Performance of intermittent sand and coke filters for the removal of size-ranged microplastics

Microplastics (MPs) are a growing environmental problem that threaten living organisms, especially in water ecosystems. One of the main sources of MPs in water environments are wastewater treatment plants, which remove the majority of these micropollutants, but large amounts keep reaching the environment daily. To achieve a larger removal on MPs in wastewater, intermittent filtration sets as an efficient and cheap alternative. In this work, three laboratory-scale filters were tested, with different filtration media (sand, sand/coke and coke) to compare their performance with PP-spiked freshwater and real wastewater samples in removing MPs from different size ranges, from larger than 32 µm to 100 µm. Sand/coke and coke filters showed the best results, with a general microplastic removal efficiency of up to 92.79 ± 2.78 % for wastewater and 89.56 ± 2.19 % for PP-spiked water. This removal efficiency decreased with smaller MPs, reaching up to 90.87 ± 3.46 % for wastewater and 76.28 ± 8.54 % for PP-spiked water. Significant differences were found on efficiencies for PP-spiked water and wastewater, especially in the range from 32 to 63 µm, where biofilm formed on pores surface with wastewater filtration may play an important role for the removal of these MPs.