Study On Biodegradation Of 2, 4-dicholrophenol On Loofa Sponge Immobilized Biomass Of White Rot Fungus

Chlorophenols(CPs), extensively used as wood preservatives, rust inhibitors, fungicides and herbicides, is rated as a priority pollutant by the US Environmental Protection Agency because of this great ubiquity. The treatment of CPs polluted waste waters has attracted more and more attention. The commonly used procedures for removing CPs from wastewater include flocculation, adsorption, filtration, oxidation and biological treatments, among which biological methods using microorganisms are preferable because of their low cost, effectiveness and the low production of byproducts. The proper carrier could be employed to immobilze efficient microorganisms to form an effective and coutinous waste water treatment system, which has shown great potential and becomes a hotspot of research.Phanerochaete chrysosporium, one kind of whit rot fungi, was immobilized on loofa sponge, and was used to remove 2,4-DCP from the aqueous system. The feasibility of two immobilization methods was investigated. The growth curves of immobilized cell and the suspended cell were made. The role of extracellular enzymes in the 2,4-DCP removal was studied. The effects of pH, temperature and rotation speed on the biodegradation were discussed. The effects of residence time and gas flow rate on the biodegradation efficiency by immobilized cell fluid bed ractor were investigated. The kinetics of the immobilized fungus biodegradation on 2,4-DCP was analyzed.The results showed that the immobilization could be realized through the growth of the cell on loofa sponge and the biomass could reach 0.791g dry weight/(g sponge discs). The growth rate and the biomass of immobilized fungus were both better than that of suspended cells. The extracellular fluid showed negligible biodegradation of 2,4-DCP, which indicated that the extracellular enzymes were not directly involved in the biodegradation process. The optimum temperature, pH and rotation rate of shaking table for biodegradation by immobilized fungus were 35℃, 6.0 and 125r/min respectively. In sequential batch experiment, the bioactivity of immobilized cells was recovered and improved during the culture and the maximum degradation rate constant of 13.95 mg/(L·d) was reached in run 5. In continuous bioreactor test, the residence time and flow rate affected greatly on the behavior of fluidized bed reactor and the kinetic behavior of the loofa immobilized on loofa sponge was found to follow the Monod equation. The maximum reaction rate was 7.002mg/(L·h), and the saturation constant was 26.045 mg/L.