biofilm in combined sewer: a wet weather pollution source ? and / or a dry weather pollution...
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Biofilm in combined sewer:Biofilm in combined sewer: a wet weather pollution source ?
and / or
a dry weather pollution indicator ?
Sewer Processes and NetworksFrance - 2002
V. Rocher, S. Azimi, R. Moilleron, G. Chebbo
Presentation plan
Sewer processes and networks - 2002
1) What is biofilm ?
2) Why study biofilm in sewer ?
3) Description of this research program
4) Main results
5) Conclusions
1)1) What is biofilm ?What is biofilm ?
What is biofilm ?
Sewer processes and networks - 2002
Gross bed sediment (GBS):Gross bed sediment (GBS): black and grey colours
high mineral content
5-40 cm thick
Organic layer (OL):Organic layer (OL): brown colour
high organic content
2-15 cm thick
Biofilm:Biofilm: brown colour
high organic content
1-5 mm thick
Waste water
Sewer trunk
One of the three kinds of sewer depositsOne of the three kinds of sewer deposits
What is biofilm ? One of the three kinds of sewer deposits
Sewer processes and networks - 2002
Biofilm in the sewer trunkBiofilm in the sewer trunk
Sewer trunkSewer trunk
fixed to the trunk wall at the mean water levelat the mean water level
10-20 cm high10-20 cm high
What is biofilm ? One of the three kinds of sewer deposits
Sewer processes and networks - 2002
Biofilm in the sewer trunk
Trunk Trunk wallwall
Organic Organic mattermatter
Cell Cell layerlayer
Biofilm architecture (TEM)Biofilm architecture (TEM)
200 µm
40 µm
5 µm
Cell layer consists of numerous bacteria compacted together and might be bound by a polysaccharide coat
Cell morphology of the dominant bacteria is a rod shaped cell of 2 µm diameter2 µm diameter and 2-5 µm long2-5 µm long
11 3322
Trunk Trunk wallwall
Organic Organic mattermatter
Cell Cell layerlayer
Biofilm architecture (TEM)Biofilm architecture (TEM)
What is biofilm ? One of the three kinds of sewer deposits
Sewer processes and networks - 2002
Biofilm in the sewer trunk
100 µm
This uniform film of bacteria totally covers an organic matrix
Mineral fragments are embedded in the cell layer
50 µm
11 22
What is biofilm ? One of the three kinds of sewer deposits
Sewer processes and networks - 2002
Biofilm in the sewer trunk
Trunk Trunk wallwall
Organic Organic mattermatter
Cell Cell layerlayer
Biofilm architecture (TEM)Biofilm architecture (TEM)
it has a fibrous structure: vegetal fibers and organic matter
the organic matrix is between the cell layer and the wall
100 µm
Cell Cell layerlayer
Organic Organic matrixmatrix
its thickness is important as it reaches several millimeters
Presentation plan
Sewer processes and networks - 2002
1) What is biofilm ?
2) Why study biofilm in sewer ?2) Why study biofilm in sewer ?
3) Description of this research program
4) Main results
5) Conclusions
Why study biofilm in sewer ?
Sewer processes and networks - 2002
it could act as a wet weather pollution sourcewet weather pollution source
External inputs
Waste water flow
In-sewer sources
Two kinds of pollutant sourcesTwo kinds of pollutant sources
Street and roof runoffs
External inputs
Bed sediment resuspension
In-sewer sources
Assessment of the biofilm contribution to the wet weather pollution
Biofilm erosion
In-sewer sources
Why study biofilm in sewer ?
Sewer processes and networks - 2002
it could act as a wet weather pollution source
it could be used as a it could be used as a dry weather pollution indicatordry weather pollution indicator
do not require specific devices (little metallic scraper)
Use of biofilm as pollution indicator might make greater Use of biofilm as pollution indicator might make greater
scale projects easier, since sampling is easy:scale projects easier, since sampling is easy:
easily accessible
Presentation plan
Sewer processes and networks - 2002
1) What is biofilm ?
2) Why study biofilm in sewer ?
3) Description of this research program 3) Description of this research program
4) Main results
5) Conclusions
Description of this research program
Sewer processes and networks - 2002
Micro-pollutants measured: hydrocarbons (HC)Micro-pollutants measured: hydrocarbons (HC)
Aliphatic hydrocarbons (TAH)
Resolved aliphatic hydrocarbons
Unresolved Complex Mixture (UCM)
Fluo
B[k]F
B[b]F
A PyrP
AcylN Acen F
B[a]A Chry B[a]P
D[ah]A BPer IP
16 US-EPA PAHs
Polycyclic Aromatic Hydrocarbons (PAH)
Non-alkylated compounds (2-6 rings)
Alkylated compounds
Description of this research program
Sewer processes and networks - 2002
Micro-pollutants measured: hydrocarbons (HC)
Two different approachesTwo different approaches
1) Quantitative approach2) Qualitative approach
Determination of the HC stockHC stock in the 3 kinds of deposits
To assess of the biofilm biofilm contribution contribution to the wet weather
pollution
Comparison between the HC HC distributiondistribution in the 3 kinds of deposits
To determine whether biofilm could be used as indicator indicator of the HC pollution or
not
Sewer network of ParisSewer network of Paris
Seine riverSeine river
Description of this research program
Sewer processes and networks - 2002
Sampling siteSampling site « Le Marais » catchment description:« Le Marais » catchment description:
located in central Paris
densely populated (295 inhabitants. ha-1)
covers an area of 42 ha in an old residential district
impervious at 90% and divided into 3 kinds of urban surfaces
Urban surface distribution
Public areas23%
Streets23%
Roofs54%
« Le Marais » network description:« Le Marais » network description:
3 main trunks : « Vieille du Temple » and « St Gilles » trunks flow into « Rivoli »
Collector characteristics:
St Gilles
Vieille du temple
Rivoli
Flow sectionCollectors Long (m) Slope (%) Height (m) Width (m)
St Gilles 798 0.04 0.7 0.6VDT 596 0.06 0.6 0.6
St St GillesGilles
Description of this research program
Sewer processes and networks - 2002
Sampling siteSampling site
it was sampled every 25mevery 25m from the St
Gilles-Rivoli junction up to 600 m
upstream
they were sampled at the top of the st top of the st
Gilles trunkGilles trunk (600 m upstream Rivoli)
BiofilmBiofilm
Bed depositsBed deposits
Description of this research program
Sewer processes and networks - 2002
Sampling site
Bed deposit sampling proceduresBed deposit sampling procedures
Gross Bed Sediment: Gross Bed Sediment: sampled with an adapted shovel that isolates the sampled with an adapted shovel that isolates the
sediment during sampling and traps the fine particles of this sediment. sediment during sampling and traps the fine particles of this sediment.
Description of this research program
Sewer processes and networks - 2002
Sampling site
Bed deposit sampling proceduresBed deposit sampling procedures
Organic layer: Organic layer: sampled with a sampled with a PVC boxPVC box (85x30x50) (Ahyerre et al, 1999). It (85x30x50) (Ahyerre et al, 1999). It
was inserted in the GBS during 10 dry weather days, then OL was scraped. was inserted in the GBS during 10 dry weather days, then OL was scraped.
Presentation plan
Sewer processes and networks - 2002
1) What is biofilm ?
2) Why study biofilm in sewer ?
3) Description of this research program
4) Main results 4) Main results
5) Conclusions
4.1) Quantitative approach 4.1) Quantitative approach
4.2) Qualitative approach
Biofilm TAH content was 3 to 5 times greater3 to 5 times greater than other deposit ones
Biofilm PAH content was 4 to 8 times smaller4 to 8 times smaller than other deposit ones
Results: quantitative approach
Sewer processes and networks - 2002
PAH and TAH contents (µg/g dw) in the 3 depositsPAH and TAH contents (µg/g dw) in the 3 deposits
Waste water
4 +/- 6
14 +/- 19
31 +/- 39
PAH contentsPAH contents TAH contentsTAH contents
BiofilmBiofilm
OLOL
GBSiGBSi
GBSsGBSs 22 +/- 18
196 +/- 59
68 +/- 18
42 +/- 21
68 +/- 80
GBSi fraction below 400 µmGBSi fraction below 400 µm
GBSs fraction above 400 µmGBSs fraction above 400 µm
Results: quantitative approach
Sewer processes and networks - 2002
PAH and TAH contents (µg/g dw) in the 3 deposits
PAH and TAH stocks in the 3 depositsPAH and TAH stocks in the 3 deposits
Deposit masses (kg)Deposit masses (kg)
Biofilm (n=14)Biofilm (n=14)
OL (n=4)OL (n=4)
GBSi (n=5)GBSi (n=5)
GBSs (n=5)GBSs (n=5)
2222
12001200
28002800
1370013700
0.10.1
1616
8686
307307
PAH stocks (g)PAH stocks (g) TAH stocks (g)TAH stocks (g)
44
8181
117117
935935
PAHs and TAHs stored in the biofilm only reached 0.1 and 4 gonly reached 0.1 and 4 g, respectively
0.10.1 44
PAHs and TAHs were mainly stored in the GBSmainly stored in the GBS
393393 10521052
Results: quantitative approach
Sewer processes and networks - 2002
PAH and TAH contents (µg/g dw) in the 3 deposits
PAH and TAH stocks in the 3 deposits
Biofilm contribution to the wet weather HC pollutionBiofilm contribution to the wet weather HC pollution
Waste water
To assess the biofilm contribution to the wet
weather HC pollution, we assumed that:we assumed that:
1) The GBS was not resuspended
2) The OL was entirely resuspended
3) The biofilm was entirely eroded
Results: quantitative approach
Sewer processes and networks - 2002
PAH and TAH contents (µg/g dw) in the 3 deposits
PAH and TAH stocks in the 3 deposits
Biofilm contribution to the wet weather HC pollutionBiofilm contribution to the wet weather HC pollution
TAHTAHPAHPAH
OL OL 99%99%
Biofilm Biofilm 1%1%
OL OL 95%95%
Biofilm Biofilm 5%5%
Conclusion 1Conclusion 1:: Low values emphasised that biofilm was not an important ow values emphasised that biofilm was not an important
in-sewer source of wet weather pollution and can be disregardedin-sewer source of wet weather pollution and can be disregarded
Presentation plan
Sewer processes and networks - 2002
1) What is biofilm ?
2) Why study biofilm in sewer ?
3) Description of this research program
4) Main results 4) Main results
5) Conclusions
4.1) Quantitative approach
4.2) Qualitative approach 4.2) Qualitative approach
Results: qualitative approach
Sewer processes and networks - 2002
HC distribution (%) in the 3 deposits: HC distribution (%) in the 3 deposits: TAHTAH %
Carbon number%
Carbon number
BiofilmBiofilm
OLOL
Biofilm and OL showed the same aliphatic distribution patternsame aliphatic distribution pattern
C29C29
C29C29
C17-18C17-18C27C27
C17-18C17-18C27C27
Results: qualitative approach
Sewer processes and networks - 2002
HC distribution (%) in the 3 deposits: HC distribution (%) in the 3 deposits: TAHTAH
%
Carbon number
GBSGBS
GBSi and GBSs exhibited almost the same the same aliphatic distributionaliphatic distribution C18C18
Biofilm-OLBiofilm-OLC17-C18C17-C18
C27 to C29C27 to C29
Predominance of Predominance of light compoundslight compounds
Predominance of Predominance of heavy compoundsheavy compounds
Aliphatic distributions of GBSi and GBSs contrasted significantly with the contrasted significantly with the biofilm and OL distributionsbiofilm and OL distributions
NAcy
l
Acen F P A
Fluo
Pyr
B(a)A
Chry
B(b, F
)F
B(a)P
B(e)P
BiofilmBiofilm
GBSsGBSs
OLOL
GBSiGBSi
Results: qualitative approach
Sewer processes and networks - 2002
HC distribution (%) in the 3 deposits: HC distribution (%) in the 3 deposits: PAHPAH
In all the deposits, the same PAHs were observedsame PAHs were observed
40%40%
15%15%
PAH distributions were almost similar in OL, GBSs and GBSi, , whereas the biofilm showed more P more P and less Fluo than other deposits.and less Fluo than other deposits.
PP PyrPyr
Fluo
Fluo
The 3 major PAHs 3 major PAHs were the same in all the deposits
Biofilm fingerprint was slightly differentwas slightly different than other deposit ones, even if the major PAHs were the same in all the deposits.
Biofilm and OL fingerprintsBiofilm and OL fingerprints were found to be similarbe similar, while GBS showed a fingerprint significantly different
Results: qualitative approach
Sewer processes and networks - 2002
Biofilm as a pollution indicator? Biofilm as a pollution indicator?
BiofilmBiofilm
OLOL GBSGBS
TAH FingerprintTAH Fingerprint
PAH FingerprintPAH Fingerprint
BiofilmBiofilm
OLOL GBSGBS
Conclusion 2Conclusion 2:: Biofilm is an Biofilm is an indicator of the aliphatic pollution of the OLindicator of the aliphatic pollution of the OL
Biofilm is Biofilm is not an indicator of the aromatic pollution of the not an indicator of the aromatic pollution of the bed depositsbed deposits, but it could be used to estimate the main , but it could be used to estimate the main PAHs present in the OL and the GBSPAHs present in the OL and the GBS
Conclusions: a wet weather pollution source and/or a dry weather pollution indicator?
Sewer processes and networks - 2002
Answer 1Answer 1
Biofilm Biofilm does not contribute significantlydoes not contribute significantly to the wet weather HC to the wet weather HC pollution pollution
Answer 2Answer 2
Biofilm is a Biofilm is a reliable indicatorreliable indicator of the of the aliphaticaliphatic pollution pollution
Biofilm is Biofilm is not a reliable indicatornot a reliable indicator of the of the aromaticaromatic pollution pollution
Thank you for your attentionThank you for your attention
Step 3: scraping
When all the water was pumped, OL was scraped until reaching the GBS.
The unit was inserted into the GBS, in the direction of the flow.
Samples were taken after each 5 to 10 dry weather day period.
GBS
Waste water
Step 1: box installation
Description of this research program
Sewer processes and networks - 2002
Sampling site
Bed deposit sampling proceduresBed deposit sampling procedures
Organic layer: Organic layer: sampled with the assistance of a sampled with the assistance of a PVC boxPVC box (85x30x50) (85x30x50)
opened on two sides so that water can flow through it. opened on two sides so that water can flow through it.
Pump
Two panels were lowered.
The water in the box was pumped out.
Step 2: pumping
Results: quantitative approach
Sewer processes and networks - 2002
PAH and TAH contents (µg/g dw) in the 3 deposits
PAH and TAH stocks in the 3 depositsPAH and TAH stocks in the 3 deposits
HC were mainly stored in the GBS
Remaining HC were mainly stored in the OL
HC stock in the biofilm wasHC stock in the biofilm was a lot smallera lot smaller than the OL and GBS onesthan the OL and GBS ones
TAHTAHPAHPAH
GBSs GBSs 75%75%
GBSi GBSi 21%21%
OL OL 4%4%
GBSs GBSs 83%83%
GBSi GBSi 10%10%
OL OL 7%7%
GBSs GBSs 83%83%
GBSi GBSi 10%10%
GBSs GBSs 75%75%
GBSi GBSi 21%21%
GBSs GBSs 83%83%
GBSi GBSi 10%10%
OL OL 7%7%
Biofilm Biofilm 0.4%0.4%
Biofilm Biofilm 0.02%0.02%
GBSs GBSs 75%75%
GBSi GBSi 21%21%
OL OL 4%4%
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