Contaminantes emergentes: ocorrência e distribuição espaço-temporal no rio do Monjolinho e avaliação da remoção pela estação de tratamento de esgotos de São Carlos

Abstract

This work aimed to investigate the occurrence of 12 emerging contaminants (pharmaceuticals, hormones and triclosan) in samples of influents and effluents, as well the removal in the sewage treatment plant (STP) of São Carlos. It was also investigated the occurrence and spatiotemporal distribution of emerging contaminants in surface waters and sediments from the Monjolinho River, the receptor of effluents, and one of its tributaries, the Água Quente Stream (AQS), which receives the discharge of non treated sewage. Influent and effluent samples were collected weekly. Surface water and sediment samples were obtained every two and four months, respectively, in points since the source until the mouth of the Monjolinho River. The target compounds in dissolved fraction of aquous samples were extracted by solid phase extraction (SPE), while for sediments it was performed ultrassonic extrations with solvents followed by SPE. The analytical determinations were made by ultra high pressure liquid chromatography coupled to mass spectrometer equipped with triplequadrupole analyser (LC-MS/MS). The hormone 17-α-ethynilestradiol was not detected in any sample. However, all the pharmaceuticals evaluated and triclosan were detected in influent samples. The STP with upflow anaerobic sludge blancket (UASB) and air dissolved flotation in São Carlos presented low removal for carbamazepine, diclofenac, propranolol and ibuprofen. On the other hand, triclosan presented the highest removal (91.2%). In surface waters and sediments from Monjolinho river the concentration of contaminants presented an increasing trend since the source of the river to the downstream of the STP effluent discharge and after the confluence of the AQS (which flows into the river at the same place), where it was observed the highest concentrations in the Monjolinho River. The AQS, in its turn, presented higher concentrations of pharmaceuticals and triclosan than the Monjolinho River, due to the discharge of non treated sewage. Carbamazepine and diclofenac were persistent in both STP and aquatic body. The strong correlations between this compounds and electrical conductivity (considered a conservative parameter) sugests that CMZ and DCF can be tracers of both treated and non treated sewage release in the study area. Ee conclude that the main sources of phamaceuticals and triclosan to the Monjolinho River are the discharge of non treated sewage (from the AQS) and effluent from STP, since their removal is very low. Unlike the studies involving endocrine disruptors, the effects of other classes of emerging contaminants have been yet little explained in literature. Therefore, more surveys on the occurrence of these compounds combined with ecotoxicological studies must be conducted to make clear the magnitude of the impact that these substances can cause in the environment. Based on this information, adjustments in the effluent treatment may be investigated in the future, if there is interest in effectively removing this compounds in STP.