7 April 2021
Biological pathogens and antibiotic-resistant bacteria can grow on microplastics. That this poses a potential danger for human and animal health has been known for a long time. But it now appears that a commonly used water purification technology is helping spread potential pathogens on microplastics. This worrying research was published in Journal of Hazardous Materials Letters.
Researchers
at the New Jersey Institute of Technology examined wastewater treatment plants
(WWTPs) and looked at the growth of bacteria on microplastics. After the
water purification process, many microplastics are ending up in the surface
water and are then spreading in the environment.
HOW DOES IT
WORK?
Wastewater
is purified in WWTPs before it is released into the surface water. The most
common method of water purification is a biologically activated sludge system
in which microorganisms purify the water.
The
wastewater to be purified contains countless microplastics from households.
These come from products like personal care products or from machine washed or
dried synthetic clothing. The wastewater also contains a lot of pathogenic
bacteria that are excreted by humans, for example.
The microplastics then come into contact with the bacteria. The millions of pieces of contaminated microplastics are released by the WWTPs into the surface water. The RIVM (in Dutch) assumes that the WWTPs only remove between 50% and 90% of the microplastics from the wastewater. In the Netherlands, this is incinerated along with the sewage sludge. In other countries, sewage sludge is spread on fields as fertiliser. The microplastics that are caught by the wastewater treatment plants are in these cases released into the environment.
PLASTISPHERE
However
small the microplastics, all microplastics in water have a layer of life. This
layer – the ‘plastisphere’ – consists of algae, bacteria and single-cell
organisms. Given that microplastics stay in the environment for a very long
time, they become a vector of transport in spreading the bacteria that live and
form colonies on the microplastics.
Some of
these bacteria can cause infections that, with increasing antibiotic
resistance, are becoming ever more life threatening.
CONCLUSIONS
Bacteria
feel at home in WWTPs and form colonies on the microplastics there. The research
shows that microplastics act as a hub of both antibiotic resistant bacteria as
well as other pathogens. Once in the surface water, the microplastics can
further spread these bacteria.
The
researchers analysed samples from three local WWTPs that use active sludge and
compared them to sand samples. The microplastics with polyethylene (PE) and
polystyrene (PS) in the active sludge had much more bacterial growth than the
microplastics in the sand. Certain types of bacteria also appeared to promote
the development of the plastisphere (or biofilm) containing pathogens and
antibiotic resistance.
In October,
check the new scientific breakthroughs that will be presented at our Plastic
Health Summit.
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