When water runs down the drain or we flush it down the toilet, we usually don’t care where it ends up. This is because with adequate basic sanitation, wastewater shouldn’t be a concern. Yet, although humanity has already taken man to space and plans to colonize Mars, it continues to fail to provide basic living conditions for a large part of its population. A comprehensive study estimates that 48% of global wastewater production is released into the environment untreated. The UN, in turn, presents a much less encouraging figure, citing that 80% of the world’s sewage is released without treatment. But returning to the question of the title, there are basically two destinations for sewage if it is not being released directly into the natural environment: it can be treated locally through septic tanks, or connected to a sewage treatment plant through the sewage network, eventually returning to nature after a series of treatment processes.