Martin Seidl

Toxicity of combined sewer overflows on river phytoplankton: the role of heavy metals.

The toxic effect of a combined sewer overflow (CSO) on the phytoplankton community of the river Seine has been studied by means of short-term primary production measurements. As the discharged solids usually do not remain in the water column, only filtered or centrifugated fractions were tested. The collected phytoplankton were grown in the laboratory for 2 days, after addition of N, P and EDTA. Stock cultures in exponential growth were directly tested with heavy metals, but resuspended algal cells were used for effluent testing. The results show an increase of EC50 value for the single metal species in the order Cu<<Zn</=Pb. Free metal contents were calculated with the chemical speciation model Mineql+. The EC50 dilution of the tested CSOs effluent was 50%. This value increased by 30% after addition of 5 10(-6) M EDTA, indicating that the effluent toxicity is only partially due to its metallic compounds.

Effect of substrate depth and rain-event history on the pollutant abatement of green roofs

This study compares the effectiveness of two different thickness of green roof substrate with respect to nutrient and heavy metal retention and release. To understand and evaluate the long term behaviour of green roofs, substrate columns with the same structure and composition as the green roofs, were exposed in laboratory to artificial rain. The roofs act as a sink for C, N, P, zinc and copper for small rain events if the previous period was principally dry. Otherwise the roofs may behave as a source of pollutants, principally for carbon and phosphorus. Both field and column studies showed an important retention for Zn and Cu. The column showed, however, lower SS, DOC and metal concentrations in the percolate than could be observed in the field even if corrected for run-off. This is most probably due to the difference in exposition history and weathering processes.

Organic carbon biodegradability and heterotrophic bacteria along a combined sewer catchment during rain events

The aim of this study was the evaluation of fluxes of organic carbon and biodegradability of waste waters during rain events in order to better predict the impacts of combined sewer overflows (CSO). The combined sewer system studied was located in a densely populated urban catchment adjacent to Paris. Five subcatchments of different size, have been monitored during several rain events for suspended solids, conductivity, ammonium, chemical and biological oxygen demand. In addition, two of these subcathments have been evaluated for dissolved and particulate organic carbon, their biodegradable fractions, and the total bacterial biomass. Several indexes, indicate a lower degradability of waste water during dry weather at the downstream stations, accompanied by an increase of bacterial size and bacterial biomass. A further decrease of biodegradable organic carbon related to rain intensity can be seen at all stations. Our results show a higher proportion of refractory organic carbon during rain events than during dry weather with a possible contribution of the in-sewer sediments to the bacterial wet weather flux.

Comparison of parameters characterizing organic matter in a combined sewer during rainfall events and dry weather

To understand the effect of combined sewer overflows on the river Seine (France), a characterization of effluent in terms of organic matter and bacterial biomass was carried out during several sampling campaigns performed in a combined sewer located in Parisian suburbs under wet and dry weather conditions. Measurements classically used to study wastewater (suspended matter, chemical oxygen demand [COD] and biochemical oxygen demand [BOD]) were compared with the estimate of biodegradable and refractory fractions of particulate and dissolved organic carbon. Relationships among different parameters used to describe organic material in effluent were established. Even for large fluctuations in organic matter concentrations, highly homogeneous ratios between the different descriptors during wet and dry weather were observed, and no significant differences could be observed in two catchments strongly differing by their sizes. The only two small differences in relative composition that could be observed between dry and wet weather were slightly lower content of organic carbon in suspended solids and a lower biodegradability of this material during rain events. Accordingly, with the help of obtained relationships and values of classical variables like turbidity, BOD, and COD for a given effluent, it is possible to make reasonably accurate estimates of its composition in terms of biodegradable and refractory fractions of dissolved and particulate organic matter and bacterial biomass.

Assessment of storm water ecotoxicity using a battery of biotests

As part of the European Union 5th Framework Programme (EU FP5) sustainable storm water management project DayWater, an international monitoring programme was established to investigate the ecotoxicity of highway and urban runoff samples. This involved the collection of samples from a total of 35 storm events from sites in Sweden (Lulea and Stockholm), Germany (Wuppertal), and France (Nantes). To enable both chronic and acute end points to be addressed, the ecotoxicity tests were performed using rotifers (Brachionus calyciflorus), bacteria (Vibrio ficherii), and algae (Pseudokirchneriella subcapitata). Samples collected at the Stockholm site were additionally analysed for a range of water quality parameters enabling this site to be considered from a combined physico-chemical and ecotoxicological perspective. This paper provides an overview of the results of the whole monitoring programme and demonstrates that storm water frequently exerts a toxic effect. Although the levels of ecotoxicity detected were found to vary greatly in relation to sites, storm events and test organisms, further analysis demonstrated a moderately strong correlation between the responses of algae and rotifer tests. Microtox was generally found to be the most responsive test in terms of both frequency of detection of toxicity and level at which a toxic impact could be detected.

Élimination des parabènes et du triclosan dans un filtre non drainé de l'assainissement non collectif (ANC)@@@Elimination of Parabens and Triclosan in a Non Drained Filter of On-Site Sewage Treatment

On-site waste water treatment (ANC) is a device ensuring the collection, the treatment and the evacuation of domestic waste waters in an autonomous way, near the dwelling where collective infrastructure would be too expensive. The research carried out within the framework of the project Gessol Ancres considers the efficiency of such a system and in particular of its non drained sand filter in the elimination of carbon, nitrogen and of the emerging micropolluants parabens and triclosan. A new ANC device was equipped with a sampling system and was monitored during 18 months. The first results indicate a reduction of more than 80% of the carbonaceous pollution entering, with a considerable contribution from the ground. With regard to parabens and triclosan, in the first case we observed an elimination of 87% between the septic tank and the outlet of the sand filter. The ground does not contribute significantly to the elimination of parabens. The overall abatement of triclosan was 72% with a major contribution (47%) in the soil. The differences between the two substances are probably due to their molecular structure.

Élimination des parabènes et du triclosan dans un filtre non drainé de l'assainissement non collectif (ANC)

On-site waste water treatment (ANC) is a device ensuring the collection, the treatment and the evacuation of domestic waste waters in an autonomous way, near the dwelling where collective infrastructure would be too expensive. The research carried out within the framework of the project Gessol Ancres considers the efficiency of such a system and in particular of its non drained sand filter in the elimination of carbon, nitrogen and of the emerging micropolluants parabens and triclosan. A new ANC device was equipped with a sampling system and was monitored during 18 months. The first results indicate a reduction of more than 80% of the carbonaceous pollution entering, with a considerable contribution from the ground. With regard to parabens and triclosan, in the first case we observed an elimination of 87% between the septic tank and the outlet of the sand filter. The ground does not contribute significantly to the elimination of parabens. The overall abatement of triclosan was 72% with a major contribution (47%) in the soil. The differences between the two substances are probably due to their molecular structure.