Possibility of the Use of Hollow Fiber Membrane Contactors for Phenol Biodegradation in Saline Solutions
Sustainable process-product development & green chemistry
Environmental Engineering & Management (T1-3)
Keywords: Biodegradation; Phenol; Saline solution; Hollow fiber membrane contactors
Many of the point-source effluents containing priority organic pollutants emanate in organic synthesis operations and exhibit high salt concentrations and/or extremes of pH, one or both of which prevents microbial growth or makes it difficult to sustain. These effluents often come from the synthesis of aromatic compounds, which produces waste streams containing traces of aromatic compounds at levels near their saturated solubility in water, usually of the order 100-1000 mg/L. While the organic compounds themselves are biodegradable, the inorganic compositions of industrially produced effluents may make biological oxidation unfeasible. In the past 15 years, the extractive membrane bioreactor has been proposed to solve the problems outlined above because it uses a dense membrane, which is permeable to aromatic and aliphatic compounds but virtually non-permeable to water or ionic species. The membrane separates wastewater from cell medium where biodegradation occurs under controlled conditions, making it useful for the treatment of high-salinity effluents. However, the treatment is time-consuming due to slow mass transfer within dense membrane.
To enhance such biodegradation process, an attempt was thus made to use a microporous hollow fiber membrane contactor as a reactor to remove phenol in saline solutions by Pseudomonas putida BCRC 14365 at 30oC. Phenol was selected as model substrate because it is one of the most common representatives of toxic organics even at extremely low levels. The fibers were pre-wetted by ethanol to make them more hydrophilic. The initial cell density was fixed at 0.025 g/L. The effects of added NaCl concentration (0-1.78 M) and pH (3-8) in substrate solution on the biodegradation were investigated. The experimental results by suspended cells were also discussed. It was shown that the cells in microporous hollow fibers were unable to tolerate substrate solution pH to a larger range than those in suspensions. The suspended cells grew well on 100 mg/L of phenol only at NaCl concentrations below 0.44 M. However, the cells in microporous hollow fibers could completely degrade 500 mg/L of phenol in solutions containing NaCl concentration up to 1.52 M, which was due to the enhanced tolerance limit to salinity effect by the membrane-attached biofilm and the sufficiently slow mass transfer of NaCl through the membrane pores.
Presented Tuesday 18, 16:20 to 16:40, in session Environmental Engineering & Management (T1-3).
