There are various ways to control wastewater treatment plant odors — chemical scrubbers, biofilters, carbon adsorption systems and others. They involve varying levels of capital, operation and maintenance costs.

Aerisa has developed an alternate approach that it says can deliver effective odor control at lower total cost of ownership while creating healthier work environments. The system is engineered to address a wide range of airflows and to suit applications that include headworks buildings, dewatering rooms, truck loading facilities, process tank headspaces and pump stations.

The Aerisa technology pushes ionized air containing positively and negatively charged oxygen molecules (O2+ and O2-) into the spaces where the odors are released. These ions attack contaminants there and odorless air is then discharged to the outside.

The company says the technology can be easily retrofitted in most municipal wastewater treatment facilities. Andrew Weiller, director of sales and marketing, talked about the technology in an interview with Treatment Plant Operator.

TPO: Why is this technology a good fit for the municipal wastewater sector?

Weiller: The legacy types of odor control equipment work quite well, whether that’s chemical scrubbers or biofilters. Our technology is equally effective but offers lower cost of ownership, uses significantly less energy and has a much smaller footprint. And there are no hazardous chemicals or spent carbon to replace and dispose of.

TPO: How does this technology help improve indoor environments?

Weiller: An aspect on odor control that has always been muted in the industry is protecting the workers inside the buildings. In headworks and dewatering buildings, for example, people have to go inside and change pumps and valves and do maintenance. They’re in atmospheres that may have 5, 10 or 15 ppm or higher hydrogen sulfide and other gases. Legacy odor systems treat the air after it is exhausted from the building. Our technology creates a highly ionized airflow, delivers that to the space, and removes the gases as they’re produced.

TPO: Are there other advantages to the ionization technology?

Weiller: These buildings have process equipment, pipes, valves and corrugated metal roofs. The gases removed in the exhaust stream typically contain airborne acids that can cause corrosion and deterioration of the building and the process within. Our technology creates an acid-free environment so that corrosion is under control and building life is extended.

TPO: What kind of regular maintenance does this system require?

Weiller: The only replacement parts are the ionization tubes, and they need replacing every 12 to 18 months.

TPO: Was this technology used in other industries before being introduced to the municipal market?

Weiller: Yes. Ionization has been around since the early 1900s. In the commercial sector, it’s used in facilities such as schools to clean the air where there are large occupancies. It’s used in commercial buildings for indoor air quality and the reduction of outside air requirements. Another application is in casinos to counteract cigarette smoke and bar odors.

TPO: Please briefly describe how this odor control process works.

Weiller: The equipment consists of an air-handling unit containing a blower, a bank of ion generators, and a particulate filter to protect the ion generators. We take ambient outside air and blow it across the ion generators, which strip electrons from oxygen (O2) molecules to produce clusters of positive and negative oxygen ions. These clusters are delivered to the space through specialized ductwork, and there they react with the odorous gases produced inside the building.

TPO: How are the odorous gases destroyed?  

Weiller: To take one example, when the ion clusters come in contact with ammonia, which is NH3, the ammonia molecule is converted to the byproducts of nitrogen gas (N2) and water. In the case of hydrogen sulfide (H2S) the byproducts are hydrogen, oxygen, water vapor and elemental sulfur, which is a non-odorous physical particle that falls out of the air.

TPO: How do you go about designing and sizing systems to suit a facility?

Weiller: The first step in sizing the equipment is to determine the volume of the room. Our approach is to produce 12 air changes per hour. Then we size the ion generators based on the contamination load: How many ions do we need in order to remove, say, 10 ppm of H2S?

TPO: How do you mitigate the impact of cold outside air on the indoor spaces?

Weiller: We can combine heating with the odor control. In colder climates, we can put a gas-fired heater into the air handler, so we’re not blowing zero-degree air into a building. On the other side, we can have a heat recovery system on the exhaust and reclaim some of that heat and put it back into the building.

TPO: How widely is this technology used in the municipal wastewater sector?

Weiller: It has been in the market for about 10 years. We have several installations throughout the United States and Canada. We recently closed a project in Knoxville, Tennessee, that is the largest ionization odor control project in North American history. It’s two systems, each with in excess of 40,000 cfm airflow, with heaters, automated dampers and controls that communicate with an on-site SCADA system.

TPO: How would you characterize this technology’s effectiveness?

Weiller: The proof of the pudding is the human being — it’s the nose. If you walk into one of our installations and ask the operators if the system is working, you’ll get the same reply: They never notice when it’s working, but they definitely know when it’s not working. If the system is turned off or there is a power failure, the odor will increase quickly and dramatically so that they know immediately that it’s offline. That’s the best proof we can provide.