This is especially true in developing countries where access to clean water can be difficult.

wastewater recycler

Unlike other commercial treatment systems that treat wastewater on site only for toilet flushing, the new system produces water that is odorless, colorless, and contains less bacteria than most tap water. The wastewater goes through several ultrafiltration stages, including an activated carbon filter that removes any traces of organic matter. Finally, the water is disinfected for storage using an electrolytic cell that produces chlorine from dissolved salt.


From the University of Sussex article: "The key component of the system is a fine-pored plastic (ultrafiltration) membrane, which retains pathogenic organisms. The microbial biofilm which develops on the membrane breaks down the fecal and urinary contaminants in wastewater. However, because nutrient concentrations in handwashing water are relatively low, biological treatment performance rapidly declines: in a study recently published by the research team, the assimilable organic carbon (AOC) removal rate was found to be 85 per cent. The solution, as Morgenroth explains, is simple but effective: 'If we add nutrients – such as nitrogen and phosphorus – to the handwashing soap, the bacteria perform very effectively, with a removal rate of almost 100 per cent.'"


Read more about the wastewater recycler that increases the ability for handwashing in developing countries at the ETH Zurich.