Removal of Natural Estrogens and Their Conjugates in Municipal Wastewater Treatment Plants: A Critical Review

Abstract

This article reviews studies focusing on the removal performance of natural estrogens in municipal wastewater treatment plants (WWTPs). Key factors influencing removal include: sludge retention time (SRT), aeration, temperature, mixed liquor suspended solids (MLSS), and substrate concentration. Batch studies show that natural estrogens should biodegrade well; however, batch observations do not always agree with observations from full-scale municipal WWTPs. To explain this discrepancy, deconjugation kinetics of estrogen conjugates in lab-scale studies were examined and compared. Most estrogen conjugates with slow deconjugation rates are unlikely to be easily removed; others could be cleaved in WWTP settings. Nevertheless, some estrogens cleaved from their conjugates may be found in treated effluent, because deconjugation requires several hours or longer, and there is insufficient rest time for the biodegradation of the cleaved natural estrogens in the WWTP. Therefore, WWTP removals of natural estrogens are likely to be underestimated when estrogen conjugates are present in raw wastewater. This review suggests that biodeconjugation of estrogen conjugates should be enhanced to more effectively remove natural estrogens in WWTPs.

Simultaneous detection of endocrine disrupting chemicals including conjugates in municipal wastewater and sludge with enhanced sample pretreatment and UPLC-MS/MS

“…10 As a result, an underestimation of removal efficiency will inevitably occur if the conjugated forms occupy a considerable portion of the total estrogens. 8 This necessitates the detection of conjugated estrogens in WWTPs when investigating the behavior and fate of EDCs.…”

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

“…An important reason for the inconsistencies is that the operational parameters, including temperature, hydraulic retention time (HRT) and sludge retention time (SRT), varied greatly among the different studies. However, studies that discussed the influence of operational parameters on the NE removal also showed significant discrepancies (Clara et al, 2005;Hashimoto et al, 2007;Liu et al, 2015;Nakada et al, 2006). It is particularly difficult to isolate the influence of one operational parameter, as the treatment processes and other operational parameters differed across these studies.…”

“…Among the EDCs, natural estrogens (NEs), including estrone (E1), 17 b-estradiol (E2) and estriol (E3), were the most studied because of their strong estrogenic potencies (Liu et al, 2015). Human and animal excretions constituted the main sources of NEs in the environment, while the occurrence of NEs in municipal wastewater is primarily attributed to human excretions.…”

“…NEs are predominantly excreted from human and animal bodies in their conjugated forms, so C-NEs can constitute a notable proportion in the influent of WWTPs (Johnson and Williams, 2004). C-NEs can be deconjugated into their corresponding NEs by arylsulfatase and b-glucuronidase derived from microorganisms which are abundant in WWTPs (Dray et al, 1972;Liu et al, 2015), thus leading to an inaccurate estimation on the removal efficiencies of NEs. However, limited research has been conducted on the transformation and fate of C-NEs in full-scale WWTPs, probably due to a lack of easily applicable methods for simultaneous detection of both NEs and C-NEs in complicated matrices (Zhu et al, 2015).…”

Transformation and utilization of slowly biodegradable organic matters in biological sewage treatment of anaerobic anoxic oxic systems

“…Suspended pollutants in urban sewage are characterized by their slow biodegradation (Jordao et al, 2002;Liu et al, 2015;Munoz et al, 2009). However, a few issues need to be resolved before adapting microbes for implementation in high suspended solids (SS) urban sewage treatment plants.…”