Aldehyde Removal Research Articles

Biodegradation Kinetics of Ozonated NOM and Aldehydes

The batch recycle attached growth reactor (BRAGR) was found to be a convenient technique to determine simultaneously the biodegradable dissolved organic carbon (BDOC) concentrations and the biokinetic rate constants for BDOC and aldehyde removal. The rate of biodegradation was first‐order with respect to the BDOC remaining. A second‐order, intrinsic rate constant was obtained by dividing the first‐order rate constant by the attached biomass concentration in the biofilter. The intrinsic rate constant did not increase with an increasing ozone‐to‐DOC ratio and averaged 8.5 × 10‐5 mg/L cells‐1 min‐1. The biokinetic rate constants for aldehydes were first‐order with respect to remaining substrate concentration. The second‐order, intrinsic rate constants (mg/L cells‐1 min‐1) for the aldehydes were much larger than those for BDOC, with the order being: methyl glyoxal (5.93 × 10‐4) > glyoxal (4.42 > × 10‐4) > formaldehyde (2.23 × 10‐4) >> BDOC (8.5 × 10‐5). Removal of aldehydes in a laboratory‐scale, continuous‐flow biofilter packed with anthracite and exhausted granular activated carbon (GAC) was predicted fairly well with rate constants derived from the BRAGR. BDOC removal was significantly underpredicted on GAC biofilters, possibly because of residual adsorption capacity. An empty bed contact time that achieves good natural organic matter (NOM) removal will also yield very high removal of aldehydes because aldehydes are degraded much faster than NOM, regardless of the ozonation level. Biokinetic modeling could possibly be improved by accounting for differences in the biodegradability of NOM fractions and by better techniques to measure the concentration and activity of attached biomass in calculation of the intrinsic rate constant.

Removal of mixtures of acetaldehyde and propionaldehyde from waste gas in packed column with immobilized activated sludge gel beads

The removal of mixed acetaldehyde and propionaldehyde as a model of the binary contaminants in waste gas was studied in the packed column containing the immobilized activated sludge gel beads together with the hollow plastic balls developed for the removal of a single aldehyde in the previous work. The rate of each aldehyde biodegradation by the gel beads in the aldehydes mixture was expressed by the Michaelis–Menten type rate equation with an inhibitory term due to the other coexistent aldehyde. The kinetic parameters involved were found to be the same as those determined previously for biodegradation of a single aldehyde. A model for prediction of removal of each aldehyde in the packed column was developed assuming that each aldehyde dissolved in the aqueous phase within the gel bead was biodegraded according to the above rate equation with no mass transfer effect. The packed column was stable and efficient for removal of the binary aldehydes mixture with a very low pressure drop for gas flow due to a reduced gel beads bed compaction by the hollow plastic balls. Removal of each aldehyde decreased with increasing the inlet aldehyde concentrations since each biodegradation rate itself approached asymptotically the maximum one with increase in each aldehyde concentration. The observed removals for each aldehyde in the aldehydes mixture agreed well with those calculated from the design equations developed. The contact efficiency of gel beads with the waste gas stream was estimated to be the same value of 0.24 as in the previous work, supporting that the efficiency was specific to the geometrical and physical properties of the packed column used.

Removal of Acetaldehyde and Propionaldehyde from Waste Gas in Packed Column with Immobilized Activated Sludge Gel Beads.

A new type of waste gas treatment was previously proposed in the packed column containing the immobilized activated sludge gel beads of 5 mm in diameter together with the hollow plastic balls of 10 mm in the optimal diameter with their optimal volume ratio of 1 to 2 to avoid compaction of the gel beads. The same type of biofilter is employed and analyzed for removal of acetaldehyde or propionaldehyde as a model of toxic and malodorant pollutants under a wide range of the inlet aldehyde concentrations. The same spherical gel beads as prepared previously by the PVA-boric acid method are stable and durable during storage as well as use in the removal operation. The biofilter gives a very low pressure drop to the waste gas stream through the packed bed. The acetaldehyde or propionaldehyde removal in the column decreases with an increase in the inlet aldehyde concentration. The kinetics data on the gel beads suspended in an air-tight batch reactor reveal that the Michaelis-Menten type rate equation is applicable to both respiration and pollutant biodegradation by the gel beads with negligible mass transfer effect. A model for removal of a single pollutant is developed assuming that the Henry's law constant determines the dissolved pollutant concentration in the gel bead, the pollutant is biodegraded according to the above rate equation and the contact efficiency of gel beads with waste gas has the same value of 0.24 as determined previously. The observed removals agree well with those calculated from the design equation developed. As a result the observed decrease in removal of aldehyde with its inlet concentration is due to the fact that the biodegradation rate itself approaches asymptotically the maximum one with the aldehyde concentration.

Formation and Removal of Aldehydes in Plants That Use Ozonation

Recently developed analytical techniques allow for the quantification of C1‐C1O straight‐chain aliphatic aldehydes, benzaldehyde, and the dialdehydes glyoxal and methylglyoxal down to 1 μg/L. These compounds are formed as the partial oxidation products of the reaction between disinfectants (particularly ozone) and naturally occurring organic matter. Various full‐scale and pilot treatment plants in North America that employ ozonation were surveyed using these techniques, which showed a trend toward both monoaldehyde and dialdehyde formation. Once formed, aldehydes can persist in the water and their concentrations may even increase following postdisinfection. An effective means of aldehyde removal appears to be the use of biologically active granular activated carbon filters, whose filtration mode determines the actual degree of removal. Dialdehydes require a slower filtration rate for their removal than formaldehyde and acetaldehyde.

Inhibition of xanthine oxidase by various aldehydes.

The inactivation of bovine milk xanthine oxidase by various aldehydes has been investigated. For each aldehyde, the inactivation reaction gives rise to a unique molybdenum(V) electron paramagnetic resonance signal from xanthine oxidase (the Inhibited signal). Of the aldehydes tested, only a few (mainly aromatic) failed to undergo this reaction. The g values of the Inhibited signals vary systematically from one aldehyde to another. As the substituents of the alpha-carbon atom become more electron withdrawing, so the gav increases. The inactivation rate depends on both enzyme and aldehyde concentration. Oxygen or another oxidizing substrate is also required for inhibition by 3-pyridinecarboxaldehyde and butyraldehyde but not formaldehyde. Reactivation of xanthine oxidase inhibited by an aldehyde occurs spontaneously after removal of excess aldehyde. For butyraldehyde or 3-pyridinecarboxaldehyde, greater than 95% recovery of activity was observed. The rate of reactivation is dependent both on the nature of the molecule bearing the aldehyde group and on a pK (6.6) of the complex with the enzyme. Evidence is presented that the modifying aldehyde in the Inhibited signal-giving species has (contrary to earlier assumptions) not been oxidized. These results are discussed in relation to the structure of the molybdenum center, and a mechanism for the inhibiting reaction is suggested.

Enzymatic improvement of food flavor. III. Oxidation of the soybean protein-bound aldehyde by aldehyde dehydrogenase.

Defatted soybean extract was fractionated into protein fractions and low molecular weight fractions with gel filtration. NAD-dependent aldehyde dehydrogenase from bovine liver mitochondria and from yeast was found to oxidize aldehyde in both fractions. These enzymes, therefore, were used to determine the quantity of aldehyde. When the protein fraction obtained by gel filtration was subjected to gel filtration again, aldehyde was recovered in the protein fractions. The level of aldehyde in the protein fractions was unchanged before and after digestion of the protein with pepsin. When the soybean extract was incubated beforehand with aldehyde debydrogenase and NAD+ and the subjected to gel filtration, no aldehyde was detected in the protein fractions. These results indicate that aldehyde dehydrogenase acts on the soybean protein-bound aldehyde. Alcohol dehydrogenase from horse liver in the presence of NADH did not convert the bound aldehyde to alcohol. A large portion of the aldehyde in the extract was separated from the protein by acid precipitation of the protein. Aldehyde dehydrogenase acts on the aldehyde remaining in the protein after acid precipitation. Thus acid precipitation helps to save NAD+ required for complete removal of aldehyde from the soybean protein by aldehyde dehydrogenase.

Electrochemical oxidation of reduced nicotinamide adenine dinucleotide directly and after reduction in an enzyme reactor

Reduced nicotinamide adenine dinucleotide (NADH) was oxidized coulometrically at a rotating platinum gauze electrode at 0.7 V vs. SCE at pH 9. The NAD + formed was reduced enzymatically in a reactor containing immobilized alcohol dehydrogenase. Several recyclings were made with the same lot of NADH. The coulometric results were in reasonable agreement with spectrophotometric measurements. The overall conversion to enzymatically active NAD + showed a current efficiency of 99.3%. The electrode pretreatment described is essential for high current efficiency. A continuous method of oxidation of alcohol with electrolytic regeneration of cofactor and removal of aldehyde by dialysis was tested.

Studies on nucleic acid metachromasy. I. The effect of certain fixatives on the dye stacking properties of nucleic acids in solution.

The stacking coefficients (K's) of nucleic acids have been thought to influence the color contrast between DNA and RNA in tissue sections stained with metachromatic dyes. This idea was tested by titrating toluidine blue (TB) and acridine orange (AO) in solution against DNA and RNA, native or treated with formaldehyde, acrolein, or Carnoy's fluid. Absorption spectra at varying polymer-dye ratios were used to compute K values by the methods of Bradley and colleagues. Results with both dyes fit Bradley's stacking equations. Fixatives did not block dye-binding sites but markedly altered K values. K of DNA was low, unaffected by aldehyde fixative, increased by Carnoy's fluid or heat denaturation. K of RNA was higher than that of DNA and was increased greatly by formaldehyde, almost as much by acrolein, considerably less by Carnoy's fluid. Aldehyde effects were partially reversed upon removal of aldehyde by dialysis. These observations accord with known effects of aldehydes and denaturation upon nucleic acid conformation. Differences between K's of DNA and RNA were greater after aldehyde treatment than after Carnoy's, and were greater with AO than with TB. This is generally consistent with the magnitude of the color contrasts observed in tissues. Additional factors must contribute to the intense color contrast observed in acrolein-fixed tissues stained with TB.