Search

Acrylic acid has been widely used in various industrial applications but is harmful to human health and the environment. A novel and efficient degrading acrylic acid bacterium was isolated and identified as Bacillus aryabhattai CY. In this study, batch experiments were conducted to evaluate the biodegradation of acrylic acid by B. aryabhattai CY, which were immobilized in calcium-alginate beads under different conditions. The components of the alginate beads were optimized by the response surface method, and the degradation performance of the immobilized cells was determined. Relative to the free cells, experiment results showed that the immobilized cells can achieve complete degradation of 100 mg/L acrylic acid in 24 h under the optimal conditions of SA 6% (w/v), CaCl2 1% (w/v), and immobilization time of 6 h. According to Haldane's model, the maximum specific growth rate (μmax) of the free cells and immobilized cells were 0.165/h and 0.210/h, respectively. Experiment data revealed that acrylic acid showed an inhibitory effect on biodegradation by B. aryabhattai CY, especially at concentration higher than 100 mg/L. Furthermore, the reusability of the immobilized cells revealed that the acrylic acid removal rate was above 93.70% within the eight cycles. The immobilized cells also showed higher removal efficiencies in wider ranges of temperature (20°C–60°C) and pH (5.0–10.0) than the free cells. Moreover, the possible degradation intermediates were proposed during the biodegradation of acrylic acid by GC-MS analysis. Results indicated that immobilized beads might have a potential environmental implication in the purification of practical acrylic acid wastewater. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Agro-Environment Science is the property of Journal of Agro-Environment Science Editorial Board and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A simulated wastewater containing phenol (1,000-2,500 mg/L), thiocyanate (SCN) of 800 mg/L, COD (4,200-8,150 mg/L), and ammonia-nitrogen (NH-N) of 500 mg/L was treated in a sequential anaerobic (B1)-anoxic (B2)-aerobic (B3) batch fed moving-bed reactor (MBR) system. Total hydraulic retention time (HRT) was varied from 5 to 10 days with B1 2.5 to 5 days; B2 and B3: 1.25-2.5 days each. In B1, 25-63 % of phenol and 23-53 % of COD removals were achieved and feed phenol above 1,500 mg/L, inhibited COD and phenol removals in B1. In B2, more than 90 % phenol removal was achieved along with COD removal and denitrification. In B2, with increase in phenol loading, though phenol and COD removal rates increased, SCN removal rate decreased above phenol loading of 0.28 g/L day. In B3, NH-N removal efficiency decreased above loading of 0.24 g NH-N/L day. The overall efficiency of the fed batch MBR system was independent of feed phenol concentration up to 2,500 mg/L at constant total HRT of 6 days. NH-N removal efficiency deteriorated significantly, when total HRT of fed batch MBR was less than 6 days. Modified Stover-Kincannon model showed the best fit for removal of substrates in three reactors and Haldane's inhibition model predicted NH-N removal in B3. [ABSTRACT FROM AUTHOR]

Chestnut agro-industrial companies consume a high volume of water for washing and processing fruit, generating a large volume of wastewater. This work studied the biodegradation of chestnut processing wastewater through aerobic assays, varying substrate, and biomass concentrations. In general, this wastewater presents a good biodegradability, especially in experiments with relatively low chemical oxygen demand (COD) (0.4 and 0.6 g O L) allowing a COD removal of 85-90 %. The best results were obtained in the reactor initially loaded with 2 g L of biomass and 0.4 or 0.6 g O L of COD. These experiments also showed high COD removal rates: 4.25 and 3.88 g COD g volatile suspended solids (VSS) h, respectively. The sedimentation rate, evaluated for different initial values of biomass (1, 2, and 3 g L), always presented higher values in the experiments with 2 and 3 g L of biomass, regardless of the initial COD value used. After comparing different kinetic models (Monod, Contois, and Haldane), it was observed that the Haldane inhibition model satisfactorily describes the COD biodegradation. AQUASIM software allowed calculating the kinetic constant ranges: K, 1.59-6.99 g COD L; ν, 25-40 g COD g VSS day; and K values, 0.07-0.11. These kinetic constants corresponds to maximum rates ( ν*) between 1.48 and 4.25 g COD g VSS day for substrate concentrations ( S*) from 0.38 to 0.88 g COD L. [ABSTRACT FROM AUTHOR]

Phenol biodegradation in batch systems using Cupriavidus taiwanesis 187 has been experimentally studied. To determine the various parameters of a kinetic model, combinations of rearranged equations have been evaluated using inverse polynomial techniques for parameter estimation. The correlations between lag phase and phase concentration suggest that considering phenol inhibition in kinetic analysis is helpful for characterizing phenol degradation. This study proposes a novel method to determine multiplicity of steady states in continuous stirred tank reactors (CSTRs) in order to identify the most appropriate kinetics to characterize the dynamics of phenol biodegradation. [ABSTRACT FROM AUTHOR]

Abstract: Bioconversion kinetics of γ-HCH and biological growth kinetics of Pseudomonas aeruginosa degrading technical HCH was investigated in flask experiments under aerobic condition. Degradation studies for various isomers of technical HCH were also performed. The biodegradation of the most persistent β-HCH and δ-HCH isomers was also observed. At lower technical HCH concentrations (1–10mg/l), above 99% of the degradation was observed whereas at higher concentration (20–50mg/l), the degradation efficiency was dropped. This may be due to inhibitory effect of technical HCH at higher concentrations. The technical HCH inhibitory behavior and bacterial growth kinetics could be correlated well by simple Haldane''s growth kinetic model. The value of decay and yield coefficient was also determined. Further experimental results also revealed that degradation of the γ-HCH isomer is faster (after incubation of 5 days) in the presence of other isomers of technical HCH, whereas γ-HCH alone does not degrade even after a long period of incubation (14 days), but isomerizes to α-HCH isomer by the P. aeruginosa. The rate constant for the bioisomerization was found to be 0.0474day−1. The above estimated parameters (maximum specific growth rate, half saturation coefficient, inhibition constant, decay coefficient, yield coefficient and bioisomerization rate) are invariably required for the design and simulation of batch and continuous bioreactors treating HCH containing wastewaters. [Copyright &y& Elsevier]