Evaluating Removal of Steroid Estrogens by a Model Alga as a Possible Sustainability Benefit of Hypothetical Integrated Algae Cultivation and Wastewater Treatment Systems

Abstract

The wastewater treatment field is increasing its emphasis on energy and resource recovery, while still prioritizing environmental protection. In this vein, there is growing interest in integration of algae cultivation and wastewater as a means to produce bioenergy while also removing dissolved nutrients. This paper assesses algae-mediated removal of estrogenic steroid hormones, which is an important but previously undocumented water quality benefit for municipal and livestock waste treatment facilities, because these entities discharge significant amounts of estrogens and nutrients. Bench-scale experiments were used to investigate apparent removal of four steroid hormones by a model alga, Scenedesmus dimorphus. Removal efficiencies were roughly 85% for 17α-estradiol and estrone and 95% for 17β-estradiol and estriol over eight days. Sorption, direct-photolysis, and algae-mediated biotransformation were evaluated as possible removal mechanisms. Removal was mainly achieved by algae-mediated biotransformation, and a partial mechanism has been proposed based on observed products. A bioassay indicates that removal of the parent estrogens does not always remove estrogenic activity, although estrogenicity associated with 17β-estradiol did decrease slightly. Overall, this study highlights a novel synergy between water and energy sustainability in integrated algae farming and wastewater treatment systems. These systems should be studied further to see if energy production could motivate voluntary removal of currently unregulated emerging contaminants.

Removal of pharmaceuticals and personal care products from wastewater using algae-based technologies: a review

“…As mediated by algae, 17a-estradiol and 17b-estradiol can be biotransformed into estrone, which can be biotransformed into estriol by hydroxylation and further degraded into other unknown products (Zhang et al 2014b). Biodegradation of progesterone and norgestrel by algae has also been reported, and biotransformation products identified during degradation indicate that hydroxylation, reduction and oxidation were involved in the degradation process (Peng et al 2014).…”

Using agro-industrial wastes for the cultivation of microalgae and duckweeds: Contamination risks and biomass safety concerns

“…During microalgae/duckweed cultivation estrogens are converted from one form into another; E1, E2 and EE2 can be interconverted rapidly, during a few hours of cultivation, while estrone (E1) is transformed into estriol and after an extended period (> 7 days) is further degraded into unknown lipophilic products (Lai et al, 2002;Shi et al, 2010;Zhang et al, 2014c). Among the removal mechanisms, it was shown that photodegradation and direct oxidation accounted for a small fraction of the total estrogen removal (Maes et al, 2014;Shi et al, 2010;Zhang et al, 2014c). On the other hand, even as the final removal of total estrogen can reach over than 85%, it was shown that the estrogenic activity of the medium was not reduced suggesting that the degradation products displayed the same or higher estrogenic activity compared to the parent compounds (Zhang et al, 2014c).…”

“…Among the removal mechanisms, it was shown that photodegradation and direct oxidation accounted for a small fraction of the total estrogen removal (Maes et al, 2014;Shi et al, 2010;Zhang et al, 2014c). On the other hand, even as the final removal of total estrogen can reach over than 85%, it was shown that the estrogenic activity of the medium was not reduced suggesting that the degradation products displayed the same or higher estrogenic activity compared to the parent compounds (Zhang et al, 2014c). Estrogen sorption onto biomass can range between 4 and 58% and might depend on the species of the organism, the estrogen concentration, or other cultivation parameters (Hom-Diaz et al, 2015;Zhang et al, 2014c).…”

“…On the other hand, even as the final removal of total estrogen can reach over than 85%, it was shown that the estrogenic activity of the medium was not reduced suggesting that the degradation products displayed the same or higher estrogenic activity compared to the parent compounds (Zhang et al, 2014c). Estrogen sorption onto biomass can range between 4 and 58% and might depend on the species of the organism, the estrogen concentration, or other cultivation parameters (Hom-Diaz et al, 2015;Zhang et al, 2014c). The degree of intracellular concentration of estrogen has not yet been extensively investigated; however, it was shown that the microalga Desmodesmus subspicatus incorporated around 23% EE2 from its surrounding medium after 24 h, with no further uptake.…”

Biorrelación de aguas contaminadas con nutrientes y fármacos mediante microalgas = Bioremediation of contaminated waters with nutrients and pharmaceuticals by microalgae

“…observaron una eliminación debida a procesos de adsorción mediante el cultivo de Chlorella sorokiniana < 20% para los fármacos diclofenaco, ibuprofeno, paracetamol, metopropol, carbamazepina y trimetopin. En el caso de los estrógenos, diversos autores han obtenido eliminaciones < 10% tanto por adsorción a biomasa de microalgas muerta Zhang et al, 2014) como viva (Shi et al, 2010. Norvill et al (2017) determinaron una degradación del antibiótico tetraciclina del 93-99%, siendo el principal mecanismo la fotodegradación y tan solo un 6% de la eliminación total fue atribuible a la adsorción del fármaco a la biomasa de microalgas y bacterias.…”