Risk-based public health impact assessment for drinking water contamination emergencies.

Chemical spills in surface waters pose a significant threat to public health and the environment. This study investigates the public health impacts associated with organic chemical spill emergencies and explores timely countermeasures deployable by drinking water facilities. Using a dynamic model of a typical multi-sourced New England drinking water treatment facility and its distribution network, this study assesses the impacts of various countermeasure deployment scenarios, including source switching, enhanced coagulation via poly­aluminum chloride (PACl), addition of powdered activated carbon (PAC), and temporary system shutdown. This study reveals that the deployment of multiple countermeasures yields the most significant reduction in total public health impacts, regardless of the demand and supply availability. With the combination PAC deployed first with other countermeasures proving to be the most effective strategies, followed by the combination of facility shutdowns. By understanding the potential public health impacts and evaluating the effectiveness of countermeasures, authorities can develop proactive plans, secure additional funding, and enhance their capacity to mitigate the consequences of such events. These insights contribute to safeguarding public health and improving the resilience of drinking water systems in the face of the ever-growing threat of chemical spills.

A spatial life cycle cost assessment of stormwater management systems.

Although widely implemented, the research and understanding of the economic impacts and benefits of green infrastructure (GI) systems remain limited. Currently, few studies have investigated the economics of GI systems from a spatial perspective and typically opportunity costs related to land and property tax were ignored. This study aims at bridging these gaps by investigating both the equivalent annual costs (EAC) and cost effectiveness of seven GI systems and compare them against local wastewater treatment facilities in five different US cities. To do this, we utilized capital and maintenance cost data obtained from GI systems that are currently installed at the University of New Hampshire. The costing data were then extrapolated across five different cities considering reported local material, land, tax, and labor rates. A system dynamics model was utilized to calculate the total stormwater reduction as well as the amounts of nitrogen and phosphorous removed by each GI system over its life cycle under a certain city setting. Based upon these outcomes, the cost effectiveness (CE) in terms of stormwater reduction, nitrogen treatment, and phosphorous treatment of the GI systems was calculated. Land and tax costs were found to be a significant component of the EAC for GI systems with larger footprints in cities with higher property values, accounting for up to 78% in some cities. The rankings of the GI systems differ significantly when different types of cost effectiveness are under consideration. The tree filter performs the best when the CE is calculated based on stormwater reductions, while the subsurface gravel wetland performs the best considering nitrogen treatment, and either the subsurface gravel wetland or the sand filter performs the best considering phosphorous treatment. Our study suggests recommendations of GI systems need to be made based on local needs and issues to achieve the most cost-effective solution.

A dynamic life cycle assessment of green infrastructures.

As stormwater and its associated nutrients continue to impair our nation's waterways, green infrastructures (GIs) are increasingly applied in urban and suburban communities as a means to control combined sewer system overflows and stormwater related pollutants. Although GIs have been widely studied for their life cycle impacts and benefits, most of these studies adopt a static approach which prevents that information from being scaled or transferred to different spatial and temporal settings. To overcome this limitation, this research utilizes a dynamic life cycle assessment (LCA) approach to evaluate seven different GIs by integrating a traditional LCA with a system dynamics model which simulates the daily loadings and treatments of nutrients by the GIs across a 30-year life span. A base model was first developed, calibrated, and validated for seven GIs that are currently installed on the campus of the University of New Hampshire. The base model was then expanded to assess different scenarios in terms of geographic locations, land uses, GI design sizes, and climate changes. Our results show these aforementioned factors have significant influences on GIs' life cycle performances, with life cycle nitrogen reductions varying -100.90 to 512.09kgNeq. and life cycle phosphorous reductions varying from -23.77 to 63.43kg P eq. Furthermore, nutrient loading thresholds exist for certain GIs to offset nutrient emissions from their construction and maintenance activities. Accordingly, an optimal GI design size can be estimated for a given spatial and temporal setting. Such thresholds and optimal sizes are important to be identified to inform the decision-making and future planning of GIs.