Eco-efficiency analysis of a continuous two-phase partitioning bioreactor treating 2,4-dichlorophenol synthetic wastewater

Abstract

Continuous two-phase partitioning bioreactors are a promising solution for removing poorly biodegradable pollutants, such as phenolic compounds, from wastewater. However, their combined economic and environmental feasibility has not yet been jointly evaluated, and it is crucial to ensure a minimum incorporation of sustainability aspects during design. For this purpose, four methodologies were employed. Standalone analyses were first conducted using Life Cycle Assessment and Life Cycle Costing, followed by an integrated environmental–economic sustainability assessment. The latter consisted of an eco-efficiency approach and a qualitative evaluation based on the principles of the EU Taxonomy, which functions as a key instrument within the European sustainable legal framework. The methodologies were applied to four scenarios in which the concentrations of 2,4-dichlorophenol, as targeted model phenolic compound, in the influent and the recycling ratio of the treated effluent were varied. The findings revealed that integrating recycling within the reactor resulted in a significant environmental burden across categories, with exception of ecotoxicity (with 98.2% decrease). Although the technology successfully achieved its removal objectives, the higher consumption of utilities required for proper reactor operation reduced the expected benefits. As for operating expenses, differences between scenarios were minimal due to the dominance of fixed costs, which remain constant in all cases. Comparatively, the technology aligned with performance metrics found in existing literature (around 13.7 kg CO2eq./m3 of treated wastewater and costs above 7.62 €/m3). To enhance the competitiveness of the technology, it is essential to manage energy demands for heating and aeration and to increase process automation, thereby reducing associated labor costs