Biological Air Pollution Controls

Fall 2024

Biological Principles in Environmental Engineering

Presenters: Farin Tasnuva Dhara & Tione Grant

Lesson Objectives

1. Identify the advantages and limitations of Biological Air Pollution Control Systems.
2. Explain why air emissions of Volatile Organic Compounds (VOCs) and odorous compounds such as Hydrogen Sulfide(H₂S), and Ammonia (NH₃) are a problem
3. Classify the microorganisms involved in the biological treatment of H₂S, NH₃, and VOCs. Be able to state their electron donor, electron acceptor, carbon source, and environmental conditions needed.
4. Describe the physical, chemical, and biological mechanisms involved in pollutant removal within biofilters, bio-scrubbers, and bio-trickling filters and their performance parameters.
5. Describe how Hillsborough County’s Northwest Regional Water Reclamation Facility implements biological air pollution control.

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BAPCS- Biological Air Pollution Control Systems

• Control Systems that utilize the activities of microorganisms to degrade pollutants in harmless by-products

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• Contaminants are partitioned from a gas to an aqueous phase and transported into biofilms where microorganisms break them down.

• Microbes within these systems engaged in many ecological relationships(Mutualism, territoriality, competition, etc.)

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Types of Air Pollution Control Systems

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Biological Air Pollution Control Systems

Physiochemical Air Pollution Controls Systems

Air Pollution Control Systems �Biological vs Chemical

Biological APC Systems

1. Reliance on Natural Processes; making them eco-friendly
2. Non-Hazardous By-products
3. Lower operational costs, outside costs and Energy Consumption
4. Renewable Process
5. Reduced Chemical Exposure to Workers
6. Reduced Corrosive effects on structures

Chemical APC Systems

1. Shorter Residence Times
2. Ability to treat highly toxic and inert non-biodegradable compounds
3. Small Land Requirements

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Biological Air Pollution Control Limitations

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Air Pollutants: A Reason for BAPCs

Definition:

• chemicals, physical or biological agents that contaminate the air and alter the atmosphere's natural properties.

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Forms of Air pollutants treated by BAPC

• Volatile Organic Compounds (VOCs)
• Hydrogen Sulfide (H₂S)
• Ammonia (NH₃)

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Like any form of pollutant, these air pollutants can impact the wider region differently.

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Effects of Air Pollutants: Health Implication & Odor Nuisance

Hydrogen Sulfide

Scent: “Rotten Eggs”

Low Concentrations

• Eyes, Nose, and Throat Irritation
• Significant discomfort and complaints

High Concentrations

• Neurological damage, stress
• Respiratory failure
• Death

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Volatile Organic Compounds

Scent: Range from Scentless to Strong “unnatural” scent

Short Term:

• Headaches and dizziness
• Respiratory irritation, and Nausea

Long Term:

• Liver and kidney damage
• Central nervous system issues, and Cancer

Ammonia

Scent: Strong pungent odor

Short Exposure

• Eyes and Skin Irritation
• Respiratory System Irritation

Prolonged exposure

• Exacerbate asthma and other chronic respiratory conditions

Effects of Various Pollutants: Environmental Impacts

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Ammonia

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• Soil acidification
• Eutrophication

Hydrogen Sulfide

• Acidic Disposition in soil and water
• High Toxicity to waterways

Let’s Review

Which of the following advantages belong to BAPCs

1. Shorter Residence Times
2. Ability to treat highly toxic and inert non-biodegradable compounds
3. Reduced Corrosive effects on structures
4. Small Land Requirements

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Internal Mechanisms of BAPC Systems

• BACPS can be considered open systems, with the constant influx and outflow of gas, water, and suspended or immobilized microorganisms

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• Contaminated air passes through the filter bed medium (compost, peat, synthetic material, etc.) with oxygen (O₂).
• Absorbed contaminates partitioned out of gas into the microbial biofilm/liquid phase with the filter bed.
• Microbes convert the contaminant to different harmless compounds based on the contaminant.

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Biodegradation of Pollutant: H₂S

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Microbial Classification

Sulfur-oxidizing bacteria (SOB)

Ex: Thiobacillus

Paracoccus

Metabolic Characteristics

• Electron Donor:
• H₂S or other reduced sulfur compounds
• Electron Acceptor:
• (aerobic conditions): O₂
• Carbon Source:
• Autotrophic: CO₂ (e.g., Thiobacillus)
• Heterotrophic: Organic Carbon (e.g., Paracoccus)

General Diagram of Autotrophic Bacteria

Biodegradation of Pollutant: H₂S

Environmental Conditions

• Aerobic conditions

pH

• The optimal range is typically 6–8, but some species tolerate acidic environments (e.g., Acidithiobacillus)

Temperature

• 15–45°C for mesophilic species

Moisture

Microbial activity needs to maintain biofilm integrity

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Biodegradation of Pollutant: NH₃

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Classification

• Ammonia-oxidizing bacteria (AOB)
• ex. Nitrosomonas
• Nitrite-oxidizing bacteria (NOB)
• ex. Nitrobacter

Metabolic Characteristics

• Electron Donor:
• NH₃ (AOB) or nitrite (NOB).
• Electron Acceptor:
• O₂: Aerobic conditions.
• Carbon Source:
• o Autotrophic: CO₂
• o Heterotrophic: Organic carbon

General Diagram AOM and NOB relationship

Biodegradation of Pollutant: NH₃

Environmental Conditions

• Aerobic conditions

pH

• pH: 7–8.5 is optimal for nitrification

Temperature

• 20–40°C for mesophiles; thermophilic species thrive above 40°C.

Moisture

• Moisture: Critical for biofilm stability and microbial survival.

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Biodegradation of Pollutant: VOC

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Classification

Hydrocarbon-degrading bacteria

• Pseudomonas,

Methanotrophs

• Methylosinus species for methane-like VOCs.

Fungi – Newer technologies

Metabolic Characteristics

• Electron Donor:
• VOCs (e.g., benzene, toluene, xylene, alkanes).
• Electron Acceptor:
• O₂: Aerobic conditions.
• Carbon Source:
• Organic carbon (VOC serves as both carbon and energy)
• Methane gas (Methanotrophs)

General Diagram for Hydrocarbon-degrading bacteria

Biodegradation of Pollutant: VOC

Environmental Conditions

• Aerobic conditions

pH

• pH: Neutral to slightly acidic (6–8) for bacteria; fungi tolerate a wider range (4–8).

Temperature

• 15–40°C for most bacteria; some fungi tolerate extreme conditions.

Moisture:

• Biofilm and air-liquid interface must remain moist for optimal diffusion and degradation.

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Let’s Review

Name an Environmental Impact of Ammonia Pollutants

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Answers:

• Soil acidification
• Eutrophication

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Name a type of microorganism that degrades VOC

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Answers:

• Hydrocarbon-degrading bacteria
• Methanotrophs
• Fungi

3 Forms of Biological Air Pollution Control Systems

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Biofilters: Mechanism

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Physical

• Adsorption: Pollutants adhere to the surface of the media where microorganisms are attached.
• Filtration: Pollutants are removed as the air passes through the porous media.
• Diffusion: Pollutants diffuse through the air and biofilm interface to reach microorganisms.

Chemical

• Chemical Neutralization: Pollutants can undergo neutralization reactions with biofilm excretions in the media.
• Oxidation-Reduction Reactions: Some pollutants undergo partial oxidation

Biological

• Biofilm Metabolism: Microorganisms within the biofilm degrade pollutants as carbon and energy sources.
• Cometabolism: Some pollutants are degraded incidentally during the metabolism of other compounds.

Biofilter Media Types (Left to right: Expanded Clay, Woodchips)

Biofilters Performance Parameters

Moisture Content:

• The media should remain moist but not waterlogged to support microbial activity.
• Optimal moisture content: 40–60% (by weight).
• Regular monitoring and irrigation are necessary to prevent desiccation.

pH:

• Optimal range: 6.5–8.0 for most organic pollutants.
• Hydrogen sulfide (H₂S) biodegradation can result in more acidic conditions.

Temperature:

• Optimal range: 15–35°C.
• Some thermophilic organisms can operate at higher temperatures.

Media Characteristics:

• Organic media: Peat, compost, wood chips, bark, or a mix. These provide nutrients but degrade over time (requiring periodic replacement).
• Inorganic media: Expanded clay or activated carbon. These are durable, resistant to degradation, and allow good airflow.

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Bio-Trickling Filters: Mechanism

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The system operates as a combination of biofiltration and bio-scrubbers

Physical

• Absorption: Pollutants are transferred from the gas phase to the liquid phase trickling over the media.
• Mass Transfer: Pollutants diffuse into the biofilm coating the media where biodegradation occurs.
• Filtration: Solid particles and particulates can be trapped in the media.

Chemical

• Chemical Interactions in the Liquid Phase: Oxidants or pH buffers in the trickling liquid can react with pollutants, aiding biodegradation.
• Catalytic Microbial Enzymes: Enzymes secreted by biofilms catalyze pollutant-specific transformations.

Biological

• Microbial Consortia: Biofilm on the media hosts diverse microbes, enabling multi-step degradation pathways for complex pollutants.
• Biodegradation in Liquid Phase: Trickling liquid maintains nutrient and oxygen supply to biofilms.

Types of System Media (Left to right: sponge media, lave rock

Bio-trickling Optimal Operational Parameters

Moisture Content:

• The moisture in the biofilm should be maintained close to saturation to ensure microbial activity without drying the biofilm.
• Relative humidity: ≥ 95%.

pH:

• Optimal range: 6.0–8.0 for most systems.
• Treatment of H₂S or NH₃ can create more acidic or basic conditions in the system.

Temperature:

• Optimal range: 15–40°C.
• Mesophilic conditions (20–35°C) are generally preferred for robust microbial activity.

Media Characteristics:

• High surface area-to-volume ratio: Promotes microbial growth.
• Porous and durable: Allows airflow and liquid distribution. Examples include structured plastic media, ceramic, or lava rock.
• Resistant to compaction and clogging.

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Bio scrubbers

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Biodegradation and Scrubbing occur in separate tanks

Mechanisms

Physical

• Absorption: Pollutants dissolve into the scrubbing liquid, facilitated by high solubility
• Dispersion: Air bubbles create a large surface area, enhancing pollutant transfer from gas to liquid.

Chemical

• Chemical Reactions in Scrubbing Liquid:
• Acidic gases dissolve and form acids, which may be neutralized chemically.

Biological

• Suspended Microbial Communities: Microorganisms suspended in the scrubbing liquid degrade absorbed pollutants.
• Biological Oxidation: Pollutants absorbed in the liquid are oxidized by microbes to inert compounds and biomass.

Types of System Media

Bio-scrubber Optimal Operational Parameters

Moisture Content:

• Maintained as a liquid medium with appropriate aeration for mixing and oxygen supply.

pH:

• Optimal range: 6.5–8.5 for most organic compounds.

Temperature:

• Optimal range: 15–40°C.
• Avoid temperatures above 45°C, which can inhibit microbial activity.

Media Characteristics:

1. The scrubbing liquid should contain nutrients for microbial growth.
2. Agitation or recirculation ensures homogeneity and prevents fouling.

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Advantages of Different BAPC Systems

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• Easier control reaction conditions
• Moist gas stream operation

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Disadvantages of Different BAPC Systems

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Let’s Review

Which of the Three BAPCs mentioned shares operational traits of the other 2?

1. Biofilter
2. Bio-trickling
3. Bio-Scrubbers

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BAPC Application

Northwest Regional Water Reclamation Facility Site Visit Synopsis

Facility Stats

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• Largest of 5 Hillsborough wastewater facilities

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• Treats 600-900 ppm of H₂S because of the 300 MGD Wastewater

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• Operates two Air Pollution Control Systems

Air Pollution Control Systems

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System 1: Coupled Bio-trickling –Carbon Absorption System

System 2: Carbon Adsorption System

But Northwest Regional WRF is a Wastewater facility, why do they care about Air Pollution Control??

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Reasons Northwest cares about treating air pollutants

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Northwest WRF Neighbors

• Deer Park Elementary
• The Goddard School of Tampa
• The Marq Highland Park Apartment
• Ed Radice Complex
• Old Memorial Church
• Bakas Equestrian Center

Northwest WRF does not manage air pollution for itself; it manages air pollution for its neighbors.

Air Pollution Control Procedure: System 1

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Air flows through Vacuum pipes into Headworks to collect the H₂S

H₂S feed flows through the pipe towards the bio-trickling filters

H₂S is treated down to 20-0 ppm before moving to carbon adsorption for residuals

Air Pollution Control Procedure: System 2

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H₂S produced in the flow distribution tank is collected and sent for treatment

Small H₂S concentrations are treated in the carbon adsorption system.

System 1 Operational Parameters and Reviews

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• Northwest Regional outsources maintenance of the Air pollution controls to DOer Products and Services, Inc.
• No operational issues with the system from plant operators; “Minimal monitoring”

System 2: Carbon Adsorption System Visible Concerns

• Signs of Corrosion on the Carbon System and the Flow Distribution Tank
• Conversation about system replacements to mitigate corrosion

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Conclusion

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References

• Devinny, Joseph S, et al. Biofiltration for Air Pollution Control. CRC Press, 22 Nov. 2017, pp. 1–22.
• Iranpour, Reza, et al. “Literature Review of Air Pollution Control Biofilters and Biotrickling Filters for Odor and Volatile Organic Compound Removal.” Environmental Progress, vol. 24, no. 3, 2005, pp. 254–267, https://doi.org/10.1002/ep.10077.
• Kennes, Christian, et al. “Bioprocesses for Air Pollution Control.” Journal of Chemical Technology & Biotechnology, vol. 84, no. 10, 2 June 2009, pp. 1419–1436, https://doi.org/10.1002/jctb.2216.
• Leson, Gero, and Arthur M. Winer. “Biofiltration: An Innovative Air Pollution Control Technology for VOC Emissions.” Journal of the Air & Waste Management Association, vol. 41, no. 8, Aug. 1991, pp. 1045–1054, https://doi.org/10.1080/10473289.1991.10466898. Accessed 18 Nov. 2024.
• Raúl Muñoz, et al. “Biological Technologies for the Treatment of Atmospheric Pollutants.” International Journal of Environmental Analytical Chemistry, vol. 95, no. 10, 13 July 2015, pp. 950–967, https://doi.org/10.1080/03067319.2015.1055471. Accessed 2 Nov 2024.
• Regidor-Alfageme, Enrique, et al. “Biological Treatments.” Odorous Emission Control: Monitoring and Abatement, edited by Marzio Invernizzi, vol. 63, Academic Press, 12 Sept. 2024, pp. 127–161, www.sciencedirect.com/science/article/pii/S0065237724000036?via%3Dihub.
• van Groenestijn, Johan W., and Paul G. M. Hesselink. “Biotechniques for Air Pollution Control.” Biodegradation, vol. 4, no. 4, Dec. 1993, pp. 283–301, link.springer.com/article/10.1007%2FBF00695975, https://doi.org/10.1007/bf00695975. Accessed 10 Nov. 2019.

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Thank you. Any Questions?

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