Bio – inoculation

The prototype simulates the in-situ bio-inoculation and bio-stimulation phases for bioremediation of contaminated soil.

It is a closed hydraulic circuit machine, in which six soil units, representing several lithological layers, are subjected to treatment using biological and bio-stimulant solutions. These solutions pass through the volumes of soil contained in bio-cells, by filtration. The bio-cells are made of transparent polymethylmethacrylate.

The flow through the cells is set to simulate the Bio-flushing treatment, with flow rates and pressures that can be regulated within ranges established by the fitness of microbial ecology and inoculum.

The biological treatment that takes place in the Bio-cells is aimed at the depletion of TPHs and PAHs contained in the experimental soil, carried out by autochthonous microorganism inoculum, isolated in soil samples and selected for their ability to degrade recalcitrant molecules, and by stimulated bacteria that are part of the natural ecology of the treated soil.

The prototype is equipped with different sections:

  • Dosage of biological solutions
  • Dosage of micronutrients
  • Production and dosage of nano-bubbles by means of an air-water mixer
  • Purification of eluates

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 prototype 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 eluate of the bio-cells
  • Pressure in the bio-cells and in the hydraulic circuit
  • Conductivity, pH, temperature in the eluates of the bio-cells
  • Hydraulic flows that pass through the bio-cells

The prototype is automated and controlled by process logics implemented in a PLC, which controls solenoid valves, pumps, and electric motors.

Test results are measured by analyzing soil and water samples extracted from the bio-cells every 15 days. Soil chemical analyzes are conducted to determine the variation in the concentration of target contaminants, while water analyzes 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.

The results on the consistency and diversity of the microbial community come from the metagenomic analysis based on the metabarcoding of the fungal and bacterial communities.