biofilm in combined sewer: a wet weather pollution source ? and / or a dry weather pollution...

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 ?


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


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



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








100 µm

This uniform film of bacteria totally covers an organic matrix

Mineral fragments are embedded in the cell layer

50 µm

11 22








it has a fibrous structure: vegetal fibers and organic matter

the organic matrix is between the cell layer and the wall

100 µm


Organic Organic matrixmatrix

its thickness is important as it reaches several millimeters

Presentation plan



2) Why study biofilm in sewer ?2) Why study biofilm in sewer ?


4) Main results

5) Conclusions

Why study biofilm in sewer ?


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 ?


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




3) Description of this research program 3) Description of this research program

4) Main results

5) Conclusions

Description of this research program


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



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



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



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



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.



Sampling site


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





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


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



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




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




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





4) Main results 4) Main results

5) Conclusions

4.1) Quantitative approach

4.2) Qualitative approach 4.2) Qualitative approach

Results: qualitative approach


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



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



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



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?


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



Sampling site


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




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%

biofilm in combined sewer: a wet weather pollution source ? and / or a dry weather pollution...

Documents

sewer sourceswhy study

deposits biofilm contribution

sewer trunkwhat

combined sewer

kinds of sewer depositswhat

deposits pah

quantitative approach

conclusions description