Impact of long-term partial aeration on the removal of 2,4,6-trichlorophenol in an initially methanogenic fluidized bed bioreactor

Abstract

A fluidized bed bioreactor (FBBR) was operated for more than 1000 days under two regimes, Methanogenic (M) and Methanogenic-Aerobic (M-A), to remove 2,4,6-trichlorophenol (TCP) and phenol (Phe) from a synthetic wastewater, containing different amounts of TCP and Phe, using different aeration flow-rates (0, 2.13, and 1.06 NL O(2)/L.day). M conditions (80:20 mg/L of TCP:Phe, 0 NL O(2)/L.day) showed similar TCP and Phe removal (>95%). Nevertheless accumulation of 4-chlorophenol (4CP) up to 16 mg/L and Phe up to 4 mg/L was observed, while in M-A conditions (80:20 mg/L of TCP:Phe, 2.13 NL O(2)/L.day) TCP and Phe removal achieved 99.9(+)% and after 70 days no accumulation of intermediates were detected. The increase of TCP and Phe in the influent under M-A conditions from 80:20 to 120:30 mg/L of TCP:Phe did not negatively affect the removal of TCP, intermediates and Phe; in fact, they were similar to those in previous M-A conditions. The decrease in the oxygen flow rate from 2.13 to 1.06 NL O(2)/L.day had no negative effect on pollutant removals, which were as high as in previous two M-A conditions. The specific methanogenic activity of bioparticles of the fluidized bed decreased with long-term partial aeration, starting from 1.097 mmol CH(4)/h.g(TKN) in the M regime (day 60) to <0.02 mmolCH(4)/h.g(TKN) at day 1050, suggesting aerobic regime in the bioreactor rather than an M-A regime. In conclusion, complete removal of TCP and less chlorinated intermediates could be achieved in an initially methanogenic FBBR under conditions of partial aeration, although long-term operation seemed to negatively affect the methanogenic activity of biomass. It is also likely that after extended aeration the microbial community was finally enriched with strains with the ability to attack 2,4,6-TCP under aerobic conditions. This report represents the first evidence of a long exposure to oxygen of an anaerobic microbial consortium that efficiently remove TCP.

Biological treatment of 2,4,6-trichlorophenol (TCP) containing wastewater in a hybrid bioreactor system with effluent recycle

“…A number of studies were reported in literature on biodegradation of TCP (Armenante et al, 1999;Atuanya et al, 2000;Buitron et al, 1998;Correa et al, 2003;Vallecillo et al, 1999;Wang et al, 2000b;Garibay-Orijel et al, 2006;Snyder et al, 2006;Zilouei et al, 2006) which has an IC 50 value of 40 mg L À1 according to our determinations. Literature studies on aerobic biological treatment of TCP containing wastewaters were performed with low TCP concentrations (<150 mg L À1 ).…”

WITHDRAWN: Evaluation of biohydrogen production at ambient temperature from cheese whey and assessment of the associated microbial community

“…We concluded that the heat shock treatment did not eliminate the LABs. This could be due to the microorganisms present in the reactor bioparticles were somewhat protected from environmental conditions by the biofilm itself [66]. Hence, it is possible that the temperature of the inner biofilm layers (where it seems to be the place where anaerobic microorganisms concentrate [67,68] could be lower than that at the surface of the biofilm.…”

Changes in pentachlorophenol (PCP) metabolism and physicochemical characteristics by granules responding to different oxygen availability

“…The use of a simultaneous Methanogenic-Aerobic or Methanogenic-Denitrifying environment (M-A, M-D) in bioreactors, where CO 2 /O 2 and CO 2 /NO 3 serve as the electron acceptors, appears to be an alternative for achieving a more complete removal of toxic compounds and their eventual metabolites, because they could provide more diverse catabolic pathways [8]. Coupled granulation can integrate both aerobic and anaerobic degradation in a single sludge granule.…”