Perspective: Stretching water supplies

Jack Zimmerman, an ex-classmate from the Rutgers University Class of long ago, now retired and living in Florida, recently sent me four pages describing an idea which, I presume, is not entirely original to him, but which may be of interest to readers. Zimmerman stated that articles appearing in CE News are interesting, but that he didn’t see mention of the most egregious misuse of the nation’s limited water supply—the use of potable water for flushing toilets.

"I live in the southwestern part of Florida where a huge influx of residential units is anticipated," Zimmerman wrote. "The idea of living in this wonderful pleasant land with severe water restrictions prompts this retired civil engineer to speculate on possible solutions [to current and future water shortages]. Having been involved with a large municipality [Zimmerman served as municipal engineer in Edison, N.J., for a number of years], I am aware of the frantic reactions to the loss of water or water pressure, the large investments in facilities, and the disruption of the road system [caused by] pipeline construction."

Zimmerman suggested a review of practices in water-poor areas such as Bermuda and the Virgin Islands to enlighten Americans about alternative practices used by others to stretch the limited supply. He offered the following three ideas for residential units:

  • Collect the discharge from washing machines, dishwashers, baths, and showers into a tank or sump and pump it to the toilet units with a low-volume (40-psi) pump activated by a pressure switch, maintaining a standard pressure on the grey water (non-sanitary fluid effluent) lines serving only the toilets.
  • Collect rainwater (of which there is plenty on the long-term average) and use that water for other than toilet purposes.
  • Maintain necessary water volumes in grey water and rainwater tanks with potable water lines that serve the hot water tank and cold water taps in kitchens and baths, using air gap or backflow preventers. Level controls or a timer, restricting this make-up flow to the early morning hours, would ease the peak-flow load on the utility system."

Zimmerman ended his suggestions with this: "Sounds complex, but, when compared to the sophisticated systems in current appliances, and the fact that you can purchase all the necessary components at your local Home Depot, [it’s not as complicated as it appears].

"What is needed is an organization to start campaigning and educating the public, and, particularly, the plumbing code enforcers, to a new way to use water. The current reuse thinking suggests taking clear waters, mixing them with sanitary waters, piping them to a treatment plant, separating them as best we know how, and then pumping the effluent to the home it came from for limited use for the irrigation of our lawns."

The system that Zimmerman outlined makes use of much of the water at least twice and also reduces the loading on the treatment facility. "There’s a challenge out there that we, as civil engineers, have been avoiding too long," he said. "Water, our second most important resource [after air], is being wasted in an alarming manner. The waste I’m referring to is the use of potable water for the function of flushing toilets as well as being the hydraulic carrier of sanitary waste from our homes to treatment plants."

I’m not sure if all of what Zimmerman wrote is 100-percent correct—but most of it makes a lot of sense to me. What I am sure of is that a plan for reusing grey water makes a lot of sense right now, while the burden of a burgeoning population is still sustainable. Even at the rate we waste water, it may not seem economically feasible to take all of the relatively stringent measures that Zimmerman alluded to.

However, as the population of the United States and the world grows, it will become increasingly difficult to provide for the needs of all those people who will inhabit the planet and use the limited water supply. One way to provide for the future is for governments to work on methods, as outlined above, which will permit more than 6 billion people to have a comfortable way of life.

Now is the time to address the problem outlined above—before we are faced with nationwide water rationing and widespread restrictive water laws as the population increases and as the amount of available water remains essentially constant. As engineers, we should be aware that this is a serious problem and we should be in the forefront of addressing it, since a solution certainly lies within our area of expertise.

Posted in Uncategorized | January 29th, 2014 by

The comments are closed.