Enhanced in situ bioremediation of soils contaminated - soil technology

Cleaning up industrial sites contaminated with hydrocarbons and chlorinated compounds is a major environmental challenge due to both scale and complexity. This article explores an advanced in situ bioremediation approach combining site-specific bioaugmentation and microbiome-driven biostimulation for more effective environmental restoration.

Learn more

 

Technology details:

Technology name: Enhanced in situ bioremediation of industrial site soils contaminated by complex mixtures of hydrocarbons and their chlorinated derivatives.

Context and Objective: The bioremediation of soils contaminated by complex pollutant mixtures faces different challenges. On one hand, it requires the activity of different degraders acting on different components of the pollutants’ mixture, often through different metabolic strategies (e.g., direct or co-metabolic oxidative degradation, reductive dechlorination) and under different environmental conditions (aerobic, anaerobic); on the other hand, degraders may suffer from toxicity exerted by the mixture of pollutants. The technology aims at addressing these challenges and achieve the complete biodegradation of all the target pollutants in the mixture by combining site-specific in situ (autochthonous) bioaugmentation and microbiome-tailored biostimulation strategies. 

Impact of the technology: The technology will bring bioremediation efficiency beyond that of the use of single biologics, allowing the extensive elimination of multiple pollutants in the matrices of contaminated sites, promoting their revitalisation and good ecological status including increase of local microbiome biodiversity.

Target pollutant: mixture of benzene, toluene, ethylbenzene, xylenes (BTEX), total petroleum hydrocarbons (TPH), polycyclic aromatic hydrocarbons (PAH) and chlorinated aliphatic hydrocarbons (CAH).

Enhanced in situ bioremediation of industrial site soils - technology description:

The technology addresses the in situ bioremediation of saturated soils and groundwater contaminated by complex mixtures of hydrocarbons and their chlorinated derivatives. It is based on the site-specific formulation of microbial inocula (bioaugmentation) and microbiome enhancers (biostimulation) that are introduced and distributed in the contaminated aquifer using currently available techniques, such as direct injection, push-pull, groundwater recirculation, selected on the basis of the hydrological/geological conditions at the site.

Microbial inocula are either microbial strains or communities, enriched or isolated from the contaminated site to be remediated (autochthonous) or from other sites (allochthonous), each displaying biodegradation capabilities towards a specific class/group of site contaminants. Microbial inocula are selected to complement each other’s biodegradation ability under the same redox conditions, or under redox conditions that can be sequentially established at the site through the sequential supplementation of different amendments.

Microbiome enhancers are chemicals supplied at “homeopathic-style” concentrations acting as “prebiotics” for the indigenous microbiome of the site, able to induce measurable changes in microbiome composition, structure, and functionality leading to increased pollutant biodegradation. Microbiome enhancers are selected on the basis of the site microbiome characterization, modelling and simulations carried out in a digital environment.

The application of microbial inocula and microbiome stimulants is caried out either simultaneously or sequentially, together with commercial amendments able to promote the establishment of the desired redox conditions (e.g., oxygen releasing compounds, hydrogen releasing compounds).

Why this technology goes beyond the state of the art:

Most state-of-the-art bioremediation efforts relying on single (micro)organisms often come up short when applied to real contaminated environments, due to the presence of multiple pollutants and the variability of biologics performance (lack of competitiveness and stability). For example, degrading strains and consortia for bioaugmentation have been described, but their efficiency in the environment is variable and unexplained. Moreover, conventional bioagumentation and biostimulation approaches neglect the complex metabolic interactions between inoculated degraders and the indigenous microbiome, and between pollutant degrading and non-degrading members of the microbiome. The proposed technology applies a broader, system-based approach where i) microbial degraders targeting different pollutants are selected and acclimatized to the matrix of the contaminated site before reimplantation in the site to bioremediate, and ii) modelled microbiome-wide metabolic networks and interactions are exploited for predicting viable bioaugmentation with best strains/consortia and for selecting prebiotic molecules able to boost the microbiome pollutant degradation activity. The system-based bioaugmentation and biostimulation approaches are first validated in the laboratory on real soil and groundwater samples from the Nymphe study site (TRL4) and then validated under environmentally relevant conditions with field tests at the Nymphe site (TRL5).

Results of technology:

Microbial consortia and isolates with high degradation efficiency towards BTEX, TPH and PAH with up to 3 rings have been obtained and selected for the autochthonous bioaugmentation of the Nymphe study site. Laboratory tests showed that PAH inhibit the biodegradation activity of the TPH degrading culture, and that the efficient biodegradation of all target pollutants can be stimulated and achieved through a sequential application of the selected microbial cultures (PAH and BTEX degraders, followed by TPH degraders). The microbial “assembly” is currently under production on a larger scale for bioaugmentation tests in the field. A number of chemicals with potential activity as microbiome enhancers have been identified on the basis of microbiome models.

ALL TECHNOLOGIES

This technology is developing by University of Bologna (UNIBO) and Eni Rewind under the EU-funded NYMPHE project.

In our Technology Booklet, we showcase 10 solutions currently under development:

4 wastewater treatment technologies

3 soil remediation technologies

3 microbiome modelling approaches

Read the full technology overview: https://www.nympheproject.eu/technologies

Project funded by the European Union

Grant Agreement ID: 101060625