While certain types of filtration media are great at removing pathogens from water, they do clog up over time, slowing their rate of filtration. According to new research, a solution to the problem may lie in the use of "living filtration membranes."
Led by Montana Technological University's Assoc. Prof. Katherine Zodrow, a team of scientists started by fermenting a blend of sugar, black tea, distilled white vinegar and water. When exposed to the air, the liquid formed into a thin permeable membrane known as a SCOBY (Symbiotic Culture Of Bacteria and Yeast).
The membrane was made up of stacked sheets of cellulose which were produced by Acetobacter bacteria, and inhabited by both the bacteria and yeast-family fungi. That same SCOBY is traditionally used in the production of a fermented drink known as kombucha.
Both a piece of the SCOBY and a commercial polymer filtration membrane were separately used to filter water obtained from two reservoirs and a Montana river. Although both were effective at trapping harmful microbes, it was found that the SCOBY membrane was considerably better at resisting biofouling, a condition in which colonies of bacteria produce slimy biofilms which impede water flow.
As a result, the SCOBY was able to maintain a fast rate of filtration for a longer amount of time. Additionally, when a biofilm eventually did form on it, that film contained significantly fewer bacteria than the biofilm which formed on the polymer membrane.
The scientists believe that the anti-biofouling effect may be due to the fact that the Acetobacter bacteria produce acetic acid, which discourages the growth of other types of bacteria. As an added bonus, because the SCOBY membrane is maintained by bacteria that live within it, it can self-heal when damaged.
It is additionally claimed that SCOBY-based filters would be inexpensive to manufacture, and would biodegrade when discarded. A paper on the research was recently published in the journal ACS ES&T Water.
Source: American Chemical Society
