title: How well is microlitter purified from wastewater? - A detailed study on the stepwise removal of microlitter in a tertiary level wastewater treatment plant.
abstract: Wastewater treatment plants (WWTPs) can offer a solution to reduce the point source input of microlitter and microplastics into the environment. To evaluate the contributing processes for microlitter removal, the removal of microlitter from wastewater during different treatment steps of mechanical, chemical and biological treatment (activated sludge) and biologically active filter (BAF) in a large (population equivalent 800 000) advanced WWTP was examined. Most of the microlitter was removed already during the pre-treatment and activated sludge treatment further decreased the microlitter concentration. The overall retention capacity of studied WWTP was over 99% and was achieved after secondary treatment. However, despite of the high removal performance, even an advanced WWTP may constitute a considerable source of microlitter and microplastics into the aquatic environment given the large volumes of effluent discharged constantly. The microlitter content of excess sludge, dried sludge and reject water were also examined. According to the balance analyses, approximately 20% of the microlitter removed from the process is recycled back with the reject water, whereas 80% of the microlitter is contained in the dried sludge. The study also looked at easy microlitter sampling protocol with automated composite samplers for possible future monitoring purposes.
authors.affiliation: Department of Built Environment, Aalto University, PO Box 15200, FI-00076, AALTO, Finland. Electronic address: julia.talvitie@aalto.fi.
authors.forename: Julia
authors.initials: J
authors.lastname: Talvitie
authors.affiliation: Department of Built Environment, Aalto University, PO Box 15200, FI-00076, AALTO, Finland.
authors.forename: Anna
authors.initials: A
authors.lastname: Mikola
authors.affiliation: Finnish Environment Institute, Marine Research Center, PO Box 140, FI-00251, Helsinki, Finland.
authors.forename: Outi
authors.initials: O
authors.lastname: Setälä
authors.affiliation: Helsinki Region Environmental Services Authority HSY, PO Box 100, FI-00066, HSY, Finland.
authors.forename: Mari
authors.initials: M
authors.lastname: Heinonen
authors.affiliation: University of Eastern Finland Sib Labs, PO Box 1627, FI-70211, Kuopio, Finland.
authors.forename: Arto
authors.initials: A
authors.lastname: Koistinen
mesh_terms: D012722:Sewage / Q000737:chemistry; D014865:Waste Disposal, Fluid; D062065:Wastewater / Q000737:chemistry*; D014867:Water; D014874:Water Pollutants, Chemical
chemical_list: D012722:Sewage; D062065:Wastewater; D014867:Water; D014874:Water Pollutants, Chemical
keywords: Microlitter; Microlitter budget; Microplastics; Reject water; Sludge; WWTP; Wastewater