There’s something of an internet meme out there that makes the following claim: “Statistically, at least one molecule of H2O out of every glass of water you ever drank once passed through a dinosaur.” It’s difficult to verify the claim (and similar assertions have been made about Moses and Oliver Cromwell), but the spirit of the statement—that water is perpetually recycled—is accurate. Every glass of water we’ve ever drunk includes atoms and molecules that have passed through someone or the other and probably much more recently than the Jurassic. Mother Nature is the grand recycler; however, we can short-circuit her process to address our more immediate needs. And we’ve been doing it, knowingly and unknowingly, for hundreds of years.
At the end of the day, every Texan knows that what comes around goes around—and that wet water is better than no water at all.
Although some make the argument, with some merit, that we should just refer to all reuse as simply “reuse,” it’s sometimes helpful to parse “reuse” into different types. For most places, the largest category of reuse is de facto reuse. For example, a city typically pumps water out of a river, treats that water, runs it through its distribution system, uses it, treats the resulting wastewater, and discharges the treated wastewater back in the river, and then a downstream user repeats the same process. This is known as de facto reuse because it’s simply happening (it’s unplanned and not officially recognized), and not necessarily (and typically not) for water supply purposes. This type of reuse has been occurring for hundreds of years (perhaps without the wastewater treatment part if we go far enough back in time…). “Indirect reuse” is similar (the key part is reclaimed water enters an environmental buffer prior to water treatment) but with the express purpose of augmenting water supply. “Direct reuse” refers to the lack of an environmental buffer and is sometimes called “pipe-to-pipe”. Indirect and direct reuse may also be further divided as to whether or not the water is used for potable or non-potable purposes.
The potential for reuse as a water supply in Texas is immense. First, wastewater is a local source of water already in possession of the user (assuming that there aren’t return flow requirements). Once our growing cities have fully tapped their local groundwater and surface water supplies, the pursuit of new groundwater and surface water carries them to rural areas where environmental, property right, and cost issues can make importation difficult. Secondly, the volumes from reuse can be appreciable. Although there’s not a one-to-one relationship between water put into a drinking water distribution system and water that goes into the wastewater treatment system due to leakage (both on the supply and waste sides) and uses that don’t return flows to the system (for example, landscape irrigation), there is still a considerable amount of untapped water available. For example, the Dallas-Fort Worth area discharges 500 million gallons a day to the Trinity River, enough water, if treated, to meet the needs of about 5 million Texans.