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“Waste”water No More, Arizona Sees the Value in Effluent

Our dogs love an adventure.  They also understand English and can read minds.  They know when its time for a R-I-D-E or a W-A-L-K.  So last weekend we took advantage of the gorgeous weather to take the dogs out to the Riparian Preserve at Water Ranch in Gilbert.  The place is really incredible; it's a 110-acre wildlife preserve where migrating snowbirds (the flying kind) come to live in the winter. It's also a groundwater recharge facility, where reclaimed wastewater percolates back into the aquifer.

The Water Ranch is just one example of Arizona's forward thinking on wastewater reclamation, reuse, and recharge.  Reclaimed water is highly treated effluent that has been treated to a standard deemed safe by the EPA and Arizona Department of Environmental Quality.

Most of the effluent reclaimed in Arizona is reused for industrial purposes (like power generation) and for landscape irrigation (most golf courses in the metro area can only be watered with reclaimed water).  Some is used for recharge - that is, put into basins where the water percolates back into the aquifer.

As Arizona's population continues to grow and water availability remains the same or decreases (Colorado River flows, for example, have fallen significantly), the value of reclaimed wastewater has understandably increased - it's now seen as the valuable commodity that it is, and - increasingly - as a good substitute for drinking water in a lot of uses (like irrigation).

So the headline in last week's Business Journal wasn't really a surprise: "Cities could reap $1B in effluent deal with utilities."  Since its inception, Palo Verde Nuclear Generating Station has used effluent from the 91st Avenue Wastewater Treatment Plant in Phoenix.  Nuclear power generation is an incredibly water-intensive process; Palo Verde was the first US plant not built on a major body of water.

The article brought a couple of interesting points to mind:

1) The need for treatment to match use.  While most golf courses in Phoenix may only be irrigated with reclaimed effluent, a lot of landscape irrigation is still done with the same water that we drink.  Yet treating water (no matter the source) to drinking-water standards is far more energy-intensive, and costly, than treating water to slightly-lower non-potable standards for irrigation. 

We should use reclaimed effluent, treated just to irrigation standards, for irrigation purposes and drinking water treated to drinking water standards just for drinking and bathing.  That would conserve the state's precious water resources and save on treatment costs and energy usage.

2) The need for truer-cost water pricing.  Herb Guenther, director of the Arizona Department of Water Resources has long said that the "era of cheap water is over."  That is true in part because as demand increase but supplies remain constant (or diminish), competition for the resource intensifies, and the price of water rises. 

It's also true because we've picked all of the proverbial low-hanging fruit to feed Arizona's current populations.  We've already pumped the aquifers more than we can sustainably pump them.  We've negotiated and re-negotiated water rights contracts with the Indian tribes.  Our Colorado River allotments are set.  There are no more easy answers; new water supplies to serve new populations will be more expensive.  Increasing water reclamation and reuse, for example, will require the construction of new infrastructure to reclaim wastewater and deliver it to end users.

The water chapter in the 2008 AIC Arizona Infrastructure Study explained the issue well:

Currently, water isn't being treated in places where it can be reused, and it's expensive to build pipelines to get reclaimed water to where it's needed. 

According to ADWR, a new model that providers are using to work around the problem of older infrastructure involves scalping plants, or smaller reclaimed water treatment plants located in areas where the reclaimed water can be used.  The scalping plants take the water out of the wastewater stream and treat it, sending the sludge on to the main wastewater treatment plant.

Another infrastructure issue associated with water reclamation and reuse is seasonal storage. Global Water Management LLC uses reclaimed water retention structures (effectively lakes) to store reclaimed water - which is produced at a fairly constant rate throughout the year - to be used when its most needed (use of reclaimed water is highest in the summer, when demand for water for irrigation is high).

3) The opportunities effluent poses.  Sharon Megdal, Director of the Water Resources Research Center at the U of A says that the use of effluent for potable and other water needs is the next major new water source for Arizona.  Certainly reclaimed effluent could be used for drinking water purposes - the technology exists to clean wastewater to higher standards even than drinking water is currently treated to.

So as we walked the dogs past the Gilbert Water Ranch recharge basins, I thought about how innovative the state has been in reclaiming and reusing this precious natural resource.  And about how we can - and must - do even more.

Written on Tuesday, 06 April 2010 16:00 by Gary Yaquinto

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