Recycled handwashing water helps prevent disease

Water used for washing hands usually goes down the drain. Now, an innovative system is helping reduce this wastage and prevent infectious diseases in developing countries by recycling handwashing water.

Every year around four million people, mainly in developing countries, die from diarrhoeal diseases or respiratory infections, according to WHO figures. But the number of deaths could be greatly alleviated by regular handwashing.

In countries with water shortages however, this is problematic. Now, scientists at the Federal Institute of Technology (ETH) in Zurich have developed a grid-free treatment system allowing greywater – relatively clean wastewater from showering, bathing or handwashing – to be repeatedly recycled.

While commercial systems are already available which enable greywater to be treated on-site for use in toilet flushing, the recycled water does not meet the required quality standards to be used for other purposes. With the new system however, after several treatment stages, the greywater is odour‑free and colourless, with a bacterial count lower than that of Zurich tap water, explained a statement.

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.

After ultrafiltration, any traces of organic matter remaining in the wastewater are removed by an activated carbon filter, before an electrolytic cell is used to produce chlorine from dissolved salt to disinfect the water during storage.

While the system is primarily designed for use in underdeveloped regions, it could also have applications in places such as passenger train toilets.

The functionality of the new water treatment system was demonstrated by a two-month field test carried out this summer in Zurich, according to the statement. Although the system was sometimes used by over a hundred people per day, sufficient amounts of clean, odour-free and colourless water were available at all times.

Photo credit: UNAMID/ CC BY-NC-ND 2.0

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