More than a green thumb

City's method of treating wastewater produces big yields for wheat grower

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Craig residents are still waiting for the opportunity to recycle cans and bottles, but the city has had another recycling program of sorts for a number of years.

At the Craig Wastewater Treatment Plant, human waste is turned into fertilizer for city-owned wheat fields.

The process is a cost-effective method of disposing of biosolid waste, Wastewater Treatment Plant Supervisor Mike Frazier said.

And the fertilizer the process produces raises excellent wheat crops, said Jerry Thompson, who leases the wheat fields from the city.

"Mankind produces a lot of waste, and if you can use it, it just makes sense," Frazier said.

Here's how the process works:

The waste is pumped from the treatment plant into a nearby lagoon. When it's pumped from the plant, the material is 98.5 percent water.

In the lagoon, the waste is aerated for six months. This helps stabilize the waste, and it minimizes the odor.

The sludge freezes over during the winter, and come spring, the treatment plant crew is ready to begin drying the material.

From May until the beginning of August, the sludge is stirred once a week. After four weeks it has dried from a liquid to a mud, and in a few more weeks, it's a paste.

By August, the sludge has been dried until it only contains a water content of 7 percent.

"When the drying is complete, you can't tell the difference between it and good, rich soil," Frazier said.

The process produces about 100 dry metric tons of fertilizer, and it disposes of all of the city's human waste.

The process of drying the sludge was created by the employees of the wastewater plant two years ago, with David Mondeau taking the lead, Frazier said.

Before that, the sludge was spread on the fields in a liquid form.

"As long as we're in a dry spell, we're OK, but if we go back to a wet cycle we might have to change the way we do things," Craig Public Works Director Bill Earley said.

The city is required by state law to dispose of the sludge one year after treatment is finished. In a wet year, it may not be possible to dry the sludge with the required time frame, Earley said.

But for now, treatment plant employees are happy to dry it before spreading it.

Spraying the sludge wasn't the healthiest of fertilizing methods, Frazier said. The employees constantly breathed in the sludge mist spraying from the pipes.

It was also a time-consuming process that absorbed six weeks of four employees' time. One had to constantly stir the sludge, a second had to drive, and two others had to constantly move the manifold pipe system that sprayed the sludge.

All that labor was expensive. Spraying the sludge cost the city $22,101 in labor costs in 2002, Earley.

By contrast, spreading the dry sludge with a fertilizer spreader pulled behind a tractor took one person 2 1/2 days. Labor costs totaled $1,210, plus another $4,000 to rent a tractor and manure spreader.

"The city of Craig has one of the least expensive biosolid waste disposal systems," Frazier said.

Other communities such as Telluride and Front Range cities have to truck their waste to distant agricultural sites.

The cut in labor time that spreading dry sludge provided allowed the crew to perform other duties, such as cleaning the city's sewer system.

This year, the city will pay Thompson $5,160 to spread the sludge on the fields, which are near to the wastewater treatment facility. Thompson will provide the tractor and fertilizer spreader.

During the past year, the sludge-fertilized fields produced 10 more bushels of wheat than Thompson's other fields.

"Nitrogen is the key. That's what the wheat needs the most," Thompson said.

Rob Gebhart can be reached at 824-7031 or rgebhart@craigdailypress.com.

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