Odor Removal Process May 9, 2025 sazenviro Post in Uncategorized Unpleasant odors are not only a nuisance but also an environmental and health concern across many industries. Whether it is a sewage treatment plant, chemical processing unit, food factory, or municipal manhole system, offensive smells typically originate from volatile organic compounds (VOCs), hydrogen sulfide (H₂S), ammonia (NH₃), mercaptans, and other sulfur or nitrogen-containing gases. A robust odor removal process is crucial for maintaining regulatory compliance, protecting public health, and improving workplace and community environments. This article explains the science of industrial odors and provides a comprehensive review of the most effective odor removal technologies. What Causes Odors in Industrial Exhaust?Contents1 What Causes Odors in Industrial Exhaust?2 Why Odor Control Is Essential3 Common Odor Removal Process Technologies3.1 1. Wet Scrubbing3.2 2. Activated Carbon Adsorption3.3 3. Chemical Oxidation3.4 4. UV Photolysis3.5 5. Biological Filtration (Biofilters)3.6 6. Thermal Oxidation (Incineration)4 Hybrid Odor Removal Systems5 Odor Removal Efficiency Comparison6 Odor Removal by Industry6.1 1. Sewage Treatment Plants (STPs)6.2 2. Chemical Manufacturing6.3 3. Food & Beverage Industry6.4 4. Landfills & Composting6.5 5. Manholes and Pumping Stations7 Design Considerations8 Regulatory Standards for Odor Emissions Industrial odors stem from volatile chemical emissions generated during processing, decomposition, fermentation, combustion, or storage. The exact composition varies depending on the industry: Industry Primary Odorous Gases Sewage & STPs H₂S, NH₃, VOCs, mercaptans Chemical Plants Aldehydes, amines, phenols, sulfur compounds Food & Beverage Organic acids, ethanol, cooking vapors Pharmaceuticals VOCs, solvents, nitrogen compounds Manholes & Pump Stations H₂S, methane, organic sulfur gases Composting Facilities Ammonia, VOCs, dimethyl sulfide Most odors have extremely low detection thresholds—some below 1 part per billion (ppb)—making the odor removal process even more critical and technically challenging. Why Odor Control Is Essential Public Nuisance and Complaints Occupational Safety (H₂S can be fatal at high concentrations) Corrosion Control (sulfur compounds damage metal and concrete) Environmental Regulation Compliance Product Quality and Brand Protection in food or pharma facilities Governments and municipalities often enforce strict olfactometric thresholds or VOC emission norms, requiring the deployment of dedicated odor abatement systems. Common Odor Removal Process Technologies The selection of an odor removal process depends on: The type of odor compounds (H₂S, VOCs, NH₃, etc.) Concentration and flow rate Humidity and temperature of gas Continuous vs. batch operations Space availability and budget 1. Wet Scrubbing Most common odor removal process in wastewater treatment, chemical, and food industries. Principle: Pollutants are absorbed into a liquid (typically alkaline or oxidizing). Common reagents: NaOH (for NH₃), NaOCl/H₂O₂ (for H₂S), sulfuric acid (for amines). Configuration: Vertical packed tower, multi-stage system Efficiency: Up to 99% for soluble odors Applications: STPs, chemical scrubbers for acid gases, manhole odor control 2. Activated Carbon Adsorption Principle: VOCs and odors adhere to the high surface area of activated carbon. Media: Virgin or impregnated activated carbon (e.g., with KMnO₄, NaOH) Best for: Low-flow systems, intermittent odor spikes Regeneration: Requires periodic replacement Advantages: Simple, compact No water required Effective for broad spectrum of VOCs 3. Chemical Oxidation An advanced odor removal process where gases are chemically transformed into harmless products. Agents: Ozone (O₃), chlorine dioxide (ClO₂), hydrogen peroxide Reaction examples: H2S+O3→SO2+H2OH₂S + O₃ → SO₂ + H₂OH2S+O3→SO2+H2O Setup: Gas-injection or inline reactor systems Limitations: Requires safety monitoring Generates secondary by-products if not controlled Use Case: Chemical industries, confined pump rooms 4. UV Photolysis Principle: UV-C light breaks down odor molecules and generates hydroxyl radicals (·OH) for oxidation. Combined with ozone to enhance destruction Advantages: Compact, no chemical storage Continuous treatment of VOCs and H₂S Drawbacks: Limited by light penetration Best for moderate loads 5. Biological Filtration (Biofilters) A green and sustainable odor removal process using microorganisms to metabolize odorous compounds. Media: Organic (compost, wood chips) or inorganic (ceramic, lava rock) Microbes: Thiobacillus, Nitrosomonas, fungi Setup: Open bed or closed biofilter with humidification Reaction Example: H2S+O2→SO42−H₂S + O₂ → SO₄^{2−}H2S+O2→SO42− Use Case: Municipal STPs, composting, food waste facilities 6. Thermal Oxidation (Incineration) Principle: High-temperature combustion of odorous VOCs into CO₂ and water Temperature: ~800°C in regenerative thermal oxidizer (RTO) Efficiency: >99% VOC and odor removal Used in: Pharmaceutical, chemical solvent recovery, hazardous VOCs Hybrid Odor Removal Systems In many cases, a single odor removal process may not be sufficient. Hybrid systems are designed to tackle complex odor streams: System Configuration Application Wet Scrubber + Carbon Adsorber High H₂S and VOC loads Biofilter + UV/Carbon Polishing Sewage odors with occasional spikes Chemical Scrubber + RTO Chemical plants with toxic VOCs Dual-stage Scrubbers (Alkaline + Acid) Manhole and pump station air Odor Removal Efficiency Comparison Technology Efficiency Range Odor Type Handled Wet Scrubber 95–99% H₂S, NH₃, water-soluble VOCs Carbon Adsorption 85–95% VOCs, mercaptans Biofiltration 85–98% H₂S, NH₃, organics UV Oxidation 80–95% Low-concentration VOCs Ozone Injection 90–99% H₂S, aldehydes Thermal Oxidation >99% High VOC loads Odor Removal by Industry 1. Sewage Treatment Plants (STPs) Odors from sludge digesters, clarifiers, and pumping stations Preferred: Wet scrubbers, biofilters, manhole deodorizing units 2. Chemical Manufacturing Toxic and complex odors from VOCs, sulfur/nitrogen compounds Preferred: Dual chemical scrubbers, RTOs, activated carbon 3. Food & Beverage Industry Cooking vapors, fermentation gases, organic VOCs Preferred: Carbon filtration, UV oxidation, biofilters 4. Landfills & Composting H₂S, mercaptans, VOCs from organic decay Preferred: Biofilters, chemical scrubbers, ozone injection 5. Manholes and Pumping Stations Confined space with H₂S accumulation Preferred: Compact FRP scrubbers or inline carbon filters Design Considerations To implement an effective odor removal process, consider: Type of odors and their chemical properties Inlet gas volume and concentration Peak vs. continuous operation Temperature and humidity of air Local emission and olfactory norms Space and maintenance constraints Regulatory Standards for Odor Emissions Country/Agency Odor Regulation India (CPCB) General standard, enforced locally USA (EPA & State DEP) State-specific odor thresholds (OU/m³) EU BAT/BREF Guidelines Olfactometric standards for many industries GCC (RCJY, EHS Dubai) Emissions < 1 ppm H₂S, < 100 OU/m³ Air Stripper Installation Conclusion Industrial odors can be more than just a nuisance—they’re a safety, health, and environmental concern. Selecting the right odor removal process ensures regulatory compliance and protects community well-being. Whether it’s biofiltration for sewage, chemical scrubbing in refineries, or carbon adsorbers for VOCs, modern odor control technologies offer a tailored solution for every need. As a leading supplier of turnkey odor control systems, we help industries of all types engineer and install effective, compliant, and low-maintenance odor removal processes using wet scrubbers, biofilters, activated carbon systems, and hybrid units.