How well is microlitter purified from wastewater? – A detailed study on the stepwise removal of microlitter in a tertiary level wastewater treatment plant

Julia Talvitie*, Anna Mikola, Outi Setälä, Mari Heinonen, Arto Koistinen

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

267 Citations (Scopus)

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.

Original languageEnglish
Pages (from-to)164-172
Number of pages9
JournalWater Research
Volume109
DOIs
Publication statusPublished - 1 Feb 2017
MoE publication typeA1 Journal article-refereed

Keywords

  • Microlitter
  • Microlitter budget
  • Microplastics
  • Reject water
  • Sludge
  • Wastewater
  • WWTP

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