The most biodegradable compound was the E2. The membrane fouling rates increased with the decreased of SRT and HRT. Optimal process conditions in this work was obtained at the SRT and HRT of 60 days and 12 h, respectively, with high efficient of estrogen removal, nitrification efficiencies, as well as a minimum membrane fouling rate.

The selection of a coagulant-flocculant agent which, based on the maximum chemical oxygen demand removal, warrants the best performance of the removal system for a very complex high-load chemical-pharmaceutical industry wastewater, is described. A total of 23 coagulants/flocculants was tested, including salts, poly-hidroxyaluminates, synthetic polymers as well as natural gums. In a second stage, some mixing aspects were studied. The effects of the specific impeller, the agitation speed during the coagulation and flocculation stages, and the absence or presence of baffles were evaluated in a six-place agitation system. The conventional impellers were replaced by the following types of propellers: Rushton, marine, A310 (Lightning), three flat blades, 45° inclined six blades, and conventional flat blade propeller. It was demonstrated that the appropriate coagulation-flocculation system is capable of diminishing the COD, the apparent color and the dissolved solids up to 40.6, 25.6 and 39.4%, respectively. The best results were observed when using BL-5086, guar gum, Niad II-3, Niad II-4 and locus beam gum. The impeller performance was highly dependent on the agitation speed for each fixed system. With respect to the mixing aspects, it was shown that the selection of the right propeller for the coagulation and flocculation stages is crucial in determining the quality of the treated water, as well as the quantity and quality of the residual sludges generated in the process.

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The purpose of this paper is to report the study of the fate and distribution of three endocrine disrupting compounds (estrogens); Estrone (E1), 17β-estradiol (E2), and 17α-ethinylestradiol (EE2) in a laboratory scale submerged membrane bioreactor (SMBR). For this matter, both aqueous and solids phases were analyzed for the presence of E1, E2 and EE2. The outcome of this study was that three SMBRs showed enhanced elimination of estrogens in different operational conditions; the estrogen removal was close to 100% in SMBR. Additionally, E1, E2 and EE2 were detected in SMBR sludge at concentrations of up to 41.2, 37.3 and 36.9 ng g(-1) dry weight, respectively. The estrogen removal in the SMBRs was directly influenced by a combination of simultaneous biodegradation-adsorption processes, indicating that the main removal mechanism of the estrogens in the SMBRs is the biodegradation process. The E1, E2 and EE2 were biologically degraded in the SMBR (87-100%). The sorption of estrogens onto activated sludge was from 2%. Therefore, a high potential for estrogen removal by biodegradation in the SMBR was observed, allowing less estrogen concentration in the dissolved phase available for the adsorption of these compounds onto biological flocs. Two different methods were carried out for mass balance calculations of estrogens in SMBR. For the first method, the measured data was used in both liquid and solid phases, whereas for the second one, it was in aqueous phase and solid-water distribution coefficients (K(d)) value of E1, E2 and EE2. The purpose of these methodologies is to make easier the identification of the main mechanisms involved in the removal of E1, E2 and EE2 in a SMBR. Both methods can be applied in order to determine the mechanism, fate and distribution of estrogens in a SMBR.