Anaerobic Membrane Bioreactor (AnMBR) for Treatment of Landfill Leachate and Removal of Micropollutants

• Main Author: Do, Anh Tien
• Format: Others
• Published: Scholar Commons 2011
• Subjects: biotransformation; Endocrine disrupting compound; Filtration; sorption; wastewater; American Studies; Arts and Humanities; Environmental Engineering; Other Environmental Sciences
• Online Access: http://scholarcommons.usf.edu/etd/3075; http://scholarcommons.usf.edu/cgi/viewcontent.cgi?article=4270&context=etd

To date, most studies on the fate and removal of endocrine disrupting compounds (EDCs) and pharmaceutical and personal care products (PPCPs) in wastewater focus on their fate in municipal wastewater treatment plants, and mostly under aerobic condition. There are limited studies related to anaerobic condition and (to our knowledge) no study on the removal of EDCs in landfill leachate by AnMBR. Moreover, for most studies under anaerobic condition, the removal of EDCs was only reported in the liquid phase; solid phase extraction was not reported, thereby preventing mass balance in the studies. This research was conducted to investigate the potential of AnMBR for reduction of organic strength and removal of EDCs in landfill leachate. A novel lab-scale upflow anaerobic sludge blanket (UASB) reactor equipped with dual-flat sheet ultrafiltration and microfiltration membrane modules was designed and constructed to test the potential to remove EDCs and traditional landfill leachate constituents (COD, turbidity). The target EDC was 17β-estradiol (E2), a prevalent female hormone used for contraceptives and hormone replacement therapy. Due to the nature of packaging and widespread use in households, the entry of E2 into landfills is highly likely, and has been reported. The quantification of E2 from liquid phase in this project is performed by the use of solid-phase microextraction (SPME) with GC/MS. Batch assays were conducted to determine the anaerobic biodegradability of E2 as well as to measure the respective distribution coefficients of E2 to PAC, colloids and anaerobic sludge biomass. In the adsorption batch assays, it was found that the PAC has stronger adsorption potential than anaerobic sludge. The adsorption potential of E2, E1 and EE2 on sludge follows the order E2>EE2>E1 which correlates to the Kow values (4.01, 3.67, 3.1, respectively). However, all three compounds showed the same adsorption potential to the Norit 20B PAC. The biodegradability of E2 was investigated in both liquid and solid phase and under several conditions such as methanogenesis, methanogenesis with aid from PAC, and methanogenesis with additional alternative electron acceptors added (sulfate and nitrate). E2 was found to transform to E1 under all tested conditions. The compounds are present in both liquid and solid phase. E2 and E1 were not detected (< 4ng/L and <10ng/L, respectively) in the liquid phase after 25 days in most cases except the case of adding additional sulfate. The AnMBR was designed, fabricated and operated for 2 years. During the stable condition period of the AnMBR, the high removal efficiencies of COD and E2 achieved were around 92% and 98%, respectively. However, E2 was still detected in the effluent at average concentrations of 30-40 µg/L range. To expand hormone retention and removal by the AnMBR, as well as to control membrane fouling, powder activated carbon (PAC) was added to the reactor. After the PAC was added, the concentration of E2 was reduced to less than the detection limit (4ng/L) in both MF and UF effluents. The log removal of E2 in the AnMBR system increased immediately from 1.7 without PAC to 5.2 after PAC was added. This study demonstrated that the AnMBR has high potential for removal of E2, and with aid from PAC, the AnMBR can remove E2 from landfill leachate to levels below detection limit.