FDSC585 Lecture 5: Odor Treatment Technologies

Lecture 5 - FDSC585: Food Waste/Odor Treatment Technologies

• The control of odor removal and air pollution in the food industry and wastewater treatment plants has become crucial. Negative impacts of invasive pollutants now extend to residential areas, not just the treatment plant work environments.
• Sources of odors in food waste: Waste treatment plants, MSW plants, biogas plants, and food industries.

Background

• Municipal wastewater treatment typically uses the activated sludge process.
• Odor problems often arise in collection systems, primary treatment facilities, and solids handling facilities.
• Anaerobic (septic) conditions cause odors, resulting from limited oxygen transfer in wastewater.
• Hydrogen sulfide (H₂S) is a byproduct of sulfate-reducing bacteria in an anaerobic environment, responsible for the strong rotten-egg smell.
• Solids handling creates another significant odor problem due to extreme turbulence, pH adjustment, and/or thermal treatment of biosolids. The odor compounds released can include ammonia (NH₃), hydrogen sulfide, amines, organic sulfides and mercaptans; in varying concentrations.

Background: Technologies for Odor Treatment

• Technologies are available for treating odorous air from confined areas of food plants, wastewater treatment plants, and sludge handling facilities.
  • These can be categorized based on the removal process:
    • Biochemical: biofilters, bioscrubbers
    • Chemical: scrubbers, catalytic oxidation, ozonation
    • Physical: adsorption (activated carbon), absorption (clean water scrubbers)
• Waste gases from industry have traditionally been treated using physicochemical processes.
• Biofilters are a biological odor treatment method that offers simpler operation and maintenance. Costs related to biofilter media replacement.

Biofilter

• A biofilter is a bed of organic material (media) allowing for air passage, humidity trapping and biomass growth.
• Odor-causing compounds are adsorbed by the microbes/film of water on the organic material.
• Microbes convert adsorbed compounds into carbon dioxide, water, and inorganic salts.
• Biofilters are a self-regulating ecosystem.
• Components of a biofilter: containment, biofilter media, humidifier/wetting systems, air diffusion system, air ducts, fans.
• Inflow is contaminated air and out flow is treated air(Odors and VOCs are converted to organisms + CO2 + H2O).
• Design of Biofilter-Sizing: Empty Bed Residence Time (EBRT) is required depending on the type of media and odor compound.

Biofilter Media Selection

• Soil media has longer life and lower loading rates.
• Organic media has a replacement cycle of 2-5 years and higher loading rates.
• Synthetic media is often component of a mix and is site-specific.
• Successful biofilters require careful media selection, moisture control, and airflow distribution.

Biotrickling Filter

• Biotrickling filters biologically treat odor-causing gases.

• Examples of odor causing gases include Ammonia (NH₃), H₂S, other volatile organic compounds (VOC's).

• Biotrickling filter method is a more thorough method than chemical methods.

  • NH₃ Scrubber System: The base material is neutralized with an acidic scrubber (like H₂SO₄) to remove it. The material is then saturated with water (increased humidity) to prolong the life of the packing.

• Components include: nutrients make-up tank, recycle pump, structured packing material, and acid make-up tank.

• Biofilter vs. Biotrickling Filter: A comparison of differences (see page 25)

Photoionization

• Photoionization is an effective odor elimination method.
• Primarily used for wastewater treatment, sewage, wastewater sludge, and food processing plants.
• Process relies on UV-light and catalysts.
• Environmentally stable method.
• Treats odors as a whole, not a single compound.

  • Advantages:Effective treatment, high efficiency, incorporated redundancy, low maintenance, no water/chemicals/nutrients, expandable, reduced installation costs.

  • Operations: Only electricity is required; switch ON/OFF operation, easy to handle, reliable, low maintenance demand

  • Technical specifications: off gas flow rate, dimensions, plant footprint, filter class, material of housing, location of fans, external ductwork, number of control cabinets, voltage, protection, operation power demands.