Envisaging wastewater-to-energy practices for sustainable urban water pollution control: Current achievements and future prospects

Abstract

The organic carbon in municipal wastewater is an energetic substance and can be captured and reused for bioenergy production. A comprehensive evaluation of relevant technical advances and energy recovery potential is essential to provide guidance for sustainability improvement. Although several previous works have covered this topic, most of them have mainly focused on the technical evaluation of a single step, rather than the full treatment line. In this review the currently available processes and achievements related to the capture, recovery and reuse of organic carbon from municipal wastewater for bioenergy production are summarized. The techno-economic evaluation indicates that the biological capture process fails to achieve a good effluent quality when treating wastewater with a high soluble organic content. Chemical coagulants or membranes can be applied as effective methods to assist carbon capture. A fermentation-centered bioprocessing platform is beneficial for the conversion of captured carbon into versatile products. At present, bioenergy recovery is the most promising carbon recovery mode, and the global wastewater sector possesses a 51.06 billion kWh/year bioenergy production potential. Through hydrothermal or pyrolysis treatment, the organic residue arising from the bioprocessing platform can be circularly used. Based on the above analysis, a plant-wide wastewater-to-energy route including a carbon separation system, a bioprocessing platform, and a thermochemical conversion line is envisaged. Additionally, the challenges to achieving the proposed bioenergy production paradigm from municipal wastewater are examined. This review presents the gaps and future prospects in achieving sustainable municipal water pollution control.