Wastewater Treatment for Carbon Dioxide Removal

Area of Science:

• Environmental Engineering
• Geochemistry
• Materials Science

Background:

• Wastewater treatment contributes significantly to global greenhouse gas (GHG) emissions (1-2%).
• Developing carbon dioxide removal (CDR) strategies within existing infrastructure is crucial for climate change mitigation.

Purpose of the Study:

• To investigate the potential of using calcium (Ca)-rich wastewater effluent for carbon dioxide removal (CDR) through mineralization.
• To characterize the carbonate minerals formed and assess the feasibility of this CDR approach.

Main Methods:

• Utilized Ca-rich effluent from a phosphorus (P) recovery system in municipal wastewater.
• Bubbled the effluent with concentrated CO2 to induce mineralization.
• Analyzed mineral properties using Fourier-transform infrared spectroscopy (FTIR), X-ray fluorescence (XRF), Scanning Electron Microscopy with Energy Dispersive X-ray spectroscopy (SEM-EDX), Focused Ion Beam Scanning Electron Microscopy (FIB-SEM), Transmission Electron Microscopy (TEM), and X-ray Diffraction (XRD).

Main Results:

• High-quality calcium carbonate (CaCO3) minerals, primarily aragonite and calcite, were synthesized.
• FTIR confirmed carbonate bonds, XRF/SEM-EDX indicated high Ca concentration, and SEM/FIB-SEM/TEM revealed homogeneous distribution and characteristic mineral structures.
• The process improved effluent quality, offering water reclamation benefits.

Conclusions:

• Wastewater effluent can be effectively used for carbon mineralization, sequestering CO2 into stable carbonate minerals.
• This method presents a sustainable paradigm for reducing the carbon footprint of wastewater treatment and offers opportunities for material valorization and circular economy.
• The approach is potentially applicable to other alkaline Ca-rich wastewaters, such as steel slag leachates.