DEEPAK LEO JOHN
CE 5328
INTRODUCTIONAir Pollution : The presence in external
atmosphere of one or more contaminants/pollutants/combination that may induce harmful effects on humans/living being’s health.
Types of PollutantsPrimary Pollutants : Directly emitted from sourceSecondary Pollutants : Not emitted dirctly but are
formed in the atmosphere by chemical reactionsSourcesPoint / StationaryArea / Mobile
Structure of AtmosphereAtmosphere is divided into layers based on the thermal
structureTroposphere, Stratosphere, Mesosphere and Thermosphere.Troposhere is where the weather changes happen and the
pollutants are emitted, mixed, dispersed and transported.Stratosphere contains the protective ozone layer.Troposphere + Stratosphere accounts for 99.9% of earth’s
atmospheric mass
Fig : Structure of atmosphere (http://www.kowoma.de/en/gps/additional/atmosphere.htm)
Properties of AirComposition of airMolecular weight of airViscosityReynolds NumberIdeal Gas Law (PV=nRT)Concentration Measurements
Types of Air PollutantsPrimary Air Pollutants Particulates Sulfur Dioxide Carbon Monoxide Lead VOC’s Nitrogen Oxides CFC’s Greenhouse gases
Secondary Air Pollutants Ozone Particulates
Various sources of the pollutants and the effects of the pollutants were discussed.
Clean Air Act Federal standards to protect public health NAAQS : National Ambient Air Quality Standards Two Kinds Primary : protects public health (people) Secondary : protects public welfare (buildings, crops etc.,) Set of 6 criteria Pollutants : SO2, Nox, CO, O3, PM and Pb. However VOC’s are not included, but are regulated indirectly
through ozone levels. NAAQS says about an area meeting attainment or non-attainment. A state must submit plans to EPA telling how it is going to comply
with NAAQS State Implementation Plan (SIP). New sources or major modifications of existing sources must
obtain a New Source Review (NSR) / Construction Permit. NSR Permit 2 types Attainment Areas : PSD permits (BACT, modelling) Non-Attainment Areas : Non-Attainment New Sorce Review
(NNSR) (LAER, offsets) NSR Permits and SIP work hand-in-hand to achieve NAAQS
standards.
Clean Air ActFedreal Operating Permits (Title V)
Acid Rain Permits
Hazardous Air Pollutant Standards (MACT/NESHAPs)
Emission Inventory to know of a source is major.
Common testing methods for estimating emissions are emisson factors (AP-42) and Source Testing.
Gas Flow MeasurementContinuity Equation : Conservation of mass
Bernoulli’s Equation : Conservation of Energy
Measuring Pressure difference using a manometer (Pressure differences are important in measuring volumetric flow rates)
Measuring Volumetric flow rate using Venturimeter, Orifice meter & Rotameter.
Measuring the Velocity - Pitot tube
Measuring Wind Speed & Direction – Anemometer, wind sack/vane
Sampling and MonitoringSampling intermittentMonitoring continious
Determine Amount of emission permitting, inventories Efficiency of control equipment Compilance with regulations
Sample Collection – Gases Absorption, Adsorption, Organic traps and Whole air sampling.
Sample collection – Particulates Inertial collection (cyclones), Filtration.
Onboard System for Vehicle Emission Measurement.
Control TechnologiesGas control Technologies
IncinerationAdsorptionAbsorptionBiological control
Particulate control TechnologiesElectrostatic prcipitatorsFabric FiltersParticulate scrubbers
CE - 5320
Solid Waste HierarchySolid waste is useless, unused unwanted
or discarded material in solid form that includes semi solid food waste and municipal sludge
Solid waste in technical aspect is garbage, refuse, sludge from WWTP/WTP, including solid, liquid or semi-solid
Hierarchy of Solid Waste ManagementSource Reduction in sourceRecyclingWaste TransformationLandfilling
Sources, Types & Composition of MSWSources
Treatment plant sludgeLight Industrial WasteMixed waste (residential & commercial)
TypesResidential / CommercialInstitutionalConstruction and demolitionIndustrial
Composition depends on relative properties of sources, activity in town, living standards and economy
Physical composition can include paper, plastic, glass, metals food waste etc.,
Properties of MSWPhysical Properties
Specific weightMoisture ContentParticle size & size
distributionField capacityDegree of compactionPermeability of
compacted MSW
Chemical PropertiesProximate AnalysisFusing point of Ash
Ultimate AnalysisEnergy conent of MSW
Biological PropertiesBiodegradabilityOdorBreeding of flies
Municipal Solid WasteWaste Generation (Quantitative)
Load count analysis – recording the no. of individual loads
Weight Volume analysis – directly measuring weight and volume of each load
Waste HandlingSeperation of wastesCollection and Routing of MSWTransfer Stations – a link between community
collection and final disposal facility
Sanitary LandfillOperational Steps
UnloadSpreadCompactCover
Basic components of Sanitary LandfillCellCover layer systemGas control & recovery systemLeachate collection systemGas monitoring probesGround water monitoring wells
Sanitary LandfillDesign of Landfill
Develop preliminary site plan of fill areaCompute the solid waste sorage volume, soil
requirement volumes & site lifePrepare construction details for leachate
collection and treatment, landfill gas control systems, surface water control system, strom water runoff system access roads and monitoring wells
Prepare cost estimatesPrepare environmental impact assesmentPrepare plans for closure and post closure care.
CIRP 5357
Fundamentals of GIS conceptsTwo types of data to describe geographic
featuresSpatial data
Describes the location/coordinates (latitude, longitude)Attribute data
Specifies characteristics of the location Stored in a database and understood in a tabular form.
Spatial and attribute data are maintained seperately and then joined or linked for display and analysis
Spatial Data typesBounded area, continious area, networks and
points.Spatial data is organized by layers, with each
layer representing a common feature.
Fundamentals of GIS conceptsAttribute data types
Categorical(character field) and Numerical(integer, floating point, decimal)
Data are grouped into Vector and Raster data modelsVector data model
Location referenced by x,y coordinates, which can be linked to form lines and polygons
Attributes referenced through unique id number to tablesBest used for layers with disrete boundaries
Raster data model (requires spatial analyst models)Location is referenced by a grid cell in a rectangular arrayAttributes reffernced through a single value for the cellBest used for continious layes.
ArcGIS ComponentsArcCatalog
For organizing and managing GIS data Browse Search Define Metdata
ArcMapCental Application
Cartography Analysis Editing
ArcToolboxStandalone Geoprocessing Tools
Analysis Conversion Batch Processing
Query, Analysis and ModelingBasic Spatial
OpreationSpatial Measurement
Distance Area Centroid
Spatial Aggregation Redistricting Classification
Spatial Overlays and joins Spatial selection Spatial assignment Clipping Erasing Merging
Buffer analysisGeocodingAttribute operations
Record selectionVariable recodingRecord aggregationGeneral statistical
analysis
Data Format Conversion Vector to Raster : point
Node x,y is assigned to closest raster cell Location shift almost inevitable, error depends on raster size Two points in one cell cannot be identified Cannot be converted back without error
Vector to Raster : line Cells assigned if touched by line Brightness of line varied based on fraction cell covered by the
line Raster to Vector ( 3 step process)
1. Reduce rasters to unit width by decreasing the pixels2. Vector extraction – to identify the lines3. Topological reconstruction – recreates topological structures
PHYSICAL CHEMICAL PROCESSES ΙCE – 5318
Stiochiometery & Batch Reactor KineticsStiochiometery tells how much one chemical reacts with
another to form how much of a productStoichiometric co-eff of reactant –ve (disappearing)Stoichiometric co-eff of product +ve (appearing)Reaction Kinetics tells how fast a reaction is occurringClasses of reaction:
Homogeneous : single phase reaction Hetrogeneous : reaction occurs between different phases
reaction and transportMass Balance:
Accumulation = Inflow – Outflow + GenerationBatch Reactor:
No inflow or outflow Time is zero when reactants are added and mixed together Primary use to determine the rate and order of the reaction Possible because rate of accumulation term is equal to rate of
reaction
Complete Mix and Plug Flow ReactorThey are continuous type reactorPlug Flow reactor
Completely mixed laterally No mixing longitudinally The response of a PFR as a fn of θH at steady state is the same
as the response of a batch reactorComplete Mix Reactor
Perfectly mixed and hence the properties are uniform at any given time because of stirring
CFSTR in series Output of the first reactor will be input to the second reactor
Plug Flow with axial dispersion D/uL dispersion number ∞ complete mixing dispersion number 0 ideal plug flow
PFR & CFSTR with recycle
Hetrogeneous SystemHetrogeneous : reaction occurs between different phases
reaction and transportMechanism of Substrate removal
Transport of substrate from bulk fluid to the biofilm-water interface
Transport of substrate into biofilm Reaction in biofilm Transport of products out of biofilm Transport of product from biofilm water interface to bulk fluid
Reaction rate vs Transport Limited Reaction rate limited when shallow Transport rate limited when steep
Lake ClassificationLakes are classified by
Method of originHow often lakes undergo thermal stratification and
destratificationTrophic level
Trophic level clasificationPhotosynthetic growth levels called primary productionNutrient concentrationMeasurement of biodiversity
Modelling of Water Quality in lakesHydraulic Modelling
Detention times can be very large and mixing present hence much closer to CFSTR than PFR
Water movement largely a function of wind / thermal mixing. Mixing difficult to model
Seasonal Variation intemprature results in stratification
Lake ClassificationWater Quality
Most lakes and reservoirs are aerobic, epiliminion Nutrient levels are not static because of complex ecosystem Undesirable lake water quality is most often associated with
high algae concentration.Modelling of hydrodynamic conditions and also the
ecosystem of the lake is difficult and can be very complex
A complete model can be obtained when combining both hydrodynamic condition and ecosystem
River Model (Streeter Phelps equation)Considers the river as a PFREquation describes DO sag as a fn of θH
Actually calculates the defecit of oxygenHence can calculate DO at any point of the river
Mixing and FlocculationPerfectly mixed CFSTRHomogenity at all locations in the
reactorMixing is a fuction of turbulenceTurbulence is a result of irregular flow conditionsThe intensity of turbulence can be expressed as a fraction of
time average velocityEddies are important for flocculationParticles smaller than eddies will move together and not
colloideLarge eddies arise from the interaction of mean flow with the
boundariesThey carry most of the mixing energyUnder turbulent conditions without flow, the transfer of mass is
brought about my microscale turbulence known as turbulent or eddy diffusion
Eddy diffusion and dispersion depends primarily on the flow regime
Mixing and FlocculationPerikinetic (micro floc) Flocculation:
The aggregation of particles brought about by the random thermal motion of fluid molecules also know as Brownian Motion
Significant for particles in the range of 0.001 – 1.0 μm
Orthokinetic (Macrofloc) Flocculation :Aggregation of particles greater than 1-2μmCan be brought about by induced velocity
gradient and differential settling
SedimentationTypes of sedimentation : depends on conc of
suspension& characteristics of particlesDiscrete Settling :
Particles settle independent of each other. Flow capacity is is independent of depth A particle will accelerate until it reaches terminal velocity
Flocculant particle Settling: Particles in relatively dilute solutions will not act as
discrete particles but will colaesce during sedimentation As Colascence or flocculation occurs, the mass of the
particle increases and it settles faster
SedimentationHindered (Zone) Settling:
Because of the high concentration of particles the liquid tends to move up through the gaps of the contacting particles
As a result the contacting particles settle as a blanket or zone maintaining the same relative position with respect to each other.
Compression Settling: Occurs when particles settle by compressing the mass
below Stirring serves to compact solids in the compression
region by breaking up flocs & permitting water to escape. Heavy concentration of solids
FiltrationCharacteristics
Filtration used for removal of suspended and colloidal particles
Porous media captures solids and transports waterFiltration is a primary physical process but chemicals can
be added to improve performanceTwo phase process : solids removals during filtration
followed solids removal in backwashingFiltration is typically non continious process because it
has two phasesThe effective size of filtering medium
It is the 10% size based on massUniformity co-efficient Uc is d60/d10d10 is used in selecting filter medium Indicator of performance & Low d10 produce better quality
Gas TransferGas transfer is a hetrogeneous systemTwo Film Theory
Based on a physical model in which two film exist at the gas liquid interface
There are 2 conditions Adsorption in which gas is transferred from the gas phase to
liquid phase Desorption in which gas is transferred out of the liquid phase
into the gas phaseThe two film theory provides the resistance to the passage
of gas molecules between the bulk gaseous phaseOxygen transfer rate OTRStandard Oxygen transfer rate SOTR
TRANSPORTATION & AIR QUALITY
CE - 5324
The Mobile Source ProblemTrends of vehicle ownershipThe upside and the downside of automobilesTrends of on road transportation source
emissionTrends of off road emissionsAir pollution in developing countries
Internal Combustion EnginesPollutants that result from combustion
Oxides of NitrogenOxides of SulfurParticulatesCO
Otto cylce (4 stroke)Intake strokeCompression strokePower strokeExhaust stroke
Air to fuel ratio influneces the pollutant production
Evaporative emmisions2 stroke gasoline engines
Clean Air Act ProvisionsClean air act direct provisionsClean air act SIP provisionsConformity
CAA requires confirmity that highway and transportation projects conform to the purpose of SIP
Fuel economy standardsCorprate average fuel economy (CAFÉ)Cars 27.5 mpg
California’s Low Emission Vehicle(LEV) program
Estimating EmissionsSIP requires quatitative estimates of emission
reductionsTo ensure controls are sufficient to bring the region
into compilanceEmmisions = Emission Factor x VMTMacro scale emission model Emission Factor
(Mobile6)Mobile6 calculates basic emission rates adjusts the
emission rate based on temprature, air conditioning, humidity, gasoline content, inspection & maintainence program
Travel Demand Model VMTEstimates the amount of transportation activity occuring in a
regionTypical outputs : No. of transit trips, automobile occupancy,
average vehicle speed for each roadway segment, VMT
Ambient Concentration ModellingDispersion Modelling
uses output from emission model as inputAccounts metereology to predict atmospheric
concentrationSimulates what happens to the pollutants
emitted into the atmosphere3-D analysis system Assumes double gaussian distribution (double
bell shaped curve)
Engine Design ChangesAvoiding Stiochiometric combustion
(lower NOx) Air-to-fuel ratio Stratified charge engine Extra lean burn engine
Lowering Combustion Temprature Exhaust gas recirculation Water injection Changing engine cycle – Diesel Fuel Injection system modifications
Alternate FuelsNatural gas, propane, methanol, ethanol and
biodieselReformulated gasolineHybridsFuel cells, hydrogenAdd on tailpipe emission control
Catalytic convertersOn board vapour recovery system
Transportation System Management (TSM)Reducing emissions due to vehicle
operationsImprove traffic flow by better management
of existing transportation facilitiesCheaper than capital improvementsTravel time is decreased (mobility increased)Good management can increase roadway
capacity by 30%TSM Measures
Speed Limit ReductionIntelligent transportation systemDriver behaviour education
AIR DISPERSION MODELLINGCE - 5323
INTRODUCTION TO AIR QUALITY MODELINGAir Quality Model simulates mathematically pollutants
concentration between source and receptor It includes Pollutants transport, dispersion ,chemical and
physical removal along with the removal processThus the above factor makes it to fit into the field of air
pollutionTypes of air pollution modeling:
Gaussian dispersion modelingPhotochemical ModelingBox Modeling Receptor modelingStatistical modeling
REVIEW OF AIR POLLUTION METEOROLOGY Causes of wind :
∆T→ ∆ρ → ∆P → windWind is an important factor as its speed and direction
enables us in determining the stability condition which in turn helps us to find the concentration of the pollutant.
Wind speed increases with height as the frictional force due to obstruction (trees , buildings) decreases with height.
Wind speed at any height can be calculated from power law formula U2 = u1 *(z2/z1)p
Wind speed can be calculated by anemometer Cup anemometer and Hot wire anemometer.
Wind direction is measured using Wind vane and wind sock.
Instrument location 10 m high on a tower. Avoid rooftop location. Away from structures.
Wind rose diagram
Turbulence /Stability Types of transport
Advection → Transport of pollutant with the wind (horizontal direction) Dispersion →Transport of pollutant along vertical direction Diffusion → due to molecular diffusion or Brownian motion.
Dispersion is due to turbulenceCauses of Turbulence
Mechanical turbulence Thermal turbulence
Stability is an indication of atmospheric thermal turbulence Stable atmosphere → little turbulence → less vertical mixing. Unstable atmosphere → more turbulence → more vertical mixing.
Adiabatic Process Movement of airparcel without gaining or losing heat. Parcel rises ,expands and cools.
Box ModelsBox model is a simpler model
Mass balance is solved for one box
Not as accurate especially for regional scale
Used forIndoor air quality modelingModeling lab scale experiments
Photochemical Grid modelUsed for regional scaleThe atmosphere is divided into three dimensional grid that
may include thousands of grid cellThe model moves air and pollutant into and out of cells
through advection and dispersionMass balance is solved for each box at various time stepConcentration output of one box becomes an input to its
neighboring box. Inputs are
Emission as function of time and space Meteorological information Deposition estimates Chemical reaction information
GAUSSIAN DISPERSION MODELINGGaussian dispersion modeling enables us to find the pollutant concentation with respect to x,y and z direction.
Q is emission rate and (1/U) is downwind distance.Dispersion Parameters σy and σz are determined using
Pasquill-Gifford equation Briggs formula Wind fluctuation measurement
Methods of determining dispersion parameters σy and σz
Based on Stability classes
RURAL AREAS• Pasquill Gifford Prairie Grass experiments.• Brookhaven National Lab Scheme.• Tennessee Valley Authority (TVA) scheme.
URBAN AREAS• St.Louis Urban disperion Schemes.
Putting Together (all the above)• BRIGGS Formulas
Direct measurement of dispersion parameters Direct measurement of Wind Fluctuations
More accurate than other methods Measurements can be made at the specific site .
Stack tip downwash
When air blows past a building, stack, or other structure, a low pressure area forms behind the structure. In the low pressure area, air recirculates in eddies.
HOW TO AVOID? Clean Air Act recommends a safe engineering practice stack height of:
hs = HB + 1.5 z’. HB = height of building ; hs = stack height ; z’= smaller dimension of the building height or cross- wind width.
Relaxing Assumptions Vertical limits on dispersion due to inversions. Effects of topography. Accounting for chemical reactions Accounting for physical removal. Adjusting averaging times.
CE - 5325
Fundamentals of MicrobiologyClassification of Microorganisms
By carbon and energy source Chemosynthetic energy source obtained from redox
reactions Photosynthetic energy obtained from sunlight Heterotrophic Carbon source obtained from organic
carbon Autotrophic carbon source obtained from CO2
By cell structure Prokaryotic
Small size, single DNA molecule Eukaryotic
Larger size, several DNA molecules Method of Reproduction
Sexual, Asexual, Spore formation Environmental conditions for Growth
Oxygen requirement, temperature Motility: organism free moving in water or not
Fundamentals of MicrobiologyCatabolism :
The degradative phase of metabolism in which large and complex molecules are degraded to yeild smaller, simpler molecules
Accompanied by release of chemical energy Conversion to form energy transferring molecule Adenosine
triphosphate (ATP)Anabolism
Building up or biosynthetic phase of metabolism Requires input of chemical energy, provided by Atp generated
during catabolism
Enzymes ; catalysts of biochemical reactions Characteristics
Specific to a given reaction Both intracellular and extracellular Some enzymes requires cofactors Most enzymes lose activity at high tempratures
Fundamentals of Biochemistry
Most biological reactions are oxidation reduction reactions
BOD : measures DO used by microorganisms under specified conditions over specific time period
COD : measures the amount of organic matter that is chemically oxidized using a strong oxidant
TOC : Total organic Carbon convert C CO2 and measure
Yield: ratio of biomass (sludge) produced per mass of substrate removed from water.
Yield: depends on relative efficiencies of energy generation and utilization
Suspended Growth Systems Suspended growth of biological systems are estimated by using
monod kinetics Chemostat is a reactor used for continious growth of microbial
cultures. It is a CFSTR. Assumptions of Monod Kinetics
Monod Kinetics describe degradation Soluble substrate Single limiting substrate Constant Q Completely mixed system
Net bacterial growth rate is controlled by θH Active biomass density in the reactor depends on the inlet
substrate concentration, yield and residence time Effluent substrate concentration is controlled by
Half velocity constant (Ks) Specific growth rate (μm) Endogeneous decay (Kd) Solids Retention time (θH)
Suspended Growth SystemsCell washout : Residence time is so low that
cells wash out before any reaction occurIf mean cell residence time is somewhat less
than the growth then there would be no growth
Activated Sludge Components of AS system
Aeration Basin : completely mixed aerobic reactor with aeration
Clarifier : cells are seperated by sedimentation Removes MLSS Concentrates solids to return to bioreactor
Solids Recycle: Return Activated Sludge: a portion of the cells are returned to the aeration basin
Assumptions for modelling Aeration basin is a CFSTR Biodegradation occurs only in the aeration basin Monod Kinetics – single limiting soluble substrate
Key Conept : SRT > HRT Low SRT low effluent substrate concentration Low HRT small reactor volume, high throughput, system
economy
Activated SludgePlug flow reactor with recycle
More efficient than a CFSTR higher influent concentration leads to higher reaction rates
PFR there is higher substrate and oxygen concentration in the initial or inut phase but becomes lesser as we go down
Does not handle shock loads as well as CFSTR
Sludge BulkingGrowth of filamentous organismsEnough filaments to hold floc togetherInterferes with settling and foaming problem
occursStratergies to control filamentous organisms:
PFR : Organisms go through an area of reactor with high substrate concentration. Natural selection ofhigh growth rate under high substrate concentration
Selector : short residence time reactor with high F/M and sufficient aeration
Trickling FilterFactors affecting Trickling Filter
Influent cocentration : The rate at which the bacteria can remove the substrate reaches a maximum value as concentration increases
Substrate particle size and treatability : are limited to soluble substrate removal
Specific surface area and media configuration: Increase in surface area increases performance because of greater biomass as long as oxygen is not limiting
Hydraulic loading: Improved mass transfer but contact time is greatly reduced for a given coloumn height and also it affects the biofilm thickness
Effluent recycle : lowers influent concentration but decreases mass transfer resistance
Sludge Recirculation : should improve performance. BOD loading/Aeration : BOD loading is a product of hydraulic
loading and influent concentration Dosing Period : Resting may improve aeration but the hydraulic
and organic loading rates are instantaneously greater
Nitrification & DenitrificationNitrification : biological oxidation of
ammoniaNitrite(nitrosomonas) Nitrate (nitrobactor)
DenitrificationAssimlatory : Reduction of nitrate/nitrite
AmmoniaDissimilatory : Reduction of nitrite/Nitrate
nitrogen gasRequires
Absence of oxygen Presence of BOD Presence of nitrite and nitrate Presence of denitrifiers Sufficient time and proper environmental conditions
CE – 5316
Water Supply & Treatment Plant Design
Water QualityWater Quality Parameters
Chemical Parameters Inorganic compounds (ions) Organic compounds
Physical Parameters Temprature TSS Turbidity Color Taste and Odor
Biological Parameters
Major ProcessesScreening – process to remove suspended solids through racks
and screens
Aeration – process to increase DO concentration for taste and odor control
Pre-oxidations – oxidize dissolved compounds for taste and odor control, color reduction, achieving disinfection
Rapid mix – achieve rapid and through dispersion of chemicals required by coagulation
Coagulation – modify colloidal particles, stabilizing forces are reduced for efficient aggregation during flocculation
Flocculation – promote the growth of the floc for removal through sedimentation and filtration
Sedimentation – process to separate solids from water through gravity settling
Major ProcessesFiltration – process to remove fine particles and floc through bed
of porous granular media
Activated Carbon – process to absorb dissolved organic compounds for taste & odor control and color reduction
Softening – process to remove hardness through chemical precipitations
Recarbonation – process to neutralize and restore chemical balance of water after softening
Disinfection – process to inactivate and remove pathogens in order meet primary drinking water standards
Water Stability control – process to adjust pH and alkalinity by adding a acidic or alkaline compound for maintaining a non scaling and non corrosive finished water
Intake, Screening & AerationRaw water intake : A special structure used to draw
water from predetermined poolTypes
Floating, Submerged, Tower, Shore intake.Screening : To remove objects carried in raw water,
protect downstream equipments.Types
Coarse, fine screens and Micro strainersAeration : Add DO, remove VOC, taste and odor
causing compounds & remove CO2 and H2S by stripping
Types Gravity, Spray, Diffused & Mechanical
Water Conveyance, Measurement & PumpingWater conveyance system: A controllable hydraulic
system used to move water from one place to another Flow measurement: A technique used to collect
data regarding the quantity of water passing through the concerned point in the water conveyance system
Pumping: A technique used to impart energy into water to increase its head so that it can flow from one place to another through the water conveyance system
Kinetic: centrifugal and peripheral/recessed Positive displacement: plunger/piston, diaphragm, rotary,
screw, airlift
Coagulation & Flocculation Coagulation/Flocculation :
- Removal of turbidity- Removal of bacteria and virus- Removal of color- Preparation for filterable water
Three typically used coagulants:- Ferric Sulfate: Fe2(SO4)3- Ferric Chloride: FeCl3- Alum (aluminum sulfate): Al2(SO4)3•14H2O
Rapid Mix : Coagulation requires rapid dispersion of chemical throughout water and quick formation of precipitates under extremely violent agitation
Flocculation : Physical process used to promote the growth of the floc under slow mixing conditions.
- Agglomeration of floc after the destabilization of particles and formation of precipitates- Flocculation requires slow and gentle agitation that will not create turbulence to break
up the floc particles that already formed during coagulation process.
Sedimentation A process used to separate the settleable solids from the water
through gravity setting Preconditions:
- Specific gravity of the particles should be larger than that of the fluid. Four types of sedimentation behaviors:
- Type I sedimentation: discrete settling- individual particles settle independently, it occurs when there is a relatively low solids
concentration
- Type II sedimentation: flocculant settling- individual particles stick together into clumps called flocs settling, this occurs when
there is a greater solids concentration and chemical or biological reactions alter particle surfaces to enhance attachment
- Type II sedimentation: hindered or zone settling- particle concentration is great enough to inhibit water movement settling, water must
move in spaces between particles
- Type IV sedimentation: compression settling- occurs when particles settle by compressing the mass below
FiltrationA physical process used to remove fine particles and floc
through a bed of porous granular media.• System Components:
- Filters- Backwash system- Backwash waste recovery system
BackwashBackwash operation may be initiated by:
- Exceeding preset maximum head loss- Experiencing turbidity breakthrough- Passing pre-selected run time
Basic design considerations include:- Settling velocity of the media- Backwash rate- Expansion of bed- Head loss during backwash
Water TreatmentTaste and odor controlResidual ProcessingIon Exchange
A chemical process used to exchange anions or cations on a "resin" bed for cations or anions of the contaminant that needs to be removed from the water
Membrane process A physical process using different semipermeable membranes for
removal of dissolved solids as well as colloidal particles
Electrodyalysis An electrically driven dialysis demineralization process using
semipermeable to remove ions
ENVIRONMENTAL SYSTEMS A CHEMICAL ASPECT
EVSE - 5310
Characteristics of Natural Water The hydrogen bonding in the water molecule is unique and
very strong
Density Density of ice < waterAt 3.98 ^C max. densityWater cooler than 4 ^C will float / sink (otherwise)
Dissolved Oxygen (DO)Refers to the health of the water bodyHigh value is preferredNo direct method to measure oxygen demand in sewage
ComplexityWinkler test (titration based), electrodes (modern)Approximate indirect method to measure total oxygen
demand is Biochemical Oxygen Demand (BOD).
Characteristics of Natural WaterBiochemical Oxygen Demand (BOD)Not direct measure but gives the feel of how
much oxygen is consumed by biochemical sources present in water.
Actually measuring BOD5 = DO0 – DO5
Test is an approximation – DO measured is strictly not biological
COD (Chemical Oxygen Demand)Trying to calculate the refractory species
(chemically active rather than biologically active) in the sample.
TOD = COD + BOD5
Characteristics of Natural WaterTotal Organic Carbon (TOC) Deals with organics An instrumental test
pH pH = - log [H3O]+
Practical value = 0-14 0-7 Acid, 7Neutral, 7-14 Basic pH is often called the intensity factor.
Alkalinity The capacity of water to neutralize itself Greater the alkalinity the better it resists change in a pH or buffering effects Buffers are a combination of weak acid and its conjugate base Carbonate system is more predominant in Natural waters Alkalinity test uses phenolphthalein (pink base , colorless acid) 1st end point – phenolphthalein – 8.3 – get the measure of Carbonate [HCO3]-
2nd end point – methyl orange – 4.5 – get the measure of bicarbonate [CO3]2- and [OH]-
Total Alkalinity = [HCO3]- + 2 [CO3]2- + [OH]-
Characteristics of Natural WaterHardness Hardness is the total concentration of divalent cations (+ve charge) in natural
waters. Expressed as mg CaCO3 / L Predominant ions that contribute to the hardness is Ca2+, Mg2+ In ground water Fe2+ can be a contributor All other is called Non-Carbonate Hardness
Total Dissolved Solids (TDS) Measures the total dissolved solids Measured in ppm Increase in TDS means less desirable the water and is dangerous for aquatic
life
Total Suspended Solids (TSS) Suspended solids are a vehicle for transporting toxic materials
Turbidity It is a measure of water clarity Increase in TSS causes increase in Turbidity.
Metal Ion Co-ordination Chemistry Predominant dissolved metals is sodium and potassium in aquatic environment
(sea) Ca, Mg, K & Na can be measured in ppm or mg/L All other metals are in trace concentrations in water and generally measured in
ng/L or ppt, μg/L or ppb Metal ion concentration does not affect pH of water, they are of very low
concentration in water. A water molecule covalently bonded to a metal will be a stronger acid Hydrated metal ion when behaves as an acid is called hydrolysis
Two species can be used to see where the Reaction is going: Oxidation State
Increase in oxidation more positive it becomes stronger acidic activity pH
Increase in pH increase in degree of hydrolysis
Hydrolysis Increases with increasing pH Increases with increasing dilution Increases with increasing oxidation state.
Colloidal Systems A colloid is a material that fall in between the homogenous and
heterogeneous mixture. A colloid is a homogeneous mixture of two phases. One phase is called medium or bulk and the other is called the colloid Colloid is pictured
o As a particle, larger than the typical solutiono Which cannot dissolve in a solutiono Cannot have the precipitate or the colloid to dissolve it
Diameter of colloid is in the range of 0.0001 – 1 μm Colloids can be organic, inorganic & biological They have very large surface area to volume ratio. It provides a site
for chemical reaction and makes the reaction easier. A colloidal particle is a transporter for materials from one place to
another Colloids are measure of TSS and Turbidity
Colloidal SystemsFormation of Colloids (2 Basic models)
Dispersion : Process involving the reduction of larger particle to smaller size
Condensation : Chemical Physical process by which particles aggregate to form a size of colloidal particles
Types of ColloidsHydrophillic : affinity for waterHydrophobic : Repels water, they will stabilize in a way
that they remain suspended in water (non polar molecules)
Association : A colloid where one end is polar and the other end is non polar.
Most colloids that are of concern in environment are either hydrophobic or association.
Aquatic MicroorganismsOxidation reductiom reaction is the life forming reaction of
any microorganismMicroorganisms convert one form of chemical to another so
as to recycleFor most digestive processes in microorganisms, they use
spontaneous oxidation-reduction reactionClassification of Microorganisms
Autotrophic (Producers) : They convert inorganic materials to organic materials They depend on non-spontaneous redox process. Need a continual
source of energy to keep them going Sources come from two places
Sunlight Photosynthetic ex. Algae Chemicals Chemosynthetic ex. Bacteria
Heterotrophic (Reducers or Decomposers) : Primary function is to convert organic inorganic materials They depend on spontaneous redox process
Aerobic : Requires direct oxygen Anaerobic : Functions in the absence of oxygen Facultative : can function in both presence and absence of oxygen
Almost all reactions that happen in the atmosphere are photochemical
ScatteringThe path of the radiation is changed/redirectedThree types of scattering
Rayleigh <= 1(d/λ) Characteristic of this scattering is back scattering Type of matter capable of doing this is the smallest of the
suspended particles Mie Scattering = 1
No back scattering Large particles in suspended air scatter light
Optical Scattering >= 1 Done by Reflection, refraction and diffraction.