A comparative life cycle assessment (LCA) analysis of innovative methods employing cutting-edge technology to improve sludge reduction directly in wastewater handling units

Abstract

Sludge reduction technologies can be used as an alternative plan to dispose of excess sludge in wastewater treatment plants, but the sustainability of these strategies is a challenging task. In this study, the potential environmental implications of innovative technologies based on lab-scale results published in the literature were assessed from the life cycle assessment (LCA) view point. Accordingly, three different scenarios using various sludge reduction mechanisms were selected and analyzed. The scenarios include (1) an integrated oxic-setting-anaerobic and ultrasound process; (2) a sequencing batch reactor (SBR) with an anaerobic side-stream reactor to its return activated sludge line; and (3) the anaerobic-anoxic-oxic system in conjunction with an ozone reactor. LCA was conducted through the CML-IA (baseline 2000) method. A sensitivity analysis was also done in order to determine how changes in the inputs are affecting the overall sustainability of the system. The environmental impact evaluation of three scenarios indicated that the integrated SBR with an anaerobic side-stream reactor was the most efficient and sustainable alternative in environmental terms. Although the upgraded SBR system was not the best alternative in terms of sludge reduction (65 % versus 78 % for Scenario 1 and 70 % for Scenario 3), it showed the highest overall performance and also demonstrated the lowest environmental impact compared to other scenarios. Because the scenarios studied were cutting-edge and provided novel sludge reduction strategies based on lab-scale results published in the literature, a comprehensive economic analysis and scale-up considerations are recommended to effectively assist decision-makers in guiding the development of emerging technologies.