Research - Category III: Water Quality

Biodegradation of Estrogenic Compounds and its Enhancement in a Membrane Bioreactor
(Funded 2000-2001)

Principal Investigator: Slawomir W. Hermanowicz
Department of Civil & Environmental Engineering
UC Berkeley
(510) 642-0151
hermanowicz@ce.berkeley.edu

Executive Summary:
Main objective of the proposed project is to evaluate kinetics of biodegradation of selected estrogenic compounds and a potential for its intensification in a membrane bioreactor. Estrogenic compounds, discharged with treated wastewater have recently raised concerns because of their potential to interfere with endocrine system of various species (including possibly humans). Natural estrogens (mainly 17b-estradiol and estrone) and their synthetic counterparts (chiefly mestranol and 17a-ethinyl estradiol) are primarily excreted with urine. They are partially removed during typical wastewater treatment but the extent of removal varies from plant to plant among different estrogenic species. Despite their importance for process engineering, there are no published estimates of the removal rates during wastewater treatment. In this proposal, the removal rates were roughly estimated based on the results of a few studies that contained at least some of the required information. From this preliminary analysis it seems that the removal rate coefficient could increase significantly when estrogens are present in low mg/L concentrations comparing with ng/L values typically found in wastewaters. We postulate, based on these preliminary findings, that the increase may be related to strong sorption of estrogens on biosolids present in a treatment reactor with a potential of a hundred-fold increase in process efficiency. Even if a fraction of this potential could be realized, estrogen removal would be greatly enhanced.

In this project, we propose to provide quantitative estimates of removal rates of four selected estrogens: 17b-estradiol, estrone, estriol and 17a-ethinyl estradiol in activated sludge. WE will investiage the removal in batch conditions and the effects of biomass concentration, dissolved oxygen, temperature and presence of easily biodegradable organics. The results of the kinetic analysis will be used to design the next phase of the project where removal of two estrogens: natural 17b-estradiol and synthetic 17a-ethinyl estradiol will be investigated in a membrane bioreactor. While soluble estrogens can pass through the microfiltration membrane, we expect that they will preferentially partition onto biosolids and accumulate in this form in the reactor. This accumulation, combined with the high biomass content achievable in a membrane reactor, will yield much higher volumetric removal rates. This part of the project will be carried out concurrently with another research project, currently under way, which examines the performance of the membrane reactor for biological wastewater treatment. The reactor uses a microfiltration membrane for separation of biosolids grown in an aeration tank. Each of the selected estrogens will be continuously dosed to the influent for a period of several days and its concentration will be monitored.

Selection of analytical technique for estrogen determination will be an important part of the proposed project. WE will closely collaborate with Professor David Sedlak in our department whose research group is developing chemical analytical techniques. Complementing the chemical analyses, we plan to use recently-developed bioassay technique based on recombinant yeast cells.

The results of this project will significantly expand quantitative database for estrogen removal and will provide a starting point for further work in the area of metabolic engineering for estrogens biodegradation.