Available online: https://pub.norden.org/temanord2023-523/ Over the 15 past years, leakages of millions of plastic biocarriers - supports for bacterial growth used in certain types of Wastewater Treatment Plants have been reported in riverine and marine environments. In most cases, the biocarriers are not recovered, contributing to the issue of global plastic pollution. The objective of this report is to develop guidelines for the safe management of biocarriers based on proven-effective existing technical solutions and management measures, with the overarching goal of preventing releases of biocarriers in the marine and riverine environments. A holistic approach, encompassing every step of the biocarriers’ life cycle, helped to identify possible improvements in production, transportation, storage, engineering, facility operation, and biocarrier disposal.