air quality and air quality control

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  • 7/30/2019 Air Quality and Air Quality Control




  • 7/30/2019 Air Quality and Air Quality Control


    Air Quality

    The atmosphere is a vital component ofhuman environment. It transmits and altersthe solar energy that controls our climate. Itacts as a shield, protecting us from damagingmeteoritic impacts and from penetratingradiation. It supports the flight of birds andinsects and transports seeds and spores. Its

    gases provide the raw materials for life itself:w/o them we could not exist.

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    Atmosphere is a thin layer of gasses that envelopes theearth. Weather elements are rain, snow, heat, wind,thunder and fog. Our integrated experience of weatheris the climate; the characteristic annual cycle of

    weather. Climate is the long term trend oftemperature and precipitation (rain, snow). Weatheris the day to day variation in temperature andprecipitation.

    Pure Air is a mixture of gases, w/c contains 78% N2,20.1% O2, 0.9% Ar, 0.03% CO2, 0.002% Neon, and0.0005% Helium.

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    Climate VS Weather

    Systematic view of the components of the earths global weatherand climate system which involves mutual interactions betweencomponents of the atmosphere, hydrosphere, lithosphere andbiosphere.

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    Climate VS WeatherWeather is defined as the state of the atmosphere at a giventime and place, with respect to variables such as temperature,moisture, wind speed and direction, and barometric pressure.

    Climate is defined as the expected frequency of specific states ofthe atmosphere, ocean, and land including variables such astemperature (land, ocean, and atmosphere), salinity (oceans),soil moisture (land), wind speed and direction (atmosphere),current strength and direction (oceans), etc. Climateencompasses the weather over different periods of time and alsorelates to mutual interactions between the components of theearth system (e.g., atmospheric composition, volcanic eruptions,changes in the earths orbit around the sun, changes in theenergy from the sun itself, etc.).

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    AtmosphereIf air moves relative to the ground, we feel of see its wind, just inm0tion by a series of forces:

    > Pressure Gradient Force tending to impel air motion from areasof high to areas to low pressure.

    > Gravitation, w/c tends to accelerate the air downward at a rateof 9.8 m/s2.

    > Friction acting opposite to the wind direction and proportionalroughly to the square of the wind speed.

    > The Coriolis force caused by the rotation of the earth often

    called the deflecting force of the earth rotation. It acts at rightangles to the wind direction and is proportional to the windspeed.

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    Kinds of Wind

    Global Wind caused by the differential warming and cooling ofthe earth as it rotates under the sun.

    Local Wind caused by the differential temperature betweenland and water masses.

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    Layers of Atmosphere

    Troposphere ranges from 5km at the poles and about 18km atthe equator where the temperature decreases with altitude.Tropopause is the boundary between stratosphere andtroposphere.

    Stratosphere is a layer of air where the temperature profile is

    inverted and has high ozone concentration that absorbs the sunsshortwave ultraviolet radiation.

    Mesosphere extend from the stratosphere at 50 55km toanother temperature minimum to 85km, the mesopause. Themesosphere is windy and turbulent region, but there is actuallylittle water vapor for cloud.

    Thermosphere is above the mesopause where temperaturemeasures indefinitely upward, it is the hot upper atmosphere.

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    Layers of Atmosphere

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    Ozone Layer

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    Ozone LayerThe ozone layer extends from the top of stratosphere into the

    thermosphere. The Earths atmosphere is composed of Nitrogen78.1%, Oxygen 20.9%, Argon 0.9%, Carbon Dioxide 0.033%, Other,including Ne, He, Methane 0.003% water vapor 0.0001%. AlthoughCarbon Dioxide, water vapor and other gases are tiny component ofthe atmosphere, they have a huge impact on our weather, our

    climate, and our well being. Nitrogen is largely part of theatmosphere. Most solar radiation that passes through atmosphere isunaffected by the presence of any of these gases. Its when theradiation hits the Earths surface that things start to heat up. Solarradiation pretty much bounces off white clouds and white glaciers

    and snow cover. This is called reflectance. Solar radiation that isreflected from clouds, snow, and ice, is lost back to space withoutappreciably heating up anything on the Earths surface.

    LAPSE RATE is the change in temperature at the height of freeatmosphere.

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    Pollutants are those materials (gases, liquid, or solid) that whenadded to pure air will cause adverse effects.

    CLASSIFICATION of AIR Pollutants

    Primary Pollutants are pollutants emitted as such to the

    atmosphere.Secondary Pollutants are pollutants actually produced in theatmosphere by chemical reactions.


    a. Particulates

    b. Gaseous Pollutants

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    1. DUST is defined as solid particles that are entrained by process gasesdirectly from the material being handled or processed such as coal,ash and cement.

    2. FUME is a solid particle frequently a metallic oxide formed by the

    condensation of vapors by sublimation, distillation, calcinations, orchemical reaction process.

    3. MIST is an entrained liquid particle formed by the condensation ofvapor and perhaps by chemical reaction.

    4. SMOKE is made up of entrained solid particles formed as a result ofincomplete combustion of carbonaceous material.

    5. SPRAY is a liquid particle formed by the atomization of parentliquid.

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    1. SULFUR DIOXIDE is a colorless gas, intense choking odor, highly soluble in water toform sulfurous acid.2. SULFUR TRIOXIDE is highly corrosive soluble in water to form sulfuric acid.3. HYDROGEN SULFIDE is a highly poisonous gas with rotten egg odor at low

    concentrations, odorless at high concentration.4. NITROUS OXIDE is a colorless gas, used as carrier gas in aerosol bottles.5. NITRIC OXIDE is a colorless gas produced during high temperature, high pressure,

    and combustion Oxidize to Nitrogen dioxide.6. NITROGEN DIOXIDE is a brown to orange gas w/c is a major component in the

    formation of photochemical smog.7. CARBON MONOXIDE is a colorless, odorless, poisonous gas that is a product of

    incomplete combustion.8. CARBON DIOXIDE us a colorless, odorless, formed during complete combustion.9. OZONE is a highly reactive gas that is produced mainly during the formation of

    photochemical smog10. HYDROCARBONS emitted from automobiles and industries, others are formed in

    the atmosphere.

    11. METHANE is a colorless, odorless, flammable gaseous hydrocarbon w/c a productof decomposition of organic matter.

    12. CHLOROFUOROCARBONS is a highly stable compound that is being used in spraycans as aerosol propellants

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    Natural Processes

    PARTICULATES include pollen grains, fungus spores, salt spray, smokeparticles and dusts

    GASEOUS POLLUTANTS from natural sources include carbon monoxide

    as breakdown product in the degradation of hemoglobin,hydrocarbons in the form if terpenes from pine trees, hydrogensulfide resulting from the breakdown of cysterine and other sulfurcontaining amino acids by bacterial action, nitrogen oxides andmethane.

    People made source of pollutants classified as:Stationary combustion, Transportation, Industrial processes

    and Solid waste disposal

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    EFFECTS OF AIR POLLUTIONPeople relating AIR POLLUTION to HEALTH Existence of threshold, Total

    body burden of the pollutants, time versus dosage problem, andsynergism (synergistic effects of various combination of pollutants)

    DISEASES caused by AIR POLLUTANTS Lung cancer, asthma andemphysema


    a. Particulate, Effects on breathing and respiratory systems, aggravationof existing respiratory and cardiovascular disease, alteration of thebodys defense systems against foreign materials, damage to lungtissue, carcinogenesis and premature mortality.

    b. Carbon monoxide, The health threat of CO is greatest to those w/cardiovascular disease because it includes oxygen delivery to organs andtissues. At elevated concentration CO impairs visual perception, manualdexterity and mental ability.

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    3. Sulfur dioxide, Effects on breathing, respiratory illness, breakdown ofLung diseases, aggravation of existing respiratory and

    cardiovascular disease and death.4. Nitrogen dioxides, Irritate the Lungs, causes bronchitis and

    pneumonia, lowers resistance to respiratory infections, and plays amajor role in tropospheric ozone formation.

    5. Ozone, Reduces lung function, usually w/ association w/ coughing,sneezing, chest pain, and pulmonary congestion. Highconcentrations of ozone are frequently associated w/ eye irritation,although this may not be caused to ozone itself.

    6. High Lead exposures, Can cause seizures, mental retardation, andbehavioral disorder.

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    One way in w/c sulfur dioxide is removed from theatmosphere is the formation of acid rain. Normaluncontaminated rain has pH of 5.6 but acid rain can be as low aspH 2 even below. Acid Rain encompasses both wet and dry acidicdeposition that occurs near and downwind of areas where majoremissions of sulfur dioxide and nitrogen oxides results from

    burning fossil fuels.The most important effect of acid rain is the decline of fish

    population, w/c is specially damaging to sport fishing. Otheraquatic effects of acid rain include those on human who eat fishhaving increased concentration of metal in their flesh. Acid rain

    poses an insidious and potentially devastating threat to ourforest; it has been shown that seedlings can be damaged bymoderately acidic rain (pH4.6)

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    The formation of photochemical smog is adynamic process. Note that as the morning rush hourbegins the NO levels increase, followed quickly byNO2. As the latter reacts w/ sunlight, Ozone and otheroxidants are produced. The hydrocarbon level similarlyincreases at the beginning of the day and then dropsoff in the evening. Particularly baffling was theformation of high ozone levels, w/c for every mole ofNO2 reacting to make a atomic oxygen and hence,ozone, on mole of NO2 is created from reaction w/ozone.

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    OZONE DEPLETIONOzone is an eye irritant at usual urban levels, but urban

    ozone should not be confused with stratospheric ozone w/coccurs 7 to 10 miles above the earths surface. Stratosphericozone acts as am ultraviolet radiation shield. CFC emittedmostly from refrigeration units and spray cans can apparentlyalter the shield and increase the risk of skin cancer as well as

    change global ecology in unpredictable ways, includingcontributing to global warming.

    Two of the most important CFCs aretrichlorofuoromethane, and dichlorofluoromethane, both ofw/c are inert and nonwater soluble and therefore do notwashout the atmosphere. They drift into upper atmosphereand are eventually destroyed by the short-wave solar radiationreleasing chlorine w/c can react w/ ozone.

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    The Earth acts as a reflector to the suns rays receiving theradiation from the sun and reflecting some of it into space (calledalbedo) and absorbing the rest only to reradiate this into space asheat. Unfortunately, some gases such as methane, carbon dioxide,and nitrous oxide adsorb radiation at wavelengths approximatelythe same as the heat radiation trying to find its way back to space.

    Because the radiation is adsorbed in the atmosphere by these gases,temperature of the atmosphere increases heating the earth.

    The system works exactly like a greenhouse in that lightenergy through the greenhouse glass, but the long wavelength, lowfrequency heat radiation is prevented from escaping. The gases that

    adsorb the heat energy radiation are properly referred asgreenhouse gases since they in effect cause the Earth to heat up justlike a greenhouse.

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    ASBESTOS from fireproofing and vinyl floorsCARBON MONOXIDE from smoking, space heaters and stovesFORMALDEHYDE from carpets, ceiling tiles and panelingPARTICULATES from smoking, fireplace and dustingNITROGEN OXIDES from kerosene stoves, gas stoves

    OZONE from photocopying machine

    RADON from natural emitted gas diffused from soilSULFUR DIOXIDE from kerosene heatersVOLATILE ORGANICS from smoking, paints, solvents, cooking

    Health problems from contaminated INDOOR AIR:- Eye irritation, Headache, Nausea, Sneezing, Dermatitis,

    Heat burn, Drowsiness


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    AIR QUALITY CONTROLThe easiest way and also most economical solution to air pollution

    is to eliminate the source of the pollution. Air quality control is oftenachieved by some form of air treatment similar in concept to watertreatment.


    Selection of the correct treatment device requires matchingcharacteristics of the pollutant w/ features of the control device. It isimportant to remember that the sizes of air pollutants range manyorders of magnitude, and it is therefore not reasonable to expect onedevice to be effective and efficient for all pollutants. In addition, thetypes of chemicals in emission soften will dictate the use of somedevices.

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    CONTROL OF PARTICULATES1. Settling Chambers the simplest device for controlling particulates

    consisting of nothing more than wide places in the exhaust flue wherelarger particles can settle out, usually w/ a baffle to slow the emissionstream.

    2. Cyclone the most popular, economical and effective means ofcontrolling particulates

    3. Bag filters used for controlling particulates, operate like the commonvacuum cleaner. Bag filters are widely used in many industrialapplications, but are sensitive to high temperatures and humidity.

    4. Spray Tower or Scrubber is an effective method for removing largeparticulates, where high efficiency scrubbers promote the contactbetween air and water by violent action in a narrow throat section

    into w/c water is introduced. This method has two major drawbacks:(a) produce visible plume (b) the waste is now on liquid form.

    5. Electrostatic Precipitator widely used in power plants, mainlybecause power is available. The particulate matter is removed by firstcharging it by electros jumping from one high voltage electrode to theother migrating to the positively charged collecting electrode.

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    The control of gases involves the removal of the pollutant fromthe gaseous emissions, a chemical change in the pollutant, or achange producing the pollutant.

    1. Wet Scrubbers can remove gaseous pollutants by simplydissolving them in water; alternatively, a chemical may be injectedinto the scrubber water, w/c then reacts in the pollutants.

    2. Adsorption it is useful method when it is possible to bring thepollutant into contact w/ an efficient adsorbed like activatedcarbon.

    3. Incineration or Flaring is used when an organic pollutant can beoxidized to carbon dioxide and water. A catalytic combustion is avariation of incineration whereby the temperature of the reactionis lowered by the use of catalyst that mediates the reaction.

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    CONTROL OF SULFUR OXIDESThe major source of sulfur oxides (SO) is coal fired power plants. The

    increasingly strict standards for SO control have prompted thedevelopment of a number of options and techniques for reducingemissions of sulfur oxides. Among these options are the ff.

    1. Change to flow sulfur fuel natural gas and oil are considerably lowerin sulfur than coal, however uncertain and expensive supplies makethis option risky.

    2. Desulfurize the coal sulfur in coal is either organics or inorganic. Theinorganic form iron pyrate (FeS2), w/c since it occurs in discreteparticles can be removed by washing. The removal of the organic sulfur(generally 60% of the total) requires chemical reactions is mosteconomically accomplished if the coal is gasified. (change into a gasresembling natural gas)

    3. Tall Stacks a shortsighted method of SO2 control where incredibly tallstacks are built and disperse the SO2.

    4. Flue gas Desulfurization the last option is to reduce the SO2 emittedby cleaning the gases coming from the combustion, the so called flue gas. The most widely used method of SO2 removal is to contact thesulfur w/ lime or limestone.

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    Atmosphere conditions primarily determine the dispersion ofair pollutants. If the conclusion are super adiabatic, a great deal ofvertical air movement and turbulence are produced, and dispersionis enhanced. The super adiabatic prevailing lapse rate is bycontrast a very stable system.

    Dispersion is the process of spreading out the emission over a largearea and thereby reducing the concentration of the specificpollutants. The dispersion is dependent on both the atmosphericstability and the distance over the source.

    The Effect of atmospheric instability can be as follows:

    a. A super adiabatic lapse rate produces atmospheric instability anda looping plume.

    b. An adiabatic lapse rate evens out the plume, producing a comingplume.

    If h l i i d i i i l f i l

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    c. If the plume is emitted into an inversion layer, a fanning plumewill result; a highly descriptive name since from above it can beseen that the plume fans out horizontally w/o any verticaldispersion.

    d. A particularly nasty situation is the fumigation condition, when aninversion cap is placed on the plume, but a super adiabatic lapserate under the inversion causes mixing and high ground levelconcentrations.

    CONTROL OF MOVING SOURCESAlthough many of the previously mentioned control

    techniques can apply to moving sources as well as to stationaryones, one very special moving source - the automobile deservesspecial attention. Although the automobile has many potentialsources of pollution, there are only a few important pointsrequiring control.

    1.Evaporation of hydrocarbons (HCs) from the fuel tank.2. Evaporation of hydrocarbon from the carburetor.

    3. Emissions of unburned gasoline and partially oxidized HCs fromthe crankcase.

    4. The NOXs HCs and CO from the exhaust.

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    CONTROL OF MOVING SOURCESThe evaporative losses from the gas tanks have been reduced by the

    use of gas tank caps that prevent the vapor from escaping. Losses from

    carburetors have been reduced by use of activated carbon canisters thatstore the vapors emitted when the engine is turned off and the hot gasolinein the carburetor vaporizes. The third source of pollution, the crankcasevent, has been eliminated by closing off the vent to the atmosphere andrecycling the blow by gas into the intake manifold. POSITIVECARNKCASE VENTILATION (PCV) Valve is a small check valve thatprevents the build up of pressure in the crankcase. Nitrogen oxides from

    automobile exhausts are controlled by recirculating exhaust gas, dilutingthe air to fuel mixture being burned in engine.

    Emission control techniques (internal combustion automobile engine)

    1. Tuning the engine to burn efficiently a tune - up can have a significanteffect on emission components.

    2. Installation of catalytic reactors catalytic converters oxidizes the CO andHCs to CO2 and H2O.

    3. Engine Modifications greatest advance in engine development so as toproduce less emission.

    One of the most destructive effects of automobile emission is the deteriorationof building, statuary, and other materials.

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    RA 8749: The Philippine Clean AirAct of 1999

    A comprehensive air quality management policy and program w/caims to achieve and maintain healthy air for all Filipinos.

    Guiding Principles

    Protect and advance the right of the people to a balanced andhealthful ecology in accord w/ the rhythm and harmony of nature

    Promote and protect the global environment while recognizing theprimary responsibility of local government units to deal w/environmental problems

    Recognize that the responsibility of cleaning the habitat andenvironment is primarily area based

    Recognize that polluters must pay

    Recognize that clean and healthy environment is for the good of all andshould be concern of all

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    WHO World Health OrganizationNSCB National Statistical Coordination Board

    DENR Department of Environmental and Natural Resources

    DOTC Department of Transportation and Communication

    DOST Department of Science and TechnologyNRDF National Research and Development Program

    DTI Department of Trade and Industry

    DOE Department of Energy

    BPS Bureau of Product StandardPNS Philippine National StandardPAGASA Philippine Atmospheric, Geophysical andAstronomical Service Administration

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