Abstract
BackgroundThis study investigated the oxidation of selected progestagenic steroid hormones by potassium permanganate at pH 6.0 and 8.0 in ultrapure water and wastewater effluents, using bench-scale assays. Second order rate constants for the reaction of potassium permanganate with progestagens (levonorgestrel, medroxyprogesterone, norethindrone and progesterone) was determined as a function of pH, presence of natural organic matter and temperature. This work also illustrates the advantages of using a novel analytical method, the laser diode thermal desorption (LDTD-APCI) interface coupled to tandem mass spectrometry apparatus, allowing for the quick determination of oxidation rate constants and increasing sample throughput.ResultsThe second-order rate constants for progestagens with permanganate determined in bench-scale experiments ranged from 23 to 368 M-1 sec-1 in both wastewater and ultrapure waters with pH values of 6.0 and 8.0. Two pairs of progestagens exhibited similar reaction rate constants, i.e. progesterone and medroxyprogesterone (23 to 80 M-1 sec-1 in ultrapure water and 26 to 149 M-1 sec-1 in wastewaters, at pH 6.0 and 8.0) and levonorgestrel and norethindrone (179 to 224 M-1 sec-1 in ultrapure water and 180 to 368 M-1 sec-1 in wastewaters, at pH 6.0 and 8.0). The presence of dissolved natural organic matter and the pH conditions improved the oxidation rate constants for progestagens with potassium permanganate only at alkaline pH. Reaction rates measured in Milli-Q water could therefore be used to provide conservative estimates for the oxidation rates of the four selected progestagens in wastewaters when exposed to potassium permanganate. The progestagen removal efficiencies was lower for progesterone and medroxyprogesterone (48 to 87 %) than for levonorgestrel and norethindrone (78 to 97%) in Milli-Q and wastewaters at pH 6.0-8.2 using potassium permanganate dosages of 1 to 5 mg L-1 after contact times of 10 to 60 min.ConclusionThis work presents the first results on the permanganate-promoted oxidation of progestagens, as a function of pH, temperature as well as NOM. Progestagen concentrations used to determine rate constants were analyzed using an ultrafast laser diode thermal desorption interface coupled to tandem mass spectrometry for the analysis of water sample for progestagens.
Highlights
This study investigated the oxidation of selected progestagenic steroid hormones by potassium permanganate at pH 6.0 and 8.0 in ultrapure water and wastewater effluents, using bench-scale assays
To the best of our knowledge, this paper presents the first results on the permanganate-promoted oxidation of steroid hormones without aromatic moieties, i.e. progestagens, as a function of pH, temperature as well as natural organic matter (NOM) levels
The values of apparent first-order rate constants for permanganate, with and without the addition of steroid hormones (SH) were calculated by linear regression and resulting apparent rate constants are summarized in Table 1, in wastewaters at ambient pH 6.3 for wastewater treatment plant (WWTP) B and pH of 8.2 for WWTP A
Summary
This study investigated the oxidation of selected progestagenic steroid hormones by potassium permanganate at pH 6.0 and 8.0 in ultrapure water and wastewater effluents, using bench-scale assays. Many endocrine-disrupting compounds (EDCs), such as steroid hormones (SH) have been detected in waste and surface water matrices [1,2,3,4] They originate from naturally-occurring (e.g. normal urine excretion of estrogens from mammals) and synthetic (e.g. progestagens in oral contraceptives and hormone replacement therapy) sources. Synthetic progestagens can have various hormonal activities, such as estrogenic, anti-androgenic and androgenic [15] Their presence in wastewater treatment plant (WWTP) effluents can pose a risk for the aquatic environment given their potential for impact on the reproductive success and the chemoreception of fish [18,19]. Progestagenic steroid hormones will be discharged into environmental waters from WWTP effluents and such releases should be better documented
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