To find out more about the effect of microplastics on the UV inactivation of bacteria in water, we talked to Mrs. Antrea Naziri, Research Specialist at the "Nireas" International Water Research Center of University of Cyprus.
Internationally, microplastics have been found in municipal wastewater, due to many daily activities, such as washing synthetic clothes. Microfibers of plastic are released by washing and through the sewage systems they end up in the treatment stations. Although a fairly large percentage of microplastics is removed from the various treatments, microplastics remain in the treated municipal wastewater. When this wastewater is discharged into surface water or reused to irrigate crops, microplastics are introduced into the environment.
The presence of microplastics both in the inflow and outflow of the stations, and therefore in every intermediate stage of municipal wastewater treatment, created additional questions regarding their effect on the performance of the applied processes. One of the most important processes is disinfection using UV, which is carried out as the final stage of urban wastewater treatment to destroy pathogenic microorganisms, such as bacteria and viruses.
The research of the "Nirea" International Water Research Center aims to understand the effects of the UV inactivation and bacteria in the Water. When municipal sewage is exposed to ultraviolet radiation, it is absorbed by the genetic material of microorganisms, resulting in their destruction. But how can the presence of microplastics affect this process?
Microplastics may act as a protective shield for microorganisms, preventing them from absorbing UV radiation, thus reducing the efficiency of disinfection. That is, microplastics are interposed between ultraviolet radiation and micro-organisms with the result that the micro-organisms do not absorb the required radiation to destroy them. The first experimental results confirm this hypothesis, since a reduced destruction of microorganisms is observed in the presence of microplastics compared to their absence.
Another survey was also conducted by NIREAS to see the effect of microplastics and nano plastics in treated wastewater on edible plants after irrigation. Treated wastewater is used to meet the demand for irrigation water in Cyprus. Considering the presence of pollutants in treated wastewater, its use for land irrigation might have an impact in the environment. Their research focused on the combined effects of microplastics and nanoplastics and other environmental contaminants present in treated wastewater on edible plants after irrigation. Their results show that negative effects depend on the size of MPs/NPs and their mixing ratio with co-contaminants.
To improve the water treatment in wastewater plants, Mrs. Nasiri suggested that we could use the filters and magnetic particles that destroy or collect the smallest particles of microplastic.
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