Existing and emerging technologies for microplastics removal : Review report of the FanpLESStic-sea project

Abstract

In this review, existing and emerging technologies and methods for removal of microplastics (MPs) especially from urban aquatic environments are presented. In recent years, several physical, chemical and biological technologies and methods for MP removal have been investigated and developed mainly for wastewaters. Filtration-based technologies include sand and disc filters, biofilters, membrane bioreactors and ultrafiltration methods. Coagulation/flocculation, electrocoagulation and sol-gel induced agglomeration are chemical methods investigated for MP removal. MP removal efficiencies higher than 90% have been reported for several technologies and methods. Potential methods based on activities of microorganisms, higher marine organisms and plants are also discussed. In general, MP particles are efficiently removed from wastewaters during wastewater treatment. However, as wastewater treatment plants receive vast amounts of MP-containing wastewaters, these treatment processes are in the need for further optimization to retain MPs even more efficiently. On the other hand, present wastewater treatment technologies and methods can be replaced with novel technologies to better meet the stringent requirements for treated waters, together with efficient removal of MPs. Membrane bioreactor is an example of such a technology with higher removal rates for organic pollutants and MPs than in conventional activated sludge process. In addition to wastewaters, also stormwaters contain significant amounts of MPs. However, most stormwaters end up in aquatic environments either untreated or only partially purified. The solutions for removal of MPs from stormwaters should be locally adaptable, cost-efficient and with minimal need for management. Recently, removal of stormwater MPs has been the subject of studies focusing on sedimentation ponds, filtration and bioretention systems. New and innovative MP removal technologies and methods suitable especially for stormwaters including urban snow meltwaters are still needed and the MP removal efficiency of these methods should be demonstrated in pilot studies. Finally, treatment methods of MP-laden matrices (e.g. sewage sludge, pond sediments, sand, plant biomass, membrane retentate) created with MP retainment processes are lacking. Therefore, research and development of sustainable and cost-effective methods are urgently needed to avoid mere shifting of MPs and their effects from one environmental compartment to another.