Making The Most From Wastewater

Wastewater plant managers are well aware that they can put a price tag on the water they treat and the byproducts that result. But many still wonder: what number should that tag show and where will they find the highest bidder?

Dr. Craig Criddle, a professor of civil and environmental engineering at Stanford University, was inspired to find out.

“I attended a workshop in 2008 where Professor Willy Verstraete of Ghent University presented his analysis of the value of wastewater,” Criddle recalled. “His work inspired me to take a more detailed look at what might be possible. I wondered how high the value could be if different value chains and markets are considered.”

Following that workshop, Criddle began doing research of his own. He found that, when purified and sold, the water recycled from a cubic meter of typical domestic wastewater could generate $3 per 1,000 gallons for agriculture or $6 per 1,000 gallons for potable use[1]. The organic matter found in a cubic meter of domestic wastewater, when composted, is worth four cents per 1,000 gallons — but if it’s converted to methane, it can be much more valuable. If used to produce power, the methane could generate 20 cents per 1,000 gallons. If the biogas is used to produce compressed biomethane, it has potential revenue of 32 cents per 1,000 gallons.

Criddle also explored some options that may be new to wastewater plants looking for sources of cash. He found that using methane as feedstock can produce even higher value. Converting organic waste into methane and then that methane into a fish food supplement can potentially generate revenues of more than $1.25 per 1,000 gallons, per Criddle’s findings. However, it may be some time before this is a practical option for many plants.

“Conversion of methane into fish food supplement is something we can do at the bench now, but we need to scale it up,” he said. “This scale-up is something we are working on in Bangladesh, where there is a large shrimp industry that might benefit from the product.”

As for why more wastewater plants aren’t taking advantage of the opportunity to sell recycled water, Criddle offered several explanations. He cited the high cost of treatment and delivery, as well as the popular opinion that recycled water may have trace contaminants, which drives down its value.

“Clearly, local markets are needed,” he said. “Some places, like the arid West, have severe water scarcity so markets are present and demand is high. Other places have abundant clean freshwater so demand is low. Of course, it is also possible that some municipalities just are not aware of the revenue potential.”

When it comes time for a wastewater plant to pursue one of the revenue opportunities he recommends, Criddle urges diligent research of their own to determine which avenue is best for them.

“I would begin with a market analysis for different products,” he said. “If stable markets can be identified, then it is a question of the cost required to create the products of interest.”

Wastewater treatment plants know that what they’re doing has value, but a little more research might tell them, and potential buyers, just how much.