Electric Potential in Electroactive Biofilm-based Constructed Wetlands: Current flow density as a performance indicator

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An Electroactive Biofilm-based Constructed Wetland (EABB-CW) is a wastewater treatment system that relies on the presence of electroactive bacteria (EAB) to enhance the degradation of pollutants. Compared to other microbial electrochemical setups, EABB-CW is designed in short-circuit mode (dispensing of external circuits) and uses an electro-conductive substrate acting as a single-piece electrode. A major challenge of this type of system is to correlate the EAB metabolism with the electrical current generation and hence with the removal of pollutants. In environments with the presence of EAB, electric fields are created by anodic and cathodic reactions, therefore generating ionic/electron currents that can be quantified. That quantification can be done by measuring electric potentials (EP), with the aid of sensors insensible to redox active compounds, but able to collect low current signals in highly conductive matrixes.
The aim of this research was to test the removal of organic matter and nutrients in an EABB-CW, and their correlation with the presence of EAB through measurements of electron current density (J) and electron transfer rates (R) in the tested columns. The experiment was carried out testing mesocosm (EABB-CW) with two different types of electro-conductive materials (PK-A and PK-LSN), fed with real wastewater at two different flow regimes (up and downflow). The results show that the electroconductive systems are able to reach removal efficiencies between 85% and 95% for COD, between 29% and 48% for NH4-N, up to 20% for NO3-N, and between 82% and 89% for PO4-P.
The EP profiles show differences among the tested systems, indicate the development of different conditions for the establishment of EAB. Derived electron current densities (J) indicate that electroconductive systems have maximum values of 0.015 mA cm-2 for PK-LSN systems and of 0.024 mA cm-2 for PK-A, whereas 0 mA cm-2 for gravel systems.
The measure of electric profiles (EP), electron current densities (J) and electron transfer rates (R), seems to be a promising approach to characterize the dynamics inside electro-conductive systems that uses electro-conductive matrixes like in the EABB-CW systems tested in this study. For example, the correlation between COD concentrations at outlet and J densities could be used to monitor the performance of this kind of CW set-ups.
It was possible to identify a positive impact in the removal of organic matter and up to certain extend the removal of nutrients with the tested electroconductive systems. The obtained results open the possibilities of exploring the development of modifications to improve nitrification that will redound in better total nitrogen, like implementation of unsaturated zones, assisted aeration at minimal rates, recirculation of part of treated effluent, among others.
OriginalsprogEngelsk
Udgivelsesår2019
Antal sider1
StatusUdgivet - 2019
BegivenhedWETPOL2019: 8th International Symposium on Wetland Pollutants Dynamics and Control - Aarhus Universitet, Aarhus, Danmark
Varighed: 17 jun. 201921 jun. 2019
Konferencens nummer: 8
http://wetpol.com

Konference

KonferenceWETPOL2019: 8th International Symposium on Wetland Pollutants Dynamics and Control
Nummer8
LokationAarhus Universitet
LandDanmark
ByAarhus
Periode17/06/201921/06/2019
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