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Ecotoxicological analysis of daily and weekly profile of influent and effluent waste waters of the city of Čakovec, Croatia

Effluents from waste water treatment plants present a major source of surface water pollution and intensive research has been directed to improve treatment technology and reduce concentration of contaminants in effluents. One of the research goals of the ongoing project « ; Reduction of environmental risks, posed by emerging contaminants, through advanced treatment of municipal and industrial wastes» ; (EMCO ; 6thFWP INCO CT 2004-509188) was to test the membrane bioreactor (MBR) “ Zenon” for improved elimination of emerging contaminants from waste waters. Čakovec (Croatia) city municipal sewage treatment plant was selected to make daily and weekly analysis of influent and effluent waste waters. In addition to the chemical analysis, several bioassays were aplied to determine concentrations of biologicaly active compounds in waste waters. Samples were extracted by using HLB Oasis cartridge and finally concentrated 10.000 x in the DMSO for the bioassay analysis. Effectiveness of xenoestrogen elimination was measured using “ Yeast estrogen screen” (YES) bioassay. The results showed that average concentration of estrogen like substance expressed in 17β -estradiol equivalents (EEQ) in influent waste water was 19 ng/L. After primary treatment concentration of xenoestrogens decline to 8 ng/L, while after secondary treatment EEQ dropped to 2 ng/L. However, after the MBR treatment final concentration of xenoestrogens in effluents was further reduced below 1 ng/L of EEQ. The P-glycoprotein (Pgp) inhibition assay was used to determine concentration of xenobiotics that can inhibit Pgp transport activity in NIH 3T3/MDR1 cell line. The results indicated that average concentration of Pgp-inhibitors expressed in verapamil (VER, model Pgp-inhibitor) equivalents in primary effluent decline from 150 to 50 µ ; g/L VER EQ after secondary treatment with no additional effect when MBR was included. Induction potential of samples toward CYP1A enzyme was measured using PLHC-1 fish cell line and the EROD assay. Data, expressed as fixed-effect-level toxicity equivalents (FEL-TEQ ; pg/L) indicate that MBR have ability to eliminate certain chemicals, inducers of CYP1A enzyme, although in some cases we noticed increase in inducers concentration. This inconsistency will be cleared up in the highly controlled in vitro experiment that will be executed in the final stage of the project.

waste water ; membrane bioreactors ; bBioassays ; YES bioassay ; Pgp-inhibition assay ; EROD assay

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