EcoImpact 2.0

EcoImpact 2.0: Impacts of advanced wastewater treatments on tolerance of stream periphyton to micropollutants

The upgrade of about 100 Swiss wastewater treatment plants (WWTP) to specifically remove micropollutants (MP) offers a unique opportunity to assess the efficiency of MP removal technologies and consequent in-stream changes of aquatic organisms. In EcoImpact 1, clear biological responses related to MP exposure from WW effluents have been identified at different levels of biological organization, ranging from cells to organisms to communities. It was demonstrated that stream biofilms, also termed periphyton, downstream of WWTPs were more tolerant towards the discharged MPs than upstream. This Pollution Induced Community Tolerance (PICT) disappeared upon upgrading the WWTP for MP removal. These findings provide a first line of evidence on the relevance of using PICT and periphyton communities to assess the biological impact of MPs  from WW and their removal in the receiving waters.

Project goals and research questions:

EcoImpact 2.0 focuses on the previously observed development of periphyton tolerance as MP-related biological responses in the receiving waters. The ultimate goals are to examine how to use PICT for a comparative assessment of the biological effects of treatment technologies, and whether PICT could be established as a water quality assessment tool in practice.

We will experimentally address the following four research questions:

Q1. Can we observe PICT in periphyton growing in experimental flumes that are treated with WWTP effluents?

Q2. Is the observed PICT in periphyton downstream from WWTPs driven by MP exposure or by the release of tolerant microorganisms from the WWTP or a combination of both?

Q3. To which degree do different (combinations of) advanced WW treatment technologies affect tolerance development to MPs in periphyton?

Q4. What is the potential role of PICT for future monitoring to assess the biological effects of upgrading WWTPs?

Experimental approaches

Investigations with varying degrees of experimental control will be carried out in the Maiandros flume system, consisting of 20 channels, in which periphyton will be grown on glass plates. The flumes will be located at Eawag, and later on at the WWTP Zürich-Werdhölzli for testing advanced treatments of WWTP effluent. We will vary the chemical and biological composition of WW effluent by various combinations of WW treatment processes. We will study the effect of these manipulations on the chemical and biological water quality, focusing on periphyton tolerance, structure and function as biological effect indicators. To be able to evaluate the role of PICT for future monitoring programs, field studies at sites undergoing WWTP upgrades will accompany the flume experiments.

Project team

Project Management

Project leader: Christan Stamm

Dr. Christian StammDeputy Head of DepartmentTel. +41 58 765 5565Send Mail
Prof. Dr. Rik EggenDeputy DirectorTel. +41 58 765 5320Send Mail

Project team

Dr. Louis CarlesPostdoctoral ScientistTel. +41 58 765 5449Send Mail
Baptiste ClercScientific AssistantTel. +41 58 765 6764Send Mail
Dr. Adriano JossTel. +41 58 765 5408Send Mail
Prof. Dr. Kristin SchirmerHead of departmentTel. +41 58 765 5266Send Mail
Dr. Nele SchuwirthHead of Department, Group leader Ecological ModellingTel. +41 58 765 5528Send Mail
Dr. Ahmed TliliDeputy head of departmentTel. +41 58 765 5330Send Mail
Simon WullschlegerScientific AssistantTel. +41 58 765 6789Send Mail


Carles, L.; Wullschleger, S.; Joss, A.; Eggen, R. I. L.; Schirmer, K.; Schuwirth, N.; Stamm, C.; Tlili, A. (2021) Impact of wastewater on the microbial diversity of periphyton and its tolerance to micropollutants in an engineered flow-through channel system, Water Research, 203, 117486 (14 pp.), doi:10.1016/j.watres.2021.117486, Institutional Repository


Dr. Christian StammDeputy Head of DepartmentTel. +41 58 765 5565Send Mail


tream biofilms exposed to wastewater in the Maiandros flume system. Louis Carles in action. (Photo: Eawag)

EcotoxicoMicYR: First international webinar of young microbial ecotoxicology researchers
December 14, 2021 - Louis Carles, postdoctoral scientist in the Department of Environmental Toxicology, won the award for the best live presentation during the webinar “EcotoxicoMic for Young Researchers”. He presented his work conducted in the project EcoImpact 2.0 on the impact of wastewater on stream biofilms. Louis Carles is now invited to present his work at the EcotoxicoMic 2022 Conference (Montpellier, France, 15-18 November 2022).