Effect of Sequential Isoproturon Pulse Exposure on Scenedesmus vacuolatus

Aquatic organisms are typically exposed to fluctuating concentrations of herbicides in streams. To assess the effects on algae of repeated peak exposure to the herbicide isoproturon, we subjected the alga Scenedesmus vacuolatus to two sequential pulse exposure scenarios. Effects on growth and on the inhibition of the effective quantum yield of photosystem II (PSII) were measured. In the first scenario, algae were exposed to short, 5-h pulses at high isoproturon concentrations (400 and 1000 μg/l), each followed by a recovery period of 18 h, while the second scenario consisted of 22.5-h pulses at lower concentrations (60 and 120 μg/l), alternating with short recovery periods (1.5 h). In addition, any changes in the sensitivity of the algae to isoproturon following sequential pulses were examined by determining the growth rate-EC50 prior to and following exposure. In both exposure scenarios, we found that algal growth and its effective quantum yield were systematically inhibited during the exposures and that these effects were reversible. Sequential pulses to isoproturon could be considered a sequence of independent events. Nevertheless, a consequence of inhibited growth during the repeated exposures is the cumulative decrease in biomass production. Furthermore, in the second scenario, when the sequence of long pulses began to approach a scenario of continuous exposure, a slight increase in the tolerance of the algae to isoproturon was observed. These findings indicated that sequential pulses do affect algae during each pulse exposure, even if algae recover between the exposures. These observations could support an improved risk assessment of fluctuating exposures to reversibly acting herbicide

Multicriteria methods for assessing pharmaceuticals hazard for the environment

Among emerging pollutants found in surface and ground waters, pharmaceuticals are currently receiving a particular interest. There are several physico/chemical parameters that could describe the fate of pharmaceuticals in the environment, so as their toxicity for ecosystems and human health. The idea is to create an integrated parameter that would relate of the relative influence of these physico/chemical characteristics. Potential impact of pharmaceuticals on the environment could be then ranked using this parameter. Different methods will be tested for ranking (weighted average, mathematical distance functions from the no effect point, ELECTRE, etc). The weights were evaluated in order not to support only a scientific point of view, but also economical and social considerations. For this concern, cooperation with scientists from various fields so as human health managers was carried out. The different methods will be finally compared together so as with previous ranking published in literature. The goal here is not to impose a relative importance of the parameters we integrate, but to introduce the concept of the relative influence for environmental parameters when we deal with water quality problems that could affect ecological systems and human health

Risk of herbicide mixtures as a key parameter to explain phytoplankton fluctuation in a great lake: the case of Lake Geneva, Switzerland

Mixture risk assessment predictions have rarely been confronted with biological changes observed in the environment. In this study, long-term monitoring of a European great lake, Lake Geneva, provides the opportunity to assess to what extent the predicted toxicity of herbicide mixtures explains the changes in the composition of the phytoplankton community next to other classical limnology parameters such as nutrients. To reach this goal, the gradient of the mixture toxicity of 14 herbicides regularly detected in the lake was calculated using concentration addition and response addition models. A temporal gradient of toxicity was observed which decreased from 2004 to 2009. Redundancy analysis and partial redundancy analysis showed that this gradient explains a significant portion of the variation in phytoplankton community composition with and without having removed the effect of all other co-variables. Moreover, species that are significantly influenced, positively or negatively, by the decrease of toxicity in the lake over time are highlighted. It can be concluded that the herbicide mixture toxicity is one of the key parameters to explain phytoplankton changes in Lake Genev

Toxicity of Tamoxifen on Daphnia pulex

Daphnia pulex is a water flea considered an environmental indicator species. In this experiment we exposed Daphnia to Tamoxifen in low or high concentrations, dissolved in dimethyl sulfoxide with water, and we measured the amount of proteins at day 2 and 7. With the R package maSigPro we selected proteins changing significantly over time among the four experimental groups and we developed a cluster analysis for the behavior of profiles over time, to understand which and how these specific proteins change according to the treatment received. The information obtained from this study represents an important first step towards characterizing patterns specific to environmental contaminants

Development of a new ecotoxicological assay using the testate amoeba <i>Euglypha rotunda</i> (Rhizaria; Euglyphida) and assessment of the impact of the herbicide <i>S</i>-metolachlor

An ever-increasing diversity of potentially toxic chemical compounds are being developed and released into the environment as a result of human activities (e.g. agriculture, drugs, and cosmetics). Among these, pesticides have been shown to affect non-targeted wildlife since the 1960s. A range of ecotoxicological tests are used to assess the toxicity of pesticides on various model organisms. However most model organisms are metazoans, while the majority of Eukaryotes are unicellular microorganisms known as protists. Protists are ubiquitous organisms of key functional roles in all ecosystems but are so far little studied with respect to pesticide impact. To fill this gap, we developed a new ecotoxicological test based on Euglypha rotunda, a common soil amoeba, grown in culture flask with Escherichia coli as sole food source. We tested this assay with the herbicide S-metolachlor, which is known to affect cell division in seedling shoots and roots of weeds. Reproducible growth conditions were obtained for E. rotunda. The growth of E. coli was not affected by the herbicide. The growth of E. rotunda was affected by the herbicide in a non-linear way, growth being significantly reduced at ca. 15 μg/L, but not at 150 μg/ L. Our results show the potential for using soil protists in ecotoxicology and adds to the growing body of evidence for non-linear impacts of pesticides on non-target organisms. With the acquisition of additional data, the protocol should be suitable for standard ecotoxicological tests

Biocides in paints in urban areas: Modelling an underestimated source of environmental contamination

Biocide contamination of receiving waters is generally linked with agriculture. However, recent studies have shown that urban contributions should be also considered. One of the suspected biocide sources in the urban environment is building paint. Biocides like diuron, irgarol, terbutryn, carbendazim, etc., are conventionally used in paint to control fungi, algae, bacteria and other microorganisms that can colonize building façades. The problem of biocides in urban areas is closely linked to meteorological conditions and in particular to rain events. As a consequence, it is important to understand how rainwater collects and transports biocides from façades and how these biocides are transported in sewer systems to receiving waters. In this study, we present a conceptual model describing façade leaching and couple it with a Wind Driven Rain model and a classical hydrological model to compute the contribution of a city to the biocide load from building paint. For the entire city of Lausanne (Switzerland, 200’000 inhabitants), a global production of 2200 kg/year of terbutryn leached by rain was estimated considering local building characteristics and meteorological information. The leaching model fitted well the peak in concentration measured at the bottom of the wall at the initial stage of the rain event. However, concentrations measured in an urban river in the watershed leads to the conclusion that most of this leachate does not reach directly receiving waters, but is infiltrated into soil or reaches the sewers after some delays in drainage pipes. Release of biocides from façade leaching in the environment is systematic during rain event. It is of greater importance to estimate the dynamic of biocides during rain events and to compare these values with dedicated time varying environmental quality criteria

Traitement des micropolluants dans les eaux usées - Rapport final sur les essais pilotes à la STEP de Vidy (Lausanne)

De nombreux micropolluants organiques présents dans les eaux usées sont mal éliminés dans les stations d’épuration (STEP) conventionnelles. Pour réduire l’apport de ces substances dans les eaux de surface, des traitements avancés sont nécessaires. Deux traitements biologiques et deux traitements avancés ont été testés à grande échelle à la STEP de Vidy (Lausanne) (220'000 équivalents-habitants) pendant plus d’une année. Ces essais s’inscrivent dans le cadre du projet « Stratégie Micropoll » de l’Office fédéral de l’environnement (OFEV). Un nouveau traitement biologique à lit fluidisé avec nitrification totale (capacité de 80 l/s) a été construit en parallèle au procédé à boues activées forte charge (sans nitrification) actuellement en place (capacité de 1’200 l/s). Ceci a permis de comparer l’efficacité d’élimination des micropolluants dans ces deux types de biologie et d’étudier leur influence sur les traitements avancés qui suivent. Les deux traitements avancés testés sont l’ozonation suivie d’une filtration sur sable (ozonation-FS) (capacité de l’installation de 100 l/s) et le traitement au charbon actif en poudre suivi d’une filtration membranaire (ultrafiltration) (CAP-UF) (capacité de 10 l/s). Conçue sur la base de précédentes études du projet « Stratégie Micropoll », l’installation d’ozonation a été maîtrisée en quelques mois, et seuls quelques paramètres ont dû être améliorés. En revanche, beaucoup d’éléments techniques ont dû être corrigés sur l’installation CAP-UF (procédé nouveau pour le traitement des eaux usées). La phase de séparation du CAP par ultrafiltration n’est pas encore maîtrisée et nécessite des optimisations, notamment pour réduire le colmatage (réversible) des membranes, responsable d’une capacité hydraulique inférieure à la moitié de la capacité espérée. La séparation du CAP par un filtre à sable est une alternative possible. Sur une sélection de plus de 50 micropolluants organiques (produits pharmaceutiques, pesticides, substances à effet hormonal), le traitement biologique à boues activées forte charge a permis d’atteindre un abattement moyen de 23%. Avec un traitement biologique permettant une nitrification, le taux d’élimination a augmenté à 44% en moyenne, confirmant les résultats d’autres études. Le traitement ozonation-FS a permis d’éliminer à plus de 80% la plupart des substances analysées, avec un dosage d’ozone moyen d’environ 5.5 mgO3/l (équivalent à environ 0.9 gO3/gCOD), pour des coûts d’exploitation d’environ 6 ct./m3 traité. Une désinfection partielle de l’effluent a également pu être atteinte, conduisant ainsi au respect des normes suisses et européennes de qualité pour les eaux de baignade. Le traitement CAP-UF a permis d’éliminer à plus de 80% la plupart des micropolluants, avec un dosage de CAP compris entre 10 et 20 mg/l. La séparation du CAP par ultrafiltration permet une désinfection totale de l’effluent. A cause des faibles débits de l’installation CAP-UF (colmatage des membranes), les coûts d’exploitation étaient proches de 50 ct./m3 traité. L’alternative avec la séparation du CAP sur un filtre à sable (testée dans des essais complémentaires) coûterait entre 6 et 9 ct./m3. Sur la majorité des 25 tests écotoxicologiques effectués, une nette réduction de la toxicité a été observée en sortie des deux traitements avancés. Aucune toxicité liée aux sous-produits de réaction potentiellement formés durant l’ozonation n’a été observée. Ces deux procédés (ozonation et adsorption sur CAP) sont efficaces pour réduire l’apport de micropolluants dans les eaux de surface. Les technologies ozonation-FS et CAP-FS sont réalistes autant du point de vue de leur implantation dans les STEP que de leur exploitation, pour des coûts d’investissement et d’exploitation relativement similaires (environ 20 centimes par mètre cube d’eau traitée lors des essais). Chaque technique ayant ses avantages, le choix du procédé doit être fait au cas par cas en fonction des contraintes locales (espace à disposition, type de traitement existant, sécurité, qualifications du personnel, coûts des réactifs, lieu et type de traitement des boues, etc.), de la qualité de l’eau entrante et de la qualité voulue en sortie

Elimination of micropollutants in wastewater treatment plants : Ozonation or activated carbon? Conclusions of a one-year pilot project

Many organic micropollutants present in wastewater, such as pharmaceuticals and pesticides, are poorly removed in conventional wastewater treatment plants (WWTP). To reduce the release of these substances into the aquatic environment, advanced treatments are necessary and may be soon mandatory in Switzerland. Two advanced treatments were tested in pilot systems over more than one year at the municipal WWTP of Lausanne, Switzerland. The first pilot involves the ozonation of the effluent to oxidize organic substances. It is followed by a sand filtration (SF) to remove the readily biodegradable reaction products. The second pilot consists of a powdered activated carbon (PAC) addition into the effluent to sorb micropollutants. It is followed either by a membrane filtration (ultrafiltration) or a sand filtration to separate the PAC from the treated water. A selection of 58 potentially problematic substances (pharmaceuticals, pesticides, endocrine disruptors) were regularly measured at different stages of treatment by ultra performance liquid chromatography coupled to a tandem mass spectrometer, and a large battery of ecotoxicological tests (16 in vitro and 9 in vivo assays with different organisms) were performed to evaluate the toxicity of the effluents. The results showed that most compounds were removed over 80% with an average ozone dose of about 5.5 mgO3/l or a PAC dose between 10 and 20 mg/l. Only some single compounds, such as X-ray contrast media, were only partially eliminated in both cases. A clear reduction in toxicity was also observed after the two treatments in most of the cases. These two processes (ozonation and PAC addition) are therefore effective to reduce the release of micropollutants into surface waters. Ozonation-SF and PAC-SF proved to be feasible in terms of implementation and operation at large-scale in WWTP, for relatively similar investment and operation costs (about 0.1 to 0.15 € per m3 treated based on local costs). Each technique has its advantages and disadvantages. Therefore the method selection should be made case by case for each WWTP depending on the local constraints (e.g. space, security, energy costs, existing treatment processes, sludge disposal process, need for disinfection, etc.), the quality and the quantity of incoming water and the desired output water quality