Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.4.15.1 (ACE)
18,300 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A predictive isotherm model was developed to evaluate the extent of bioregeneration of granular activated carbon loaded with phenol and 2,4-dichlorophenol (2,4-DCP). Two basic substrates (116 mg/L of phenol and 100 g/L 2,4-DCP) as single solute were prepared. The mixture of them was provided to bisolute system for assessing the competitive adsorption. The effect of by-products, which were generated during biodegradation of substrate and measured as COD, on bioregeneration in the bisolute was investigated. Freundlich adsorption parameters (Kads and 1/n) of 2,4-DCP were obviously higher than those of phenol in both single and bisolute. By-products in the bulk solution brought an adverse effect on adsorption capacity of GAC in all cases. By taking into account the by-product effect on adsorption, the Freundlich isotherms were used to formulate a predictive model of bioregeneration. Simulated results showed good consistency of observed results. Practical relevant of the proposed model for assessing of bioregeneration in the wastewater treatment was discussed by applying model to the BAC-SBR in the steady-state operation.
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PMID:A modeling approach to bioregeneration of granular activated carbon loaded with phenol and 2,4-dichlorophenol. 1136 Apr 40

The co-immobilization and the culture of anaerobic and aerobic communities was tested for the mineralization of 2,4,6-trichlorophenol (2,4,6-TCP). At first, the anaerobic microorganisms (aggregated into granules) were cultivated in an upflow anaerobic sludge blanket (UASB) reactor, in a continuous mode, with glucose, propionate, acetate (COD loading rate = 0.5-2.0 g COD/l per day, ratio 1:1:1) and 2,4,6-TCP (2,4,6-TCP loading rate = 25-278 micromol/l per day) as substrates. 2,4,6-TCP was degraded into 2,4-DCP and 4-CP, but it was not mineralized because of the low degradation rates of 4-CP. Furthermore, the highest loading rates of 2,4,6-TCP (>126 micromol/l per day) caused the inhibition of the strains degrading the propionate. The granules were therefore tested in association with the aerobic community. They were immobilized in kappa-carrageenan/gelatin [2% (w/w) of each polymer] gel beads and cultivated in a reactor, on their own (to test the influence of the gel), and then with the aerobic community, under anaerobic and air-limited conditions, respectively. The results showed that (1) the gel did not influence the activity of the granules, (2) the anaerobic and aerobic communities could be easily co-immobilized in gel beads and cultivated in a reactor, (3) the mineralization of 2,4,6-TCP (2,4,6-TCP loading rate = 10-506 micromol/l per day), its intermediates of degradation and the other substrates [glucose + acetate + propionate (ratio 1:1:1) = COD loading rate = 500 mg COD/l per day] could be obtained under air-limited conditions if the culture parameters were strictly controlled [airflow = 36-48 vvd (volume of air/volume of liquid in the reactor per day), pH value at around 7.5]. Finally, the gel did not retain its structure during the whole culture (263 days) in the air-limited reactor, but the anaerobic and aerobic communities retained their activities and worked together for the mineralization.
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PMID:Degradation of 2,4,6-trichlorophenol (2,4,6-TCP) by co-immobilization of anaerobic and aerobic microbial communities in an upflow reactor under air-limited conditions. 1154 32

The effect of the photo-Fenton process on biodegradability enhancement of 100 mg x L(-1) aqueous 2,4-dichlorophenol (2,4-DCP) solution has been investigated. An initial concentration of 65 mg x L(-1) H2O2 and 10 mg x L(-1) Fe (II) during 35 minutes of irradiation time was sufficient for total 2,4-DCP removal. At these working conditions, biodegradability, measured as BODS/COD ratio, was increased from 0 for the original solution up to 0.15. Biological oxidation of photo-Fenton pre-treated solutions was performed in a sequencing batch reactor (SBR). After 32 days of start-up, the reactor was fed with different pre-treated solutions and cycle duration was reduced progressively. TOC removal efficiencies in the SBR went from 30 up to 70%.
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PMID:Combining photo-Fenton process with biological sequencing batch reactor for 2,4-dichlorophenol degradation. 1507 86

Effect of a biogenic substrate (peptone) concentration on the performance of sequencing batch reactor (SBR) treating 220 mg/l 4-chlorophenol (4-CP) and 110 mg/l 2,4-dichlorophenol (2,4-DCP) mixtures was investigated. In this context, peptone concentration was gradually decreased from 300 mg/l to null in which chlorophenols were fed to the reactor as sole carbon and energy sources. By this way, the effect of peptone concentration on observed yield coefficient (Y), biomass concentration, chlorophenols and COD removal performances were investigated. Decreasing peptone concentration accompanied with lower biomass concentration led to increase in peak chlorophenol and COD concentrations within the reactor during each SBR cycle. This, in turn, caused noteworthy declines in the removal rates as chlorophenol degradations followed Haldane substrate inhibition model. Also, increased peak chlorophenol concentrations led to the accumulation of 5-chloro-2-hydroxymuconic semialdehyde (CHMS), which is -meta cleavage product of 4-CP. Despite the decreased removal rates, complete chlorophenols and CHMS degradation, in addition to high COD removal efficiencies (>90%), were observed for all studied conditions, even chlorophenols were added as sole carbon and energy sources. Another significant point is that 2,4-DCP at slightly elevated concentrations (>20 mg/l) within the reactor caused a strong competitive inhibition on 4-CP degradation. In SBR, feeding the influent to the reactor within a certain period (i.e. filling period) provided dilution of coming wastewater, which decreased the chlorophenols concentrations to which microorganisms were exposed. Therefore, use of SBR may help to avoid both self and competitive inhibitions in the treatment of 4-CP and 2,4-DCP mixture especially in the presence high biogenic substrate concentrations. In addition, isolation and identification studies have indicated that Pseudomonas sp. and Pseudomonas stutzeri were dominant species in the acclimated mixed culture.
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PMID:Effect of biogenic substrate concentration on the performance of sequencing batch reactor treating 4-CP and 2,4-DCP mixtures. 1615 49

Phenolic compounds cause problems for conventional treatments due to their toxic and inhibitory properties. This work investigated the treatability of phenolic compounds by using two membrane-bioreactor systems, namely: activated sludge coupled with MBR (AS-MBR) and biological granular activated carbon coupled with MBR (BAC-MBR). Initially, the system was fed with phenol (500 mg/L) followed by adding 2,4-dichlorophenol (2,4-DCP). Phenol, 2,4-DCP, TOC and COD removal were higher than 98.99% when the organic load ranged between 1.80 and 5.76 kg/m3.d COD. In addition to MBR system development, removal mechanisms were also investigated. Relatively low values of phenol adsorption of GAC and biomass, and high maximum substrate removal rates obtained from a biokinetic experiment, proved that the removals were mainly due to biodegradation. Analysis of sludge indicated a significant difference in the sludge characteristics of the two reactors. The high EPS content in BAC-MBR led to higher viscosity and poor sludge settling properties. The relationship between sludge properties and EPS components revealed that settleability had no direct correlation with EPS, though it was better correlated to protein/carbohydrate ratios.
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PMID:Removal of inhibitory phenolic compounds by biological activated carbon coupled membrane bioreactor. 1686 78

The performance of an upflow anaerobic sludge blanket (UASB) reactor treating 2,4 dichlorophenol (2,4 DCP) was evaluated at different hydraulic retention times (HRTs) using synthetic wastewater in order to obtain the growth substrate (glucose-COD) and 2,4 DCP removal kinetics. Treatment efficiencies of the UASB reactor were investigated at different hydraulic retention times (2-20 h) corresponding to a food to mass (F/M) ratio of 1.2-1.92 g-COD g(-1) VSS day(-1). A total of 65-83% COD removal efficiencies were obtained at HRTs of 2-20 h. In all, 83% and 99% 2,4 DCP removals were achieved at the same HRTs in the UASB reactor. Conventional Monod, Grau Second-order and Modified Stover-Kincannon models were applied to determine the substrate removal kinetics of the UASB reactor. The experimental data obtained from the kinetic models showed that the Monod kinetic model is more appropriate for correlating the substrate removals compared to the other models for the UASB reactor. The maximum specific substrate utilization rate (k) (mg-COD mg(-1) SS day(-1)), half-velocity concentration (K(s)) (mg COD l(-1)), growth yield coefficient (Y) (mg mg(-1)) and bacterial decay coefficient (b) (day(-1)) were 0.954 mg-COD mg(-1) SS day(-1), 560.29 mg-COD l(-1), 0.78 mg-SS g(-1)-COD, 0.093 day(-1) in the Conventional Monod kinetic model. The second-order kinetic coefficient (k(2)) was calculated as 0.26 day(-1) in the Grau reaction kinetic model. The maximum COD removal rate constant (U(max)) and saturation value (K(B)) were calculated as 7.502 mg CODl(-1)day(-1) and 34.56 mg l(-1)day(-1) in the Modified Stover-Kincannon Model. The (k)(mg-2,4 DCP mg(-1) SS day(-1)), (K(s)) (mg 2,4 DCPl(-1)), (Y) (mg SS mg(-1) 2,4 DCP) and (k(d)) (day(-1)) were 0.0041 mg-2,4 DCP mg(-1) SS day(-1), 2.06 mg-COD l(-1), 0.0017 mg-SS mg(-1) 2,4 DCP and 3.1 x 10(-5) day(-1) in the Conventional Monod kinetic model for 2,4 DCP degradation. The second-order kinetic coefficient (k(2)) was calculated as 0.30 day(-1) in the Grau reaction kinetic model. The maximum 2,4 DCP removal rate constant (U(max)) and saturation value (K(B)) were calculated as 0.01 mg COD l(-1) day(-1) and 9.8 x 10(-3) mg l(-1) day(-1) in the Modified Stover-Kincannon model.
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PMID:Kinetic of carbonaceous substrate in an upflow anaerobic sludge sludge blanket (UASB) reactor treating 2,4 dichlorophenol (2,4 DCP). 1725 94

To gain more insight into the interactions between anaerobic bacteria and reactor performances (chemical oxygen demand-COD, 2,4 dichlorophenol-2,4 DCP removals, volatile fatty acid-VFA, and methane gas productions) and how they depended on operational conditions the microbial variations in the anaerobic granular sludge from an upflow anaerobic sludge blanket (UASB) reactor treating 2,4 DCP was studied. The study was composed of two parts. In the first part, the numbers of methanogens and acedogens in the anaerobic granular sludge were counted at different COD removal efficiencies. The relationships between the numbers of methanogens, the methane gas production and VFA production were investigated. The COD removal efficiencies increased to 74% from 30% while the number of total acedogens decreased to 10 from 30 cfu ml(-1). The number of total methanogens and acedogens varied between 11 x 10(3) and 10 x 10(9)MPN g(-1) and 10 and 30 cfu ml(-1) as the 2,4 DCP removal efficiencies were obtained between 60% and 99%, respectively. It was seen that, as the number of total acedogens decreased, the COD removal efficiencies increased. However, the number of total methanogens increased as the COD removal efficiencies increased. Correlations between the bacterial number and with the removal efficiencies obtained in different operational conditions were investigated. From the results presented in this paper a high correlation between the number of bacteria, COD removals, methane gas percentage, 2,4 DCP removals and VFA was observed. In the second part, methanogen bacteria in the anaerobic granular sludge were identified. Microbial observations and biochemical tests were applied to identify the anaerobic microorganisms from the anaerobic granular sludge. In the reactor treating 2,4 DCP, Methanobacterium bryantii, Methanobacterium formicicum, Methanobrevibacter smithii, Methanococcus voltae, Methanosarcina mazei, Methanosarcina acetivorans, Methanogenium bourgense and Methanospirillum hungatei were identified.
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PMID:Relationships between anaerobic consortia and removal efficiencies in an UASB reactor degrading 2,4 dichlorophenol (DCP). 1737 94

The degradation of a model molecule, 2,4-dichlorophenol (2,4-DCP), was studied using four biofilm processes: stand-alone hydrolytic process, stand-alone aerobic process, hydrolytic-aerobic in-series process (in-series process) and hydrolytic-aerobic recycling process (recycling process). The overall removal efficiency of 2,4-DCP was far higher in the recycling process than in the stand-alone hydrolytic process, the stand-alone aerobic process and the in-series process. 2,4-DCP removal efficiency in the recycling process was 99% with the recycling rate being 10 mL/min in 12h, while those in the stand-alone hydrolytic, stand-alone aerobic and the in-series process were 96%, 82% and 89%, respectively. COD removal efficiency could reach 91% in the recycling process in 4h whereas those were only 23%, 69% and 25% in the stand-alone hydrolytic, stand-alone aerobic and the in-series process, respectively. In the recycling process, the concentrations of volatile fatty acid (VFA) gradually increased to 3.5 mmol/L in first 5h and then declined to below 3 mmol/L, and the pH values were all around 7.5 during the whole process. The alkalinity of the solution in the recycling process was apparently higher than that in both the stand-alone processes and in-series process within 12h. Moreover, the ratios of VFA/alkalinity were all less than 0.8 in the recycling process, which indicated the activity of hydrolytic microorganisms was not inhibited and the process maintained a stable condition. Therefore, the recycling process could successfully solve the problem of over-acidification and effectively enhanced the removal efficiencies of 2,4-DCP and COD.
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PMID:High efficiency of batch operated biofilm hydrolytic-aerobic recycling process in degradation of 2,4-dichlorophenol. 1770 81

This study was carried out to determine the effect of influent pH and alkalinity on the performance of sequential UASB and RBC reactors for the removal of 2-CP and 2,4-DCP from two different simulated wastewaters. The performance of methanogens at low (<6.0) to high (>8.0) pH values and at sufficiently high alkalinity (1500-3500 mg/l as CaCO(3)) is described in this paper. Sequential reactors were capable of handling wastewaters with influent pH, 5.5-8.5. However, with influent pH 7.0+/-0.1 UASB reactor showed best performance for 2-CP (99%) and 2,4-DCP (88%) removals. Increase in alkalinity/COD ratio in the influent (>1.1) caused gradual decrease in the chlorophenol removal in UASB reactors. The UASB reactors could not tolerate wastewater with higher alkalinity/COD ratio (2.6) and showed significant deterioration of its performance in terms of chlorophenols removal achieving only 74.7% 2-CP and 60% 2,4-DCP removals, respectively.
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PMID:Effect of influent pH and alkalinity on the removal of chlorophenols in sequential anaerobic-aerobic reactors. 1901 73

A method for improving the oxidation ability of the electrode is proposed by using microwave activation in electrochemical oxidation. The electrochemical degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) with microwave radiation (MW-EC) was carried out in a continuous flow system under atmospheric pressure. In 3 h the removal of COD, ACE (average current efficiency) and Cl(-) concentration was 1.63, 2.25 and 1.67 times as that without microwave radiation, respectively. The high degradation ability was resulted from the more active centers at the electrode surface due to the microwave radiation. The decay kinetics of 2,4-D followed a pseudo first-order reaction. The rate constant was increased to 2.16x10(-4) s(-1) with the microwave radiation, while it was 8.52x10(-5) s(-1) with electrochemical treatment only (EC). Under both conditions, the main intermediates were identified and quantified by High Performance Liquid Chromatography (HPLC). The formation rate of intermediate products and further degradation rate were increased by about 50-120% with the microwave radiation. The activation of electrochemical oxidation by microwave was discussed from the diffusion process, adsorption and the temperature at boron-doped diamond (BDD) electrode.
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PMID:Microwave activated electrochemical degradation of 2,4-dichlorophenoxyacetic acid at boron-doped diamond electrode. 1917 63


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