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Endocrine disrupting chemicals (EDCs) are compounds of mainly anthropogenic origin that interfere with the endocrine system of animals and humans thus causing a series of disorders. Wastewater treatment plants are one of the major routes for transporting such chemicals to the water courses. In the context of this study, several chlorination batch tests were performed in order to assess the effectiveness of chlorination to remove bisphenol A (BPA), triclosan (TCS), nonylphenol (NP) and its ethoxylates (NP1EO and NP2EO) from secondary effluent. According to the results, an appreciable removal of NP, BPA and TCS to the order of 60-84% was observed as an effect of moderate chlorination doses. This was not the case for NP1EO and NP2EO as even at high chlorine doses, removal efficiencies were lower (37% for NP1EO and 52% for NP2EO). Removal efficiencies of NP, BPA and TCS are practically independent of contact time, although this was not the case for NP1EO and NP2EO. Based on toxicity experiments, it is anticipated that following chlorination of the target chemicals, production of more toxic metabolites is taking place. Therefore the effectiveness of chlorination to remove EDCs is questionable and more research is needed to guarantee safe wastewater reuse.

BACKGROUND: Microbial reduction of Cr(VI) to the much less toxic Cr(III), although practiced for the treatment of liquid wastes has not been implemented for the treatment of groundwater due to the absence of electron donors (organic substrates) and the lack of data on inhibition of biological Cr(VI) removal. The objective of this work is to evaluate biological groundwater treatment systems that will achieve high Cr(VI) removal with addition of a low dose of organic substrate and to estimate inhibition of microbial Cr(VI) reduction under anaerobic and anoxic conditions.

Endocrine disrupting chemicals and non-steroidal anti-inflammatory drugs are two important groups of emerging pollutants due to their toxicological and chemical characteristics and their persistent detection in the aquatic environment. Wastewater treatment plants are a significant pathway for their transfer to the water courses. It is well evidenced that these chemicals are only partially removed through biological treatment of wastewater and therefore being detected in secondary effluents. This work focuses on the evaluation of the efficiency of two well-established disinfection technologies (chlorination and UV irradiation) along with UV/H2O2 and powdered activated carbon (PAC) to remove these chemicals from biologically treated wastewater. Based on the results it is shown that appreciable removal efficiencies due to chlorination should be expected for most of the target compounds, whereas this was not the case for ibuprofen and ketoprofen. With the exemption of diclofenac and ketoprofen direct UV irradiation did not efficiently removed target compounds for UV doses usually applied for disinfection purposes. The application of advanced UV treatment through the addition of H2O2 although resulted in increased removal of the target compounds is not sufficient at moderate UV and H2O2 doses to achieve satisfactory removal efficiencies. PAC use resulted in sufficient removal of target compounds although high PAC doses were required for some chemicals. Comparison of Freundlich isotherms of this study with those of other studies, derived employing water samples, suggested that the water matrix along with the target compounds concentration range can significantly affect the outcome of the experiments.