Complaints about sulfide odors from manholes and lift stations can be a major headache for clean-water utilities. So can corrosion of wastewater infrastructure.

Traditionally, agencies have used chemicals such as calcium nitrate to mitigate hydrogen sulfide formation. As the price of chemicals has spiked in recent times, and as sustainable operation takes on higher priority, utilities are looking to alternate solutions.

One such solution is the injection of wastewater force mains and lift stations with oxygen and ozone generated on site. Anue Water Technologies offers FORSe Series treatment technologies for H2S mitigation, eliminating odor issues and preventing corrosion of infrastructure.

FORSe 2 units inject highly pure oxygen into force mains to counteract the sulfate-reducing bacteria that create H2S. FORSe 5 units inject oxygen into force mains and ozone into the air space in lift stations.

Gregory Bock, Anue vice president and general manager; Jon Amdursky, director of marketing and communications; and Kenny Graham, sales engineer with Anue channel partner Tencarva Southern Sales, talked about the technologies in an interview with Treatment Plant Operator.

What do you see as driving interest among utilities in technologies like yours?

Amdursky: One of the catalysts we’ve seen over the past year is the price of calcium nitrate, which most municipalities use to treat force mains and lift stations for H2S mitigation. In the past 12 months (as of May), the price of nitrates has gone up 149%, and it’s hitting municipalities all over the United States. They are also being incentivized on the positive side by the federal Infrastructure Investment and Jobs Act, which includes $55 billion for eco-friendly water and wastewater projects.

Is there any movement toward non-chemical solutions for sustainability reasons?

Bock: Yes, sustainability is a factor, and so is safety. After a change to on-site oxygen generation, there is no longer a need for a big truck to pull up and fill a chemical tank.

How does your technology differ from other offerings that use pure oxygen?

Bock: There are companies that supply liquid oxygen, which has a temperature of about minus 300 degrees F. We generate our oxygen and ozone on site from atmospheric air.

How does your technology concentrate oxygen?

Bock: The FORSe 2 process takes atmospheric air, compresses it and pushes it through an oxygen generator that produces 90-93% pure oxygen. We then run that pressurized and concentrated oxygen through multiple sensing technologies for flow, pressure and purity. Using that data, our software and custom control cabinet deliver the precise amount of oxygen required to keep the force main in an aerobic state, with a positive DO at the point where it finishes its path. If you have positive DO, you will not have H2S.

How does the ozone generation technology function?

Bock: The FORSe 5 system produces and injects oxygen into the force main in the same manner as the FORSe 2. It then takes a side stream of the pure oxygen and runs it through an ozone generator. It infuses ozone into some of the wastewater and sprays it into the lift station air space. That leaves a low ozone residual in the headspace of lift stations, preventing H2S odors from forming and escaping to the air outside.

What infrastructure is required to install these systems?

Bock: The system requires proper HVAC, along with 480-volt, three-phase, power. All necessary voltage changes occur inside our control cabinet.

In what forms can these technologies be delivered?

Bock: We have the flexibility to deploy individual components that can fit into an existing building at the lift station. If it’s a greenfield application, then the building can be designed around our equipment. Lastly, we have done multiple plug-and-play systems where we install the oxygen generation equipment in insulated, prefabricated containers with LED lighting, foam insulation, HVAC and electric or gas heat.

How long does it take to deploy a system?

Bock: From purchase order to delivery, typically 14 weeks. We have dealt with recent supply chain challenges by stocking the long-lead-time items in our warehouse.

How does Anue engage with clients interested in the technologies?

Bock: We share with them the return on investment and the value of using on-site oxygen generation instead of chemicals or other technologies. When a client requests a trial, we ask them to collect data before we arrive on DO, liquid sulfide and H2S gas levels. Then we bring one of our mobile demonstration units, which are full-scale trailers, 24 by 10 feet and 10 feet high.

What information does the client receive as a result of the demonstration?

Bock: Within 36 hours we can typically demonstrate reductions in H2S and liquid sulfides, and an increase in DO. The client receives that data and makes a decision. At times, after we finished the pilot, the client has persuaded us to leave the mobile unit there while they waited for their system to be built.

What is the typical simple payback on a unit versus using chemical treatment?

Bock: The typical payback is 18 to 24 months.

Can you cite an actual example where these technologies have solved a problem for a community?

Graham: The city of Pikeville, Kentucky, had an issue with odor complaints from a pump station and manholes near a large department store and commercial complex with shops and restaurants. That station pumped a little over a mile to the wastewater treatment plant, and when building a new plant they noticed more than typical odor at the headworks. We demonstrated FORSe 5 unit. Their highest H2S reading was 450 ppm, which is extremely high. We put the system online and after a couple of days we were getting readings of zero to 20 ppm. They ended up buying the system.

How can communities absorb the capital cost of a system?

Bock: For municipalities that can’t afford the upfront capital cost, we solve the problem with Anue’s unique rental or financing program through a lender. Either of these turnkey rental or financing programs immediately push the monthly cost down below what they are currently paying for chemicals.