Physical and biochemical processes in soil aquifer treatment

Soil aquifer treatment (SAT) is an engineered process in which the quality of marginal water is enhanced by infiltration through the vadose zone and is being stored in the aquifer underneath. The process combines the advantage of low-cost and low-maintenance technology, with large storage volume that allows bridging seasonal water availability and demand. We will present here a case study from central Israel where SAT is used as a tertiary treatment for wastewater, bringing the water to practically tap water quality. With an overarching goal of improving water quality and quantity, our presentation will present time-lapse geophysical monitoring of the infiltration process, monitoring of redox-related nitrogen processes in the upper soil layers, the role of entrapped air, and biochemical modeling of the nitrogen-related processes in the soil and the infiltration pond. We will demonstrate how operational parameters control the infiltration rates and the reducing or oxidizing nature of the subsurface. Our results show how the process vary spatially (in all three dimensions) and temporally, and how it can be hydraulically controlled. Our conclusion is that SAT can, and should, be treated as a pseudo-reactor and its activity can and should be optimized, and that such processes have significant advantages over conventional and expensive water treatment processes, relevant not only for arid regions.