ESB - Contribuições em Revistas Científicas / Contribution to Journals
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- Biodegradation of 2-fluorobenzoate and dichloromethane under simultaneous and sequential alternating pollutant feedingPublication . Osuna, M. Begoña; Sipma, Jan; Emanuelsson, Maria A. E.; Carvalho, M. Fátima; Castro, Paula M. L.Two up-flow fixed-bed reactors (UFBRs), inoculated with activated sludge and operated for 162 days,were fed 1 mmol Lˉ¹ dˉ¹ with twomodel halogenated compounds, 2-fluorobenzoate (2-FB) and dichloromethane (DCM). Expanded clay (EC) and granular activated carbon (GAC)were used as biofilm carrier. EC did not have any adsorption capacity for both model compounds tested, whereas GAC could adsorb 1.3 mmol gˉ¹ GAC for 2-FB and 4.5mmol gˉ¹ GAC for DCM. Both pollutants were degraded in both reactors under simultaneous feeding. However, biodegradation in the EC reactor was more pronounced, and re-inoculation of the GAC reactorwas required to initiate 2-FB degradation. Imposing sequential alternating pollutant (SAP) feeding caused starvation periods in the EC reactor, requiring time-consuming recovery of 2-FB biodegradation after resuming its feeding, whereas DCMdegradation recovered significantly faster. The SAP feeding did not affect performance in the GAC reactor as biodegradation of both pollutants was continuously observed during SAP feeding, indicating the absence of true starvation.
- Biodegradation of 2-fluorobenzoate in upflow fixed bed bioreactors operated with different growth support materialsPublication . Emanuelsson, Maria A.E.; Henriques, Isabel S.; Jorge, Ruben M Ferreira; Castro, Paula M. L.Three upflow fixed bed bioreactors treating an aqueous stream containing 2-fluorobenzoate were operated for a period of 7months, during which they were exposed to high organic loading rates and starvation. The reactors contained granular activated carbon (GAC), polyethylene (PE) particles and expanded clay (EC) respectively as growth support for microbial biofilms. The performance of the reactors was compared and the biofilm microbial population was followed by cell counting and denaturing gradient gel electrophoresis (DGGE). The reactor containing GAC always had 100% removal efficiency owing to the adsorption properties of thematerial combined with biodegradation. The GAC reactor also recovered better after starvation periods in the sense that it showed more stable behaviour than the reactors containing EC and PE. The highest biological elimination capacity was observed for the reactor containing EC, which reached 200mg day−1 L−1 during reactor start-up, but during long-termoperation the reactor containing GAC showed the highest biological elimination capacity, 140mg day−1 L−1. DGGE analysis indicated that starvation periods seemed to be responsible for shifts in the microbial population.
- Treatment of halogenated organic compounds and monitoring of microbial dynamics in up-flow fixed bed reactors under sequentially alternating pollutant scenariosPublication . Emanuelsson, Maria A. E.; Osuna, M. Begoña; Sipma, Jan; Castro, Paula M. L.Two up-flow fixed bed reactors (UFBR) were operated for 8 months treating a model synthetic wastewater containing 2-fluorobenzoate (2-FB) and dichloromethane (DCM). The stability of the reactors under dynamic conditions, that is, sequentially alternating pollutants (SAP), shock loads, and starvation periods was assessed. Two support materials were used: expanded clay (EC) that does not adsorb 2-FB or DCM, and granular-activated carbon (GAC) that adsorbs 180 mg gg⁻¹ of 2-FB and 390 mg gg⁻¹ of DCM. The reactors were inoculated with a 2-FB-degrading strain (FB2) and a DCM degrader (TM1). 2-FB was fed at organic loads ranging from 0 to 800 mg L⁻¹ d⁻¹, while DCM was fed at 0–250 mg L⁻¹ d⁻¹. 2-FB or DCM were never detected at the outlet of the GAC reactor, while in the EC reactor outlet small amounts were observed. Nevertheless, the highest biological elimination capacity was observed in the EC reactor (over 700 mg L⁻¹ d⁻¹ of 2-FB). DGGE analysis revealed a fairly stable bacterial community with the largest shifts occurring during starvation periods and changes in feed composition. Several bacterial strains isolated from the reactors showed capacity for 2-FB degradation, while only strain TM1 degraded DCM.