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Combination Degradation of Chlor Pyrifos Via Biodegradation and Photodegradation

Author: WangQiJin
Tutor: TaoYuGui
School: Anhui University of Engineering
Course: Microbiology
Keywords: Chlorpyrifos Degradation Micellar capillary electrophoresis (MEKC) Degrading bacteria Photocatalytic
CLC: X592
Type: Master's thesis
Year: 2011
Downloads: 8
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Abstract

The residule and pollutant are attended by the whole world,the pesticides are yielded and used much in China. So, it is an important issue of environment protection to approach for an economic,high efficient treatment of chlorpyrifos wastewater degradation.The efficiency is low with single biological or chemical treatment.In the hope of providing foundations to establish a kind of new degradation technology,the subject intended to explore the feasibility and regulations of the synergetic treatment for chlorpyrifos wastewater degradation which combined biodegradation and photocatalysis.A method for chlorpyrifos determ ination in water based on micellar electrokinetic capillary chromatography has been developed.The assay conditions including inspection wavelength,pH and the concentration of running buffer,organic additive,the concentration of sodium deoxycholate (NaDCh),and the separation voltage were optimized.Under the optimized conditions (25 mmol·L-1 borate buffer (pH9,containing 20%(V/V) acetonitrile,50 mmo·L-1 NaDCh),the chlorpyrifos can be separated within 15 min,with the linearworking range of 15.625～500 mg·L-1(r2=0.999 8) and a lim it of detection (S/N=3) of 0.135 mg·L-1.It had good recoveries (98.91%～100.9%) and the relative standard deviations lower than 3%.The method is simple,rapid,sensitive,highly reproducible and can be successfully applied in the determination of chlorpyrifos in water.A bacterial strain designated as TW-1 capable of degrading chlorpyrifos was isolated from sludges by enrichment culture,Strain TW-1 can grow with chlorpyrifos as its sole carbon source.The effects of initial pH,culture temperature,initial chlorpyrifos concentration,carbon source concentration,inoculation amount and chlorpyrifos-degradation of strains were studied. Response surface methodology (RSM) was used to determine the optimal conditions for degradation of chlorpyrifos,and to establish a model of the degradation kinetics.Response surface methodology based on the Box-behnken design of experiment was used to determine the optimum conditions.On the basis of the response surface and contour plots,the optimum conditions for chlorpyrifos degradation were;0.31%(w/v) glucose,initial chlorpyrifos concentration 51.33mg/L,and culture temperature 30.67℃.The predicted extent of chlorpyrifos degradation under these optimum conditions was 74.7%.According to the hypothetical kinetic model for chlorpyrifos degradation,the kinetics for chlorpyrifos degradation could be described by a first-order rate equation.The feasibility and performances of photocatalysis technology were explored to degrade chlorpyrifos.Based on TiO2 photocatalytic process, experiments were carried out to evaluate influence of time,pH, temperature,light intensity and light source on removal of chlorpyrifos residue in water.It arrived at a higher level when pH was over 7.The removal rate decreased with decreased light intensity and was 70.6% when the treating distance was 5cm. It was discovered that removal rates increased with treating times, but no significant alteration between 30min and 60min after treatment. Under all tested temperatures, the removal rate of more than 60.0% was achieved,not significantly different between 20～30℃and increased significantly when the temperature was over 45℃,the removal rate achieved 77.9% when the temperature was 65℃.Based on the study of photocatalysis and biology treatment,the photocatalysis and bioreactor was integrated for chlorpyrifos degradation. The feasibility and integrated mode was primary explored.Results showed that the reaction time was efficiently shortened, and the degradation concentration was raised,simultaneously,in the combined chlorpyrifos/biological system.The least reaction time for this system was determined to be 81h at biological treatment reaction time of 87h with bi-energy fields reaction time of 6h.Time was saving of 12.1% compared to using biological treatment exclusively,chlorpyrifos degradability was enhancing of 5 times compared to using photocatalysis exclusively.

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