Extreme weather events and wastewater infrastructure: A system dynamics model of a multi-level, socio-technical transition.

Coastal communities and their wastewater treatment systems are vulnerable to the impacts of extreme events. Decision-making about transitioning critical infrastructure across scale - onsite, community, or centralized - to an improved treatment portfolio is complex as it couples financial, social, policy, technological, and environmental factors with impacts to public health and aquatic ecosystems. In this paper, we propose a system dynamics approach to consider important factors and dynamics that influence municipalities' decision-making process for wastewater infrastructure transitions in the Florida Keys, particularly considering some impacts of a changing climate. Our research utilizes social-technical transition theories to develop an adaptable and dynamic decision-making tool for transitioning to an improved portfolio of wastewater technologies and to determine strategies that improve the portfolio's performance measures (i.e. nutrient loading and reliability) under extreme weather scenarios. The initial simulation results demonstrate that it is important to incorporate the impacts from extreme events into the wastewater infrastructure decision-making process because they increased nutrient loading by >20% and decreased reliability by nearly 10%. With this climate-informed decision-making structure, strategies were developed to facilitate the transition to an improved wastewater treatment portfolio. The strategies include a new socio-economic decision-making approach, technology and economic policies, and socio-technical behavior change. The socio-technical strategy simulated widespread adoption of urine diversion technologies which made the greatest improvement to nutrient loading with an 81% decrease. Furthermore, the best approach to improve the reliability performance measure (from 81% to 83%) was the technology and economic policy which economically disincentivized investment in centralized wastewater systems and changed the community-level technology option.