Effect of loading types on performance characteristics of a trickle-bed bioreactor and biofilter during styrene/acetone vapor biofiltration.

A 2:1 (w/w) mixture of styrene (STY) and acetone (AC) was subjected to lab-scale biofiltration under varied loading in both a trickle bed reactor (TBR) and biofilter (BF) to investigate substrate interactions and determine the limits of biofiltration efficiency of typical binary air pollutant mixtures containing both hydrophobic and polar components. A comparison of the STY/AC mixture degradation in the TBR and BF revealed higher pollutant removal efficiencies and degradation rates in the TBR, with the pollutant concentrations increasing up to the overloading limit. The maximum styrene degradation rates were 12 and 8 gc m(-3) h(-1) for the TBR and BF, respectively.

A two-stage combined trickle bed reactor/biofilter for treatment of styrene/acetone vapor mixtures.

Performance of a two-stage biofiltration system was investigated for removal of styrene-acetone mixtures. High steady-state acetone loadings (above C(in)(Ac) = 0.5 g.

Biofiltration of gasoline and diesel aliphatic hydrocarbons.

The ability of a biofilm to switch between the mixtures of mostly aromatic and aliphatic hydrocarbons was investigated to assess biofiltration efficiency and potential substrate interactions. A switch from gasoline, which consisted of both aliphatic and aromatic hydrocarbons, to a mixture of volatile diesel n-alkanes resulted in a significant increase in biofiltration efficiency, despite the lack of readily biodegradable aromatic hydrocarbons in the diesel mixture. This improved biofilter performance was shown to be the result of the presence of larger size (C₉-C(12)) linear alkanes in diesel, which turned out to be more degradable than their shorter-chain (C₆-C₈) homologues in gasoline.

Interactions among mononitrophenol isomers during biodegradation of their mixtures.

Continuous aerobic biodegradation of 4-NP, 3-NP and 2-NP mixture was monitored in a packed bed reactor in simulated wastewater with a mixed microbial culture immobilized on expanded slate. Substrate loading was varied by increasing the concentration of one isomer while keeping the other two at constant levels, all at a constant residence time of 60 min. At large concentrations, all of the individual NP isomers suppressed the degradation rates of the other isomers at steady state; however, the observed patterns and threshold concentrations were different for all three substrates.

Biodegradation of nitroglycerin and ethylene glycol dinitrate by free and immobilized mixed cultures.

Aerobic biodegradation of nitroglycerin (NG) and ethylene glycol dinitrate (EGDN), both as individual substrates and in their mixture, was tested using batch or fed-batch cultivation with free suspended cells enriched from a soil sample subjected to a long-term contamination with explosives. EGDN was degraded only in the presence of glycerol as a co-substrate whereas NG could serve as a sole carbon, energy and nitrogen source for growth, its degradation being only slightly boosted by either glycerol or pyruvate. NG was not sufficient as a co-substrate for microbial growth on EGDN; furthermore, the presence of EGDN inhibited the NG degradation.

Pollutant interactions during the biodegradation of phenolic mixtures with either 2- or 3-mononitrophenol in a continuously operated packed bed reactor.

Pollutant interactions during the aerobic biodegradation of phenolic mixtures with either 2-nitrophenol (2-NP) or 3-nitrophenol (3-NP) by a NP-adapted microbial consortium in simulated wastewater were studied in a packed-bed bench scale bioreactor continuously operated in a flow mode. Phenol/2-NP and phenol/3-NP mixtures with varied phenol/nitrophenol ratios were shown to exhibit different biodegradability patterns. The presence of 2-NP led to a much lower overall elimination capacity and lower process stability in comparison to mixtures with 3-NP.

Biodegradation of a mixture of mononitrophenols in a packed-bed aerobic reactor.

Aerobic biodegradation of individual mononitrophenols (4-, 3- and 2-NPs) and their mixture in simulated wastewater was investigated in a packed-bed bench scale bioreactor continuously operated in a flow mode, with a mixed microbial culture adsorbed on expanded slate. Under a low, suboptimal hydraulic retention time (HRT) of 30 min the reactor removed more than 3 g.L(-1).

Activation and detoxification metabolism of urban air pollutants 2-nitrobenzanthrone and carcinogenic 3-nitrobenzanthrone by rat and mouse hepatic microsomes.

Objectives: 2-Nitrobenzanthrone (2-NBA) has recently been detected in ambient air particulate matter. Its isomer 3-nitrobenzanthrone (3-NBA) is a potent mutagen and suspected human carcinogen identified in diesel exhaust. Understanding which enzymes are involved in metabolism of these toxicants is important in the assessment of individual susceptibility.

Biofiltration of paint solvent mixtures in two reactor types: overloading by polar components.

Steady-state performances of a trickle bed reactor (TBR) and a biofilter (BF) in loading experiments with increasing inlet concentrations of polar solvents, acetone, methyl ethyl ketone, methyl isobutyl ketone and n-butyl acetate, were investigated, along with the system's dynamic responses. Throughout the entire experimentation time, a constant loading rate of aromatic components of 4 g(c)·m(-3)·h(-1) was maintained to observe the interactions between the polar substrates and aromatic hydrocarbons. Under low combined substrate loadings, the BF outperformed TBR not only in the removal of aromatic hydrocarbons but also in the removal of polar substrates.

Biofiltration of gasoline and ethanol-amended gasoline vapors.

Assuming the projected increase in use of ethanol as a biofuel, the current study was conducted to compare the biofiltration efficiencies for plain and 25% ethanol-containing gasoline. Two biofilters were operated in a downflow mode for 7 months, one of them being compost-based whereas the other using a synthetic packing material, granulated tire rubber, inoculated with gasoline-degrading microorganisms. Inlet concentrations measured as total hydrocarbon (TH) ranged from 1.

Preferences in removal of aliphatic and aromatic gasoline components by biofiltration under varied loading.

Removal of gasoline vapors from waste air was investigated in a bench-scale perlite biofilter for three aromatic-to-aliphatic mass ratios (62/38, 92/8 and 44/56) under different loads, varied by changing both the substrate inlet concentration and air flow rate. The measurement of concentration profiles along the bed height allowed for an assessment of interactions between the aromatic and aliphatic fractions of gasoline. Variations in both the inlet concentrations and empty bed residence time significantly influenced the removal of aliphatic gasoline components.

Parameters affecting HS emissions removal and re-circulating water quality in a pilot-scale sequential biological treatment system at a wastewater lift station in Brownsville, Texas, USA.

In this study, a pilot-scale sequential biological treatment system combining a biotrickling filter and biofilter was used to optimize the removal of variable emission H(2)S loadings ranging from 30 to 120 g m(-3) h(-1)at a wastewater lift station in Brownsville, Texas USA. The biotrickling filter recycle water pH remained between 2.0 to 3.

Microbial monitoring and performance evaluation for H2S biological air emissions control at a wastewater lift station in South Texas, USA.

A pilot-scale biological sequential treatment system consisting of a biotrickling filter and two biofilters was installed at Waste Water Lift Station # 64 in Brownsville, Texas, USA to evaluate the performance of the system being loaded with variable concentrations of wastewater hydrogen sulfide (H(2)S) emissions. In this study, the effectiveness of sulfur oxidizing bacteria along with the distribution of various sulfur species and their correlation with the performance of the biofilters was evaluated. The biofilters were packed with engineered media consisting of plastic cylinders with compacted organic material which was supplied by Met-Pro Environmental Air Solutions (formerly Bio·Reaction Industries).

Isolation and partial characterization of extracellular NADPH-dependent phenol hydroxylase oxidizing phenol to catechol in Comamonas testosteroni.

Objective: Comamonas testosteroni Pb50 is a microorganism that possesses high tolerance for phenol and shows strong phenol degrading activity. This bacterial strain is capable of utilizing phenol as the sole carbon and energy source. Although examples are known in which the C.

Factors influencing the aerobic biodegradation of 2,4-dinitrotoluene in continuous packed bed reactors.

Factors affecting continuous 2,4-DNT degradation by an immobilized mixed microbial culture were investigated including the cell adaptation to this toxic substrate, 4-NT co-degradation, packing material porosity and substrate mass loading. Experiments were carried out in two packed bed reactors, with poraver (porous glass) and expanded slate as packing materials, using a concurrent water-air flow with ample oxygen. Running the system as a batch reactor with re-circulated medium showed that the immobilized cells adapted to higher 2,4-DNT concentrations yielding higher substrate biodegradation rates.

Aerobic degradation of 2,4-dinitrotoluene by individual bacterial strains and defined mixed population in submerged cultures.

The degradation efficiencies of isomeric mononitrotoluenes (2- and 4-NTs) and dinitrotoluenes (2,4-DNT and 2,6-DNT) by either individual bacterial strains (Bacillus cereus NDT4, Pseudomonas putida NDT1, Pseudomonas fluorescens NDT2, and Achromobacter sp. NDT3) or their mixture were compared in submerged batch cultivations. The mixed culture degraded 2,4-DNT nearly 50 times faster than any of the individual strains.

Biofiltration of paint solvent mixtures in two reactor types: overloading by hydrophobic components.

Steady-state performance characteristics of a trickle bed reactor (TBR) and a biofilter (BF) in loading experiments with increasing toluene/xylenes inlet concentrations while maintaining a constant loading rate of hydrophilic components (methyl ethyl and methyl isobutyl ketones, acetone, and n-butyl acetate) of 4 g m⁻³ h⁻¹ were evaluated and compared, along with the systems' dynamic responses. At the same combined substrate loading of 55 g m⁻³ h⁻¹ for both reactors, the TBR achieved more than 1.5 times higher overall removal efficiency (RE(W)) than the BF.

Removal of saturated aliphatic hydrocarbons (gasoline components) from air via bacterial biofiltration.

Two-stage biofilters (using perlite and granular activated carbon, GAC, as packing materials) were used for the removal of several linear, branched, and cyclic C(5)-C(8)saturated aliphatic hydrocarbons from air, both as individual chemicals and in mixtures. The acclimation of biofilters from styrene to n-heptane was complete in 14-18 days. The substrate switch resulted in significant changes in pH and microbial composition of biofilters.

Isolation and partial characterization of catechol 1,2-dioxygenase of phenol degrading yeast Candida tropicalis.

Objectives: Candida tropicalis yeast is a microorganism that possesses high tolerance for phenol and shows strong phenol degrading activity. This yeast is capable of utilizing phenol as the sole carbon and energy source. While the enzyme participating on the first step of phenol biodegradation, NADPH-dependent phenol hydroxylase, has already been characterized, information on the enzyme participating in the second step of its degradation, catechol 1,2-dioxygenase, is scarce.

Steady-state performance of an activated carbon biofilter degrading styrene: effects of residence time and inlet concentration.

A granular-activated-carbon-packed biofilter receiving a constant loading rate of styrene was subjected to changes in residence time and concentration, and the effects on performance characteristics and the composition of biofilm along the bed height in the biofilter were studied. This study was carried out during the last 3 months of the entire biofilter operation of 16 months. The total bed height of the biofilter was physically divided into four individual reactor stages in series.

Isolation of cytoplasmic NADPH-dependent phenol hydroxylase and catechol-1,2-dioxygenase from Candida tropicalis yeast.

The efficiencies of NADPH-dependent phenol hydroxylase (EC 1.14.13.