Measuring Localized Surface Infiltration Rates in Secondary Effluent Recharge Basins

Soil aquifer treatment is the managed infiltration of water, often treated wastewater in recharge basins. Optimal operation of those basins is related to the rate of infiltration and achieving desired water quality improvement. Most often, a mass balance is used to compute the average basin infiltration rate. This averaging method does not provide insight into potential temporal changes in the infiltration rate during the recharge period and spatially varying rates of infiltration across the basin surface. Knowledge of both these factors is critical to engineering optimal basin operation. In order to address this shortcoming, automated infiltrometers have been developed and tested which can measure local infiltration rates (areal scale of ∼0.19 m ² or ∼2 ft ²) in near real time (time steps of ∼1.0 min). The automated infiltrometers were tested in a recharge basin operated by Tucson Water in Tucson, Arizona and performance data is presented.