Modeling BOD Removal in Constructed Wetlands with Mixing Cell Method

U.S. EPA (Environmental Protection Agency) staff developed a field procedure to measure hydraulic conductivity using a direct-push system to obtain vertical profiles of hydraulic conductivity. Vertical profiles were obtained using an in situ field device-composed of a Geoprobe direct-push drive, threaded steel pipes with an openslotted section, and a drive point at the bottom-PVC tubing, and a peristaltic pump. Simple mathematical formulas were derived for estimating hydraulic conductivity from the field measurements. The field procedure and mathematical formulas were applied in an unconfined sand aquifer. A vertical profile of hydraulic conductivity at a measurement location was plotted with the value obtained from a conventional slug test from a nearby monitoring well. The hydraulic conductivity in the middle of the aquifer was found to be an order of magnitude higher than that at the water table depth. The conductivity from the slug test at the monitoring well was half of the maximum value in the profile. The in situ direct-push method provided valuable information on site characterization in a short time, with minimal disturbance and without installing additional wells.