Comparing centralized and point‐of‐use treatments of per‐ and polyfluoroalkyl substances

Abstract

Per‐ and polyfluoroalkyl substances (PFAS) chemicals are a growing threat to public health and safety. This study seeks to compare the life cycle environmental, economic, and human health performances of centralized and point‐of‐use (POU) systems used to upgrade existing drinking water treatment facilities for enhanced PFAS removal, using Merrimack, NH as a testbed. Out of all studied system upgrade scenarios, a POU scenario that combines granular activated carbon and ion exchange filters has the lowest environmental and human health impacts and relatively low economic impact. Despite all drinking water taps in the house being protected, the centralized scenario does not perform the best in terms of the health impacts because of its relatively low perfluorooctane sulfonate removal efficiency. This suggests a potential tradeoff between protecting the highest number of taps and achieving the highest removal efficiency at limited taps as two water treatment objectives.

Triple‐bottom‐line approach for comparing point‐of‐use/point‐of‐entry to centralized water treatment

“… Cost modeling needs to include the useful life and replacement frequency of all components of either a centralized improvement or a POU/POE device to capture the total cost over time of operating and maintaining the improvement. Other studies (Bixler et al, 2021) have examined net present value or worth using an average useful life and a functional unit based on the volume of water treated which may not accurately account for the total cost over time to a community. State and CWS‐specific cost assumptions need to be clearly documented and reported so that future studies can accurately compare results and make informed decisions. When reviewing the literature to conduct this study, we identified several different cost models and assumptions that needed careful evaluation to determine their applicability to our study.…”

“…Cost modeling needs to include the useful life and replacement frequency of all components of either a centralized improvement or a POU/POE device to capture the total cost over time of operating and maintaining the improvement. Other studies (Bixler et al, 2021) have examined net present value or worth using an average useful life and a functional unit based on the volume of water treated which may not accurately account for the total cost over time to a community. 2.…”

“…In the drinking water industry, we cannot achieve a “zero risk” scenario by removing 100% of a contaminant from drinking water; therefore, solutions need to remove a sufficient amount of the contaminant (i.e., below a regulatory standard such as a maximum contaminant level [MCL]) to protect public health while also considering environmental impact and economic cost. Previous studies of POU/POE devices in comparison to centralized systems have largely focused on one of these three elements examined in isolation, primarily public health protection from microbial contaminants (Abbaszadegan et al, 1997; Momba et al, 2009; Ren et al, 2013; Siwila, 2019), or upfront cost to a community (USEPA, 2006b; Speth et al, 2020) and do not include community engagement and SDWA compliance considerations for POU/POE devices (Bixler et al, 2021) and therefore may generate results that are not community specific.…”

“…In previous exposure assessment literature, exposure assessment is not considered over a specific time frame (USEPA, 2011) or studies do not consider multiple exposure pathways (AWWARF, 2005; Boffetta et al, 2012; Fox, 1989; Zhou et al, 2011). Life cycle analysis literature studies on water systems use a functional unit related to the production of water (Barjoveanu et al, 2019; Bilec et al, 2006; Bixler et al, 2021; Garfí et al, 2016; Jeong et al, 2015; Jones et al, 2018) which is not appropriate for this study, consider inputs and outputs instead of process components (Matthews et al, 2014) or use methodologies and databases that are not specifically applicable to the system boundaries being considered in this study. Life cycle cost literature provides a strong starting point with examples from the USEPA and other agencies (AWWARF, 2005; Bixler et al, 2021; Corona Environmental Engineering, 2021; Speth et al, 2020; USEPA, 2006b, 2007); however, these studies do not consider in detail the impact that replacement frequency has on the outcomes of the life cycle cost analysis.…”

“…Studies comparing centralized treatment to POU/POE treatment have also largely considered completely new centralized treatment systems (Bixler et al, 2021; USEPA, 2006b; Speth et al, 2020), which, while viable for some systems, do not represent the majority of small systems, which only require improvements or upgrades to an existing system to treat a specific inorganic contaminant. A very small water system is not likely to build a completely new centralized treatment facility for a specific contaminant; a small system is more likely to consider a variety of solutions, such as drilling a new well, improving the existing treatment system, or connection to or consolidation with a consecutive water system (Fox, 1989, C. Klevens, personal communication, July 2020, E. Leung, personal communication, September 2020).…”