english – The story behind a study on microplastics
”Sewage pipes cause microplastics” - we got to the core of this story and discoverd astonishing facts.
by Dipl.-Journ. Reinhild Haacker
The motivation for this article
"Can we still order civil construction projects with plastic products in good conscience in the future?" "What about the microplastics that come from sewage pipes?" These are questions we and our members have been asked more frequently lately. In particular, a press release about a study is cited again and again in this context. We have now taken a closer look at this and have written a statement.
Thumbs up for a press release
"Microplastics: Abrasion in wastewater pipes made of plastics" - this is the title of a press release issued by the "Fachvereinigung Betonrohre und Stahlbetonrohre (FBS)", in November 2021. It is a German association that represents companies of the concrete pipe industry.
It refers to results of a current study of the institute "Fraunhofer Umsicht". The press release did not miss its PR effect. Many times the article was published in trade meia, it has since been shared in social media channels and the thumbs always go up. This is possibly due to the fact that the central result of the study remains unmentioned in the press release. In addition, it hadn't been directly clear who actually commissioned the study: The FBS itself.
How the headline would have actually read...
Looking at the Fraunhofer Institute's assessment, the headline could have read: Wastewater pipes cause less microplastics than previously expected or New Fraunhofer study: exposure from plastic pipes to microplastics "rather low". Indeed, when reviewing the original Fraunhofer Institute study, this result is clearly stated and clearly prefaced in the first sentence under the title "Assessment": "The estimates show that currently the amounts of plastic abrasion are rather low compared to the total amount of microplastic emissions." Background: In the 2018 consortium study, the Fraunhofer Umsicht Institute still assumed a value of 12.0 grams per person per year (g/cap a) for wastewater pipes made of plastic as the polluter - with the new study, it is "only" 1.45 grams per person per year.
Emission from pipes corrected significantly downward in comparison
When asked at the institute, one of the authors of the study confirmed that the detailed study showed a significant downward correction of the microplastics emission from plastic sewer pipes. The reason for this is the inclusion of the filtering of the wastewater and the detailed view on the general abrasion behavior as well as expected conditions during wastewater transmission.
The value of microplastic emissions in the consortium study would now be at the level of lawn trimmers and power scythes - 24th out of a total of 30 polluter groups of microplastics. The study authors also make it clear that these are calculations and estimates, not real measurements. Actual data can only be obtained by continuously measuring and analyzing microplastics in wastewater, they say.
"Very conservatively assumed"
"The abrasion on a quarter of the pipe surface assumed in the study for the calculation is, in my view, very conservatively assumed," says Andreas Haacker, managing director of Siebert + Knipschild and honorary chairman of the RSV. In his laboratory, approval tests are regularly carried out for plastic pipes with the Darmstadt tipping trough. "The actual stress takes place on an average of about ten percent of the surface - that is, the pipe channel width," Haacker says.
Another point: the study refers to the presence of plasticizers and additives in the construction sector, but does not explain their use in pipes. "Precisely in order to produce a high level of durability, plasticizers are not used in principle for the production of sewer pipes. Thus, plasticizer migration is excluded for sewage pipes."
The RSV's statement on this
How should we as an association of pipeline rehabilitation react to this? Ignoring the issue is certainly not a solution. After all, the worldwide problem of microplastics in oceans, rivers or drinking and waste water is present and urgent. On the other hand, it is clear to anyone who sees old, rusty or broken water pipes at construction sites: The ravages of time eat away ceaselessly at water and wastewater pipes. Without plastics - whether in new construction or in renovation - there is no way.
Tires, bitumen, artificial turf: Known and unknown polluters of microplastics
Incidentally, the biggest microplastic polluters in wastewater are abrasion from tires (1228.5 g/cap a), release during waste disposal (302.8 g/cap a) and abrasion from bitumen in asphalt (228 g/cap a). The consortium study caused a nationwide stir when it was published because shoe soles and artificial turf were also among the top ten polluters. The study, which is well worth reading, is available here.
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