MPs are an emerging pollutant that can be found worldwide, raising concerns especially in aquatic ecosystems. WWTPs are the ultimate barrier preventing MPs from being discharged into natural waters. For this reason, the MPFs behavior in secondary treatment was evaluated. The analysis of the MPFs concentration in the SBR sludge showed a clear decrease in the first 40 days of the experiment, after which remained quite stable. The analysis of the MPFs concentration in the SBR effluent showed a similar trend. The decreasing trends were expected, as before the start of the experiment the sludge was treating influents with a much higher concentration of MPs compared to the simulated wastewater.