
Cydzik-Kwiatkowska Agnieszka
University of Warmia and Mazury in Olsztyn, Poland
Title: Transformations of nitrogen compounds in granular sludge batch reactors treating municipal wastewater containing bisphenol A (BPA)
Biography
Abstract
Bisphenol A (BPA) is an endocrine disrupting micro pollutant. It can be biologically removed from wastewater by sorption and biodegradation. In this study, aerobic granular sludge was used, which enables a high concentration of active microorganisms per unit volume of the reactor and a high absorptive capacity due to the high content of extracellular polymers in its structure. The study determined how the concentration of BPA in wastewater influenced the transformations of nitrogen compounds. The study was conducted in five constantly aerated reactors with granules (GSBR) operated at an HRT of 16h. Influent to the control reactor did not contain BPA. BPA concentrations in the wastewater fed to the other four reactors were 2, 4, 6 and 12 mg/L. The overall COD and ammonium concentrations in synthetic wastewater were about 400 mg/L and 50 mg/L, respectively. In all reactors at least 200 cycles were performed. Ammonium nitrogen removal efficiency, resulting from nitrification and biomass synthesis, exceeded 99.5% regardless of the operational conditions. In both the control and the experimental reactors, partial nitrification (oxidation of ammonia nitrogen to nitrites) predominated. The efficiency of nitrification in the control reactor was 88.5±3.7%, and at all tested concentrations; BPA in the influent did not reduce nitrification efficiency. The highest nitrification efficiency (91.4±2.6%) was noted in the reactor fed with wastewater containing 2 mg BPA/L. In the control reactor, the efficiency of nitrogen removal from wastewater by de-nitrification and biomass synthesis was 15.8±8.6%. At concentrations of 2 and 4 mg/L, BPA in wastewater had no effect on nitrogen removal efficiency, but further increasing the concentration of BPA reduced nitrogen removal efficiency by a few percent. In the control reactor, 63% of total nitrogen removal was due to de-nitrification. In the reactor fed with wastewater containing 2 mg BPA/L, de-nitrification made the largest contribution to total nitrogen removal (70.3%).

Magdalena Zielińska
University of Warmia and Mazury in Olsztyn, Poland
Title: Microfiltration and ultrafiltration of the effluent from granular sequencing batch reactors treating municipal wastewater containing bisphenol A (BPA)
Biography
Abstract
Bisphenol A (BPA), an endocrine disrupting compound, is almost completely removed from wastewater through biological processes in activated sludge or immobilized biomass. However, the biological effluent may contain high concentrations of suspended solids or organic compounds (COD). In this study, wastewater treated in granular sequencing batch reactors (GSBRs) was characterised by COD concentrations from 107.1 to 145.5 mg/L and suspended solid concentrations from 101 to 171 mg/L. This wastewater (feed solution) was post-treated with ceramic membranes that are characterised by mechanical and chemical stability, long life and good antifouling properties. Microfiltration (MF) and ultrafiltration (UF) were conducted at transmembrane pressures (TMP) of 0.2 MPa and 0.3 MPa, respectively. Both MF and UF caused complete rejection of suspended solids. COD rejection during MF was 81.1±1.1%, independently of the composition of the feed solution. The use of UF did not increased COD rejection significantly. During MF, from 34 to 60% of COD was adsorbed to the membrane surface, as determined from the mass balance of membrane filtration. The use of UF increased COD adsorption to 71%. Permeate flux changed from 24.0 to 29.5 L/(m2∙h), and volumetric concentration factor ranged from 2.0 to 2.4; these hydraulic parameters were influenced neither by the type of filtration process nor by TMP. Although filtration capacity decreased with time because of fouling, this decrease was not affected by the composition of the feed solution. These results suggest that the use of both MF and UF ceramic membranes is a good solution for post-treatment of secondary effluent from GSBRs that treat wastewater containing BPA. However, taking everything into consideration, MF is more advantageous because it can be operated at lower TMP, thus requiring less energy for filtration.