Spatialization of saturated hydraulic conductivity using the Bayesian Maximum Entropy method: Application to wastewater infiltration areas.

Wastewater treatment, a major issue at the European level, focuses on improving surface water and groundwater quality, preserving the receiving environment, and ensuring a sustainable use of water. Soil infiltration is increasingly practiced downstream of wastewater treatment plants, particularly in rural areas without surface water bodies, as is the use of soil as an additional buffer and treatment step. However, the design of infiltration areas on heterogeneous soils remains an extremely complex task due to the costly and time-consuming spatial measurement of saturated hydraulic conductivity (Ks). This article proposes integrating 2D electrical resistivity tomography and infiltration tests into a Bayesian Maximum Entropy method, yielding a vertical mapping of soil heterogeneities at a metric scale. This updated method will facilitate infiltration area design in a heterogeneous soil setting.

OhmPi: An open source data logger for dedicated applications of electrical resistivity imaging at the small and laboratory scale.

The use of electrical resistivity tomography in laboratory or field experiments for environmental purposes has been increasing in recent years. The development of commercial devices has thus far focused on the quality of measurements and their robustness in all field cases. However, both their costs and lack of flexibility to adapt to specific applications have limited their prevalence in the environmental sector. This article presents the development of a low-cost, open hardware resistivity meter to provide the scientific community with a robust and flexible tool for small-scale experiments. Called OhmPi, this basic resistivity meter features current injection and measurement functions associated with a multiplexer that allows performing automatic measurements with up to 32 electrodes (at a cost of less than $500). The device was first tested using a soil-analog electrical circuit to verify the reliability and robustness of the measurements. Results show that OhmPi offers a wide range of resistance measurements, from 0.2 to 1000 O, for contact resistances between 100 and 5000 O. Measurements were then carried out on a small field experiment, in demonstrating good stability of the OhmPi measurements, as well as a strong correlation with the output of a commercial reference instrument.