Fate, modeling, and risk of pharmaceuticals in wastewater treatment plants and Iberian rivers

Abstract

In view of the concerns about the presence of pharmaceuticals in the aquatic environment, two main lines of research regarding these substances were followed within this thesis:

Their fate was assessed along waste water treatment plants (WWTPs) and Iberian River basins.

Their potential ecotoxicological risks to non-target aquatic organisms were evaluated.

On this basis, the more specific objectives and the subsequent findings achieved within this thesis are reported as follows:

I. The fate and behavior of pharmaceuticals under nitrifying activated sludge treatment in WWTPs and after their release into receiving surface waters (SW) via wastewater (WW) effluent discharge were studied. To that aim, a sensitive analytical protocol based on off-line SPE-LC—MS/MS was developed and validated for the simultaneous determination of diclofenac their metabolites and their transformation products (TPs) in WW. The method was further optimized and validated for additional analysis of sulfamethoxazole and its TPs in WW and SW. The method was applied to the analysis of WW and SW reporting the occurrence of the metabolites and TPs of diclofenac and sulfamethoxazole in the ng L-1 range. Additionally, the microbial mediated biotransformation of diclofenac and other related pharmaceutical structures into nitro and nitroso derivates in the nitrifying activated sludge was investigated. The use of HR-MS/MS allowed the identification of tentative chemical structures of nitrosation/nitration TPs confirmed for all compounds to generate via biotic mechanisms.

II. Afterwards, the presence of a list of up to 96 selected pharmaceuticals in SW and sediments from four Iberian River basins characterized by high anthropogenic pressure was assessed. To that, the spatial and temporal distribution of pharmaceuticals were evaluated. pharmaceuticals were widespread and pseudo-persistent micropollutants in the Iberian aquatic environment. Concentration of pharmaceuticals in SW varied from the low to high ng L-1 range; while in sediments they were at the low ng g-1 level. Analgesics/antiinflammatories were the most relevant therapeutic group in SW; while for sediments these were antibiotics. Factors affecting their occurrence (i.e. hydrological conditions and human and animal uses) were also assessed by the application of modeling approaches and statistical tools. Overall, response of pharmaceuticals to river flow was negative, principally due to expected dilution effects. A “plug-flow” model approach was successfully applied to describe the fate of 14 selected pharmaceuticals in terms of attenuation downstream the water course of their main emission source considered as the WWTPs. Significantly positive relationships were found among levels of pharmaceuticals and population density and livestock units in both SW and sediment matrices, thus responding to the anthropic pressures in the catchments. III. Finally, this thesis contributed to the knowledge about the ecotoxicological risk of pharmaceuticals to aquatic ecosystems. To that, individual and combined acute toxicity of pharmaceuticals and other relevant micropollutants to D. magna and V. fischeri were assessed. Individual pharmaceuticals and TPs did not showed acute toxicity to the target aquatic organisms. However PhACs and TPs displayed synergistic effects in mixtures with other toxicants of the same environmental compartments. Additionally, an ecotoxicological risk assessment of 55 pharmaceuticals to D. magna, V. fischeri and fish along four Iberian River basins was conducted. The extensive data presented on the predicted ecotoxicological risk and the computation of pharmaceuticals relative contribution to the whole toxicity of the sample, provided valuable information for further prioritization exercices in the risk assessment of Spanish river basins. Then, the impact of changing pharmaceuticals levels and water flow conditions on the structure and function of river biofilms was studied. PhACs affected the structure and functioning of fluvial biofilms. The biotic response to the two main stressors studied PhACs and hydrology, varied among the different biofilm compartments (photoautotrophs and bacteria).

En vista de las preocupaciones acerca de la presencia de productos farmacéuticos en el medio ambiente acuático, dentro de esta tesis se estudiaron y evaluaron:

Su destino a lo largo de las plantas de tratamiento de aguas residuales y de las cuencas de los ríos Ibéricos.

Los riesgos ecotoxicológicos que pueden representar para los organismos acuáticos no diana.

Sobre esta base, las investigaciones más específicas en esta tesis fueron:

I. Se estudió el destino y el comportamiento de los fármacos durante el tratamiento de lodos activados nitrificantes en las plantas de tratamiento de aguas residuales y después de su liberación en las aguas superficiales receptoras a través de los efluentes de aguas residuales. Con ese objetivo, se desarrolló y se validó un protocolo de análisis sensible para la determinación simultánea de diclofenaco sus metabolitos y sus productos de transformación en aguas residuales. Posteriormente, el método fue optimizado y validado para el análisis adicional de sulfametoxazol y sus productos de transformación en las aguas residuales y aguas superficiales. Además, se investigó la biotransformación, mediada por la comunidad microbiana del lodo activado nitrificante, de diclofenaco y otras estructuras farmacéuticas relacionadas a nitro y nitroso derivados.

II. Se evaluó la presencia de fármacos en las aguas superficiales y sedimentos de cuatro cuencas hidrográficas Ibéricas caracterizadas por una elevada presión antropogénica. Para ese fin, se evaluó la distribución espacial y temporal de los fármacos. También se evaluaron los factores que influyen en su aparición (es decir, las condiciones hidrológicas y uso humano/animal) mediante la aplicación de métodos de modelización y herramientas estadísticas.

III. Finalmente, se contribuyó al conocimiento del riesgo ecotoxicológico de los fármacos en los ecosistemas acuáticos. Para esto, se evaluó la toxicidad aguda individual y combinada de fármacos y otros microcontaminantes a Daphnia magna y Vibrio fischeri. Además, se realizó una evaluación del riesgo ecotoxicológico de los fármacos a D. magna, V. fischeri y peces en las cuencas hidrográficas ibéricas. A continuación, se estudió el impacto de los cambios en los niveles de los fármacos y las condiciones de caudal sobre la estructura y función de los biofilms fluviales.