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Biofilm in combined sewer:  a wet weather pollution source ? and / or

Sewer Processes and Networks France - 2002. V. Rocher, S. Azimi, R. Moilleron, G. Chebbo. Biofilm in combined sewer:  a wet weather pollution source ? and / or  a dry weather pollution indicator ?. Sewer processes and networks - 2002. Presentation plan. 1) What is biofilm ?.

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Biofilm in combined sewer:  a wet weather pollution source ? and / or

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  1. Sewer Processes and NetworksFrance - 2002 V. Rocher, S. Azimi, R. Moilleron, G. Chebbo Biofilm in combined sewer:  a wet weather pollution source ? and / or  a dry weather pollution indicator ?

  2. Sewer processes and networks - 2002 Presentation plan 1) What is biofilm ? 1)What is biofilm ? 2) Why study biofilm in sewer ? 3) Description of this research program 4) Main results 5) Conclusions

  3. One of the three kinds of sewer deposits Waste water Organic layer (OL):  brown colour  high organic content  2-15 cm thick Sewer trunk Gross bed sediment (GBS):  black and grey colours  high mineral content  5-40 cm thick Sewer processes and networks - 2002 What is biofilm ? Biofilm:  brown colour  high organic content  1-5 mm thick

  4. Biofilm in the sewer trunk Sewer trunk  fixed to the trunk wall at the mean water level 10-20 cm high Sewer processes and networks - 2002 • What is biofilm ? • One of the three kinds of sewer deposits

  5. Biofilm architecture (TEM) 1 2 3 Trunk wall 5 µm 200 µm 40 µm Organic matter  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 diameter and 2-5 µm long Cell layer Sewer processes and networks - 2002 • What is biofilm ? • One of the three kinds of sewer deposits • Biofilm in the sewer trunk

  6. Biofilm architecture (TEM) 1 2 Trunk wall Organic matter 50 µm 100 µm Cell layer  This uniform film of bacteria totally covers an organic matrix  Mineral fragments are embedded in the cell layer Sewer processes and networks - 2002 • What is biofilm ? • One of the three kinds of sewer deposits • Biofilm in the sewer trunk

  7. Biofilm architecture (TEM) Organic matrix Cell layer Trunk wall Organic matter 100 µm  the organic matrix is between the cell layer and the wall Cell layer  its thickness is important as it reaches several millimeters Sewer processes and networks - 2002 • What is biofilm ? • One of the three kinds of sewer deposits • Biofilm in the sewer trunk  it has a fibrous structure: vegetal fibers and organic matter

  8. Sewer processes and networks - 2002 Presentation plan 1) What is biofilm ? 2) Why study biofilm in sewer ? 3) Description of this research program 4) Main results 5) Conclusions

  9. Street and roof runoffs • External inputs • In-sewer sources Biofilm erosion Bed sediment resuspension Assessment of the biofilm contribution to the wet weather pollution Sewer processes and networks - 2002 Why study biofilm in sewer ? • it could act as a wet weather pollution source Waste water flow Two kinds of pollutant sources • External inputs • In-sewer sources • In-sewer sources

  10. it could be used as a dry weather pollution indicator Use of biofilm as pollution indicator might make greater scale projects easier, since sampling is easy:  easily accessible  do not require specific devices (little metallic scraper) Sewer processes and networks - 2002 Why study biofilm in sewer ? • it could act as a wet weather pollution source

  11. Sewer processes and networks - 2002 Presentation plan 1) What is biofilm ? 2) Why study biofilm in sewer ? 3) Description of this research program 4) Main results 5) Conclusions

  12. N Acen Acyl F  Aliphatic hydrocarbons (TAH) Resolved aliphatic hydrocarbons  Unresolved Complex Mixture (UCM)  Polycyclic Aromatic Hydrocarbons (PAH)  Non-alkylated compounds (2-6 rings)  Alkylated compounds P A Fluo Pyr 16 US-EPA PAHs B[a]A Chry B[a]P B[k]F B[b]F D[ah]A BPer IP Sewer processes and networks - 2002 Description of this research program • Micro-pollutants measured: hydrocarbons (HC)

  13. Two different approaches 1) Quantitative approach 2) Qualitative approach Determination of the HC stock in the 3 kinds of deposits Comparison between the HC distribution in the 3 kinds of deposits To assess of the biofilm contribution to the wet weather pollution To determine whether biofilm could be used as indicator of the HC pollution or not Sewer processes and networks - 2002 Description of this research program • Micro-pollutants measured: hydrocarbons (HC)

  14. « Le Marais » network description: 3 main trunks : « Vieille du Temple » and « St Gilles » trunks flow into « Rivoli » Collector characteristics: « 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 Sewer network of Paris Vieille du temple Seine river Urban surface distribution St Gilles Rivoli St Gilles Sewer processes and networks - 2002 Description of this research program • Sampling site

  15. Biofilm it was sampled every 25m from the St Gilles-Rivoli junction up to 600 m upstream Bed deposits they were sampled at the top of the st Gilles trunk (600 m upstream Rivoli) Sewer processes and networks - 2002 Description of this research program • Sampling site

  16. Sewer processes and networks - 2002 Description of this research program • Sampling site • Bed deposit sampling procedures  Gross Bed Sediment: sampled with an adapted shovel that isolates the sediment during sampling and traps the fine particles of this sediment.

  17. Sewer processes and networks - 2002 Description of this research program • Sampling site • Bed deposit sampling procedures  Organic layer: sampled with a PVC box (85x30x50) (Ahyerre et al, 1999). It was inserted in the GBS during 10 dry weather days, then OL was scraped.

  18. Sewer processes and networks - 2002 Presentation plan 1) What is biofilm ? 2) Why study biofilm in sewer ? 3) Description of this research program 4) Main results 4.1) Quantitative approach 4.2) Qualitative approach 5) Conclusions

  19. Waste water GBSi fraction below 400 µm GBSs fraction above 400 µm  Biofilm PAH content was 4 to 8 times smaller than other deposit ones  Biofilm TAH content was 3 to 5 times greater than other deposit ones Sewer processes and networks - 2002 Results: quantitative approach • PAH and TAH contents (µg/g dw) in the 3 deposits PAH contents TAH contents Biofilm 4 +/- 6 196 +/- 59 OL 14 +/- 19 68 +/- 18 31 +/- 39 42 +/- 21 GBSi GBSs 22 +/- 18 68 +/- 80

  20. PAH and TAH stocks in the 3 deposits Deposit masses (kg) PAH stocks (g) TAH stocks (g) 393 1052 22 1200 2800 13700 4 81 117 935 Biofilm (n=14) OL (n=4) GBSi (n=5) GBSs (n=5) 0.1 16 86 307 0.1 4  PAHs and TAHs stored in the biofilm only reached 0.1 and 4 g, respectively  PAHs and TAHs were mainly stored in the GBS Sewer processes and networks - 2002 Results: quantitative approach • PAH and TAH contents (µg/g dw) in the 3 deposits

  21.   Sewer processes and networks - 2002 Results: quantitative approach • 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 pollution To assess the biofilm contribution to the wet weather HC pollution, we assumed that: Waste water 1) The GBS was not resuspended 2) The OL was entirely resuspended 3) The biofilm was entirely eroded

  22. Biofilm 1% Biofilm 5% PAH TAH OL 99% OL 95% Sewer processes and networks - 2002 Results: quantitative approach • 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 pollution Conclusion 1: Low values emphasised that biofilm was not an important in-sewer source of wet weather pollution and can be disregarded

  23. Sewer processes and networks - 2002 Presentation plan 1) What is biofilm ? 2) Why study biofilm in sewer ? 3) Description of this research program 4) Main results 4.1) Quantitative approach 4.2) Qualitative approach 5) Conclusions

  24. C27 C29 % C17-18 Biofilm  C29 Carbon number % C27 OL C17-18 Carbon number  Biofilm and OL showed the same aliphatic distribution pattern Sewer processes and networks - 2002 Results: qualitative approach • HC distribution (%) in the 3 deposits: TAH

  25. C27 to C29 C17-C18 Biofilm-OL Predominance of heavy compounds  % C18 Predominance of light compounds GBS Carbon number  Aliphatic distributions of GBSi and GBSs contrasted significantly with the biofilm and OL distributions Sewer processes and networks - 2002 Results: qualitative approach • HC distribution (%) in the 3 deposits: TAH GBSi and GBSs exhibited almost the same aliphatic distribution

  26. In all the deposits, the same PAHs were observed The 3 major PAHs were the same in all the deposits 40% GBSs GBSi 15% OL Biofilm PAH distributions were almost similar in OL, GBSs and GBSi, whereasthe biofilm showed more Pand less Fluo than other deposits. Fluo Pyr P Sewer processes and networks - 2002 Results: qualitative approach • HC distribution (%) in the 3 deposits: PAH

  27. TAH Fingerprint PAH Fingerprint Biofilm Biofilm     OL GBS OL GBS Biofilm and OL fingerprints were found to be similar, while GBS showed a fingerprint significantly different Biofilm fingerprint was slightly different than other deposit ones, even if the major PAHs were the same in all the deposits. Sewer processes and networks - 2002 Results: qualitative approach • Biofilm as a pollution indicator? Conclusion 2:Biofilm is an indicator of the aliphatic pollution of the OL Biofilm is not an indicator of the aromatic pollution of the bed deposits, but it could be used to estimate the main PAHs present in the OL and the GBS

  28. Sewer processes and networks - 2002 Conclusions: a wet weather pollution source and/or a dry weather pollution indicator? Answer 1 Biofilm does not contribute significantly to the wet weather HC pollution Answer 2 Biofilm is a reliable indicator of the aliphatic pollution Biofilm is not a reliable indicator of the aromatic pollution Thank you for your attention

  29. Step 1: box installation  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. Step 2: pumping Waste water Pump GBS  Two panels were lowered.  The water in the box was pumped out. Step 3: scraping  When all the water was pumped, OL was scraped until reaching the GBS. Sewer processes and networks - 2002 Description of this research program • Sampling site • Bed deposit sampling procedures  Organic layer: sampled with the assistance of a PVC box (85x30x50) opened on two sides so that water can flow through it.

  30. OL 4% OL 4% Biofilm 0.02% OL 7% OL 7% Biofilm 0.4% GBSi 10% GBSi 21% GBSi 10% GBSi 21% GBSi 10% GBSi 21% GBSs 75% GBSs 83% GBSs 75% GBSs 83% GBSs 75% GBSs 83% Sewer processes and networks - 2002 Results: quantitative approach • PAH and TAH contents (µg/g dw) in the 3 deposits • PAH and TAH stocks in the 3 deposits PAH TAH  HC were mainly stored in the GBS  Remaining HC were mainly stored in the OL  HC stock in the biofilm wasa lot smallerthan the OL and GBS ones

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