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.