Odor Control Technician flashcards
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32 cards. Read the term and the definition here. The deck at the top of this page is optional.
- Olfactory epithelium
- Tissue at the top of the nasal cavity containing receptor neurons that bind odorant molecules and send signals to the olfactory bulb; it is the primary site of odor detection in humans.
- Detection threshold
- The lowest concentration of an odorant that a panel can just perceive as an odor, distinct from the recognition threshold at which the odor quality can be identified.
- Weber-Fechner law
- Perceived odor intensity increases with the logarithm of concentration, so large concentration increases produce relatively small perceived changes; this underlies why dilution reduces complaints slowly.
- Olfactory adaptation
- A temporary decrease in sensitivity after continuous exposure to an odor, requiring rest in clean air to recover; it makes panelists unreliable without rest periods between samples.
- Odor unit
- A measure of odor concentration equal to the number of dilutions with neutral air required to bring a sample to the panel detection threshold; higher values mean stronger odor.
- Reduced sulfur compounds
- A family of odorants including hydrogen sulfide, mercaptans, and dimethyl sulfide, characterized by rotten-egg, cabbage, or garlic notes and very low odor thresholds.
- Hydrogen sulfide threshold
- H2S is detectable at low parts-per-billion levels, but at higher concentrations it rapidly fatigues the sense of smell, so odor is not a safe exposure indicator.
- Septic wastewater
- Wastewater depleted of dissolved oxygen that supports sulfate-reducing bacteria, producing hydrogen sulfide and other odorous reduced sulfur compounds in collection systems.
- Geosmin
- A microbial compound with an earthy, musty odor detectable at parts-per-trillion levels in water; it is associated with cyanobacteria and actinomycetes and is a common drinking-water odor problem.
- Bioeffluents
- Odorous compounds emitted by people, including sweat, breath, and skin emissions; they are a major contributor to indoor air quality complaints in crowded or poorly ventilated spaces.
- Dynamic olfactometry
- A laboratory method that dilutes an odor sample with neutral air and presents it to a panel to determine the odor concentration in odor units, following standards such as EN 13725.
- Hedonic tone
- A rating of how pleasant or unpleasant an odor is, usually on a bipolar scale; it is assessed separately from concentration and intensity because unpleasantness drives complaints.
- Field olfactometer
- A portable dilution device used to estimate odor concentration on site; it is useful for screening and trends but is less reproducible than laboratory olfactometry.
- Total reduced sulfur
- A summed measurement of reduced sulfur compounds such as hydrogen sulfide and mercaptans, often used as an indicator of odor potential in wastewater and industrial emissions.
- Sorbent tube sampling
- A method that draws air through a tube packed with adsorbent, later analyzed by gas chromatography to identify and quantify specific odorants; holding time and contamination must be controlled.
- Odor intensity scale
- A categorical or numeric rating of perceived odor strength, often from zero to five or ten, assessed by trained panelists separately from concentration and hedonic tone.
- Dilution as control
- A strategy that reduces odor concentration by mixing with clean air through stacks or ventilation; it lowers concentration but does not destroy the odorant and can spread impact.
- Henry's law constant
- The ratio of a compound's partial pressure to its concentration in liquid; a high value means the compound tends to strip into air, while a low value favors absorption into water.
- Empty bed residence time
- The volume of biological treatment media divided by the air flow rate, expressed in seconds; it is a key design parameter for biofilters and biotrickling filters.
- Activated carbon adsorption
- A process in which odorous molecules adhere to the porous surface of carbon; capacity depends on compound size, polarity, and competing moisture, and breakthrough must be monitored.
- FIDOL factors
- Frequency, intensity, duration, offensiveness, and location: the five factors used to assess odor impact on a community, since average concentration alone misses nuisance events.
- Packed-bed scrubber
- A vessel filled with packing over which scrubbing liquid flows countercurrent to odorous air; it is effective for soluble, low-Henry's-law compounds such as ammonia and amines.
- Biofilter
- A bed of organic media supporting microorganisms that oxidize odorous compounds as air passes through; it suits large, low-concentration streams and needs moisture and nutrient control.
- Biotrickling filter
- A biological treatment vessel with inert packing and recirculated water that supports a biofilm; it offers better control of pH, nutrients, and pressure drop than a traditional biofilter.
- Regenerative thermal oxidizer
- A combustion device that destroys odorous volatile organic compounds at high temperature and recovers heat through ceramic media; it suits high-concentration or difficult-to-absorb streams.
- Photoionization detector
- A portable instrument that ionizes volatile organic compounds with ultraviolet light to estimate total VOC concentration; it is a screening tool, not a specific odor measurement.
- Iron salt dosing
- Adding ferrous or ferric salts to wastewater to precipitate sulfide and reduce hydrogen sulfide release; it is a common in-sewer odor control method with pH and corrosion effects.
- Nitrate addition
- A preventive in-sewer treatment that favors nitrate-reducing bacteria over sulfate reducers, suppressing hydrogen sulfide formation in force mains and long collection lines.
- Hypochlorite scrubbing
- Using sodium hypochlorite solution to oxidize mercaptans, amines, and other odorous compounds in a scrubber; it must never be mixed with acids or ammonia because of toxic gas formation.
- Masking agent
- A compound added to add a stronger or more pleasant odor that covers the original; it does not remove the odorant and can worsen perception for some observers.
- Counteractant
- An agent designed to reduce the perceived intensity of a target odor through pairing rather than covering; its effectiveness is compound-specific and must be verified by panel testing.
- Compost biofiltration
- Passing exhaust air from composting through a moist media bed where microbes oxidize ammonia, amines, and sulfur compounds; aeration and porosity of the compost must be maintained.