The biofactories: Quantifying environmental benefits of the wastewater circular economy in Chile using life cycle assessment

The wastewater circular economy promises improved environmental impacts within the food-water-energy nexus. This requires verification as the global sanitation sectors seek to improve environmental impacts and achieve integrated water management. Life cycle assessment (LCA) has been used to compare novel technologies for wastewater treatment and recovery, but research addressing plant-wide improvements of co-product resource recovery using real data from full-scale plants is still needed, particularly in a Latin American context. In Chile, two wastewater treatment plants (WWTPs) have embraced the circular economy configuration, recovering treated effluent, biosolids, and biogas, in addition to implementing advanced nitrogen removal using different technologies. The LCA of these two WWTPs demonstrated that Plant A improved 8 out of 10 impact categories compared to the baseline conventional scenario, while Plant B improved 5 categories out of 10. The analysis of the two plants showed the influence of influent quality on environmental impacts and the trade-off that occurs between the different technologies implemented. Plant B generated larger environmental credits through increased biogas and biosolids recovery due to thermal hydrolysis pre-treatment and anaerobic digestion, combined with cogeneration of heat and power. Plant A implemented water recovery, which provided benefits on a smaller magnitude but to more impact categories. Therefore, both plants improved environmental impacts through the wastewater circular economy, but further improvements in system configurations are recommended in each.