Sustainability Comparison: Centralized Treatment Upgrades and POU/ POE Treatment for Small System Compliance to the SDWA. Learn about this study, in which WQRF set out to examine the sustainability of point-of-use (POU) and point-of-entry (POE) devices in comparison to upgrades at existing small centralized systems for Safe Drinking Water Act (SDWA) compliance. The study examined four real-world case studies through the lens of a “triple bottom line analysis” (people, profit, and planet) over a thirty-year time period.