Occurrence and behavior of pesticides in wastewater treatment plants and their environmental impact.

Reports on pesticides elimination during wastewater treatment are rare since these substances are typically considered of agricultural rather than of urban origin. In this context, the aim of this work was to evaluate the presence, removal and environmental relevance of 22 selected pesticides in three different wastewater treatment plants (WWTPs), paying attention not only to their occurrence and elimination but also to the toxicity of each pesticide against three aquatic micro organisms (algae, daphnia and fish) through the calculation of the so-named Environmental Relevance of Pesticides from Wastewater treatment plants Index (ERPWI). For this purpose, an analytical method based on isotope dilution on-line solid phase extraction-liquid chromatography-tandem mass spectrometry (SPE-LC-MS/MS) was optimized, allowing the determination of the 22 target pesticides in wastewater with satisfactory sensitivity (limits of detection below 30 ng/L), accuracy and precision. Concerning the results, total pesticide levels were in most instances below 1 µg/L but removal in the WWTPs was variable and often poor, with concentrations in the effluent sometimes higher than in the corresponding influent. Possible explanations for these poor or negative removal rates are, among many others considered (e.g. sampling, sample preservation, method biases, atmospheric deposition), deconjugation of metabolites and/or transformation products of the pesticides, hydrolysis, and desorption from particulate matter during wastewater treatment. The most significant pesticides in terms of concentration and frequency of detection were diazinon and diuron. These two pesticides, followed by atrazine, simazine and malathion, were also the most relevant from the environmental point of view, according to the calculated ERPWI.

Response of stream invertebrates to short-term salinization: a mesocosm approach.

Salinization is a major and growing threat to freshwater ecosystems, yet its effects on aquatic invertebrates have been poorly described at a community-level. Here we use a controlled experimental setting to evaluate short-term stream community responses to salinization, under conditions designed to replicate the duration (72 h) and intensity (up to 5 mS cm(-1)) of salinity pulses common to Mediterranean rivers subjected to mining pollution during runoff events. There was a significant overall effect, but differences between individual treatments and the control were only significant for the highest salinity treatment. The community response to salinization was characterized by a decline in total invertebrate density, taxon richness and diversity, an increase in invertebrate drift and loss of the most sensitive taxa. The findings indicate that short-term salinity increases have a significant impact on the stream invertebrate community, but concentrations of 5 mS cm(-1) are needed to produce a significant ecological response.

Monitoring of (bio)available labile metal fraction in a drinking water treatment plant by diffusive gradients in thin films.

A performance study of diffusive gradients in thin films (DGT) and inductively coupled plasma optical emission spectrometry (ICP-OES) was applied for the monitoring of the labile fraction of metals Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn, in Sant Joan Despí Drinking Water Treatment Plant located in the South of Barcelona's Metropolitan Area (Spain). The DWTP monitoring protocol was optimized by working for 1 day of deployment (24 h) with the DGT device in contact with both treated and river water matrixes. Additionally, it was demonstrated that an increase in the deployment time of 1 week did not decrease the evaluated concentrations of the studied metals. The quality parameters of the DGT device and ICP-OES determination, such as limit of quantification, accuracy expressed as relative error (%) and reproducibility expressed as relative standard deviation, were evaluated. Good results were obtained for all the metals in ultrapure water; limits of quantification ranged from 1.5 µg L( - 1) for cadmium to 28 µg L( - 1) for zinc when deployment time of 24 h was used and from 0.2 µg L( - 1) for cadmium to 4 µg L( - 1) for zinc when this time was increased by 1 week. Accuracy and precisions lower than or equal to 10% were obtained at a parametric concentration value of the metals regulated in the European Drinking Water Guidelines (98/83/EC). DGT deployment was tested in river and treated water, and good results were obtained for Cd, Ni, Co and Zn, whereas for the other metals, a continuous control of their metallic labile fractions was monitored. Therefore, DGT device allows the continuous monitoring of the labile metal species in a drinking water treatment plant.

Occurrence, partition and removal of pharmaceuticals in sewage water and sludge during wastewater treatment.

During 8 sampling campaigns carried out over a period of two years, 72 samples, including influent and effluent wastewater, and sludge samples from three conventional wastewater treatment plants (WWTPs), were analyzed to assess the occurrence and fate of 43 pharmaceutical compounds. The selected pharmaceuticals belong to different therapeutic classes, i.e. non-steroidal anti-inflammatory drugs, lipid modifying agents (fibrates and statins), psychiatric drugs (benzodiazepine derivative drugs and antiepileptics), histamine H2-receptor antagonists, antibacterials for systemic use, beta blocking agents, beta-agonists, diuretics, angiotensin converting enzyme (ACE) inhibitors and anti-diabetics. The obtained results showed the presence of 32 target compounds in wastewater influent and 29 in effluent, in concentrations ranging from low ng/L to a few µg/L (e.g. NSAIDs). The analysis of sludge samples showed that 21 pharmaceuticals accumulated in sewage sludge from all three WWTPs in concentrations up to 100 ng/g. This indicates that even good removal rates obtained in aqueous phase (i.e. comparison of influent and effluent wastewater concentrations) do not imply degradation to the same extent. For this reason, the overall removal was estimated as a sum of all the losses of a parent compound produces by different mechanisms of chemical and physical transformation, biodegradation and sorption to solid matter. The target compounds showed very different removal rates and no logical pattern in behaviour even if they belong to the same therapeutic groups. What is clear is that the elimination of most of the substances is incomplete and improvements of the wastewater treatment and subsequent treatments of the produced sludge are required to prevent the introduction of these micro-pollutants in the environment.