(426b) Improving Anaerobic Digestibility of Natural Estrogens by the Application of Advanced Oxidation Processes

Charu Chawla^a, George Nakhla^b, Madhumita B. Ray^c

Chemical and Biochemical Engineering, The University of Western Ontario, London, CA, N6A5B9

^acchawla2@uwo.ca, ^bgnakhla@uwo.ca, ^cmray@eng.uwo.ca,

Keywords: wastewater, micropollutants, endocrine disrupting chemicals, estrogens, biosolids, advanced oxidation processes

Endocrine disrupting chemicals (EDCs) are emerging environmental contaminants which have gained significant attention of scientific community due to their potential health risks.  The conventional wastewater treatment plants are not designed to treat micropollutants causing low overall removal of these compounds.  Many of these compounds such as estrogens are hydrophobic and partition onto the suspended solids, which is a key parameter that controls their fate in waste water treatment plants.  Subsequently these compounds make their way to anaerobic digester where they have been found to degrade poorly.  In an earlier project we have tested various oxidative pre-treatment technologies to enhance anaerobic digestion of waste activated sludge.  The effects of various pretreatment methods have been established with respect to enhanced volatile suspended solids reduction, bio-gas production, and odor reduction.  The objective of the present work is to establish the effects of various pretreatment methods on the anaerobic digestibility of the estrogenic compounds such as estrone and estradiol.  

The present research is focussed on evaluating different advanced oxidation processes (AOPs) such as ultrasonication, hydrogen peroxide and ozone to enhance the biodegradation of estrogenic compounds under anaerobic conditions.  The detection of estrogenic compounds in ng/L range in wastewater and sludge is challenging.  At the onset, EPA 1698 method was modified and analytical protocol was developed using SPE extraction method followed by GC-MS analysis. Thereby, experiments were conducted to characterize the partitioning of estrone and estradiol on waste activated sludge from Adelaide Pollution Control Plant, London (ON, Canada). Adsorption of the compounds was studied on both heat inactivated sludge (to separate adsorption from biodegradation) and anaerobic seed (microorganisms).  The adsorption data were fitted to Freundlich isotherm and adsorption coefficients were calculated.  The isotherm coefficients for estrone and estradiol on the seed and sludge are comparable and are in the range of 0.1- 0.123 mg ^(1-1/n) L^1/n gTSS^-1 and 1/n≈ 0.87.  Subsequently,   ultrasonication was tested as pre-treatment method to study the degradation of estrogenic compounds in ultra pure water at 7 different specific energies in the range of 15 - 1600 kJ/L. The effect of ultrasonication on degradation of estrone occurred only above 500 kJ /L of clean water. It was concluded that high energy inputs are required to break the sterane core of heavy molecules like estrogen.  In the next step, different doses of hydrogen (0.5-2.5 g/L) peroxide and ozone (0.015 and 0.05 gO₃/gTSS) were combined with ultrasonication for enhanced degradation in control tests.  Currently, batch anaerobic digestion experiments are being conducted with pretreated estrogenic compounds to establish the optimum pretreatment conditions.