Abstract: Freshwater scarcity is expected to increase over the coming decades due to population growth, migration to urban centers in water-scarce regions, and climate change. Increased scarcity will in turn drive price increases and potential for conflict. The ability of a country to equitably deliver freshwater may thus be the difference between survival and peace or war. Past solutions have relied upon massive water projects that convey freshwater from water-rich to water-scarce regions, but such strategies are energy intensive, costly, and contentious when political boundaries are crossed. Seawater desalination can be even more energy intensive, and is constrained to near-ocean locations. By contrast, reuse of treated water creates local supplies that offset demand for imported water. In the developed world, such systems are typically add-ons to existing centralized treatment plants, and purified water is pumped from these facilities to local users. In the developing world, the costs of such systems are prohibitive, and a new approach is needed. What might be done with mass-produced modular systems equipped with accurate and rapid monitoring technology? What would be the obstacles and the pay-offs?