Sustainability: Phoenix Wastewater Biogas

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The City of Phoenix Water Services Department will soon be selling biogas from its 91st Avenue Wastewater Treatment Plant. The gas is a result of the natural breakdown of organic matter in the wastewater treatment process, and currently most of it is burned off. Kathryn Sorensen, water services director for Phoenix, and Dennis Porter, assistant water services director, will discuss the venture.

Ted Simons: Tonight's edition of Arizona sustainability looks at turning waste into cash. The city of Phoenix water services departments will soon Selby yogas from its 91st avenue wastewater treatment plant. Here is Katherine Sorensen, Phoenix water services director, Dennis Porter, the department's assistant director. Good to have you here.

Kathryn Sorensen: Thanks for having us.

Ted Simons: What is biogas?

Kathryn Sorensen: So wastewater treatment plant does a couple of things. We reclaim water itself, wastewater, to a really high standard for reuse. That wastewater is then reused at the Palo Verde nuclear plant. It's also reused in local agriculture and for wetlands out of the Tres Rios facility. The biogas is actually a process related to digestion of the solids at the plant. Just like your body treats both liquids and solids a wastewater treatment plant basically does the same. When we treat the solids a natural buy product is methane gas. What we can do is actually take that methane gas, clean it and then put it into a natural gas pipeline. We can sell that gas on the green energy market in California.

Ted Simons: Interesting, as far as the process for this, what's happening to all this waste right now? Is it being burned off?

Dennis Porter: That's exactly what's happening now. We have three large flares and we flare off that gas product as a waste by product into the atmosphere.

Ted Simons: Interesting, so instead of doing that, I read as well -- [speaking simultaneously]

Dennis Porter: Very little.

Ted Simons: Now instead you're going to sell it.

Dennis Porter: That's correct.

Ted Simons: Who you going to sell it to?

Dennis Porter: We're going to sell it to AMARESCO, a third party developer that is going to construct and operate the facility. It will be up to them to sell it on the market. We'll just sell them the gas directly.

Ted Simons: How much does -- what kind of market we got here?

Kathryn Sorensen: Actually apparently it's a robust market, particularly in California where there are targets set for use of renewable energy. We're able to sell it and make a pretty decent profit, which is a great thing not only for the city of Phoenix but people don't recognize the treatment plant is jointly owned by the cities of Phoenix, Mesa, Scottsdale, Tempe and Glendale.

Ted Simons: I read 50% of the revenue will go to Phoenix.

Dennis Porter: That's correct.

Ted Simons: Where does the other 50 go?

Dennis Porter: Shared amongst the other cities they will benefit as well.

Ted Simons: We have shots of the plant. Tell us; run us through the process how this works. Water comes in, it's treated how?

Dennis Porter: The water we're basically treating two streams, the liquid stream and the solid stream, what we call the biosolids. Everything else that's flushed down through your sinks, your toilets. We treat both of those. With respect to the biogas we're treating the biosolids. Right now we are treating them in the aerobic digesters, dry them a little bit more and they are taken out and used as fertilizer for nonfood crops. Methane is generated during the process which is right now burned off. We'll take that, scrub it, clean it and reuse it.

Ted Simons: Transfer it by way -- I think we have a shot of the pipeline. Is this a new pipeline? Something built for this purpose?

Kathryn Sorensen: It's something that will be built for this purpose. There's an old pipeline there. Apparently the city of Phoenix did this many decades ago but didn't find it lucrative enough because back then there wasn't a market for renewable energy. It's that market that makes it so worth doing.

Ted Simons: Again, this is -- we have done a number of stories on this plant. Tres Rios, now this. A lot of stuff out there is being recycled.

Kathryn Sorensen: It's cool. For the first time ever what we're able to say is that everything that comes out of that plant is beneficially reused. It's part of a circular economy idea. We'll be reclaiming the water. What's interesting about that is that a lot of people don't understand that the city of Phoenix and partner cities have been reclaiming this wastewater for 40 years. A lot of communities across the west are only just now realizing how valuable this resource is. So we have really been leaders. We will be raising the wastewater itself, reclaimed water, biosolids now the biogas in the California green energy market.

Ted Simons: The goal is 15% renewable energy city-wide?

Dennis Porter: That's correct. We'll be meeting that goal earlier than we had hoped.

Ted Simons: The original goal was 20 something?

Dennis Porter: 2025.

Ted Simons: Now what?

Dennis Porter: We think we'll be there by 2018.

Ted Simons: Is this online already?

Dennis Porter: It will be online spring of 2018.

Ted Simons: All right, good luck with this. Congratulations. Sounds like a great deal. Good to have you here. Thanks for joining us.

Dennis Porter: Thank you.

Kathryn Sorensen: Thank you.

Kathryn Sorensen: Water Services Director for Phoenix, Dennis Porter: Assistant Water Services Director

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