Preventing Odor Problems

Oxygen injection eliminates concerns over stagnant flow in wastewater system.

Preventing Odor Problems

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An old golf course went out of business in Granby, Colorado, leaving a large parcel of vacant land that a development company soon acquired. An RV park was built and the remaining land was prepared for a planned neighborhood and modular home construction.

The RV park needed an immediate option to handle waste flow, but at the same time, the system needed to be able to handle the planned neighborhood as occupation grew.

A study was done to see how they could relay wastewater from the new developments to the treatment plant while accounting for expansion and varying flows. Gravity sewer was out of the question, so the developer opted for force main.

A predicted problem with the design was realized right away; the force main was long, and its use was going to be largely seasonal until the housing development was fully occupied. The RV park would create a situation that was busy in the summer and mostly stagnant in the winter. 

Roughly 3,500 feet of 4- and 8-inch force main was installed. The 4-inch pipe was installed for the slower months and times with minimal use, and it would switch to the 8-inch during the busy season. But the long retention time of stagnant water in the pipes not being used would create odor issues and action was needed to keep the smell under control. 

In situations like this, chemical treatment for odor control is a common practice, but the superintendent of operations for Granby Sanitation District, Andrew Becker, shied away from that method for a few reasons. 

“Supply is something I worried about right away,” he says. “Due to the remote nature of our location and the fact that shipments need to get over a mountain pass.” Also, with the harsh winters in the Rocky Mountains area, he had concerns about chemical storage during the long periods of subzero weather. 

The most important reason to avoid chemicals in his opinion was that the discharge from the treatment plant goes into the Fraser River, which eventually empties into the headwaters of the Colorado River. 

“The Colorado River is in a crisis right now, and with that, the state continues to change regulations to protect the river,” Becker says. “I was really wary of any kind of treatment process that involved chemical addition that could potentially add constituents that would need to be removed to be in compliance with my discharge permit.” 

Becker had another option in mind that he wanted to investigate further — oxygen injection.

Getting started 

Becker consulted with Steve Hanson, president of Ambient H2O. The environmental engineering company was involved with the force main installation, and together they discussed oxygen injection options. Hanson knew about a system from Anue Water Technologies called the FORSe oxygen injection system and contacted the company. 

Anue began working with the team in Granby right away to learn the specifics. “Every application goes through an engineering study by Anue where we collect data upfront, such as the length, diameter, detention time and information on the resident pumps like if they are on/off or variable frequency drive,” says Greg Bock, vice president and general manager of Anue.

Following the gathering of information, in December 2020, Anue technicians set up and ran a pilot at the location to prove the technology worked and to dial in the engineering further.

Once the engineering was dialed in and the final system arrived in Granby, the Anue technicians took everything off the flatbed, placed it on a concrete pad and had everything up and operational in under 48 hours. “It was very plug-and-play on our end for setup,” Becker says. “It came all set up from Anue and ready for us to use.”

Nuts and bolts

Hanson was familiar with how the FORSe worked, which was a large part of why he felt comfortable trying the system.

“Anue is a pure oxygen injection system whereas other injection systems inject atmospheric air, which is almost 80% nitrogen,” Hanson says. “Oxygen, or air, has a fairly low solubility in liquid, so if you’re wasting 80% of it on something that doesn’t improve the process, that’s not efficient.”

The FORSe is designed to increase productivity by eliminating the unnecessary gases. “The Anue system can take ambient air, compress it, store it and run it through oxygen generating equipment producing 90-93% pure oxygen,” says Bock. “Then we utilize the pressure of the force main to keep the oxygen solubilized.” 

Since it has been up and running, Becker says maintaining the equipment has been easy. “There are compressors that we monitor and oil that needs to be changed, but that’s about it,” he says. “We have log sheets we use to record everything from purity of the oxygen being generated to hours run. It’s really very simple.”

Along with stress-free general maintenance, Becker notes a draw for him is the components used within the technology.

“A lot of the system is built from things I can purchase from any electronic supply warehouse,” Becker says. “We are in the Rockies, if I need a specialized part, I have to question how fast I can get that stuff out here. This system is nice and simple and our guys are able to find relays or basic parts locally.”

Results matter

The system has been functional for almost two years now. Since the development is still not at full capacity, the system hasn’t yet been tested at peak flow, but Bock says the current low capacity is as good a test as any other. 

“The largest problem you’re going to have is during the slow times or winter months due to the detention time of the waste sitting in the lift station,” he says. “As it sits, it’s going to go anaerobic and when that happens, it will generate the hydrogen sulfate gas. So right now, when the waste is sitting without high flow is the toughest test for the system. High flow is actually beneficial.” 

Testing and monitoring hydrogen sulfide and other gases have been ongoing and so far, the Granby development has had zero odor or hydrogen sulfide issues. Testing will go on as the development continues to fill out.  

Most test samples are sent to an outside lab for detailed results, but Becker says one of the more critical tests they have is the least scientific.

“Because of the nature of the system being in the middle of town and surrounded by people, for us the most important test is the ol’ sniff test,” he says. “And so far, zero public complaints, and right there is testament to the effectiveness of the system.”

The success of the technology is critical to Becker and the Granby Sanitation District. “It’s very important that the district is taken care of. My job is to operate a publicly owned facility. I am working for the constituents,” Becker says. “And because of that, I require that I get the best service, the best product and that the people are taken care of for the next however many years. And through this whole process, I got what I wanted.”


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