Removal Of VOCs From Contaminanted Water By Membrane Air Stripping And Bioenhancement

Membrane air stripping (MAS) and bioenhancement technology are predominant and promising treatment methods for removing volatile organic compounds (VOCs) from wastewater. MAS is an innovatory removal and recovery technique which fits for treating VOCs contaminated water at a wide range of concentration, especially economic for high VOC levels, whereas bioenhancement technology is more clean and effective at low VOC concentrations. This study mainly focused on the removal of methyl tert-butyl ether (MTBE), which is one of the most typical VOCs, from model wastewater when membrane air stripping or/and bioenhancement involved.A two-dimension axial symmetry model was presented to describe mass transfer in the process of membrane air stripping based on equations of continuity, motion and mass transfer. The removal of MTBE from model water was studied using membrane air stripping. Results showed that the increase of temperature, air/liquid flux was helpful to the removal of dissolved MTBE, but the initial concentration, air/liquid pressure was hardly influenced on the the removal of MTBE. Simulation result was in good agreement with the experimental data.Oxygen dissolved into wastewater through membrane during the membrane air stripping process. As a result, oxygen supply and removal/recovery VOCs by membrane air stripping could be simultaneouslly performed using one setting. The course of oxygen transfer from air into water through membrane comprised four steps; the layer of micro-bubble could influence the effectiveness of oxygen supply when the pressure of air was larger than that of liquid; and the coefficient of oxygen mass transfer increased as air pressure increased.One stain NERC0401 identified as Klebsiella oxytoca that could degrade MTBE quickly was isolated by enriching, screening and culturing from the soil at Dagang Oil Field, Tianjin, China, and the proper conditions for MTBE aerobic biodegradation were determined by experiments. The bioenhancement results showed that the enhancement of dissolved oxygen (DO) could improve the biodegradation of MTBE by strain NERC0401, and the coexiting of ethanol at some concentrations was helpful for the process. In addition, the degradation ability of NERC0401 could be improved when the microbe was immobilized by calcium alginate.A one-dimension model of column filled with immobilized microbe, which was used as one part of combined technics of membrane air stripping and bioenhancement, was developed for forecasting the removal of MTBE. Simulation results fitted well with the experimental data, and the residence time was a key factor for MTBE biodegradation. This study will be useful for treating VOCs contaminated water by using the combined technics.