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Let’s Use Bacteria to Filter Water With Bacteria

Access to clean and potable water is a bigger problem than we can imagine. According to statistics, more than one in 10 people worldwide have no access to basic drinking water. Meanwhile, in 2025, half of the world’s population is expected to be living in areas with a shortage of clean water source.

To tackle this problem, experts at Washington University in St. Louis have designed a new water filter that kills bacteria. Ironically, they used bacteria to create such filters.

Five Years

Biofouling, or the accumulation of microorganisms, plants, and algae in wetted surfaces such as pipes, is responsible for about half of all fouling of filter membranes. Srikanth Singamaneni and Young-Shin Jun, engineering professors at Washington University used five years to solve this problem.

In a paper published in the EnvironmentalScience & Technology, the research team revealed the science behind the newly-developed ultrafiltration. It uses graphene oxide and bacterial nanocellulose that the researchers claimed to be highly efficient, long-lasting and environmentally friendly.

The new technology can clean water twice as fast as commercially available ultrafiltration membranes. However, their functions do not stop from purifying water. It also prevents the buildup of bacteria and other harmful microorganisms in the filter.

Previously, the team was able to develop membranes with similar functions using gold nanostars. However, what they wanted is something with less expensive materials.

And what can be cheaper than bacteria?

Fighting Bacteria with Bacteria 

To create the filter, researchers fed the Gluconacetobacter hansenii bacteria with a sugary substance which caused the bacteria to form cellulose nanofibers when submerged in water.

The researchers claimed that operating under high pressure, an excellently made membrane with a high quality of nanocellulose fibers has the ability to filter water twice as fast as commercially available ultrafiltration membranes.

However, to kill bacteria another compound is needed. The team incorporated flakes of graphene oxide (GO) into the bacterial nanocellulose as it was growing. With this, the GO will be trapped in the membrane, making it stable and durable.

The membrane was then treated with a base solution to kill Gluconacetobacter. This process eliminated the oxygen groups of GO, making it reduced GO. 

The team tried to expose the membrane in sunlight. The reduced GO flakes generated heat, which is dissipated into the surrounding water and bacteria nanocellulose, killing the bacteria in the water.

“If you want to purify water with microorganisms in it, the reduced graphene oxide in the membrane can absorb the sunlight, heat the membrane and kill the bacteria,” Singamaneni explained.

The researchers tested the membrane by using water which is contaminated by bacteria. After exposing it to the sun for about three minutes, the E. coli bacteria died. When heated to a temperature of above the 70 degrees Celsius, the membrane can deteriorate the cell walls of E. coli bacteria.

Finding these low-cost substitutes has been a hard and long journey for the team, however, it is worth the cause. The new invention would be a big benefit especially to poorer areas where there are shortages of drinkable water.  

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