Transformation and fate of natural estrogens and their conjugates in wastewater treatment plants: Influence of operational parameters and removal pathways

Abstract

a b s t r a c tNatural estrogens (NEs) discharged from wastewater treatment plants (WWTPs) have drawn great attention because of their potential risks to aquatic ecosystems. However, neglect of the conjugated natural estrogens (C-NEs) has caused large discrepancies among different studies on the removal of NEs in WWTPs. The present work investigated the transformation and fate of three NEs and six corresponding C-NEs along wastewater treatment processes. The removal efficiencies of the target estrogens (i.e., NEs and C-NEs) and their correlations with the operational parameters were determined over a twelve-month monitoring period at a typical WWTP adopting a combined bio-treatment process (i.e., anaerobic/anoxic/oxic process followed by a moving-bed biofilm reactor). The concentration variations of the target estrogens along the treatment processes were examined to differentiate the transformation and fate of NEs and C-NEs. Moreover, lab-scale experiments were conducted to clarify the removal pathways of C-NEs in the bio-treatment process. Results indicate that both NEs and C-NEs could pass through the treatment processes, thus being frequently detected in the effluent and excess sludge. The aqueous removal efficiencies of NEs and C-NEs were significantly correlated with the sludge retention time and temperature, respectively. C-NEs were more persistent than NEs, so considerably high conjugated ratios (13.5e100.0%) were detected in the effluent. Sulfate conjugates presented a lower adsorption affinity to sludge and a slower hydrolysis rate than glucuronide conjugates, which makes the former more recalcitrant to biodegradation. This study highlights the challenge on the elimination of NEs, particularly their conjugates, by wastewater treatment processes.

Simultaneous measurement of free and conjugated estrogens in surface water using capillary liquid chromatography tandem mass spectrometry

“…In contrast, the prevalence of sulphates was observed, which was attributed to lower MDLs the sulphates possessed; additionally, the transformation of glucuronides to free estrogens was inferred in natural water while the sulphates were more recalcitrant to biodegradation induced by microorganisms, as reported prior to this study. 84…”

Broad diversity of bacteria degrading 17ß-estradiol-3-sulfate isolated from river sediment and biofilm at a wastewater treatment plant discharge

“…Wastewater treatment plants (WWTP) were shown as an entry point into the environment of not only the estrogenic compounds like E2 and E1 (Khanal et al 2006 ; Ying et al 2009 ; Naldi et al 2016 ), but also of conjugated estrogens, excreted by humans mainly in the urine, that can all enter the aquatic environment at low ng/L concentrations (D’Ascenzo et al 2003 ; Reddy et al 2005 ; Kumar et al 2012 ; Liu et al 2015 ; Ma et al 2016 ; Naldi et al 2016 ; Ben et al 2017 ; Ma and Yates 2018 ).Glucuronide- or sulfate-conjugated estrogens are more polar than the corresponding free estrogens (Anstead et al 1997 ; Fang et al 2001 ) and consequently exhibit lower binding affinity for estrogen receptors rendering them biologically inactive (Desbrow et al 1998 ; Griffith et al 2014 ; Ma and Yates 2018 ). However, conjugated estrogens may be converted to the free form via hydrolysis by bacterial enzymes (Tyler and Routledge 1998 ; Bai et al 2013 ).…”

Organic contaminants of emerging concern in Norwegian digestates from biogas production

“…The role of conjugate cleavage for the remobilisation of previously immobilised contaminants in biologically active matrices has been reported previously for similar matrices to those studied here. [60][61][62][63][64][65] There is apparent degradation for some compounds (e.g., ACE and OCR) but not for the majority of target substances (Fig. 4).…”