CONICET | Buscador de Institutos y Recursos Humanos

Treatment wetlands are applied worldwide on the depuration of industrial and urban wastewater. Organic contaminants and nitrogen compounds are removed from polluted waters by the joint action of plants, microorganisms, and physicochemical mechanisms, in a process that resembles a natural wetland ecosystem. Being a passive technology (with no external energy input) its main limitation lies on the big space they require for its implantation.Electro-active microorganisms are naturally present in most wastewaters. They grow on polarized electrodes either by using them both as source (cathodic microorganisms) or sink (anodic microorganisms) of electrons, generating an electric current associated to the degradation of contaminated compounds. Also, they have metabolic features as a low sensitivity to temperature variations and a high metabolic rate which are interesting for boosting wastewater treatment systems efficiency. Recently, the application of these microorganisms in treatment wetlands has been proposed giving rise to the so called bioelectrochemical wetlands. In this system two electrodes are buried in the treatment bed; an anode where the oxidation of organic matter occurs and a cathode where the reduction of oxygen and/or nitrate takes place. Unfortunately, the electrochemical potentials at which the electrodes equilibrate are not entirely favorable for the growth and activity of electro-active microorganisms. Therefore, the electric current produced on the bioelectrochemical wetlands is still very low and electro-active microorganisms have a negligible effect on the treatment of the wastewater. In this work an alternative strategy that consists on the external application of electric energy to boost electro-active microorganisms performance in bioelectrochemical wetlands is studied. By the external application electric energy with a power source the potentials of the electrodes may be set on values favorable for electro-active bacteria in both the anode and the cathode. To test this hypothesis, different voltages were externally applied to polarize cathodes and anodes in experimental bioelectrochemical wetlands. The electric current, electrode potentials and microbial activity were measured, and contaminants removal was quantified to identify the most favorable operational conditions for enhancing the growth of electroactive microorganisms and the performance of the treatment system.

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