4. Evaluation of Microplastic Removal Efficiency in Wastewater Treatment Plants

Microplastics (MPs) concentration in aquatic ecosystems rises as plastic manufacture rises year after year. MPs are a persistent and subtle environmental hazard that have already been linked to adverse effects on human health and aquatic environments. The objective of this paper was to discuss about the conventional wastewater treatment methods along with the modern treatment techniques for removal of MPs from wastewater. Conventional wastewater treatment involves the removal of suspended sediments, dissolved solids, biological degradation of organic materials, and nutrients from wastewater using a combination of physical, chemical, and biological processes. Primary method includes primary sedimentation viz., basic treatment, coagulation and sedimentation and secondary method are physical, chemical and biological factor involve for removal of MPs. In this paper about six different modern treatment techniques were examined for the removal of MPs from municipal wastewater treatment facilities to reduce the possible hazards of MPs. Some advanced methods such as membrane bioreactors, reverse osmosis, bioremediation, rapid sand filtration (RSF), electrocoagulation, magnetic separation and sol–gel method. Membrane bioreactors is one of the most efficient methods of wastewater treatment with 99.5% MPs removal. Use of dynamic membranes aided in achieving higher percentage of MPs removal. The reverse osmosis process includes pushing of water through a semi-permeable membrane rejecting the particles at the membrane but particles with size smaller than the membrane can pass through the membrane leading to 90% of removal efficiency. Recently bio-remediation is also introduced in the elimination of MPs which includes certain microbial species such as Bacillus, Paenibacillus, Stenotrophomonas and Pseudomonas species. Rapid sand filtration (RSF) is a method of passing of water through sand beds/sheets of various size sand particles and with removal is about 97.7% for MPs. Electrocoagulation method involves anodes which are broken down to release the coagulant precursors, electrolysis occurs at the cathode, and flotation is used to promote the separation of the MPs. Fibrous MPs can be removed with this process with removal efficiency of about 99%. Another advanced method is magnetic separation, which involves utilization of Fe nanoparticles, which bind to the surface of nano-plastic or MPs. The efficiency for various kind of plastics was recorded between 74 and 105%. Sol–gel method technique for extracting polymers from wastewater by causing large particle agglomerates using sol–gel induced agglomeration. Synthetic amorphous Silica (SAS) is used as agglomerates catalyst for the process. This analysis provides a comprehensive perspective of the entire MPs removal strategy and minimizing the potentially dangerous consequences of MPs in aquatic systems.