The system simulates the in-situ bioaugmentation and biostimulation phases for bioremediation of contaminated soil. The biological solutions pass through the volumes of soil by filtration. The flow through the soil is set to simulate the bio soil washing treatment, with flow rates and pressures that can be regulated within ranges established by the fitness of microbial ecology and the specific inoculum.
The biological treatment that takes place in the soil is aimed at the depletion of organic contaminants, such as TPHs and PAHs. The degradation is carried out by the inoculated autochthonous microorganism, isolated from the soil samples and selected for their ability to degrade recalcitrant molecules, and/or by stimulated bacteria that are part of the natural ecology of the treated soil.
The process is controlled through sensors inserted in various points of the circuit. The sensors allow to monitor and adjust the operation of the system through feedback to the PLC, so that the conditions inside the system remain similar to those in-situ and favorable for bioremediation.
In the process, the following parameters are measured:
– Oxygen dissolved in the biostimulation flow and in the leachates
– Pressure in the soil and in the hydraulic circuit
– Conductivity, pH, temperature in the leachate
– Hydraulic flows that pass through the soil
The system is automated and controlled by process logics implemented in a PLC, which controls solenoid valves, pumps, and electric motors. Soil chemical analyses are conducted to determine the variation in the concentration of target contaminants, while water analyses have the objective to determine the toxicity of the matrices being treated. The degradation kinetics of the contaminants and the detoxification curve do not go in parallel, due to the byproducts of biological degradation, which may have similar or greater toxicity than the parent compounds. Accordingly, the toxicity curve decreases more slowly than the contamination curve. Data on the consistency and diversity of the microbial community are obtained by metagenomic analysis, based on the metabarcoding of the fungal and bacterial communities.