Christine Bazin

Daily physicochemical, microbiological and ecotoxicological fluctuations of a hospital effluent according to technical and care activities

The problem of hospital effluents falls into the framework of hazardous substances due to the specific substances used and discharged for the most part into urban drainage networks without prior treatment. This in-depth study has led to greater understanding of the effluents discharged by hospitals. The experimental program implemented consisted in carrying out parallel sampling of the effluents of one hospital: a 24 h-average sample and 5 periodic samples corresponding to fractions of times and hospital activities. The samples were characterized by physicochemical, microbiological and ecotoxicological analyses. The results highlight that the effluents contained very little bacterial flora and a moderate organic pollution. However, a numerous of specific pollutants were detected: AOX, glutaraldehyde, free chlorine, detergents, Freon 113 as well as alcohols, acetone, formaldehyde, acetaldehyde, ammonium, phenols and several metals. The battery of bioassays showed that the effluents had a high level of ecotoxicity partly linked to particles in suspension and, that pollution fluctuated greatly during the day in connection with hospital activities. Finally, the PNEC values compared to the concentrations of pollutants dosed in the effluents highlighted that their toxicity was mainly due to several major pollutants, in particular free chlorine. Some hypotheses require additional experiments to be carried out. They concern: reactions of fermentations likely to occur in the drainage network and to form secondary toxic compounds, retention of chlorine by particles and physicochemical characterization of suspended solids.

A posteriori assessment of ecotoxicological risks linked to building a hospital.

Hospital wastewater (HWW) contain a large number of chemical pollutants such as disinfectants, surfactants, and pharmaceutical residues. A part of these pollutants is not eliminated by traditional urban wastewater treatment plants (WWTP), leading to a risk for the aquatic ecosystems receiving these effluents. In order to assess this risk, we formulated a specific methodology based on the ecotoxicological characterisation of the hospital wastewater using a battery of three chronic bioassays (Pseudokirchneriella subcapitata, Heterocypris incongruens and Brachionus calyciflorus). We used it for the posteriori risk assessment of a hospital recently built in south-east France, and we studied the evolution of this risk during two years. We also used it to assess the decrease of the ecotoxicological risk after treatment of the effluent in a specific line of the local WWTP. Lastly, we compared these results with the risk assessment made before the building of the hospital in the context of a priori risk assessment. The results obtained showed an important evolution of the risk overtime, according to the hospital activities and the river flows, and a real decrease of the risk after treatment in the dedicated line. They also showed that the a priori assessment of ecotoxicological risks, made previously, was overstated, mainly because of the application of the precautionary principle.

Evaluation of Ecotoxicological Risks Related to the Discharge of Combined Sewer Overflows (CSOs) in a Periurban River

Discharges of Combined Sewer Overflows (CSOs) into periurban rivers present risks for the concerned aquatic ecosystems. In this work, a specific ecotoxicological risk assessment methodology has been developed as management tool to municipalities equipped with CSOs. This methodology comprises a detailed description of the spatio-temporal system involved, the choice of ecological targets to be preserved, and carrying out bioassays adapted to each compartment of the river receiving CSOs. Once formulated, this methodology was applied to a river flowing through the outskirts of the city of Lyon in France. The results obtained for the scenario studied showed a moderate risk for organisms of the water column and a major risk for organisms of the benthic and hyporheic zones of the river. The methodology enabled identifying the critical points of the spatio-temporal systems studied, and then making proposals for improving the management of CSOs.

Spatial variability of sediment ecotoxicity in a large storm water detention basin

Detention basins are valuable facilities for urban storm water management, from both the standpoint of flood control and the trapping of pollutants. Studies performed on storm water have shown that suspended solids often constitute the main vector of pollutants (heavy metals, polycyclic aromatic hydrocarbon (PAH), etc.). In order to characterise the ecotoxicity of urban sediments from storm water detention basins, the sediments accumulated over a 6-year period were sampled at five different points through the surface of a large detention basin localised in the east of Lyon, France. A specific ecotoxicological test battery was implemented on the solid phase (raw sediment) and the liquid phase (interstitial water of sediments). The results of the study validated the method formulated for the ecotoxicological characterization of urban sediments. They show that the ecotoxicological effect of the sediments over the basin is heterogeneous and greater in areas often flooded. They also show the relationship between, on one hand, the physical and chemical characteristics of the sediments and, on the other hand, their ecotoxicity. Lastly, they contribute to a better understanding of the dynamics of the pollution close to the bottom of detention basins, which can be useful for improving their design. The results of this research raise particularly the issue of using oil separators on the surface of detention basins.

Ecotoxicological characterisation of sediments from stormwater retention basins

Retention-detention basins are important structures for managing stormwater. However, their long-term operation raises the problem of managing the sediments they accumulate. Potential uses for such sediments have been envisaged, but each sediment must be characterised beforehand to verify its harmlessness. In this paper we address this issue through the development of a battery of bioassays specifically adapted to such sediments. We tested the method on samples taken from four retention basins in the region of Lyon (France). This battery focuses on the toxic effects linked to both the solid phase (ostracod and Microtox(®) solid-phase tests) and the liquid-phase (interstitial water) of sediments (rotifer and Microtox(®) liquid-phase tests). The results obtained permit the sorting of sediments presenting little toxicity, and which could therefore be potentially exploitable, from those from more polluted areas presenting higher toxicity that limits their use.

Ecotoxicity and antibiotic resistance of a mixture of hospital and urban sewage in a wastewater treatment plant

Hospital and urban effluents are a source of diverse pollutants such as organic compounds, heavy metals, detergents, disinfectants, pharmaceuticals, and microorganisms resistant to antibiotics. Usually, these two types of effluent are mixed in the sewage network, but a pilot site in France now allows studying them separately or mixed to understand more about their characteristics and the phenomena that occur following their mixing. In this study, their ecotoxicity (Daphnia magna mobility, Pseudokirchneriella subcapitata growth, Brachionus calyciflorus reproduction, and SOS Chromotest) and antibiotic resistance (integron quantification) were assessed during mixing and treatment steps. The main results of this study are (i) the ecotoxicity and antibiotic resistance potentials of hospital wastewater are higher than in urban wastewater and (ii) mixing two different effluents does not lead to global synergistic or antagonistic effects on ecotoxicity and antibiotic resistance potential. The global additivity effect observed in this case must be confirmed by other studies on hospital and urban effluents on other sites to improve knowledge relating to this source of pollution and its management.

Assessment of long term ecotoxicity of urban stormwaters using a multigenerational bioassay on Ceriodaphnia dubia: A preliminary study

ABSTRACT Standardized ecotoxicity bioassays show some limits to assess properly long-term residual toxicity of complex mixture of pollutants often present at low concentration, such as stormwaters. Among invertebrate organisms used for ecotoxicity testing, the microcrustacean Ceriodaphnia dubia (C. dubia) is considered as one of the most sensitive, especially regarding reproduction impairment as a toxicity endpoint. Consequently, this work explores the interest to perform a multigenerational assay based on the study of the reproduction of C. dubia to assess long-term ecotoxicity of complex mixture, using stormwater samples. With this in mind, a battery of standardized bioassays (Daphnia magna mobility, Pseudokirchneriella subcapitata population growth, Heterocypris incongruens growth and one generation C. dubia reproduction inhibition assays) was performed in parallel to a three generation C. dubia reproduction inhibition assay on 2 stormwater samples. Results highlighted that while all standardized bioassays failed to reveal residual toxicity in the stormwater samples, the C. dubia multigenerational assay exhibited an higher sensitivity than the previous ones. No adverse effect was observed for the first exposed generation, but an increase in mortality and a reproduction disturbance was obtained in the second and third exposed generation depending of the sample. Further experiments are now needed to optimize the exposure protocol of this multigenerational assay.

Assessment of ecological risks linked to the discharge of saline industrial effluent into a river

Discharges of saline effluents into rivers can lead to risks for local aquatic ecosystems. A specific ecological risk assessment methodology has been developed to propose a management tool to organisations responsible for managing rivers and industrial companies producing saline effluents. This methodology involves the detailed description of the spatiotemporal system concerned, the choice of ecological targets to be preserved, and the performance of bioassays adapted to each of the compartments of the river. Following development, it was applied to an industrial effluent in eastern France. For the scenario studied, results obtained suggest a high risk for the organisms of the water column and a low risk for the organisms of the periphyton. This difference can be explained by the structure of the latter which integrate extracellular polymers secreted by the organisms of the biofilm, forming a gel with a porous structure that acts as a barrier to diffusion. The methodology formulated permitted identifying the critical points of the spatiotemporal system studied and then using them as the basis for making well-grounded proposals for management. Lastly, proposals to improve the methodology itself are made, especially concerning the integration of the sediment compartment in the version formulated initially.