Date of Award
5-2013
Document Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Legacy Department
Environmental Toxicology
Committee Chair/Advisor
White, Sarah A
Committee Member
Lee , Cindy
Committee Member
Klaine , Steve
Committee Member
Hitchcock , Dan
Abstract
Estrone, 17beta-estradiol (E2), and estriol are three of the most relevant natural hormones and are often found to contaminate the environment. When emanating from endogenous sources, these three compounds are not toxic or of concern; however, when estrogens are released into the environment from wastewater effluent they become a concern. The overall goal of the project was to evaluate abiotic and biotic techniques for removal of E2 and to quantify survival and reproduction impacts on an algal species and on an invertebrate species. We accomplished this goal by: 1) quantifying E2 sorption rates to crushed brick, an industrial mineral aggregate (calcined clay) and sand media by exposing each to increasing concentrations of E2; 2) determining the removal efficacy of E2 by the three media from wastewater sources in a pilot scale fixed bed bioreactor; 3) defining the capacity of algal cells to facilitate E2 removal whether via sorption or metabolism-aided degradation processes; 4) establishing the impacts of increasing E2 concentrations on the density and growth of algal communities; 5) determining if food-borne exposure was a critical exposure route to invertebrate species by feeding Daphnia magna E2 inoculated algae; and 6) assessing the impact of aqueous E2 exposure on the survival and reproduction of D. magna for two generations.
Sorption onto mineral media, activated sludge, and extended sludge retention time are key processes influencing EDC degradation in wastewater treatment facilities. Calcined clay sorbed significantly more E2 from simulated wastewater than either crushed brick or sand. At concentrations less than 100 ng/L E2, the clay media sorbed more than 60% of E2 from solution. When the three media were tested in a static bed biofilter to examine both sorption and biodegradation by bacterial films established in the biofilter, nearly all the E2 was removed from solution after 24 hours in the fixed-bed bioreactor filled with clay. Wastewater collected directly from the activated sludge unit and the final settling stage were spiked with E2; the concentration E2 in solution was reduced to below our detection limits (nearly 0 ng/L) after as little as four hours (activated sludge) to 24 hours (final settling stage), with no media added to provide surface area for microbial colonization.
Increasing densities of algal (Pseudokirchneriella subcapitata) populations enhanced removal of E2 from wastewater over a 24-hour period. At algal densities > 24 million cells/mL more than 95% of E2 was removed from solution. When algal populations of the same density (12 million cells/mL) were exposed to increasing concentrations of E2 over a 24-hour period, between 85 and 100% of aqueous E2 was removed at 55, 500 and 1000 ng/L exposure concentrations. Removal of E2 by algae exposed to higher concentrations (3000 and 10000 ng/L) of E2 averaged ¡Ü 90%, and both exposure concentrations were significantly different (P = 0.05) from lower concentrations (55, 500 and 1000 ng/L). Results suggest that sorption to organic material and photodegradation are not the main mechanisms driving E2 removal from aqueous solution, but rather that biological processes (metabolism and degradation) are the primary removal mechanisms in these lab-scale algal treatment systems.
Finally, invertebrate organisms offer a unique opportunity to evaluate endocrine disruption activity in lower food level organisms. Daphnia magna were utilized as a model organism to characterize the effects of E2 on food chain micro-fauna. Endpoints evaluated were the survival and reproduction of D. magna after exposure to E2. Survival and reproduction were recorded for both the first and second generation of D. magna. During the second generation D. magna experiments, neonates from the first generation experiments were collected and divided into a group subjected to continued E2 exposure and a group where E2 was removed and recovery/depuration permitted. Results for food-borne exposure expressed E2 influence on D. magna populations via aqueous exposure (bioconcentration) and not by way of food-borne exposure (bioaccumulation). The three aqueous exposure results emphasized generational effects of E2 exposure to D. magna, indicating potential generational effects were possible with carryover impacts magnified in second generation organisms, if exposure to E2 was not removed. When E2 exposure ceased, D. magna recovered almost immediately and reproduced at levels similar to control organisms. Results from these experiments will give some insight into treatment processes to aid in reduction or removal of E2. Reducing E2 levels entering the natural environment can be beneficial in maintaining a healthy balanced ecosystem.
Recommended Citation
Beecher, Lance, "ASSESSMENT OF 17BETA-ESTRADIOL REMOVAL FROM WASTEWATER VIA ABIOTIC AND BIOTIC ROUTES AND POTENTIAL EFFECTS ON FOOD CHAIN PATHWAYS" (2013). All Dissertations. 1083.
https://open.clemson.edu/all_dissertations/1083