Odor control

The U.S. Environmental Protection Agency (EPA) says that poor indoor air quality is one of the USA’s biggest environmental health concerns. In fact, they estimate that the air you breathe inside your home or business is typically 4 to 40 times worse than the air outside. Many countries citizens spend over 90% of their time indoors. The air inside retains odors from a number of common sources, from cooking and waste to pets and smoke. These types of contaminants present air quality challenges for even the best-kept homes or tight run businesses, especially when windows are kept closed while heating and air conditioning units run year-round. Stale air is trapped and recirculated throughout the house or building. Even though ventilation systems have filters, these particulate filters are only designed to physically trap larger airborne particles, like dust and dander. They are not effective with bacteria, viruses, mold or microscopic contaminants that can cause odor.

Ozone systems are available that offer a variety of air treatment systems for commercial and residential applications that can reduce many of these indoor pollutants. One method is to ozonate the air circulating through HVAC duct systems. After the air is scrubbed, an ozone ambient monitor is required to make sure the cleaned air entering a room where people may be located contains no residual O₃. Other devices are designed to destroy and prevent mold and other microbial growth from rooftop fan coils, walk-in a/c coils and the air.

Health Canada regulations say that 24/7 human exposure to Ozone should be no more than a daily time weighted average of 40ppb and the FDA say no more than 50ppb.

Ozone neutralizes hydrogen sulfide and other odors from lift stations, wet wells and sewage treatment plants. Ozone may be delivered into headspace via direct injection or a blower for in-situ odor control, or odors may be exhausted into a contact chamber for ex-situ treatment. A contact chamber is used when treating odors from a sewage treatment plant. Food and industrial processing odors are also controllable through neutralization with ozone. Ozone is consumed in the reaction process, so with proper dosage in relation to the odor load and sufficient reaction time, the end result is no odor and no ozone residual. The contact time for O₃ reaction with H₂S is generally accepted as 20-30 seconds. A typical ozone system consists of an ozone generator, a source of compressed air, and an air dryer for ozone generator feed gas preparation and a contact chamber.

Systems should have ozone monitors and modulating controls to regulate ozone production. An ozone contact chamber is utilized to provide reaction time that is not achievable in a stack or duct. Ozone is introduced into the contact chamber by a sparger inserted in the odor supply duct. This injection point may be at the entrance to the contact chamber or further upstream of the odor supply duct. If ozone is being introduced into a smaller scale (wet well) this application is often designed for ozone to be delivered directly into the headspace of the wet well. Since ozone is heavier than air, if it is introduced near the water surface, an ozone blanket will form. As odors escape from the water they are oxidized.