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What is biofiltration?
How does biofiltration work?
What are the differences between organic and in-organic biofilter media?
What is the difference between biological odor control and other treatment methods?
What is a biotrickling filter?
What are volatile organic compounds?
What is hydrogen sulfide (H2S)?
What are the effects of hydrogen sulfide (H2S) on human health?
What is Biogas?
What are the advantages of conditioning biogas prior to use?
What can be done with the captured biogas?
What is EBRT, and how does media type affect EBRT selection?
What is ‘total odour’, and why is it the best indicator of system performance?
Q: What is biofiltration?
A: Biofiltration uses naturally occurring microbes to biologically break down odors, solvents and other VOCs present in waste air streams, into carbon dioxide and water. It is a completely natural process that does not use chemicals or produce waste. Biofiltration is a reliable and cost-effective way to eliminate odors, volatile organic compounds (VOCs) and H2S at manufacturing, municipal and processing facilities.
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Q: How does biofiltration work?
A: The foul air is collected from various sources and directed to the inlet of the biofilter. The processed air is humidified prior to the biofilter to ensure the air is saturated with moisture. The humidified air is then distributed across the media surface. Microorganisms which reside on the surface of the media use the pollutants as a food source, thereby destroying the odor causing compounds. The clean, odor free air is then discharged to the environment.
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Q: What are the differences between organic and in-organic biofilter media?
A: Organic media, such as wood chips or compost material have been used in biofilters for many years. However after a short time (often less than three years) the media begins to degrade and compact which causes performance problems such as reduced contaminant removal efficiency, increased pressure loss, decreased air flow and air distribution inconsistency. Once these issues arise the media must be removed and replaced and the spent media must be properly disposed of, significantly increasing the maintenance and operating costs. In-organic biofilter media such as Biorem’s Biosorbens® and XLD have been designed to overcome deficiencies typically experienced with organic media. Biosorbens® media does not degrade or compact and is resistant to temperature, mechanical and chemical impacts. Biosorbens® is an engineered product; therefore it provides an ideal habitat for the biology necessary for odor treatment, low pressure drop, high moisture retention and long operating life. Biorem’s in-organic medias reduce the footprint space required, have low maintenance and operating costs and have a guaranteed bed life of over 10 years.
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Q: What is the difference between biological odor control and other treatment methods?
A: Biological odor control has emerged as the most cost effective option for controlling odors, volatile organic compounds, hydrogen sulfide and other hazardous air pollutants. One of the primary benefits of biological odor control is that it has much lower operating and maintenance costs than carbon, chemical scrubbers or thermal oxidizers. Biological treatment utilizes microorganisms to remove contaminants; therefore it does not require frequent, repetitive purchases and storage of chemicals. Also, because the media does not absorb the contaminants, it does not require frequent removal, disposal and replacement as is required with carbon systems. Biological treatment is as effective as thermal oxidation but without the high energy consumption costs.
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Q: What is a biotrickling filter?
A: A biotrickling filter is a vessel that is designed to capture and biologically degrade high levels of hydrogen sulfide and other water soluble compounds from the air stream. The biotrickling filter process, converts the contaminants to the liquid phase for absorption onto the media surface and subsequent biological degradation. Biotrickling filters are a reliable and cost-effective way to eliminate hydrogen sulfide at manufacturing, municipal and processing facilities.
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Q: What are volatile organic compounds?
A: Volatile organic compounds or VOCs are a large diverse family of chemicals that are emitted from a wide variety of sources including household products, furnishing and building materials1. VOCs are organic chemical compounds that have high enough vapor pressures under normal conditions to significantly vaporize and enter the earth's atmosphere. These vapors can negatively affect the environment and human health.
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Q: What is hydrogen sulfide (H2S)?
A: Hydrogen sulfide is an extremely hazardous, toxic compound. It is a colorless, flammable gas that can be identified in relatively low concentrations through a characteristics rotten egg smell. Hydrogen sulfide is a naturally occurring gas that can be found in coal pits, sulfur springs, gas wells and as a by-product of decaying sulfur-containing organic matter. It is most commonly found in such places as sewers, sewage treatment plants and manure. Hydrogen sulfide is also commonly found in industrial applications such as petroleum and natural gas extraction, refining, pulp & paper manufacturing, chemical manufacturing and waste disposal1.
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Q: What are the effects of hydrogen sulfide (H2S) on human health?
A: Hydrogen sulfide is classed as a chemical asphyxiate, similar to carbon monoxide and cyanide gases. It has a very low odor threshold, it is easily perceptible at concentrations well below 1 part per million (ppm) in air. Beacuase it is a gas, the most common form of exposure is through inhalation. At concentrations above 100 ppm, a human’s ability to detect the gas is affected by rapid temporary paralysis of the olfactory nerves in the nose, which can lead to a loss of the sense of smell. Prolonged exposure to lower concentrations can also have dangerous effects to the olfactory nerves and can lead to bronchitis, pneumonia, headaches, pulmonary edema and loss of motor skills1.
Exposure symptoms include;
Low 0-10 ppm Irritation of the eyes, nose & throat
Medium 10-50 ppm Headache, dizziness, nausea, vomiting & breathing difficulty
High 50-200 ppm Severe respiratory tract irritation, eye irritation, shock, convulsions, coma and even death in severe cases.
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Q: What is Biogas?
A: Biogas is a gas that is produced by the biological breakdown of organic matter in the absence of oxygen. Biogas is produced through the anaerobic digestion or fermentation of biodegradable material such as biosolids, manures, sewage, municipal waste, green waste, plant material and energy crops. Biogas is comprised primarily of methane and carbon dioxide.
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Q: What are the advantages of conditioning biogas prior to use?
A: By removing hydrogen sulfide and siloxanes from the biogas stream prior to use it allows the gas to be burned in an engine with minimal detrimental effects. The significant reduction in operation and maintenance costs on the engine allow the engines to have a higher availability rating and maximum electricity generation. Therefore the advantages of conditioning biogas prior to use is significant operation and maintenance savings as well as the prevention of engine downtime.
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Q: What can be done with the captured biogas?
A: Biogas can be captured and combusted or oxidized with oxygen. The energy release allows biogas to be used as a low cost fuel source for heating or electrical purposes and can also be compressed and used to power motor vehicles. Biogas is a renewable fuel and therefore qualifies for renewable energy subsidies in some parts of the world.
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Q: What is EBRT, and how does media type affect EBRT selection?
EBRT stands for Empty Bed Residence Time. It is an approximate method of determining the detention time of air within the biological reactor. In general terms, the longer the retention time of impacted air within a reactor, the greater the destruction efficiency. Time is required to allow for distribution and phase transfer of the contaminant from the gaseous phase to the aqueous phase and also for the subsequent biological oxidation.
Various media’s have a wide range of parameters that impact the efficiency for air distribution, diffusion, absorption, adsorption, oxidation and available surface area for microbial immobilization. Medias that optimize these key parameters offer increased performance over a wider range of compounds with reduced retention times. EBRT’s generally cannot be compared across various medias due to these differences. For example, a standard organic woodchip media may require 45-60 seconds of contact time to achieve the same performance as a 15s XLD biofilter.
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Q: What is ‘total odor’, and why is it the best indicator of system performance?
Total odor refers to the perceived impact of an odiferous air stream on an individual’s senses. It comprises of the complete range of chemicals or compounds that may be present in the air stream. Since air streams typically contain a wide variety of compounds that can cause an odor, sampling for individual components may not capture the true odor destruction efficiency of the abatement device. This is why sampling for total odor provides a more accurate representation of what a neighbor or community might experience. Total odor is usually measured through a process known as “dynamic olfactometry’.
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1 Sourced from Health Canada www.hc-sc.gc.ca/ewh-semt/
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