MFC-based biosensor for domestic wastewater COD assessment in constructed wetlands

Area of Science:

• Environmental Science
• Biotechnology
• Wastewater Treatment

Background:

• Natural-based wastewater treatment, like constructed wetlands (CW), requires effective tools for optimizing operational management.
• Continuous monitoring of chemical oxygen demand (COD) is crucial for efficient wastewater treatment plant performance.

Purpose of the Study:

• To evaluate the feasibility of using constructed wetland microbial fuel cells (CW-MFCs) as a biosensor for assessing domestic wastewater COD.
• To determine the suitability of different anodic materials and operational parameters for CW-MFCs in COD assessment.

Main Methods:

• Four laboratory-scale CW-MFCs were constructed and fed with domestic wastewater of varying COD concentrations.
• Two anodic materials, graphite rods and gravel, were tested under controlled laboratory conditions.
• A pilot-plant experiment was conducted to validate laboratory findings.

Main Results:

• Both gravel and graphite anodes in CW-MFCs demonstrated suitability for domestic wastewater COD assessment, despite low coulombic efficiencies.
• Significant linear correlations between inlet COD and CW-MFC cell potential (Ecell) were observed with contact times exceeding 10 hours.
• CW-MFC accuracy diminished significantly after several weeks of continuous operation, with optimal bio-indication noted between weeks 3 and 7.

Conclusions:

• CW-MFCs can serve as an effective 'alarm tool' for qualitative, continuous monitoring of influent water quality.
• Due to a decline in precision over time, CW-MFCs are better suited for initial assessment rather than precise quantitative COD measurement.
• Further research may focus on improving the long-term stability and precision of CW-MFCs for wastewater monitoring applications.