Comparative Analysis of Methods of RemovingAir, Water and Soil PollutantsGroup 5

PanelGroup # 52012-MS-EM- 16Furqan Ahmed Khan2012-MS-EM-22Ahmed Sattar2012-MS-EM-22 Jahangir ul Hassan2012-MS-EM- 25Muhammad Usman Tariq

Sequence of PresentationIntroduction2012-MS-EM-16Air pollutants removal methods and comparative analysis Water pollutants removal methods and comparative analysis 2012-MS-EM-22Soil pollutants removal methods and comparative analysisConclusion2012-MS-EM-16Question

IntroductionMan is the architect ofhisenvironment and has to accept full responsibility for his environmentHe is responsible for air, water and soil pollution and all its effects on man, fauna, flora, and all kinds of buildingsTo meet this responsibility, man has to observe following general rules:Stop the production of pollutants, orReduce the production of pollutants to the lowest possible level

IntroductionProduce the unavoidable amount of pollutants in such a way, that the properties of the pollutants will guarantee easy separation from the carrier fluid, or effective conversion into harmless productsDevelop processes and equipment for effective separation of the pollutants from the carrier fluid or conversion into harmless productsIn our presentation we have tried to bring out the comparative analysis of air, water and soil pollutants removal methods

Air PollutionDefinitionAny undesirable substance mixed with open airThe definition is not limited to gaseous substance onlyParticles or droplets less than 0.001 diameter thats remains in suspension for a long period of time

Forms of Atmospheric ContaminationMistFumesDustSmokeParticulate MaterialVapors

Atmospheric ContaminantsFine ParticlesOxides of Sulphur and NitrogenAirborne carcinogensSulfatesVolatileFugitive

Air Pollution ControlApplication of control technology requires knowledge of source, effluents from the source, air pollution regulations and waste generated from the technologySome times it is possible to develop a successful air pollution control technology which leads to the problem of disposing the wastePurpose is to prevent pollution rather than control it at the point of releaseThe techniques for controlling air pollution can be either Without an air pollution control deviceWith air pollution control equipment

Air Pollution ControlWithout Control DeviceThe general methods for this techniques include:Process changeChange in fuelImprove dispersionGood operating practicesPlant shutdown/relocationWith Control DeviceControl equipment remove the pollutant, convert to less harmful contaminant or recover a valuable material for further use

Without Control Device

Process ChangeModification of an existing process or the introduction of a new processAlso known as Pollution PreventionPainting operations in automobile industryLarge quantities of volatile organic compounds and hazardous air pollutants releasedMany operations have substituted water based, low HAP (hazardous air pollutant) paints for oil based paints New implemented processes such as electro-deposition, dip tank and powder coatingNew oxy furnaces are being developed to reduce ozone emissions during glass manufacturing

Changes in industrial processes to reduce raw materials and fuels also lead to reduction in air emissionsUseenergy savers/LED and Conduct energy audits are examples of less electricity demandResults in less fuel use at the power plant and hence less air pollutants are emittedThe use of wind energy, geothermal energy, hydroelectric power and solar energy is increasing and is helping in reducing air pollutionProcess Change

This technique involves the use of less polluting fuel to reduce air pollutionUse of low sulfur fuel instead of high sulfur fuel by electric or natural gas is an example of this methodLow sulfur fuel is more expensive than high sulfur fuelChange in Fuel

This approach is based on the concept that dilution of air contaminants before they reach ground will lower the concentrations to which the population is exposedThe use of this approach for industry is discouraged by the US EPAHowever, local and state agencies use the concept to develop air pollution control strategies for their areaImprove Dispersion

This approach attempts to control source emission rate during the periods of high ground level concentrationsProduction curtailments, a plant shutdown, fuel switching, or other strategies achieve the reduction in source emission rateThe critical periods are determined from weather related data in the areaMany cities in Canada and US have regulations to curtail industrial and other activities during times of observed poor air qualityAir Quality Prediction System

Alberta Environment asks industry to cut production during early morning hours of poor air quality in City of Calgary and EdmontonHigh CO emissions are observed in many communities during winter monthsOzone action days are declared during summer months to avoid violationsAir Quality Prediction System

Release of unnecessary air pollutants could be avoided by maintaining good housekeeping in the plant and performing proper maintenanceLiquid chemicals spread over the floor evaporates rapidly and will cause an increase in emission rate for that chemicalGood Operating Practices

Most cities develop land-use planning and industrial zoning regulations to avoid this situationNot a pleasant solution for a community because of economic impactPlant Shutdown/Relocation

Comparison of Techniques for Without Control Device

ProcessTypeInitial costFlexibilityMaintenance Process ChangeModification or new processPreventiveLess costlyFlexible & multiple approachNo recurring/ maintenance expenditureChange in FuelNormally at plant levelPreventiveCostlyLess flexible Routine maintenanceImprove DispersionImplementation by regulationsReactiveCost variesRigid-Air Quality Prediction SystemImplementation by regulationsReactiveNo direct but indirect cost of shut downFlexible No maintenance cost other may have chargesGood Operating PracticesHouse keeping &maintenance orientedPreventiveNo direct costFlexible Maintenance cost may be highPlant Shutdown / RelocationImplementation by regulationsReactiveMost costly & uneconomicalRigid-

With Control Device

The emissions from the plant are passed through a control device before releasing to atmosphereThe pollutants are removed, destroyed or transformed in the control device before discharging into ambient airMust consider other methods as discussed in previous slide before deciding to use of control devicesWith Control Device

Disposal Solutions for Gaseous WastesDiffusion and dilutionAbsorptionCombustion(Chemical Waste Gas Treatment)Cleaning the particulate material

Disposal Solutions for Gaseous WastesGaseous pollutants can be removed from air by means of gas washing (removal of gas by dissolving it in a liquid), by adsorption on a solid or by converting it to other, less damaging gassesSometimes certain powders or granule solids can absorb an air pollutantThe air that needs to be purified is directed through an active carbon system or through metal oxidesThe gasses can be freed again afterwards, by heating the absorbent

Commonly Used Methods For Air Pollution ControlGases Adsorption Towers Thermal Incineration Catalytic Combustion

Commonly Used Methods For Air Pollution ControlParticulate MaterialCyclones Electrostatic Precipitators Fabric Filter Wet Scrubbers

Air Pollution Control For Gases And Vapors

Adsorption Towers Thermal Incineration Catalytic Combustion

Air Correction Equipment for Gases and Vapors

Adsorption Towers Principle Adsorption towers use adsorbents to remove the impurities from the gas streamThe impurities bind either physically or chemically to the adsorbing materialThe impurities can be recovered by regenerating the adsorbentAdsorption towers can remove low concentrations of impurities from the flue gas stream

Advantages of Adsorption Towers Very low concentrations of pollutants can be removedEnergy consumption is lowDo not need much maintenanceEconomically valuable material can be recovered during regenerationAdsorption Towers

Diffusion and dilutionOxides of sulfur can be removed from industrial smokestack gases by "scrubbing" the emissions, by electrostatically precipitating the sulfur, by filtration, or by combining them with water, thereby producing sulfuric acid which can be used commerciallyOxides of nitrogen (include: nitric oxide (NO), nitrogen dioxide (NO2), and nitrous oxide (N2O)), these pollutants can be reduced by catalytic converters which convert them to molecular nitrogen and oxygen

AbsorptionThe sulphur compound that exists in the atmosphere in big quantities can be removed by chemical and electrochemical methodsThe chemical methods involve obtaining big quantities of waste products are very expensiveThe electrochemical methods are used more often than the chemical methods because of the fact that are not pollutingThe rate of the processes can be rigorously controlled and they are not big energy consumers

Bio-filters are unsuitable for bio-treatment of waste gas stream containing biodegradable chlorine and sulphur compounds, because of acid formationBio-scrubbers are recommended in this case^

^ Ref: The removal of volatile ketone mixtures from air in bio-filters by M. A. Deshusses,Prof. Dr. G. Hamer

Methods For Air Pollution Control For Some Pollutants

SOX CONTROL

GENERAL METHODS FOR CONTROL OF SO2 EMISSIONSUse of Low Sulfur Fuel Natural Gas Liquefied Natural Gas Low Sulfur Oil Low Sulfur CoalUse Alternative Energy Sources, such as Hydro-Power or Nuclear-Power Use Flue Gas Desulfurization Systems

GENERAL METHODS FOR CONTROL OF SO2 EMISSIONS

Flue Gas DesulfurizationThe most widely used method is scrubbingThe installation and operation of these air pollution control device is expensive and require large capital expenditureSO2 scrubbing, or Flue Gas Desulfurization processes can be classified in following ways:Throwaway or Regenerative, depending upon whether the recovered sulfur is discarded or recycledWet or Dry, depending upon whether the scrubber is a liquid or a solid

Flue Gas Desulfurization ProcessesLimestone ScrubbingLime ScrubbingDual Alkali ProcessesLime Spray DryingWellman-Lord Process

Limestone Scrubbing

Limestone slurry is sprayed on the incoming flue gasThe sulfur dioxide gets absorbedThe limestone and the sulfur dioxide react as follows : CaCO3 + H2O + 2SO2 ----> Ca+2 + 2HSO3-+ CO2

CaCO3 + 2HSO3-+ Ca+2 ----> 2CaSO3 + CO2 + H2O Limestone Scrubbing

Lime Scrubbing

Lime Scrubbing

The equipment and the processes are similar to those in limestone scrubbing but Lime Scrubbing offers better utilization of the reagentThe operation is more flexibleThe major disadvantage is the high cost of lime compared to limestoneThe reactions occurring during lime scrubbing are :CaO + H2O -----> Ca(OH)2SO2 + H2O H2SO3H2SO3 + Ca(OH)2 -----> CaSO3.2 H2OCaSO3.2 H2O + (1/2)O2 -----> CaSO4.2 H2OLime Scrubbing

Dual Alkali System

Dual Alkali System

Lime and Limestone scrubbing lead to deposits inside spray towerThe deposits can lead to plugging of the nozzles through which the scrubbing slurry is sprayedThe Dual Alkali system uses two regents to remove the sulfur dioxideSodium sulfite / Sodium hydroxide are used for the absorption of sulfur dioxide inside the spray chamberDual Alkali System

The resulting sodium salts are soluble in water, so no deposits are formedThe spray water is treated with lime or limestone, along with make-up sodium hydroxide or sodium carbonateThe sulfite / sulfate ions are precipitated, and the sodium hydroxide is regenerated

Dual Alkali System

Lime Spray Drying

Lime Spray DryingLime Slurry is sprayed into the chamber The sulfur dioxide is absorbed by the slurryThe liquid-to-gas ratio is maintained such that the spray dries before it reaches the bottom of the chamberThe dry solids are carried out with the gas, and are collected in fabric filtration unitThis system needs lower maintenance, lower capital costs, and lower energy usage

Wellman Lord ProcessSchematic process flow diagram SO2 scrubbing and recovery system

Wellman Lord Process

The flue gas is pre - treated to remove the particulateThis process consists of the following sub processes:Flue gas pre-treatmentSulfur dioxide absorption by sodium sulfitePurge treatmentSodium sulfite regenerationThe concentrated sulfur dioxide stream is processed to a marketable productThe sodium sulfite neutralizes the sulfur dioxide : Na2SO3 + SO2 + H2O -----> 2NaHSO3Wellman Lord Process

Some of the Na2SO3 reacts with O2 and the SO3 present in the flue gas to form Na2SO4 and NaHSO3Sodium sulfate does not help in the removal of sulfur dioxide, and is removedPart of the bisulfate stream is chilled to precipitate the remaining bisulfateThe remaining bisulfate stream is evaporated to release the sulfur dioxide, and regenerate the bisulfiteWellman Lord Process

Comparison of Methods For Control Of SO2

Re-agentInitial costMaintenance costProcess typeEnd productFlexibilityLimestone Scrubbinglime stoneLargeHighWetThrow away by-productLess flexibleLime ScrubbingLimeHigherHighWet/dryThrow away by-productMore flexibleDual Alkali ProcessesSodium sulfite / Sodium hydroxide HigherLowWetRegenerativeFlexibleLime Spray DryingLime stoneLowLowDryThrow away by productiveLess FlexibleWellman-Lord Processsodium sulfite HighLowWetRegenerative and marketableFlexible

CARBON DIOXIDE CONTROL

Sources of Carbon DioxideHuman-Related SourcesCombustion of fossil fuels: Coal, Oil, and Natural Gas in power plants, automobiles, and industrial facilitiesUse of petroleum-based productsIndustrial processes: Iron and steel production, cement, lime, and aluminum manufacturesNatural SourcesVolcanic eruptionsOcean-atmosphere exchangePlant photosynthesis

CO2 Emissions from Fossil Fuel Combustion by Sector and Fuel TypeSource: USEPA(y-axis units are teragrams of CO2 equivalent)

General Methods For Control of CO2 Emissions Reducing energy consumption, increasing the efficiency of energy conversionSwitching to less carbon intensive fuelsIncreasing the use of renewable sourcesSequestering CO2 through biological, chemical, or physical processes

CONTROL OF MERCURY EMISSIONS

Mercury EmissionsMercury exists in trace amounts in Fossil fuels such as Coal, Oil, and Natural GasVegetationWaste productsMercury is released to the atmosphere through combustion or natural processesIt creates both human and environmental risks

Control Technologies for Mercury EmissionsCurrently installed control devices for SO2, NOX, and particulates, in a power plant, remove some of the mercury before releasing from the stackActivated Carbon Injection: Particles of activated carbon are injected into the exit gas flow, downstream of the boiler. The mercury attaches to the carbon particles and is removed in a particle control deviceThief process for the removal of mercury from flue gas: It is a process which extracts partially burned coal from a pulverized coal-fired combustor using a suction pipe, or "thief," and injects the resulting sorbent into the flue gas to capture the mercury.

PARTICULATE MATTER CONTROL

PARTICULATE MATTER CONTROLRange: 20 to 40000 mg/m**3First step: Process controlSecond step: Use of collection device

Industrial Sources of Particulate Emissions Iron & Steel Mills, the blast furnaces, steel making furnaces. Petroleum Refineries, the catalyst regenerators, air-blown asphalt stills, and sludge burners. Portland cement industry Asphalt batching plants Production of sulfuric acid Production of phosphoric acid Soap and Synthetic detergent manufacturing Glass & glass fiber industry Instant coffee plants

General Methods For Control Of Particulate Emissions Basic Types of Dust Collectors :Gravity and Momentum collectors Settling chambers, louvers, baffle chambers Centrifugal Collectors Cyclones Mechanical centrifugal collectorsFabric Filters Bag houses Fabric collectors

Electrostatic Precipitators Tubular Plate Wet Dry Wet Collectors Spray towers Impingement scrubbers Wet cyclones Peaked towers Mobile bed scrubbers General Methods For Control Of Particulate Emissions

General Methods For Control Of Particulate Emissions

Particulate Collection Mechanism Gravity Settling Centrifugal Impaction Inertial Impaction Direct Interception Diffusion Electrostatic Effects

Tubular Dust Collector Arrangement

Cyclones Principle, Construction and Operation The particles are removed by the application of a centrifugal forceThe gas enters through the inlet, and is forced into a spiralThe polluted gas stream is forced into a vortexThe motion of the gas exerts a centrifugal force on the particles, and they get deposited on the inner surface of the cyclonesAt the bottom, the gas reverses direction and flows upwardsTo prevent particles in the incoming stream from contaminatingthe clean gas, a vortex finder is provided to separate them. the cleaned gas flows out through the vortex finder

Cyclones

CyclonesAdvantages of Cyclones Cyclones have a less capital cost Reasonable high efficiency for specially designed cyclones They can be used under almost any operating conditionCyclones can be constructed of a wide variety of materials There are no moving parts, so there are no maintenance requirementsDisadvantages of Cyclones They can be used for small particles High pressure drops contribute to increased costs of operation

Fabric Filters Principle The filters retain particles larger than the mesh size Air and most of the smaller particles flow throughSome of the smaller particles are retained due to interception and diffusionThe retained particles cause a reduction in the mesh sizeThe primary collection is on the layer of previously deposited particles

Filter Cloth

Fabric Filters Fabric Filter

Advantages of Fabric Filters Very high collection efficiency They can operate over a wide range of volumetric flow rates The pressure drops are reasonably low. Fabric Filter houses are modular in design, and can be pre-assembled at the factory

Fabric Filters require a large floor areaThe fabric is damaged at high temperatureOrdinary fabrics cannot handle corrosive gasesFabric Filters cannot handle moist gas streams A fabric filtration unit is a potential fire hazardDisadvantages of Fabric Filters

Electrostatic Precipitator Principle The particles in a polluted gas stream are charged by passing them through an electric fieldThe charged particles are led through collector plates The collector plates carry charges opposite to that on the particles The particles are attracted to these collector plates and are thus removed from the gas steam Construction and Operation of Electrostatic Precipitator Charging Electrodes in the form of thin wires are placed in the path of the influent gasThe charging electrodes generate a strong electric field, which charges the particles as they flow through itThe collector plates get deposited with the particlesThe particles are occasionally removed either by rapping or by washing the collector plates

Electrostatic Precipitator Electrostatic Charging of Dust ParticlesCutaway of Electrostatic Precipitator

Electrostatic PrecipitatorAdvantages of Electrostatic Precipitators Electrostatic precipitators are capable very high efficiency, generally of the order of 99.5-99.9%Can handle higher loads with lower pressure dropsCan operate at higher temperaturesThe operating costs are generally lowDisadvantages of Electrostatic Precipitators The initial capital costs are highAlthough they can be designed for a variety of operating conditions, they are not very flexible to changes in the operating conditions, once installedParticulate with high resistivity may go uncollected

Wet Scrubbers Principle Wet scrubbers are used for removal of particles which have a diameter of the order of 0.2 mm or higherWet scrubbers work by spraying a stream of fine liquid droplets on the incoming streamThe droplets capture the particles The liquid is subsequently removed for treatment

Construction and Operation A wet scrubber consists of a rectangular or circular chamber in which nozzles are mountedThe nozzles spray a stream of droplets on the incoming gas stream The droplets contact the particulate matter, and the particles get sobbedThe droplet size has to be optimizedSmaller droplets provide better cleaning, but are more difficult to remove from the cleaned streamThe polluted spray is collectedParticles are settled out or otherwise removed from the liquidThe liquid is recycledWet scrubbers are also used for the removal of gases from the air streamsWet Scrubbers

Wet Scrubbers Aeromix Wet Scrubber

Wet Scrubbers

Advantages of Wet Scrubbers Wet Scrubbers can handle incoming streams at high temperature, thus removing the need for temperature control equipmentWet scrubbers can handle high particle loadingLoading fluctuations do not affect the removal efficiencyThey can handle explosive gases with little riskGas adsorption and dust collection are handled in one unitCorrosive gases and dusts are neutralizedDisadvantages of Wet Scrubbers High potential for corrosive problems Effluent scrubbing liquid poses a water pollution problemWet Scrubbers

Comparison of Methods For Control Of Particulate Emission

TypeEfficiencyInitial costOperating costFlexibilitySettling ChamberGravityLowLowLowLess flexibleCyclonesCentrifugalHighLowNo maintenanceLess flexibleFabric FiltersMesh/ seiveVery highLow LowLess flexibleTubular Dust collectorElecrto-static precipitationVery highHighLowIn-flexibleSpray TowersWet collectorModerateModerateHighIn-flexible

Volatile Organic Compounds (VOCs) And Hydrocarbon Control

Volatile Organic Compounds (VOCs) And Hydrocarbon ControlVolatile organic compounds (VOCs) include hydrocarbons such as methane (CH4), propane (C3H8), and octane (C8H18), and chlorofluorocarbons (CFCs) such as dichlorodifluoromethane (CCl2F2)Volatile organic compound emissions can be reduced by using vapor-recovery gasoline nozzles at service stations and by burning oxygenated gasoline in automobile engines

Methods For Control Of VOC & Hydrocarbon Emissions Thermal Incineration (Types)Direct flame incinerationCatalytic incineration

Direct Flame Incineration

Catalytic Incineration

Thermal Incinerator

Catalytic Incinerator with Heat Recovery

VOC Incinerators Principle VOC incinerators thermally oxidize the effluent stream, in the presence of excess airThe complete oxidation of the VOC results in the formation of carbon monoxide and waterThe reaction proceeds as follows: CxHy + ( x + y/4 ) O2 x CO2 + (y/2) H2O Operation The most important parameters in the design and operation of an incineration system are what are called the ' three T's ' Temperature, Turbulence, and residence Time

Temperature The reaction kinetics are very sensitive to temperature The higher the temperature, the faster the reaction Timing A certain time has to be provided for the reaction to proceed Turbulence Turbulence promotes mixing between the VOC's and oxygen Proper mixing helps the reaction to proceed and to complete in the given timehttp://yosemite.epa.gov/oaqps/eogtrain.nsf/ae20ef1becae534385256b4100770781/86549ba361577a5a85256da3005cc39c/$FILE/SI%20445_9.pdfVOC Incinerators

VOC Incinerators

Comparison of Techniques

ProcessImpurities can be recoveredOperating concentrationOperating temperatureOperational costmaintenanceDirect flame incinerationDirect burningNon-regenerativeVOC inlet kept b/w 500-7500 ppm for safety670-700 CRelatively higherDifficultCatalytic incinerationIncineration with catalystNon-regenerative370-480 CLow due to catalystRelatively easier

Waste water treatment

Waste water Treatment methodsOn the basis of level of removal of contaminants, treatment methods are classified into

Preliminary TreatmentPrimary TreatmentSecondary TreatmentTertiary Treatment

Comparison of treatment methods

Preliminary TreatmentPrimary TreatmentSecondary TreatmentTertiary TreatmentIt is a physical method of treatment

Prepares waste water for further treatmentIt includes physical and chemical treatment method.

It acts as precursor for secondary treatment.It is biological treatment method.

Purpose is to remove contaminants which escaped form primary treatment.It is chemical treatment method.

It is a treatment that goes beyond the level of conventional secondary treatment.

Classification based of level of treatment

Preliminary TreatmentPrimary TreatmentSecondary TreatmentTertiary TreatmentRemoval of large solid, rags, abrasive grits, debris etc.

Includes screening, comminution, flow equalization etc.Removal of large solid and organic material

Includes screening, sedimentation, pre-aeration, mechanical flocculation with chemical additions.Removal of Colloidal organics and suspended solids

It includes activated sludge, fixed film reactors, lagoons system and sedimentation etc.Removal of nitrogen, phosphorus, heavy metals, bacteria and viruses.

Less frequently used process includes ion exchange methods and reverse osmosis etc.

Waste water Treatment methodsWater treatment methods are also classified in to three types on the basis of methods used for treatment.

Physical methodsChemical methodsBiological methods

Physical methodsPhysical methods are those methods in which physical forces are used to remove contaminants.

ScreeningComminutionSedimentationFloatation

Comparison of Physical methods

ScreeningComminutionSedimentationFloatationOldest method to remove gross pollutant

Used for protection of downstream equipment's

Consists of bars, mesh, wires or gratings etc.To pulverize large floating material

Used where handling of screens is impractical

Consists of rotating or oscillating cutters or both.Gravitational settling of heavy particles, grit etc.

Fundamental operation in treatment process

Carried out in sedimentation tank, also called settling tank/clarifierRemoval of suspended matter such as oil and solids

Used for Industry, petrochemical and chemical plants.

Carried out in floatation tank

Chemical MethodsChemical methods treatment methods bring about some form change by means of chemicals. These are always used in conjunction with physical and chemical processes.

Chemical precipitationAdsorptionDisinfectionDe-chlorinationReverse osmosisIon exchange method

Comparison of Chemical methods

Chemical PrecipitationAdsorptionDisinfectionDe-chlorinationRemoval of suspended solids using chemical treatment.

Helps in removal of suspended solids, BODs etc.

Can be used on small and large scale.Removal of soluble substances form solution

Usually follows normal biological treatment

Used in field and industrial processDestruction of disease causing micro-organisms

To minimize waterborne disease from spreading

Final stage of treatment is disinfectionRemoval of free/combined chlorine.

Protects aquatic life from toxic effects ofresidual chlorine.

Also used at final stages of discharge.

Comparison of Chemical methods

Chemical PrecipitationAdsorptionDisinfectionDe-chlorinationChemical coagulants like Alum is used for this purposeActivated carbon is used for this treatment in activated carbon contactorChlorine, Ozone, UV radiations etc. are used for this treatmentSulfur dioxide is most commonly used for this purpose.

Comparison of Chemical methods

Reverse osmosisIon exchange methodReverse osmosis (RO) is a water purification technology that uses a semipermeable membrane.

RO can remove many types ofmoleculesandionsfrom solutions

Used for fresh water and wastewater treatment on small and large scale.

Semi permeable membrane is used and solvent is forced to move through this leaving behind contaminants.Process of replacing a toxic ion with some other ionic species

Can remove heavy metals found in wastewaters are lead, copper, nickel, cadmium, zinc, mercury, arsenic, and chromium.

Used for the treatment of contaminated wastewater/sludge

Expensive method and is being varied out in ion exchange chamber

Biological Methods The use of bacteria to degrade and decompose organic materials in waste water.Activated sludge processAerated lagoonTrickling filtersRotating biological contactorsPond stabilizationAnaerobic digestionBiological nutrient removal

Comparison of Biological methods

Activated sludge processAerated LagoonsTrickling filtersRotating Biological Cont.Treatingsewageand industrial wastewater using air

Oxidizingcarbonaceous biological matter, nitrogenous matter and removing phosphates etc.

Used for primary treated sewerage and industrial wastewater.Aerated lagoons are relatively shallow lagoons used for treatment

Used for treatment of distillery and industrial wastes

Use oxygenor air and microbialaction to bio-treat the pollutants in wastewaters.It is an economical and easy biological treatment method.

Removing B.O.D, ammonia from wastewater and settled sewerage etc.

Consist of Bed of crushedrockor other coarse media is used.Secondary treatment process, waste water is treated by biological medium

Used to treat sludge waste before dumping

This process is carried out in rotating biological Contractor

Comparison of Biological methods

Pond StabilizationAnaerobic DigestionBiological Nutrient RemovalCost effective natural treatment method. It is a shallow man-made basins

Removal of pathogenic micro-organisms and suspended particles.

Used in tropical and subtropical countries because the intensity of the sunlight and temperature are key factors for the efficiency of heat removalCost effective and environmentally sound Process of treating sludge

Sludge treatment and Removal of microorganisms in the absence of air

Used inindustrial or domestic purposes to manage waste and/or to produce fuelBiological pollutant treatment process before discharging into surface or ground water.

Removal biological pollutants (bacteria, etc.) nitrogen and phosphorus etc. from wastewater.

Used for industrial and domestic wastewater

Soil treatment methods

Soil Remediation MethodPhysical, chemical, thermal and biological techniques (In-situ and ex-situ) are used to remove soil pollutants.

CappingExcavationSolidification and StabilizationIncinerationSoil washingVitrificationVapor strippingThermal Treatments MethodsBioremediationNatural attenuation

Comparison of Techniques

CappingCheapest and above ground treatment methodPurpose is to prevent surface water from infiltrating the plume/site Natural and synthetic materials in single/multiple layers can be usedExcavationPermanent, rapid and interim method but expensive and destructive methodPurpose is to remove polluted soil and its disposal. It can be treated further at site or off siteMechanical system is used for removal and disposal purpose.SolidificationEasy and Cheap in-situ method, binding waste into a high-integrity structure.chemical or radiological hazard by converting the waste into its leastsoluble, mobile, or toxic formBinders are used to stop mobility of contaminantsIncinerationCombustion of waste in incinerators at high temperaturesEffective method to reduce volume of contaminants.Rotary kiln,infrared furnaces, liquid injection, plasma arc etc. are used.

Comparison of Techniques

Soil washingMechanical process that uses liquids to remove chemical pollutants from soils.Removal of Diesel range organics, Petroleum range organics, Volatile organic compounds, Heavy metals, pesticides etcMechanical systems for washing purpose and water treatment plant for remaining mixture of water.VitrificationDestructive and expensive process. Can be carried out at site or off site. Soil is melted at high temperatureUsed for the treatment of organics, inorganic and radio nuclides.Electrodes are inserted into the contaminated area at sufficiently close spacing and energizing with a high electrical resistance heating.Vapor strippingLow environmental impact, economical method of removal of contaminants by use of a vacuum to draw air down through the soilUsed to remove volatile and Semi-volatile organic compoundsPositioning of well through the contaminated region and use of vacuum to draw vapors

Comparison of Techniques

Thermal TreatmentsQuick cleanup but expensive, Cost is driven by energy, equipment, Operation & Maintenance.Thermal processes use heat to increase the volatility, to burn, decompose, destroy or melt the contaminants.Thermal desorption, Vitrification etc. are few examples of thermal treatment.BioremediationIt is a biological treatment method with Low land requirement, low capital and operating costs, and good process control.Biodegradation generally refers to the breakdown of organic compounds by living organisms.Removal of hydrocarbons, VOCs, SVOCs and pesticides.Involves the addition of microorganisms or nutrients to the subsurface environment, in order to accelerate the natural biodegradation process.

Sub surface volatilization and AerationIt is expensive and Thermal treatment method. It is modified vapor stripping method.Removal of Volatile and Semi-volatile organic compoundsQuite similar to vapor stripping except an additional pump used to suck vapors

Comparison of Techniques

Natural Attenuation methodsThe reduction of contaminant concentrations in the environment through biological processes and physical phenomenaRemoval of contaminants from soil and ground water.Biodegradation, dispersion, dilution, diffusion, volatilization etc. are some biological and physical natural phenomena

ConclusionAir, water and soil pollution problem is a function of amount and type of pollutants emitted to that medium and the rate and mechanisms of their removalIn any of the method, there are so many factors or the variables that practically it is impossible to compare any method with other with ideal similar conditionsIn fact, keeping in view the variation in chemical and physical conditions/properties of pollutants and the medium itself, each method may have so much variety in application and thus lot of variation in efficiency, cost and results that practically comparison becomes less relevant^Tried to give comparative analysis as nearer as possible

Physical properties of both air, pollutants and media incl following:TemperatureConcentrationPressureChemical properties of both air, pollutants and media incl following:

No one method is fit for all the situations

An ExampleThe SO2 removal efficiency increased from 66.1% to 71.5% when the reactor slurry pH was changed from 3.5 to 5.5Addition of Cl (in the form of CaCl22H2O) to the slurry (25gCl/L) increased the degree of desulphurisation to above 99%, due to the onset of extensive foaming, which substantially increased the gasliquid contact areaAn increase in the inlet flue gas SO2 concentration from 502 to 991 ppm led to a decrease in the SO2 removal efficiency from 80.1% to 69.4%

An ExampleA temperature increase from 296 to 323 K caused a reduction in the degree of desulphurisation from 69.4% to 68.1%, but this result is almost within the experimental uncertaintyThe residual limestone level in the gypsum formed increased with increasing values of reactor slurry pH, inlet flue gas SO2 concentration, and slurry concentration of Cl

DESULPHURISATION OF WASTE GASES FROM THE INDUSTRIAL PROCESSES by M.L. Ungurean, E.M. Pic, L. Jntschi (http://lori.academicdirect.org/works/?f=83)

Questions

References^1 Gas-diffusion separation and flow injection potentiometry by Wolfgang Frenzel (http://link.springer.com/article/10.1007/BF00348508)^2 Ref: The removal of volatile ketone mixtures from air in bio-filters by M. A. Deshusses,Prof. Dr. G. Hamer (http://link.springer.com/article/10.1007/BF00389921)Introduction to baseline source inspection techniques , chapter 9 (p 95 103) http://yosemite.epa.gov/oaqps/eogtrain.nsf/ae20ef1becae534385256b4100770781/86549ba361577a5a85256da3005cc39c/$FILE/SI%20445_9.pdfCritical Reviews in Environmental Science and Technology Volume 24,Issue 3, 1994http://www.epa.gov/oms/06-clean.htmhttp://www.eng.utoledo.edu/~akumar/IAP1/Pollution%20Control.htm

http://www.eugris.info/FurtherDescription.asp?e=26&Ca=2&Cy=0&T=In%20situ%20treatment%20technologieshttp://www.vertasefli.co.uk/soil-washing-c53.htmlhttp://www.egr.msu.edu/tosc/dutchboy/factsheets/what%20is%20soil%20washing.pdfhttp://toxics.usgs.gov/definitions/natural_attenuation.htmlhttp://web.engr.oregonstate.edu/~hambydm/papers/remedrev.pdfhttp://en.wikipedia.org/wiki/Reverse_osmosishttp://nptel.iitm.ac.in/courses/Webcourse-contents/IIT-KANPUR/wasteWater/Lecture%2024.htmhttp://en.wikipedia.org/wiki/Activated_sludgehttp://en.wikipedia.org/wiki/Trickling_filterReferences

Referenceshttp://en.wikipedia.org/wiki/Anaerobic_digestionhttp://www.rpi.edu/dept/chem-eng/Biotech-Environ/Environmental/Sludge/start.htmlhttp://www.britannica.com/EBchecked/topic/532321/sedimentation-tankhttp://en.wikipedia.org/wiki/Dissolved_air_flotationhttp://www.cleanh2o.com/ww/chemppt.htmlhttp://water.me.vccs.edu/concepts/disinfect.html

References^1 Gas-diffusion separation and flow injection potentiometry by Wolfgang Frenzel (http://link.springer.com/article/10.1007/BF00348508)^2 Ref: The removal of volatile ketone mixtures from air in bio-filters by M. A. Deshusses,Prof. Dr. G. Hamer (http://link.springer.com/article/10.1007/BF00389921)Introduction to baseline source inspection techniques , chapter 9 (p 95 103) http://yosemite.epa.gov/oaqps/eogtrain.nsf/ae20ef1becae534385256b4100770781/86549ba361577a5a85256da3005cc39c/$FILE/SI%20445_9.pdfCritical Reviews in Environmental Science and Technology Volume 24,Issue 3, 1994http://www.epa.gov/oms/06-clean.htmhttp://www.eng.utoledo.edu/~akumar/IAP1/Pollution%20Control.htm