Flushing with reclaimed water: A roadside rest stop takes on the drought

Fri, 2015-05-01 06:00 -- Doug Peeples

For a state withering in the midst of a persistent drought, the current National Weather Service forecast for California isn’t pretty: "… there is little chance if any for improvement." That’s why water conservation efforts, like one underway at a state highway rest stop, is a source for real optimism. And a solution other cities and jurisdictions concerned about saving water may want to consider.


The amount of water the California Department of Transportation’s (Caltrans) 87 rest stop toilets use is staggering: between one and five million gallons per year. The Dunnigan rest stop north of Sacramento on State Highway 5 alone uses 4,000 to 5,000 gallons of water every day.

Reclaiming the lost wastewater
But, as an article in Huff Post Green reported, the rest stop will soon have a closed loop wastewater system to filter out the sewage, with the remaining water used over and over to flush its toilets. Jerry Marcott, senior sanitary engineer for Caltrans, said the Dunnigan water system won’t be a one-off. The agency is looking at taking the technology to other rest stops over the next several years.

Rest area wastewater systems aren’t going to solve California’s water shortage, but they are a step in the right direction. And they get bonus points for taking sustainability even further.

Filtering wastewater with plastic trash
Discarded plastic, in the form of water bottles and other items, has long been considered a serious environmental problem. But it turns out that it’s an ideal material to use in the closed loop wastewater system filtration process. Shredded plastic offers a low-volume material with a lot of surface area that is essential to the treatment process.

University of California at Davis scientists were given the opportunity to run the Dunnigan system for eight months. A problem they encountered was the plastic bottles they used in the filtration process had to be shredded by hand, a laborious and time-consuming chore. Replacing plastic bottles with polypropylene plastic took care of that problem because it can be mechanically shredded. Also, the systems for relatively small-scale use in rest stops are fairly simple because they don’t require the more extensive filtration procedures required by larger operations.

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Doug Peeples is a Portland, Oregon-based writer specializing in technology and energy. Follow @smartccouncil on Twitter.

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