Identification, assessment and prioritization of ecotoxicological risks on the scale of a territory: Application to WWTP discharges in a geographical area located in northeast Lyon, France

The ecotoxicological risk assessment methodologies developed up to now mainly focus on local pollution and do not incorporate an evaluation and prioritization of the different risk situations present in the same territory. This article presents the different phases of formulating an innovative methodology developed to fill this gap, and its application to all the 18 WasteWater Treatment Plants (WWTP) of a geographical area located northeast of Lyon, France. The aim was also take into account emerging pollutants that are very often "forgotten" in ecotoxicological risk assessments. The results of the study show the extreme diversity of the ecotoxicity of the pollutants present in discharges, with "minimum" PNEC values in the region of a millionth of a microgram (10^-6 μg/l) and "maximum" PNEC values in the region of several tens of micrograms. They also show very considerable diversity of the flows of the receiving watercourses in the territory concerned (from several m³/s to 600 m³/s). The Risk Quotients (RQ) resulting from these 2 datasets, calculated for each WWTP and for each of the 10 pollutants most implicated in ecotoxicological risks (Diclofenac, Amoxicillin, Trimethoprim, Roxithromycin, 17β-estradiol, 17α-Ethynylestradiol, Estrone, Nonylphenol, Octylphenol, Nickel, et NH₄⁺), vary from 0.000002 to 187.7 when using the median concentration values of these pollutants, and from 0.000007 to 3750 when using their maximum concentration values. Globally, they show that: (1) the risks are higher for small streams that receive WWTP discharges of average size, (2) the risks are low to very low for discharges into watercourses with high flow rates.

A priori assessment of ecotoxicological risks linked to building a hospital

Hospital wastewaters contain a large number of chemical pollutants such as disinfectants, detergents, and drug residues. A part of these pollutants is not eliminated by traditional urban waste water treatment plants, leading to a major risk for the aquatic ecosystems receiving these effluents. After having formulated a specific methodology in order to assessment ecotoxicological risk for such a situation, we applied it to the project to build a new hospital shared by several towns in the French Alps. This methodology is based on the ecotoxicological characterisation of the hospital wastewater using a battery of three chronic bioassays (Pseudokirchneriella subcapitata, Heterocypris incongruens and Brachionus calyciflorus) and of genotoxicity tests (Ames fluctuation assay on Salmonella typhimurium, and a Fpg-modified comet assay on the trout liver cell line RTL-W1). The formulated methodology highlights a moderate risk of the hospital wastewater for the organisms of the water column of the river concerned. Nevertheless, this discharge contributes significantly to the global ecotoxicological risk when taking into account all the releases of the watershed into the river. This leads to recommending the implementation of a specific treatment system in the urban WWTP, or upstream to it, in view to protecting the aquatic organisms.

Use of a novel battery of bioassays for the biological characterisation of hazardous wastes

Four toxicity bioassays were used for the biological characterisation of nine hazardous wastes and extracts. This evaluation included conventional and novel bioassays, and combined in vivo and in vitro tests in order to facilitate the effect characterisation. This test battery incorporated different relevant taxonomic groups for the aquatic compartment and covered several ecotoxicological endpoints. The toxicity bioassays used for this characterisation were the acute immobilisation daphnia test, an acute toxicity test with larvae of Xenopus laevis, an in vitro test with the fish cell line RTG-2 comprising endpoints for cellular defence and viability, and finally the DR-CALUX assay to detect dioxin-like compounds. The aim of this study is to contribute to the development of a cost-effective battery of toxicity tests for the acute screening of hazardous and toxic wastes for the aquatic compartment. For this objective, the correlations between toxicity data derived from all bioassay were studied using a multivariate analysis, including the Principal Component Analysis. The results showed that Daphnia and Xenopus were effective assays to detect toxicity and they could be incorporated to a screening test battery. On the other hand, the toxicity results with the in vitro test RTG-2 showed that this test could be a good alternative to in vivo tests, demonstrating an acceptable sensitivity for toxicity detection and contributing other advantages as reducing assays cost and animal testing. Finally DR-CALUX test implemented the tests-batteries in the screening of hazardous wastes when there is a suspicious that dioxin-like compounds are presented in the samples.