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maximum of 473 fibers L 1. In comparison, another study found similar values
about 180 textile fibersL 1 [19].
Unlikefibers, fragmentswereonly rarelycollected,probablybecauseof the low
volumes of the samples (100–400 mL). In the 20 samples studied, 16 did not
contain any fragments. For the four remaining samples, three contained one frag-
ment, while the other contained two fragments. These small values indicate a
potential upper limit for the concentration of these particles. No fragments in a
400 mL sample, for instance, imply a concentration<2.5 particles L 1. Larger
valueswere observed in other studies: 430 particles L 1 [19] or 13 particles L 1
[20]. If this variation in fragment concentrations is site dependent or is related to
differentmethodologies, it remainsunknownat themoment.Fragmentscould, inan
oversized sewage network, settle inside the sewer during dryweather periods and
reach theWWTP only at low concentrations. It is known that Paris wastewater
sewerage system is oversized leading to a very lowflowvelocity and therefore a
high sedimentationof particles inside the sewer.
TwoWWTPswere selected inorder to estimate the treatment efficiency. Seine
CentreWWTPwasconsidered for thecaseofa treatmentbybiofilters,whileSeine
Aval WWTP is a conventional activated sludge plant. For Seine Centre, three
sampling campaigns on three consecutive working days were carried out. Raw
wastewater after pretreatment, settledwastewater (after the primary clarifier), and
treated water (after the biofilters treatment) were all considered. Only limited
volumeswere consideredhere.As the disposal channel of SeineAval is large and
longenoughtobenavigable,amantatrawlwitha330μmmeshsizewastowedbya
motor boat in theupstreamdirection inorder to sample highvolumes (68m3) and
count fragments.
In thecaseofSeineCentre, onlyfiberswereencountered.The results suggested
a removal from83 to95%of thefiber contamination.Otherworks showedhigher
removal efficiencies ofMPsbyWWTPs, i.e., between95and99%[20,21].How-
ever, all these results are hardly comparable since methods used vary from one
study to another.
Fragmentswere detected at the outlet of theWWTPSeineAval because larger
volumeswere integrated. Irregular fragmentswereobservedprimarily, and foams,
films,andsphereswerefoundpunctually.Thenumberof fragmentsobserved in the
treatedwater varies between 6 10 5 and 3 10 4 fragmentsL 1. The concen-
trations of fragments are much lower than the levels of fibers observed in the
automatic sampler samples (105more fibers). Being able to observe fragments in
themanta trawl samples is also an additional indication that fragments are present
inWWTPeffluents but just too scarce to beobserved in small sample volumes.
A combined sewer system collects rainwater runoff and domestic sewage.
However, during heavy rainfall events, the volume of water may exceed the
capacity of the sewer and can cause flood events. In this situation, untreated
water is dischargeddirectly into thewater bodies. In this context, 500mLsamples
were collected atLaBricheCSOoutlet during three events.
Both fragments and fibers were encountered in the CSO samples. For fibers,
levelsof190,898and1,046fibersL 1weredetected.Thepresenceoffibers ismost
Sources andFate ofMicroplastics inUrbanAreas:AFocusonParisMegacity 75
Freshwater Microplastics
Emerging Environmental Contaminants?
- Title
- Freshwater Microplastics
- Subtitle
- Emerging Environmental Contaminants?
- Authors
- Martin Wagner
- Scott Lambert
- Publisher
- Springer Open
- Date
- 2018
- Language
- English
- License
- CC BY 4.0
- ISBN
- 978-3-319-61615-5
- Size
- 15.5 x 24.1 cm
- Pages
- 316
- Categories
- Naturwissenschaften Chemie