A reactor model for pulsed pumping groundwater remediation

Pulsed pumping process optimization using a potential flow model

A computational model is applied to the optimization of pulsed pumping systems for efficient in situ remediation of groundwater contaminants. In the pulsed pumping mode of operation, periodic rather than continuous pumping is used. During the pump-off or trapping phase, natural gradient flow transports contaminated groundwater into a treatment zone surrounding a line of injection and extraction wells that transect the contaminant plume. Prior to breakthrough of the contaminated water from the treatment zone, the wells are activated and the pump-on or treatment phase ensues, wherein extracted water is augmented to stimulate pollutant degradation and recirculated for a sufficient period of time to achieve mandated levels of contaminant removal. An important design consideration in pulsed pumping groundwater remediation systems is the pumping schedule adopted to best minimize operational costs for the well grid while still satisfying treatment requirements. Using an analytic two-dimensional potential flow model, optimal pumping frequencies and pumping event durations have been investigated for a set of model aquifer-well systems with different well spacings and well-line lengths, and varying aquifer physical properties. The results for homogeneous systems with greater than five wells and moderate to high pumping rates are reduced to a single, dimensionless correlation. Results for heterogeneous systems are presented graphically in terms of dimensionless parameters to serve as an efficient tool for initial design and selection of the pumping regimen best suited for pulsed pumping operation for a particular well configuration and extraction rate. In the absence of significant retardation or degradation during the pump-off phase, average pumping rates for pulsed operation were found to be greater than the continuous pumping rate required to prevent contaminant breakthrough.

Basic studies on the treatment of volatile organic pollutant in sand by microwave radiation

The heating characteristics of water and sand were investigated to understand the basic features of a microwave soil pollution treatment system and the reasonableness of this method was examined. The evaporation and temperature change of water by microwave irradiation were dependent on its volume and sand showed a three-fold temperature change compared with water. When microwave energy was applied, water showed an even variation in temperature on the whole, however, there was approximately 30 square difference according to the location inside the sand. Sand temperature was observed to show a larger difference as it was horizontally and vertically closer to the microwave irradiation point and horizontal temperature variations were more evenly distributed than vertical variations. Heating characteristics according to the particle size of sand showed that the temperature change was larger when the particle size became smaller and the moisture content of sand was found to influence its heating behavior. In the conditions of experiment, about 50% of the benzene in sand was volatized after 23 minutes of heating and 85% of the total benzene was removed from the sand after 60 minutes of microwave irradiation. For real soil test, more than 70% of BTEX was successfully removed from the soil after 120 minutes of heating.