| This research investigated the application of an integrated membrane bioadsorber reactor (MBAR) process for the removal of gasoline contaminants from water supplies. These contaminants include aromatics such as benzene, toluene, ethyl benzene, and xylenes (BTEX); oxygenates exemplified by methyl-tert-butyl ether (MTBE); and other organic constituents. The process employs bioactive powdered activated carbon (PAC) in continuous flow bioreactor systems with recycle stream, and tubular cross-flow membrane filtration (microfiltration) module for biomass and solids retention.; The present study (i) evaluated the efficiency of the MBAR process for purification of gasoline-contaminated groundwater, (ii) developed a modeling protocol for process design, and (iii) investigated membrane fouling potential and permeate-flux-decline control strategies. The sub-processes of the MBAR model incorporated the following aspects: (a) biological reaction in the bulk liquid phase, (b) film transfer from the bulk liquid phase to the biofilm, (c) diffusion with biological reaction inside the biofilm, (d) adsorption equilibrium at the biofilm-adsorbent interface, and (e) diffusion within the adsorbent particle. The model parameters were determined from carefully-designed and independent experiments. Adsorption equilibrium and rate studies estimated the Freundlich isotherm and sorption kinetic parameters, respectively. Chemostat studies determined biological parameters including the Monod kinetic coefficients, microbial yield coefficient, microbial decay coefficient, and biomass concentrations. Total organic carbon (TOC) was successfully used as a surrogate parameter in the process evaluation and modeling techniques described herein.; The MBAR experiments evaluated three aspects, namely: contaminant removals under different process conditions, membrane permeate flux decline patterns as functions of operation time, and predictive/simulative capability of the model from a design perspective. The model provided reasonably good predictions of MBAR process performance under different operating conditions. Model sensitivity studies investigated the influence of biological, adsorption and transport parameters on the MBAR process dynamics. A process upscaling strategy employing dimensional analysis and similitude was proposed to effect a systematic transition from laboratory-scale to pilot-scale, and eventually, full-scale design. The experimental results indicated that the MBAR process could achieve high efficiencies in groundwater treatment, and has the potential for applications in wastewater treatment and water reclamation. |
