Phenol biodegradation and its effect on the nitrification process

Phenol biodegradation under aerobic conditions and its effect on the nitrification process were studied, first in batch assays and then in an activated sludge reactor. In batch assays, phenol was completely biodegraded at concentrations ranging from 100 to 2500 mg l(-1). Phenol was inhibitory to the nitrification process, showing more inhibition at higher initial phenol concentrations. At initial phenol concentrations above 1000 mg l(-1), the level of nitrification decreased. In the activated sludge reactor, the applied ammonium loading rate was maintained at 140 mg N-NH(4)(+)l(-1)d(-1) (350 mg N-NH(4)(+)l(-1)) during the operation time. However, the applied organic loading rate was increased stepwise from 30 to 2700 mg COD l(-1)d(-1) by increasing the phenol concentration from 35 up to 2800 mg l(-1). High phenol removal efficiencies, above 99.9%, were maintained at all the applied organic loading rates. Ammonium removal was also very high during the operation period, around 99.8%, indicating that there was no inhibition of nitrification by phenol.

Biodegradation and effect of formaldehyde and phenol on the denitrification process

Formaldehyde and phenol biodegradation during the denitrification process was studied at lab-scale, first in anoxic batch assays and then in a continuous anoxic reactor. The biodegradation of formaldehyde (260 mgl(-1)) as single carbon source and at phenol concentrations ranging from 30 to 580 mgl(-1) was investigated in batch assays, obtaining an initial biodegradation rate around 0.5g CH(2)OgVSS(-1)d(-1). With regard to phenol, its complete biodegradation was only observed at initial concentrations of 30 and 180 mgl(-1). The denitrification process was inhibited at phenol concentrations higher than 360 mgl(-1). Studies were also done using a continuous anoxic upflow sludge blanket reactor in which formaldehyde removal efficiencies above 99.5% were obtained at all the applied formaldehyde loading rates, between 0.89 and 0.14g COD (CH(2)O)l(-1)d(-1). The phenol loading rate was increased from 0.03 to 1.3g COD (C(6)H(6)O)l(-1)d(-1). Phenol removal efficiencies above 90.6% were obtained at phenol concentrations in the influent between 27 and 755 mgl(-1). However, when the phenol concentration was increased to 1010 mgl(-1), its removal efficiency decreased. Denitrification percentages around 98.4% were obtained with phenol concentrations in the influent up to 755 mgl(-1). After increasing phenol concentration to 1010 mgl(-1), the denitrification percentage decreased because of the inhibition caused by phenol.

Kinetics of inhibition in the biodegradation of monoaromatic hydrocarbons in presence of heavy metals

The toxicity and inhibitory effects of heavy metals such as cadmium, nickel and zinc on alkylbenzene removal were evaluated with a Bacillus strain. The kinetics of alkylbenzene biodegradation with the different heavy metals at various concentrations were modeled using the Andrews equation which yielded a good fit between model and experimental data. Additional experiments undertaken with a Pseudomonas sp. in presence of nickel confirmed a good fit between experimental data and the Andrews model for this strain as well. The heavy metals inhibition constants (Ki) were calculated for different combinations of volatile organic compounds (VOC) and heavy metals. The present approach provides a method for evaluating and quantifying the inhibition effect of heavy metals on the biodegradtion of pollutants by specific microbial strains.

Biofilter performance and characterization of a biocatalyst degrading alkylbenzene gases

A biofilter treating alkylbenzene vapors was characterized for its optimal running conditions and kinetic parameters. Kinetics of the continuous biofilter were compared to batch kinetic data obtained with biofilm samples as well as with defined microbial consortia and with pure culture isolates from the biofilter. Both bacteria and fungi were present in the bioreactor. Five strains were isolated. Two bacteria, Bacillus and Pseudomonas, were shown to be dominant, as well as a Trichosporon strain which could, however, hardly grow on alkylbenzenes in pure culture. The remaining two strains were most often overgrown by the other three organisms in liquid phase batch cultures. mu max, KS, KI values and biodegradation rates were calculated and compared for the different mixed and pure cultures. Since filter bed acidification was observed during biofiltration studies reaching a pH of about 4, experiments were also undertaken to study the influence of pH on performance of the different cultures. Biodegradation and growth were possible in all cases, over the pH range 3.5-7.0 at appreciable rates, both with mixed cultures and with pure bacterial cultures. Under certain conditions, microbial activity was even observed in the presence of alkylbenzenes down to pH 2.5 with mixed cultures, which is quite unusual and explains the ability of the present biocatalyst to remove alkylbenzenes with high efficiency in biofilters under acidic conditions.