Design of in-situ microbial filter for the remediation of naphthalene

The in-situ microbial filter (ISMF) is a specific application of in-situ bi oremediation (ISB) for the treatment of groundwater contaminated plumes. Th e ISMF filter consists of an in-situ reactor, composed of sand mixed with n on-indigenous microorganisms, that is placed ahead of migrating contaminant plumes and removes contaminants by biological and abiological processes. T his paper presents the results of an experimental study investigating the r emediation of naphthalene contaminated water through a lab scale ISMF. Math ematical modeling was performed to determine the optimum dimensions and con figuration of the ISMF, and to stimulate the migration of naphthalene throu gh the ISMF. Soil column tests were carried out to determine the biomass co ncentration and hydraulic conductivity to attain effective biodegradation w ithin an ISMF. The optimum biomass concentration was determined to be 1.4 m g VSS/g sand and the optimum hydraulic conductivity was determined to be ap proximately 1 x 10(-5) m/s. FLOTRANS, a two-dimensional finite element hydr ogeological model based on the advection-dispersion equation, was used to i llustrate the effect of different filter and barrier configurations on the discharge through the filter and to stimulate naphthalene migration through an ISMF. Experimental results and the mean simulation values obtained thro ugh Crystal Ball(R), a forecasting and risk analysis program, were used as the input parameters for the FLOTRANS model. Optimum dimensions and configu rations of the filter were determined for effective remediation of naphthal ene. Modeling results indicated that an ISMF, with the how and transport pr operties determined in this study, has the capacity to substantially attenu ate naphthalene contaminated groundwater. A sensitivity analysis was perfor med using Crystal Ball(R) to determine the relative influence of the basic parameters from the advection-dispersion equation on the contaminant concen tration. (C) 1999 Elsevier Science Ltd. All rights reserved.