Quantifying Resilience and Sustainability of Different Plant Operations at a Wastewater Plant Experiencing Wet Weather

Abstract

Water resource recovery facilities (WRRFs) face growing challenges maintaining stable nutrient removal under variable wet weather conditions. This study evaluates those challenges using data from a five-stage Bardenpho plant (7.5 MGD design capacity). Dynamic process simulation was used to measure system response to hydraulic disturbances through three resilience metrics: maximum performance reduction (mpr), recovery time (t_r), and recovery phase performance reduction (rppr). Life cycle assessment (LCA) was then applied to assess how different operational responses affect environmental impacts, focusing exclusively on the liquid treatment train and excluding solids treatment processes. The results showed that direct N₂O emissions dominated the plant carbon footprint within this system boundary, exceeding CH₄ contributions by several orders of magnitude. Wet weather prolonged recovery times to about 6 days and raised global warming and eutrophication impacts by 20–60%. Flow equalization improved resilience by shortening recovery time and lowering environmental burdens by up to 40% through more stable hydraulic loading and reduced aeration demand. Chemical addition further improved nutrient removal but created additional upstream impacts from reagent production. Overall, resilience and environmental sustainability were not always aligned; the plant could maintain stable performance (low mpr) while still generating higher indirect emissions. These findings support the development of nutrient management strategies that balance operational stability with environmental sustainability.