New research from the Chinese Academy of Sciences suggests that, in wastewater treatment plants, an integrated membrane system may be more efficient at removing microplastics than conventional activated sludge systems.
Microplastic is growing environmental pollution problem. Microplastics are ubiquitous and have been detected in more than 2,000 marine organisms. The large amount of chemicals released by microplastics can affect living organisms and threaten their health. In addition, hydrophobic microplastics can adsorb on endocrine disruptors, antibiotics, and other organic pollutants in water, which can aggravate aquatic environment pollution.
Various studies have shown that wastewater treatment plants are highly successful at preventing emerging contaminants, including microplastics, from entering an environment.
One prospective treatment method for removing various pollutants from wastewater is membrane technology. Membrane technology has an excellent removal rate for ammoniacal nitrogen, bacteria, and organic pollutants. With the shortage of water resources and water pollution, integrated membrane system (IMS) technology for reclaimed water reuse has attracted more and more attention. Can wastewater treatment plants prevent microplastics from entering the marine environment? And what is the fate of microplastics in the IMS system used for water reclamation?
To answer these questions, researchers Jian Lu and Ying Cai from the Chinese Academy of Sciences and their team members investigated the fate of microplastics in a conventional activated sludge system (CAS) and an IMS system in a coastal reclaimed water plant.
Their work found that the IMS system could prevent the re-entry of most of the microplastics into the marine environment and convert the wastewater into renewable water, which can subsequently reduce pollution and bolster water resiliency. This study, entitled “Fate of microplastics in a coastal wastewater treatment plant: Microfibers could partially break through the integrated membrane system,” has been published online in Frontiers of Environmental Science & Engineering.
In the study, the removal rate of microplastics in the IMS system reached 93.2 percent after membrane bioreactor (MBR) treatment. That rate further increased to 98.0 percent after the reverse osmosis (RO) membrane process. The flux of microplastics in MBR effluent was reduced from 1.5×1013 MPs/d to 10.2 ×1011 MPs/d while that of the RO treatment decreased to 2.7×1011 MPs/d. The application of the IMS system in the reclaimed water plant could prevent most of the microplastics from being discharged into coastal water.
These findings suggested that the IMS system was more efficient than CAS in removing of microplastics. However, small scale fiber plastics (< 200 μm) could still break through the RO system.
