Remediation technologies - Water & Soil sediment | Greener

Phycoremediation is the use of either macro-algae or micro-algae for removal or biotransformation of different pollutants & nutrients like organic/inorganic carbon, Nitrogen, Phosphorous, sulfates, heavy Metals etc. During Phycoremediation process, micro algae use carbon, nitrogen, phosphorus & other salts from the waste water which act as nutrients for them. In GREENER, the consortium focuses on the improvement of azo dyes removal using microalgae (e.g. Chlorella pyrenoidosa, Chlorella vulgaris, Cosmarium sp., etc.). This will be achieved by using bioreactors (with controlled conditions) for axenic cultivation of different microalgae for testing toxicity of azo dyes. The effectiveness of azo dyes biodegradation and possible production of toxic aromatic amines will be then tested. Special attention will be paid on the toxicity assessment of the resulting biodegradation products, including aromatic amines produced during degradation of azo dyes.

The use of plants through phytoremediation technology is an alternative solution to treat heavy metal contaminated areas. Several plants have been proposed for heavy metals remediation. Each plant has different responses to different heavy metals exposure. Some plants are sensitive to several heavy metals while others have a high tolerance and can maintain growth and development. In GREENER, the reinforcement of phytostabilisation will be studied on the basis of preliminary screening of plants, in order to promote the absorption (phytoextraction), utilization and accumulation of nutrients, and to increase the tolerance of plants to environmental stress.
Local plant species with hyperaccumulator properties and plant cultivation on the adsorption of potentially toxic metals and metalloids (Pb, Zn, Cd and Cu) will be studied. Moreover, the joint action mechanism of plant probiotics with plants in water remediation will be investigated. The effect of the plant growth regulators, chelating agents, antibiotics and other substances secreted by microorganisms on plant environment adaptation ability will be studied. The optimized plants and strengthen measures will be selected, while characterisation of metal resistant/tolerant bacterial strains, evaluation of selected bacterial/plant combinations and their response to heavy metal challenge will be investigated.

Globally, billions of euros are spent treating trillions of litres of wastewater every year, consuming substantial amounts of energy. However, this wastewater could act as a renewable resource, saving significant quantities of energy and money, as it contains organic pollutants which can be used to produce electricity, hydrogen and high-value chemicals, such as caustic soda. This can be achieved if the organic matter is broken down by electrically-active bacteria in an electrochemical cell, which, at the same time, helps clean up the wastewater. Examples of such ‘bioelectrochemical systems’ (BES) are microbial fuel cells (MFCs) and microbial electrolysis cells (MECs). Novel systems for groundwater and wastewater remediation based on BES reactors will be developed under the GREENER project. This approach will lead to an enhancement on existing remediation technologies for target pollutants (including TPHs, PAHs, antibiotics, potentially toxic metals and metalloids and pesticides). The system will be monitored and analysed to determine the best operational conditions for enhancing pollutant removal and energy output. Moreover, a mathematical model of the system will be developed: the model will combine equations of bio-electrochemical and electrochemical reactions, transport phenomena, and current distribution, with electric conduction within the biofilm.

Depending on the metallic contamination to be tackled, different bacterial strains or consortia of bacteria will be employed. Microbial communities will be subjected to feedstocks containing diverse metal ions at different concentrations. Tests will be performed and optimised in common reactors. Recovery efficiency of metals as nanoparticles will be determined by physical-chemical techniques as well as electron microscope techniques. Finally, long-term performance will be studied and optimized.

Hybrid systems combining BES reactors with phytoremediation will be developed, for the removal of pesticides, TPHs, metals and antibiotics. Integrated systems will be designed for the treatment of leachates from conventional bioremediation processes such as anaerobic digestion, generally rich in metal ions, volatile fatty acids, and residues of antibiotics and bioactive molecules. Biofilm activity will be evaluated by measurement of the electrochemical performance of the system, and monitoring of its physico-chemical parameters, using the efficiency of bioconversion or bioremediation as the optimization parameter.

Guidelines for scaling-up the above mentioned technologies will be established. All the information resulting from previous tasks will be gathered in order to establish a successful strategy. Moreover, technologies developed will be validated in a relevant environment. For this purpose, different reactors (one technology for partner) will be scaled-up from mL to liter scale (in the range of 5 to 100 liters). Pollution abatement at pilot scale will be undertaken using real contaminated samples. These pilot scale experiments will serve as input for the GREENER decision-making tool. The outputs from the pilot scale experiments will define the guidelines for successful field test experiments.

Biostimulation involves the modification of the local environment in order to stimulate endogenous bacteria capable of bioremediation. This can be done by addition of various forms of rate limiting nutrients and electron acceptors, such as phosphorus, nitrogen, oxygen, or carbon (e.g. in the form of molasses). Bioaugmentation is the addition of archaea or bacterial cultures required to speed up the rate of degradation of a contaminant. Biostimulation and bioaugmentation techniques will be optimised for the depollution of TPHs and PAHs of soils in presence of potentially toxic metals and metalloids. In addition, the possible addition of microalgae as biofertilizing or the application of alternative enrichment treatments, such organic amendments, nontoxic synthetic chelators and/or biosurfactants, will be studied. In order to check the efficiency of the treatment, laboratory experiments (on mesocosmos scale) will be designed.

The Ecopile process will involve biostimulation of indigenous hydrocarbon degraders, bioaugmentation through inoculation with known pollutant degrading consortia and phytoremediation, through the effect of root growth and penetration throughout the soil and the resulting stimulation of microbial activity in the rhizosphere. A number of ecopiles will be established under a number of different conditions to include mixed contaminants e.g. TPH, PAH, potentially toxic metals and metalloids and different sites (EU & China), which will be prepared using current procedures and monitored over a 6 – 12 month period.

Hybrid systems for soil remediation based on the combination of BES reactors with phytoremediation will be developed. This approach will lead to an enhancement of existing remediation technologies for target pollutants. In GREENER, endogenous microorganism activity in soil will be combined with the use of plants for faster and enhanced bioremediation. Plants will also act as a source of organic substrate for the anodic bacteria, which in turn can lead to higher power output. The ability of the resulting system to degrade simple and complex mixtures of PAHs, potentially toxic metals, pesticides and pharmaceuticals in soils will be investigated. Finally, the BES system will be combined with the biopile approach and a mathematical model will be developed to simulate the process, and the related phenomena.

Guidelines will be established and data will be gathered aiming to scaling-up the above-mentioned developed technologies. All the technologies will be analysed, and the ones with better performances in terms of degradation times will be tested at pilot scale in selected locations. At least two different types of soil with different mixtures of pollutants will be selected for the pilot scale experiments. These pilot scale experiments will serve as input for the decision-making tool that will be evaluated. A scale-up procedure for carrier preparation and for binding of bacterial cells to the carrier surface will be developed. Finally, the assessment of the effectiveness of the preparation process, survivability of the bacteria and the kinetics of their release will be assessed.