Odor Control with Ozone

Ozone is an excellent tool in odor elimination applications as ozone will oxidize (reduce) odorous compounds to fully eliminate the odorous compound rather than mask or alter the odor profile. 

Ozone is generated from oxygen requiring only electrical power for operation.  Ozone is generated as a gas and is mixed with odorous air to oxidize odorous compounds and eliminate odor from air completely. 

Primary benefits of ozone use for odor control:

- Natural solution, naturally a green solution with no chemicals

- Chemical free (no residiuals)

- Fast and complete oxidation reactions

- Broad spectrum odor control

- Ozone is useful in both air and water applications for odor elimination

Common ozone odor removal applications:

Waste Management

- Landfils

- Garbage transfer stations

- Recycling centers

- Composting operations

Wastewater treatment

- Lift-stations and sump pits

- Force-mains

- Areation basins (ozone can be added to aeration air)

- Headworks and sludge handling

Food processing

- Wet scrubbers from rendering or other odorous processes

- Storage warehouse to eliminate cross odors, and long-term storage

- Meat, especially seafood processing rooms

- Aging rooms

- Spice warehouses

- Livestock facilities and livestock lagoons

Industrial exhaust, chemical manufacturing

- VOC control in exhaust gasses

As an oxidant, Ozone (O3) reacts directly with a wide variety of odorous compounds to reduce the compound and eliminate odors.  Due to the oxidation mechanism of ozone (O3) to naturally and quickly break-down to O2 and an unstable O atom the ozone reactions reduces, odorous compounds to create safe, non-hazardous, non-odorous compounds.

In ambient air applications where humidity is present Ozone (O3) will react with the H2O in the air to create -OH radical, a more powerful oxidant than ozone alone.

Ozone reactions with Common Odorous Compounds:

Below is selected list of some of the most common odorous compounds causing offensive odors and how ozone oxidizes these compounds.  While not comprehensive, these are excellent examples of the wide spectrum of odorous compounds that ozone will oxidize effectively to eliminate odors completely.

Hydrogen sulfide (H₂S)

- H₂S + O₃ → SO₂ + H₂O

- Odor Threshold0005 to 0.01 parts per million (ppm) or 0.5 to 10 parts per billion (ppb)

- H₂S is a common odor-causing compound from anaerobic decomposition of organic matter (e.g., food waste, sewage sludge). Its low odor threshold means even trace amounts contribute significantly to foul odors. Ozone efficiently and completely oxidizes H2S to only Surfer compounds and Water vapor.

Methyl Mercaptan (CH3SH)

- CH3​SH+O3​→CO2​+SO2​+H2​O

- Odor Threshold001 to 0.002 parts per million (ppm) or 1 to 2 parts per billion (ppb)

- Methyl mercaptan has a strong, unpleasant smell often described as resembling rotten cabbage, garlic, or sewer gas. Methyl mercaptan is a significant contributor to odors, and its low odor threshold means even trace amounts (e.g., from decomposing food waste or proteins) can cause noticeable smells.  Ozone oxidation of Methyl Mercaptan is efficient and complete requiring only one ozone molecule for each Methyl Mercaptan molecule.

Dimethyl Sulfide

- (CH₃)₂S + O₃ → (CH₃)₂SO + O₂

- Odor Threshold = 0.001 to 0.01 parts per million (ppm) or 1 to 10 parts per billion (ppb)

- Dimethyl Sulfide is produced during the anaerobic decomposition of organic matter, particularly from food waste or sulfur-containing materials. Its low odor threshold makes it a significant contributor to the characteristic "garbage" smell, requiring targeted odor control. Ozone efficiently oxidizes Dimethyl Sulfide to Dimethyl Sulfoxide, an odorless gas.

Ammonia

- NH₃ + O₃ → NH₂ + HO₂

- Alternative in humid environments (AOP reaction) = NH₃ + OH· → NH₂ + H₂O

- Odor Threshold04 to 0.05 parts per million (ppm) or 40 to 50 parts per billion (ppb)

- Ammonia is a significant contributor to odors, produced from the decomposition of nitrogen-rich organic matter (e.g., food waste, animal feces). Its relatively low odor threshold means that even small amounts can cause noticeable smells. Ozone can oxidize Ammonia to NH₂ and HO₂ which will create further reactions of HO2.  In environments where humidity is present the AOP reactions using -OH radical will speed these reactions.

Amines

- Trimethylamine

    (CH3​)3​N+O3​→CO2​+H2​O+NOx​

     Odor threshold: 0.21–2.1 ppb

- Dimethylamine

     (CH3​)2​NH+O3​→(CH3​)2​N+–O−

      Odor threshold: 34-47 ppb

- Methylamine

       CH3​NH2​+O3​→CO2​+NH3​+H2​O

       Odor threshold: 21-4700 ppb

       Amines are nitrogen-containing organic compounds produced during the decomposition of organic matter (e.g., proteins, fish,                 meat) in garbage transfer stations and landfills. The odor thresholds of common amines vary depending on their structure.                     Ozone efficiently oxidizes amines to odorless nitrogen based by-products, CO2 and water vapor.

Organic Acids

- Acetic acid

        Odor Threshold = 0.006 to 1.0 parts per million (ppm) or 6 to 1000 parts per billion (ppb)

         Partial Oxidation - CH₃COOH + O₃ → CH₃COOOH + O₂

         Alternative in humid environments (AOP reactions) = CH₃COOH + OH· → CH₂COOH· + H₂O

- Butyric acid,

         Odor Threshold = 0.0003 to 0.001 parts per million (ppm) or 0.3 to 1 parts per billion (ppb)

         C3​H7​COOH+O3​→CO2​+H2​O+Smaller organic acids (intermediates)

         Organic Acids are produced during the anaerobic fermentation of organic matter (e.g., food waste, dairy products). Its low odor               threshold makes it a significant contributor to the sour or rancid odors in these facilities, necessitating effective odor control                     strategies like ozone treatment or neutralizers.

VOC’s

- VOC = Volatile Organic Compound. This is a broad, generic term that encompasses many compounds.  VOC’s are defined as organic compounds, containing carbon that have high vapor pressure and are able to evaporate into the air at ambient temperatures.

- Ozone efficiently oxidizes VOC’s as there is a natural Aphinity for the valent oxygen molecule from ozone reactions to combine with the carbon from VOC’s to produce CO2.

- Some very common odorous VOC’s are listed above such as Dimethyl Sulfide, Methyl Mercaptans, Acetic Acid, etc. A few less common odorous VOC’s listed below:

- Formaldehyde (HCHO)

         Odor Threshold: 0.05–1.0 ppm (50–1000 ppb)

         HCHO + O₃ → CO₂ + H₂O or HCOOH (formic acid)

         Pungent, irritating, chemical-like odor, often associated with industrial processes or secondary reactions. Less common in waste           but may occur in chemical industries or as a byproduct of other VOC oxidations.

- Dimethylamine ((CH₃)₂NH)

          Odor Threshold: 0.034–0.047 ppm (34–47 ppb)

          (CH₃)₂NH + O₃ → (CH₃)₂NHO or (CH₃)₂N-NO (N-nitrosodimethylamine)

          Fishy or ammonia-like odor, less intense than trimethylamine, from protein decomposition. Found in waste facilities and                         livestock operations.

- Trimethylamine ((CH₃)₃N)

        Odor Threshold: 0.00021–0.0021 ppm (0.21–2.1 ppb)

        (CH₃)₃N + O₃ → (CH₃)₃NO (trimethylamine N-oxide) + O₂

         Fishy, ammonia-like odor, emitted from decaying proteins (e.g., fish, meat). Prevalent in transfer stations, composting, and food             processing.

- Toluene (C₇H₈)

         Odor Threshold: 0.17–33 ppm (170–33,000 ppb

         C₇H₈ + O₃ → benzaldehyde (C₇H₆O) or cresols → CO₂ + H₂O

         Sweet, solvent-like odor, less offensive but noticeable at higher concentrations.  Found in waste facilities handling industrial                    solvents or mixed waste.

- Ozone oxidizes all VOC’s

- Acetic acid

          Odor Threshold = 0.006 to 1.0 parts per million (ppm) or 6 to 1000 parts per billion (ppb)

          Partial Oxidation - CH₃COOH + O₃ → CH₃COOOH + O₂

          Alternative in humid environments (AOP reactions) = CH₃COOH + OH· → CH₂COOH· + H₂O

- Butyric acid

           Odor Threshold = 0.0003 to 0.001 parts per million (ppm) or 0.3 to 1 parts per billion (ppb)

           C3​H7​COOH+O3​→CO2​+H2​O+Smaller organic acids (intermediates)

           Organic Acids are produced during the anaerobic fermentation of organic matter (e.g., food waste, dairy products). Its low odor              threshold makes it a significant contributor to the sour or rancid odors in these facilities, necessitating effective odor control                    strategies like ozone treatment or neutralizers.

Ozone Applications – how is ozone implemented?

Odor control is an extremely broad field, there are a wide variety of uses of ozone in odor control applications.  Below are some examples and general suggestions for ozone implementation.

Lift Stations

Lift stations accumulate odors from stagnant wastewater within the lift station sump.  As water levels rise in the lift station sump, odorous air is displaced and pushed into potentially undesirable areas.  Ozone can be used to eliminate odors in the sump.

- Inject ozone into the headspace of lift station wet wells or enclosed areas where odors accumulate. This targets odorous gases directly at the source

- Introduce ozone into exhaust or ventilation systems to treat odorous air before release

- Bubble ozone gas into the wastewater in the sump to eliminate odors in the water and air. This may be useful for downstream applications such as a force-main.

Wastewater Force Mains

Force-mains are pressurized wastewater pipes that force wastewater under pressure against gravity.  These may be long distances and wastewater may be confined in this pipe for long periods of time.  During this time the anerobic environment promotes the creation of Hydrogen Sulfide (H2S) and Sulfate Reducing Bacteria (SRB).  Ozone efficiently oxidizes the H2S into non odorous compounds while the oxygen that Is also added with the ozone is used to promote aerobic environments.

- Ozone gas is pushed directly into the force-main pipe, under pressure

- Ozone can be bubbled into the sump prior to the force-main preventing odors and anerobic water conditions.

Garbage Transfer Stations, Recycling Center

Garbage or refuse transfer stations, recycling centers, or holding areas generate many undesirable odors and may be located in urban areas where these odors create a nuisance.  These odors are all organic in nature and readily oxidized with ozone despite the wide variety of odors present. 

- Ozone gas can be introduced into building or holding center through ventilation fans using the building itself for contact time ensuring odors both inside and outside the building are limited

- Exhaust fans with dedicated vents or stacks may be used to isolate and remove odors. Ozone gas can be diluted into these gas streams to eliminate odors prior to the exit into the outside air

- Open sheds or buildings with large open doors can use vent fans with distribution fans and piping to dilute ozone gas in the building and create a positive pressure pushing fresh air with ozone into the space to eliminate odors prior to escaping

Livestock facilities

Poultry and swine are primary railed in confined, environmentally controlled spaces.  These spaces may be above a manure lagoon or “pit” leaving few opportunities to eliminate odors and a general build-up of ammonia and hydrogen sulfide gasses.  Ozone gas can be diluted into the air in these buildings to lower odors, but more importantly create healthier air spaces for livestock and the occasional worker.  Due to the negative charge of ozone gas dust in the air is also lowered, further improving air quality.

- Ozone gas is implemented in a large tube with a fan that circulates air in the room, mixes ozone gas with the air and disperses diluted room air + ozone into the room safely and evenly.

- Ozone gas can be added to the incoming air from outside of the building as it flows through the building

- Accurate and reliable ozone measurement is of high importance in this application to ensure a safe environment for animals and people

Livestock manure lagoons

Livestock manure is collected and held in large lagoons so it can be land applied 1 or 2 times per year on crop ground.  During the long holding period this manure can release high levels of odors due to decomposition of the manure over time.

- Lagoons can be covered to isolate the air exchanges. Ozone can be added to the air far from an exhaust fan moving air from the covered lagoon.  This way all released air has been treated with ozone to eliminate odors prior to release.

Food storage warehouse

Food storage warehouses may have a wide variety of products with various odors that should not cross contaminated other foods.  Spice warehouses create extreme levels of odors.  Garlic, onions, ect may be stored with less odorous foods in cardboard boxes that may absorb the garlic/onion odor.  In many food warehouses isolation of odors is desired.  Implementing ozone in the air space to eliminate odors will be desirable for indoor air quality to eliminate cross-contamination of odors, and in severely odorous applications such as spice warehouses, ozone can eliminate odors to appease neighboring communities.

Wet Scrubbers

Wet scrubbers use water in an air stack to absorb odorous or noxious compounds that should be released into the air.  Adding ozone to the water used in the wet scrubber will allow direct oxidation of odors in air, reduce water discharge (blow-down) from the wet scrubber all while increasing efficiencies due to the negative charged ozone water attracting odorous compounds to the water more efficiently.

Odor Removal Questionnaire:

Please complete our Odor Removal Questionnaire to help us better understand your situation. This includes identifying the source of the odor, any steps you've already taken to address it, and your desired timeline for resolution. Once completed, email the form to [email protected], and a member of our team will follow up with you promptly.

Case Studies and White Papers:

Below are references for the use of ozone in some industrial applications for odor control and air treatment.

Should you have an application you have questions on, need more information on one of these papers, or want to learn what ozone can do for you, please contact our ozone experts.

The Application of Ozone for Air Treatment: Case Study of a Bingo Hall HVAC System

Most of the application of ozone has been for the treatment of water. Recently, ozone increasingly is being employed commercially for air treatment odor control (removal of VOCs from the air). This is conveniently and practically achieved by integrating the ozone generator system into the HVAC system. Ozone sensors are installed to maintain ozone concentrations at an optimum level.

The majority of projects so far are for the gaming and hospitality industries, where there is a high return on investment in systems which create and maintain high quality air. It has been found that ozone works well with particulate filters. It eliminates the need for costly carbon VOC filters and reduces the makeup air required which is costly to condition. Paybacks for ozone systems are typically about one year, and facilities customers and managements are very pleased with the noticeably higher air quality. This paper will present data from a bingo hall in Washington.

Read the full study here.

Gas-Phase Ozone Oxidation of Hydrogen Sulfide for Odor Treatment in Water Reclamation Plants

Abstract

Gas-phase O₃ oxidation is effective to treat H₂S emitted from wastewater treatment processes. The reaction is fast for full-scale applications. In most cases, 67–96% of total H₂S removed in 40-s reaction time was achieved within the first 8 s of reaction time. The initial [O₃]/[H₂S] ratio of 8 was sufficient to reduce H₂S from up to 8 ppmv to less than 0.5 ppmv in 40-s reaction time. The reaction stoichiometry ratio of [O₃]/[H₂S] ranged from 2.0 to 3.7, depending on the initial [O₃]/[H₂S] ratio. The moisture content, dimethyl sulfide, and dimethyl disulfide in the odorous air influence H₂S removal.

Read the full study here.

Ozonation of Odorous Air in Wastewater Treatment Plants

Abstract:

This study was conducted to evaluate the effects of gasscrubbing techniques for the  elimination of odorous com-pounds in wastewater treatment plants. A pilot plant wasinstalled and operated at Tuzla Wastewater TreatmentPlant in Istanbul, Turkey for this purpose. Gas scrubbingexperiments conducted using water, ozonated water, causticand ozone injected caustic revealed different removal efficien-cies. The highest and reliable hydrogen sulfide removal effi-ciencies were obtained in the ozone oxidation experiments

Read the full study here.

Ozonation of Swine Manure Wastes to Control Odors and Reduce the Concentrations of Pathogens and Toxic Fermentation Metabolites

Abstract:

The use of ozone for the remediation of nuisance odorous chemicals in liquid swine manure slurry was investigated. Gaseous ozone was bubbled directly into stored swine manure slurry in a continuously stirred batch reactor. One‐liter samples of swine slurry were ozonated to achieve ozone dosages of 1.0, 2.0 and 3.0 g ozone/liter of waste. Olfactometric determinations demonstrated a significant reduction in odors in ozonated samples as compared to raw and oxygenated samples. Volatile fatty acids, nitrate, phosphate and ammonia concentrations were unchanged by ozonation. The biochemical oxygen demand (BOD) and the chemical oxygen demand (COD) were essentially unaffected by ozonation. The concentrations of odorous phenolic microbial metabolites (e.g., phenol, p‐cresol and p‐ethylphenol) and odorous indolic microbial metabolites (e.g., 3‐methylindole and indole) were reduced to non‐detectable levels by ozonation. Hydrogen sulfide concentrations were reduced slightly by the process, with a concurrent increase in the sulfate concentration. E. coli counts were reduced by a factor of three log units and total coliforms showed a one log decrease in concentration after treatment with ozone at 1.0 g/L.

The results of this study demonstrate clearly that at the pH values studied (ca. 7), ozonation is effective for the elimination of the malodors associated with stored swine slurry and for killing potentially pathogenic bacteria, without increasing the concentrations of major pollutants of current concern, (i.e., nitrate and phosphate) and without oxidizing ammonia, which is a major plant nutrient.

Read the full study here.

Non-Thermal Plasma Coupled with a Wet Scrubber for Removing Odorus VOC

Abstract:

Odorous volatile organic compounds (VOCs) deteriorate the quality of life and affect human health. In this study, a process was developed to remove an odorous VOC using a combined non-thermal plasma (NTP) and wet scrubber (WS) system. The low removal efficiency of WSs and the large amount of ozone generated by NTP were resolved. Compared to the decomposition effects when using a WS and NTP separately, the NTP + WS system improved the removal efficiency of ethyl acrylate (EA) and significantly reduced ozone emissions. The maximum EA removal efficiency was 99.9%. Additionally, an EA removal efficiency of over 53.4% and a 100% ozone removal efficiency were achieved even at discharge voltages lower than 4.5 kV. Ozone catalysis was confirmed to occur in the NTP + WS system. Furthermore, we verified the removal of by-products such as residual ozone and formaldehyde, which is a representative organic intermediate of EA. This study demonstrates that the NTP + WS system is a green technology for removing odorous VOCs.

Read the full study here.

Treatment of Airborne Pollutants in Livestock Buidlings with Ozone as Potential Abatement Option

Abstract:

Previous research has demonstrated the negative effects of sub-optimal air quality on profitability, production efficiency, occupational health and safety, environmental sustainability and animal welfare. Ozone application has been used in North America to reduce internal air pollutant concentrations in livestock buildings and as a result potentially reduce airborne pollution emission. The main objective of this research was to evaluate the potential of using low concentration ozone (0.03 ppm) in Australian piggery buildings to reduce airborne pollution levels within piggery buildings and thus reduce pollution emission potentially. The data collected during the experiments demonstrated that ozone could be used effectively to reduce airborne bacteria (on average by 30% within this study) and reduce the concentration of inhalable particles (by 21% on average within this study). However, it appeared that ozone treatment did increase the concentration of respirable particles in the airspace of piggery buildings (within this study by approximately 26% on average).

Read the full study here.

Gas-Phase Ozone Oxidation of Hydrogen Sulfide for Odor Treatment in Water Reclamation Plants

Authors: Yanming Zhang & Krishna R. Pagilla

Abstract

Gas-phase O3 oxidation is effective to treat H2S emitted from wastewater treatment processes. The reaction is fast for full-scale applications. In most cases, 67–96% of total H2S removed in 40-s reaction time was achieved within the first 8 s of reaction time. The initial [O3]/[H2S] ratio of 8 was suffi-cient to reduce H2S from up to 8 ppmv to less than 0.5 ppmv in 40-s reaction time. The reaction stoichiometry ratio of [O3]/[H2S] ranged from 2.0 to 3.7, depending on the initial [O3]/[H2S] ratio. The moisture content, dimethyl sulfide, and dimethyl disulfide in the odorous air influence H2S removal.

Read the full study here.