Examinando por Autor "Mohedano, Angel F."

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Comparison of UASB and EGSB performance on the anaerobic biodegradation of 2, 4-dichlorophenol
(Elsevier, 2009-07-04) Puyol, Daniel; Mohedano, Angel F.; Sanz, José Luis; Rodríguez, Juan José
The anaerobic degradation of 2,4-dichlorophenol (2,4-DCP) in upflow anaerobic sludge blanket (UASB) and expanded granular sludge bed (EGSB) reactors using glucose as main carbon source was studied. The performance of both systems was compared in terms of 2,4-DCP and COD removal efficiencies, methane production, stability, granular sludge adaptability as well as reversion of the bacterial inhibition. Both organic and 2,4-DCP loading rates were incrementally varied through the experiments. With loading rates of 1.9 g COD L 1d 1 and 100mg 2,4-DCP L 1d 1, 75% and 84% removal efficiencies of this compound, accompanied by COD consumption efficiencies of 61% and 80% were achieved in the UASB and EGSB reactors, respectively. In these conditions, methane production reached 0.088 L CH4 g 1 COD in the EGSB reactor whereas in the UASB reactor was almost negligible. Decreasing the 2,4-DCP loading rate to 30 mgL 1d 1 an improvement in the methane production was observed in both reactors (methanogenic activity of 0.148 and 0.192 L CH4 g 1 COD in UASB and EGSB reactors, respectively). Efficiency of dechlorination was improved in both reactors from around 30% to 80% by reducing to one-half the COD due to a decreasing of the 4-chlorophenol concentration accumulated in the effluents of both reactors. The dechlorination efficiency of the UASB reactor was dramatically inhibited at a 2,4-DCP feed concentration above around 210 mg L 1 because of 2,4-DCP accumulation in the effluent. SEM studies revealed no significant morphological changes in the sludge granules.
Effect of 2,4,6-trichlorophenol on the microbial activity of adapted anaerobic granular sludge bioaugmented with Desulfitobacterium strains
(Elsevier, 2011-12-15) Puyol, Daniel; Mohedano, Angel F.; Rodríguez, Juan José; Sanz, José Luis
The anaerobic degradation of 2,4,6-trichlorophenol (246TCP) has been studied in batch experiments. Granular sludges previously acclimated to 2,4-dichlorophenol (24DCP) and then adapted to at a load of 330 μM 246TCP d−1 in two expanded granular sludge bed (EGSB) reactors were used. One of the reactors had been bioaugmented with Desulfitobacterium strains whereas the other served as control. 246TCP was tested at concentrations between 250 and 760 μM. The study focused on the fate of both fermentation products and chlorophenols derived from dechlorination of 246TCP. This compound mainly affected the biodegradation of acetate and propionate, which were inhibited at 246TCP concentrations above 380 μM. Lactate and ethanol were also accumulated at 760 μM 246TCP. Methanogenesis was strongly inhibited at 246TCP concentrations higher than 380 μM. A diauxic production of methane was observed, which can be described by a kinetic model in which acetoclastic methanogenesis was inhibited, whereas hydrogenotrophic methanogenesis was hardly affected by 246TCP. The similarity of the kinetic parameters obtained for the control and the bioaugmented sludges (Ki = 175–200 μM 246TCP and n = 7) suggests that methanogenesis is not affected by the bioaugmentation. Moreover, the 246TCP dechlorination occurred mainly at ortho position, successively generating 24DCP and 4-chlorophenol (4CP), which was identified as final product. The bioaugmentation does not significantly improve the anaerobic biodegradation of 246TCP. It has been shown that the active biomass is capable of bioaccumulating 246TCP and products from dechlorination, which are subsequently excreted to the bulk medium when the biomass becomes active again. A kinetic model is proposed which simultaneously explains 246TCP and 24DCP reductive dechlorinations and includes the 246TCP bioaccumulation. The values of the kinetic parameters for 246TCP dechlorination were not affected by bioaugmentation (Vmax = 5.3 and 5.1 μM h−1 and Ks = 5.8 and 13.1 μM for control and bioaugmented sludges, respectively)