Final Comprehensive Examination


Published on

complete layout of course design in Masters program :)

  • Be the first to comment

  • Be the first to like this

No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide
  • Need to explain in brief about the various properties of air.
  • Final Comprehensive Examination

    2. 2. CE 5328
    3. 3. INTRODUCTION <ul><li>Air Pollution : The presence in external atmosphere of one or more contaminants/pollutants/combination that may induce harmful effects on humans/living being’s health. </li></ul><ul><li>Types of Pollutants </li></ul><ul><li>Primary Pollutants : Directly emitted from source </li></ul><ul><li>Secondary Pollutants : Not emitted dirctly but are formed in the atmosphere by chemical reactions </li></ul><ul><li>Sources </li></ul><ul><li>Point / Stationary </li></ul><ul><li>Area / Mobile </li></ul>
    4. 4. Structure of Atmosphere <ul><li>Atmosphere is divided into layers based on the thermal structure </li></ul><ul><li>Troposphere, Stratosphere, Mesosphere and Thermosphere. </li></ul><ul><li>Troposhere is where the weather changes happen and the pollutants are emitted, mixed, dispersed and transported. </li></ul><ul><li>Stratosphere contains the protective ozone layer. </li></ul><ul><li>Troposphere + Stratosphere accounts for 99.9% of earth’s atmospheric mass </li></ul><ul><li>Fig : Structure of atmosphere ( </li></ul>
    5. 5. Properties of Air <ul><li>Composition of air </li></ul><ul><li>Molecular weight of air </li></ul><ul><li>Viscosity </li></ul><ul><li>Reynolds Number </li></ul><ul><li>Ideal Gas Law (PV=nRT) </li></ul><ul><li>Concentration Measurements </li></ul>
    6. 6. Types of Air Pollutants <ul><li>Primary Air Pollutants </li></ul><ul><li>Particulates </li></ul><ul><li>Sulfur Dioxide </li></ul><ul><li>Carbon Monoxide </li></ul><ul><li>Lead </li></ul><ul><li>VOC’s </li></ul><ul><li>Nitrogen Oxides </li></ul><ul><li>CFC’s </li></ul><ul><li>Greenhouse gases </li></ul><ul><li>Secondary Air Pollutants </li></ul><ul><li>Ozone </li></ul><ul><li>Particulates </li></ul><ul><li>Various sources of the pollutants and the effects of the pollutants were discussed. </li></ul>
    7. 7. Clean Air Act <ul><li>Federal standards to protect public health </li></ul><ul><li>NAAQS : National Ambient Air Quality Standards </li></ul><ul><li>Two Kinds </li></ul><ul><li>Primary : protects public health (people) </li></ul><ul><li>Secondary : protects public welfare (buildings, crops etc.,) </li></ul><ul><li>Set of 6 criteria Pollutants : SO 2 , No x , CO, O 3 , PM and Pb. </li></ul><ul><li>However VOC’s are not included, but are regulated indirectly through ozone levels. </li></ul><ul><li>NAAQS says about an area meeting attainment or non-attainment. </li></ul><ul><li>A state must submit plans to EPA telling how it is going to comply with NAAQS  State Implementation Plan (SIP). </li></ul><ul><li>New sources or major modifications of existing sources must obtain a New Source Review (NSR) / Construction Permit. </li></ul><ul><li>NSR Permit  2 types </li></ul><ul><li>Attainment Areas : PSD permits (BACT, modelling) </li></ul><ul><li>Non-Attainment Areas : Non-Attainment New Sorce Review (NNSR) (LAER, offsets) </li></ul><ul><li>NSR Permits and SIP work hand-in-hand to achieve NAAQS standards. </li></ul>
    8. 8. Clean Air Act <ul><li>Fedreal Operating Permits (Title V) </li></ul><ul><li>Acid Rain Permits </li></ul><ul><li>Hazardous Air Pollutant Standards (MACT/NESHAPs) </li></ul><ul><li>Emission Inventory to know of a source is major. </li></ul><ul><li>Common testing methods for estimating emissions are emisson factors (AP-42) and Source Testing. </li></ul>
    9. 9. Gas Flow Measurement <ul><li>Continuity Equation : Conservation of mass </li></ul><ul><li>Bernoulli’s Equation : Conservation of Energy </li></ul><ul><li>Measuring Pressure difference using a manometer ( Pressure differences are important in measuring volumetric flow rates) </li></ul><ul><li>Measuring Volumetric flow rate using Venturimeter, Orifice meter & Rotameter. </li></ul><ul><li>Measuring the Velocity - Pitot tube </li></ul><ul><li>Measuring Wind Speed & Direction – Anemometer, wind sack/vane </li></ul>
    10. 10. Sampling and Monitoring <ul><li>Sampling  intermittent </li></ul><ul><li>Monitoring  continious </li></ul><ul><li>Determine </li></ul><ul><li>Amount of emission permitting, inventories </li></ul><ul><li>Efficiency of control equipment </li></ul><ul><li>Compilance with regulations </li></ul><ul><li>Sample Collection – Gases  Absorption, Adsorption, Organic traps and Whole air sampling. </li></ul><ul><li>Sample collection – Particulates  Inertial collection (cyclones), Filtration. </li></ul><ul><li>Onboard System for Vehicle Emission Measurement. </li></ul>
    11. 11. Control Technologies <ul><li>Gas control Technologies </li></ul><ul><ul><li>Incineration </li></ul></ul><ul><ul><li>Adsorption </li></ul></ul><ul><ul><li>Absorption </li></ul></ul><ul><ul><li>Biological control </li></ul></ul><ul><li>Particulate control Technologies </li></ul><ul><ul><li>Electrostatic prcipitators </li></ul></ul><ul><ul><li>Fabric Filters </li></ul></ul><ul><ul><li>Particulate scrubbers </li></ul></ul>
    12. 12. CE - 5320
    13. 13. Solid Waste Hierarchy <ul><li>Solid waste is useless, unused unwanted or discarded material in solid form that includes semi solid food waste and municipal sludge </li></ul><ul><li>Solid waste in technical aspect is garbage, refuse, sludge from WWTP/WTP, including solid, liquid or semi-solid </li></ul><ul><li>Hierarchy of Solid Waste Management </li></ul><ul><ul><li>Source Reduction in source </li></ul></ul><ul><ul><li>Recycling </li></ul></ul><ul><ul><li>Waste Transformation </li></ul></ul><ul><ul><li>Landfilling </li></ul></ul>
    14. 14. Sources, Types & Composition of MSW <ul><li>Sources </li></ul><ul><ul><li>Treatment plant sludge </li></ul></ul><ul><ul><li>Light Industrial Waste </li></ul></ul><ul><ul><li>Mixed waste (residential & commercial) </li></ul></ul><ul><li>Types </li></ul><ul><ul><li>Residential / Commercial </li></ul></ul><ul><ul><li>Institutional </li></ul></ul><ul><ul><li>Construction and demolition </li></ul></ul><ul><ul><li>Industrial </li></ul></ul><ul><li>Composition depends on relative properties of sources, activity in town, living standards and economy </li></ul><ul><li>Physical composition can include paper, plastic, glass, metals food waste etc., </li></ul>
    15. 15. Properties of MSW <ul><li>Physical Properties </li></ul><ul><ul><li>Specific weight </li></ul></ul><ul><ul><li>Moisture Content </li></ul></ul><ul><ul><li>Particle size & size distribution </li></ul></ul><ul><ul><li>Field capacity </li></ul></ul><ul><ul><li>Degree of compaction </li></ul></ul><ul><ul><li>Permeability of compacted MSW </li></ul></ul><ul><li>Chemical Properties </li></ul><ul><ul><li>Proximate Analysis </li></ul></ul><ul><ul><li>Fusing point of Ash </li></ul></ul><ul><ul><li>Ultimate Analysis </li></ul></ul><ul><ul><li>Energy conent of MSW </li></ul></ul><ul><li>Biological Properties </li></ul><ul><ul><li>Biodegradability </li></ul></ul><ul><ul><li>Odor </li></ul></ul><ul><ul><li>Breeding of flies </li></ul></ul>
    16. 16. Municipal Solid Waste <ul><li>Waste Generation (Quantitative) </li></ul><ul><ul><li>Load count analysis – recording the no. of individual loads </li></ul></ul><ul><ul><li>Weight Volume analysis – directly measuring weight and volume of each load </li></ul></ul><ul><li>Waste Handling </li></ul><ul><ul><li>Seperation of wastes </li></ul></ul><ul><ul><li>Collection and Routing of MSW </li></ul></ul><ul><ul><li>Transfer Stations – a link between community collection and final disposal facility </li></ul></ul>
    17. 17. Sanitary Landfill <ul><li>Operational Steps </li></ul><ul><ul><li>Unload </li></ul></ul><ul><ul><li>Spread </li></ul></ul><ul><ul><li>Compact </li></ul></ul><ul><ul><li>Cover </li></ul></ul><ul><li>Basic components of Sanitary Landfill </li></ul><ul><ul><li>Cell </li></ul></ul><ul><ul><li>Cover layer system </li></ul></ul><ul><ul><li>Gas control & recovery system </li></ul></ul><ul><ul><li>Leachate collection system </li></ul></ul><ul><ul><li>Gas monitoring probes </li></ul></ul><ul><ul><li>Ground water monitoring wells </li></ul></ul>
    18. 18. Sanitary Landfill <ul><li>Design of Landfill </li></ul><ul><ul><li>Develop preliminary site plan of fill area </li></ul></ul><ul><ul><li>Compute the solid waste sorage volume, soil requirement volumes & site life </li></ul></ul><ul><ul><li>Prepare construction details for leachate collection and treatment, landfill gas control systems, surface water control system, strom water runoff system access roads and monitoring wells </li></ul></ul><ul><ul><li>Prepare cost estimates </li></ul></ul><ul><ul><li>Prepare environmental impact assesment </li></ul></ul><ul><ul><li>Prepare plans for closure and post closure care. </li></ul></ul>
    19. 19. CIRP 5357
    20. 20. Fundamentals of GIS concepts <ul><li>Two types of data to describe geographic features </li></ul><ul><ul><li>Spatial data </li></ul></ul><ul><ul><ul><li>Describes the location/coordinates (latitude, longitude) </li></ul></ul></ul><ul><ul><li>Attribute data </li></ul></ul><ul><ul><ul><li>Specifies characteristics of the location </li></ul></ul></ul><ul><ul><ul><li>Stored in a database and understood in a tabular form. </li></ul></ul></ul><ul><li>Spatial and attribute data are maintained seperately and then joined or linked for display and analysis </li></ul><ul><li>Spatial Data types </li></ul><ul><ul><li>Bounded area, continious area, networks and points. </li></ul></ul><ul><li>Spatial data is organized by layers, with each layer representing a common feature. </li></ul>
    21. 21. Fundamentals of GIS concepts <ul><li>Attribute data types </li></ul><ul><ul><li>Categorical(character field) and Numerical(integer, floating point, decimal) </li></ul></ul><ul><li>Data are grouped into Vector and Raster data models </li></ul><ul><li>Vector data model </li></ul><ul><ul><li>Location referenced by x,y coordinates, which can be linked to form lines and polygons </li></ul></ul><ul><ul><li>Attributes referenced through unique id number to tables </li></ul></ul><ul><ul><li>Best used for layers with disrete boundaries </li></ul></ul><ul><li>Raster data model (requires spatial analyst models) </li></ul><ul><ul><li>Location is referenced by a grid cell in a rectangular array </li></ul></ul><ul><ul><li>Attributes reffernced through a single value for the cell </li></ul></ul><ul><ul><li>Best used for continious layes. </li></ul></ul>
    22. 22. ArcGIS Components <ul><li>ArcCatalog </li></ul><ul><ul><li>For organizing and managing GIS data </li></ul></ul><ul><ul><ul><li>Browse </li></ul></ul></ul><ul><ul><ul><li>Search </li></ul></ul></ul><ul><ul><ul><li>Define </li></ul></ul></ul><ul><ul><ul><li>Metdata </li></ul></ul></ul><ul><li>ArcMap </li></ul><ul><ul><li>Cental Application </li></ul></ul><ul><ul><ul><li>Cartography </li></ul></ul></ul><ul><ul><ul><li>Analysis </li></ul></ul></ul><ul><ul><ul><li>Editing </li></ul></ul></ul><ul><li>ArcToolbox </li></ul><ul><ul><li>Standalone Geoprocessing Tools </li></ul></ul><ul><ul><ul><li>Analysis </li></ul></ul></ul><ul><ul><ul><li>Conversion </li></ul></ul></ul><ul><ul><ul><li>Batch Processing </li></ul></ul></ul>
    23. 23. Query, Analysis and Modeling <ul><li>Basic Spatial Opreation </li></ul><ul><ul><li>Spatial Measurement </li></ul></ul><ul><ul><ul><li>Distance </li></ul></ul></ul><ul><ul><ul><li>Area </li></ul></ul></ul><ul><ul><ul><li>Centroid </li></ul></ul></ul><ul><ul><li>Spatial Aggregation </li></ul></ul><ul><ul><ul><li>Redistricting </li></ul></ul></ul><ul><ul><ul><li>Classification </li></ul></ul></ul><ul><ul><li>Spatial Overlays and joins </li></ul></ul><ul><ul><ul><li>Spatial selection </li></ul></ul></ul><ul><ul><ul><li>Spatial assignment </li></ul></ul></ul><ul><ul><ul><li>Clipping </li></ul></ul></ul><ul><ul><ul><li>Erasing </li></ul></ul></ul><ul><ul><ul><li>Merging </li></ul></ul></ul><ul><li>Buffer analysis </li></ul><ul><li>Geocoding </li></ul><ul><li>Attribute operations </li></ul><ul><ul><li>Record selection </li></ul></ul><ul><ul><li>Variable recoding </li></ul></ul><ul><ul><li>Record aggregation </li></ul></ul><ul><ul><li>General statistical analysis </li></ul></ul>
    24. 24. Data Format Conversion <ul><li>Vector to Raster : point </li></ul><ul><ul><li>Node x,y is assigned to closest raster cell </li></ul></ul><ul><ul><li>Location shift almost inevitable, error depends on raster size </li></ul></ul><ul><ul><li>Two points in one cell cannot be identified </li></ul></ul><ul><ul><li>Cannot be converted back without error </li></ul></ul><ul><li>Vector to Raster : line </li></ul><ul><ul><li>Cells assigned if touched by line </li></ul></ul><ul><ul><li>Brightness of line varied based on fraction cell covered by the line </li></ul></ul><ul><li>Raster to Vector ( 3 step process) </li></ul><ul><ul><li>Reduce rasters to unit width by decreasing the pixels </li></ul></ul><ul><ul><li>Vector extraction – to identify the lines </li></ul></ul><ul><ul><li>Topological reconstruction – recreates topological structures </li></ul></ul>
    26. 26. Stiochiometery & Batch Reactor Kinetics <ul><li>Stiochiometery tells how much one chemical reacts with another to form how much of a product </li></ul><ul><li>Stoichiometric co-eff of reactant –ve (disappearing) </li></ul><ul><li>Stoichiometric co-eff of product +ve (appearing) </li></ul><ul><li>Reaction Kinetics tells how fast a reaction is occurring </li></ul><ul><li>Classes of reaction: </li></ul><ul><ul><li>Homogeneous : single phase  reaction </li></ul></ul><ul><ul><li>Hetrogeneous : reaction occurs between different phases  reaction and transport </li></ul></ul><ul><li>Mass Balance: </li></ul><ul><ul><ul><li>Accumulation = Inflow – Outflow + Generation </li></ul></ul></ul><ul><li>Batch Reactor: </li></ul><ul><ul><li>No inflow or outflow </li></ul></ul><ul><ul><li>Time is zero when reactants are added and mixed together </li></ul></ul><ul><ul><li>Primary use  to determine the rate and order of the reaction </li></ul></ul><ul><ul><li>Possible because rate of accumulation term is equal to rate of reaction </li></ul></ul>
    27. 27. Complete Mix and Plug Flow Reactor <ul><li>They are continuous type reactor </li></ul><ul><li>Plug Flow reactor </li></ul><ul><ul><li>Completely mixed laterally </li></ul></ul><ul><ul><li>No mixing longitudinally </li></ul></ul><ul><ul><li>The response of a PFR as a fn of θ H at steady state is the same as the response of a batch reactor </li></ul></ul><ul><li>Complete Mix Reactor </li></ul><ul><ul><li>Perfectly mixed and hence the properties are uniform at any given time because of stirring </li></ul></ul><ul><li>CFSTR in series </li></ul><ul><ul><li>Output of the first reactor will be input to the second reactor </li></ul></ul><ul><li>Plug Flow with axial dispersion </li></ul><ul><ul><li>D/uL  dispersion number  ∞  complete mixing </li></ul></ul><ul><ul><li>dispersion number  0  ideal plug flow </li></ul></ul><ul><li>PFR & CFSTR with recycle </li></ul>
    28. 28. Hetrogeneous System <ul><li>Hetrogeneous : reaction occurs between different phases  reaction and transport </li></ul><ul><li>Mechanism of Substrate removal </li></ul><ul><ul><li>Transport of substrate from bulk fluid to the biofilm-water interface </li></ul></ul><ul><ul><li>Transport of substrate into biofilm </li></ul></ul><ul><ul><li>Reaction in biofilm </li></ul></ul><ul><ul><li>Transport of products out of biofilm </li></ul></ul><ul><ul><li>Transport of product from biofilm water interface to bulk fluid </li></ul></ul><ul><li>Reaction rate vs Transport Limited </li></ul><ul><ul><li>Reaction rate limited when shallow </li></ul></ul><ul><ul><li>Transport rate limited when steep </li></ul></ul>
    29. 29. Lake Classification <ul><li>Lakes are classified by </li></ul><ul><ul><li>Method of origin </li></ul></ul><ul><ul><li>How often lakes undergo thermal stratification and destratification </li></ul></ul><ul><ul><li>Trophic level </li></ul></ul><ul><li>Trophic level clasification </li></ul><ul><ul><li>Photosynthetic growth levels called primary production </li></ul></ul><ul><ul><li>Nutrient concentration </li></ul></ul><ul><ul><li>Measurement of biodiversity </li></ul></ul><ul><li>Modelling of Water Quality in lakes </li></ul><ul><ul><li>Hydraulic Modelling </li></ul></ul><ul><ul><ul><li>Detention times can be very large and mixing present hence much closer to CFSTR than PFR </li></ul></ul></ul><ul><ul><ul><li>Water movement largely a function of wind / thermal mixing. Mixing difficult to model </li></ul></ul></ul><ul><ul><ul><li>Seasonal Variation intemprature results in stratification </li></ul></ul></ul>
    30. 30. Lake Classification <ul><ul><li>Water Quality </li></ul></ul><ul><ul><ul><li>Most lakes and reservoirs are aerobic, epiliminion </li></ul></ul></ul><ul><ul><ul><li>Nutrient levels are not static because of complex ecosystem </li></ul></ul></ul><ul><ul><ul><li>Undesirable lake water quality is most often associated with high algae concentration. </li></ul></ul></ul><ul><li>Modelling of hydrodynamic conditions and also the ecosystem of the lake is difficult and can be very complex </li></ul><ul><li>A complete model can be obtained when combining both hydrodynamic condition and ecosystem </li></ul><ul><li>River Model (Streeter Phelps equation) </li></ul><ul><ul><li>Considers the river as a PFR </li></ul></ul><ul><ul><li>Equation describes DO sag as a fn of θ H </li></ul></ul><ul><ul><li>Actually calculates the defecit of oxygen </li></ul></ul><ul><ul><li>Hence can calculate DO at any point of the river </li></ul></ul>
    31. 31. Mixing and Flocculation <ul><li>Perfectly mixed  CFSTR  Homogenity at all locations in the reactor </li></ul><ul><li>Mixing is a fuction of turbulence </li></ul><ul><li>Turbulence is a result of irregular flow conditions </li></ul><ul><li>The intensity of turbulence can be expressed as a fraction of time average velocity </li></ul><ul><li>Eddies are important for flocculation </li></ul><ul><li>Particles smaller than eddies will move together and not colloide </li></ul><ul><li>Large eddies arise from the interaction of mean flow with the boundaries </li></ul><ul><li>They carry most of the mixing energy </li></ul><ul><li>Under turbulent conditions without flow, the transfer of mass is brought about my microscale turbulence known as turbulent or eddy diffusion </li></ul><ul><li>Eddy diffusion and dispersion depends primarily on the flow regime </li></ul>
    32. 32. Mixing and Flocculation <ul><li>Perikinetic (micro floc) Flocculation: </li></ul><ul><ul><li>The aggregation of particles brought about by the random thermal motion of fluid molecules also know as Brownian Motion </li></ul></ul><ul><ul><li>Significant for particles in the range of 0.001 – 1.0 μ m </li></ul></ul><ul><li>Orthokinetic (Macrofloc) Flocculation : </li></ul><ul><ul><li>Aggregation of particles greater than 1-2 μ m </li></ul></ul><ul><ul><li>Can be brought about by induced velocity gradient and differential settling </li></ul></ul>
    33. 33. Sedimentation <ul><li>Types of sedimentation : depends on conc of suspension& characteristics of particles </li></ul><ul><ul><li>Discrete Settling : </li></ul></ul><ul><ul><ul><li>Particles settle independent of each other. </li></ul></ul></ul><ul><ul><ul><li>Flow capacity is is independent of depth </li></ul></ul></ul><ul><ul><ul><li>A particle will accelerate until it reaches terminal velocity </li></ul></ul></ul><ul><ul><li>Flocculant particle Settling: </li></ul></ul><ul><ul><ul><li>Particles in relatively dilute solutions will not act as discrete particles but will colaesce during sedimentation </li></ul></ul></ul><ul><ul><ul><li>As Colascence or flocculation occurs, the mass of the particle increases and it settles faster </li></ul></ul></ul>
    34. 34. Sedimentation <ul><ul><li>Hindered (Zone) Settling: </li></ul></ul><ul><ul><ul><li>Because of the high concentration of particles the liquid tends to move up through the gaps of the contacting particles </li></ul></ul></ul><ul><ul><ul><li>As a result the contacting particles settle as a blanket or zone maintaining the same relative position with respect to each other. </li></ul></ul></ul><ul><ul><li>Compression Settling: </li></ul></ul><ul><ul><ul><li>Occurs when particles settle by compressing the mass below </li></ul></ul></ul><ul><ul><ul><li>Stirring serves to compact solids in the compression region by breaking up flocs & permitting water to escape. </li></ul></ul></ul><ul><ul><ul><li>Heavy concentration of solids </li></ul></ul></ul>
    35. 35. Filtration <ul><li>Characteristics </li></ul><ul><ul><li>Filtration used for removal of suspended and colloidal particles </li></ul></ul><ul><ul><li>Porous media captures solids and transports water </li></ul></ul><ul><ul><li>Filtration is a primary physical process but chemicals can be added to improve performance </li></ul></ul><ul><ul><li>Two phase process : solids removals during filtration followed solids removal in backwashing </li></ul></ul><ul><ul><li>Filtration is typically non continious process because it has two phases </li></ul></ul><ul><li>The effective size of filtering medium </li></ul><ul><ul><li>It is the 10% size based on mass </li></ul></ul><ul><ul><li>Uniformity co-efficient Uc is d 60 /d 10 </li></ul></ul><ul><ul><li>d 10 is used in selecting filter medium </li></ul></ul><ul><ul><li>Indicator of performance & Low d 10 produce better quality </li></ul></ul>
    36. 36. Gas Transfer <ul><li>Gas transfer is a hetrogeneous system </li></ul><ul><li>Two Film Theory </li></ul><ul><ul><li>Based on a physical model in which two film exist at the gas liquid interface </li></ul></ul><ul><ul><li>There are 2 conditions </li></ul></ul><ul><ul><ul><li>Adsorption in which gas is transferred from the gas phase to liquid phase </li></ul></ul></ul><ul><ul><ul><li>Desorption in which gas is transferred out of the liquid phase into the gas phase </li></ul></ul></ul><ul><ul><li>The two film theory provides the resistance to the passage of gas molecules between the bulk gaseous phase </li></ul></ul><ul><li>Oxygen transfer rate OTR </li></ul><ul><li>Standard Oxygen transfer rate SOTR </li></ul>
    38. 38. The Mobile Source Problem <ul><li>Trends of vehicle ownership </li></ul><ul><li>The upside and the downside of automobiles </li></ul><ul><li>Trends of on road transportation source emission </li></ul><ul><li>Trends of off road emissions </li></ul><ul><li>Air pollution in developing countries </li></ul>
    39. 39. Internal Combustion Engines <ul><li>Pollutants that result from combustion </li></ul><ul><ul><li>Oxides of Nitrogen </li></ul></ul><ul><ul><li>Oxides of Sulfur </li></ul></ul><ul><ul><li>Particulates </li></ul></ul><ul><ul><li>CO </li></ul></ul><ul><li>Otto cylce (4 stroke) </li></ul><ul><ul><li>Intake stroke </li></ul></ul><ul><ul><li>Compression stroke </li></ul></ul><ul><ul><li>Power stroke </li></ul></ul><ul><ul><li>Exhaust stroke </li></ul></ul><ul><li>Air to fuel ratio influneces the pollutant production </li></ul><ul><li>Evaporative emmisions </li></ul><ul><li>2 stroke gasoline engines </li></ul>
    40. 40. Clean Air Act Provisions <ul><li>Clean air act direct provisions </li></ul><ul><li>Clean air act SIP provisions </li></ul><ul><li>Conformity </li></ul><ul><ul><li>CAA requires confirmity that highway and transportation projects conform to the purpose of SIP </li></ul></ul><ul><li>Fuel economy standards </li></ul><ul><ul><li>Corprate average fuel economy (CAFÉ) </li></ul></ul><ul><ul><li>Cars  27.5 mpg </li></ul></ul><ul><li>California’s Low Emission Vehicle(LEV) program </li></ul>
    41. 41. Estimating Emissions <ul><li>SIP requires quatitative estimates of emission reductions </li></ul><ul><li>To ensure controls are sufficient to bring the region into compilance </li></ul><ul><li>Emmisions = Emission Factor x VMT </li></ul><ul><li>Macro scale emission model  Emission Factor (Mobile6) </li></ul><ul><ul><li>Mobile6 calculates basic emission rates  adjusts the emission rate based on temprature, air conditioning, humidity, gasoline content, inspection & maintainence program </li></ul></ul><ul><li>Travel Demand Model  VMT </li></ul><ul><ul><li>Estimates the amount of transportation activity occuring in a region </li></ul></ul><ul><ul><li>Typical outputs : No. of transit trips, automobile occupancy, average vehicle speed for each roadway segment, VMT </li></ul></ul>
    42. 42. Ambient Concentration Modelling <ul><li>Dispersion Modelling </li></ul><ul><ul><li>uses output from emission model as input </li></ul></ul><ul><ul><li>Accounts metereology to predict atmospheric concentration </li></ul></ul><ul><ul><li>Simulates what happens to the pollutants emitted into the atmosphere </li></ul></ul><ul><ul><li>3-D analysis system </li></ul></ul><ul><ul><li>Assumes double gaussian distribution (double bell shaped curve) </li></ul></ul>
    43. 43. Engine Design Changes <ul><li>Avoiding Stiochiometric combustion (lower NOx) </li></ul><ul><ul><li>Air-to-fuel ratio </li></ul></ul><ul><ul><li>Stratified charge engine </li></ul></ul><ul><ul><li>Extra lean burn engine </li></ul></ul><ul><li>Lowering Combustion Temprature </li></ul><ul><ul><li>Exhaust gas recirculation </li></ul></ul><ul><ul><li>Water injection </li></ul></ul><ul><ul><li>Changing engine cycle – Diesel </li></ul></ul><ul><ul><li>Fuel Injection system modifications </li></ul></ul>
    44. 44. Alternate Fuels <ul><li>Natural gas, propane, methanol, ethanol and biodiesel </li></ul><ul><li>Reformulated gasoline </li></ul><ul><li>Hybrids </li></ul><ul><li>Fuel cells, hydrogen </li></ul><ul><li>Add on tailpipe emission control </li></ul><ul><ul><li>Catalytic converters </li></ul></ul><ul><ul><li>On board vapour recovery system </li></ul></ul>
    45. 45. Transportation System Management (TSM) <ul><li>Reducing emissions due to vehicle operations </li></ul><ul><li>Improve traffic flow by better management of existing transportation facilities </li></ul><ul><li>Cheaper than capital improvements </li></ul><ul><li>Travel time is decreased (mobility increased) </li></ul><ul><li>Good management can increase roadway capacity by 30% </li></ul><ul><li>TSM Measures </li></ul><ul><ul><li>Speed Limit Reduction </li></ul></ul><ul><ul><li>Intelligent transportation system </li></ul></ul><ul><ul><li>Driver behaviour education </li></ul></ul>
    47. 47. INTRODUCTION TO AIR QUALITY MODELING <ul><li>Air Quality Model simulates mathematically pollutants concentration between source and receptor </li></ul><ul><li>It includes Pollutants transport, dispersion ,chemical and physical removal along with the removal process </li></ul><ul><li>Thus the above factor makes it to fit into the field of air pollution </li></ul><ul><li>Types of air pollution modeling: </li></ul><ul><ul><li>Gaussian dispersion modeling </li></ul></ul><ul><ul><li>Photochemical Modeling </li></ul></ul><ul><ul><li>Box Modeling </li></ul></ul><ul><ul><li>Receptor modeling </li></ul></ul><ul><ul><li>Statistical modeling </li></ul></ul>
    48. 48. REVIEW OF AIR POLLUTION METEOROLOGY <ul><li>Causes of wind : </li></ul><ul><ul><li>∆ T-> ∆ ρ -> ∆P -> wind </li></ul></ul><ul><li>Wind 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. </li></ul><ul><li>Wind speed increases with height as the frictional force due to obstruction (trees , buildings) decreases with height. </li></ul><ul><li>Wind speed at any height can be calculated from power law formula </li></ul><ul><ul><li>U 2 = u 1 *(z2/z1) p </li></ul></ul><ul><li>Wind speed can be calculated by anemometer </li></ul><ul><ul><li>Cup anemometer and Hot wire anemometer. </li></ul></ul><ul><li>Wind direction is measured using </li></ul><ul><ul><li>Wind vane and wind sock. </li></ul></ul><ul><li>Instrument location </li></ul><ul><ul><li>10 m high on a tower. </li></ul></ul><ul><ul><li>Avoid rooftop location. </li></ul></ul><ul><ul><li>Away from structures. </li></ul></ul><ul><li>Wind rose diagram </li></ul>
    49. 49. Turbulence /Stability <ul><li>Types of transport </li></ul><ul><ul><li>Advection -> Transport of pollutant with the wind (horizontal direction) </li></ul></ul><ul><ul><li>Dispersion ->Transport of pollutant along vertical direction </li></ul></ul><ul><ul><li>Diffusion -> due to molecular diffusion or Brownian motion. </li></ul></ul><ul><li>Dispersion is due to turbulence </li></ul><ul><li>Causes of Turbulence </li></ul><ul><ul><li>Mechanical turbulence </li></ul></ul><ul><ul><li>Thermal turbulence </li></ul></ul><ul><li>Stability is an indication of atmospheric thermal turbulence </li></ul><ul><ul><li>Stable atmosphere -> little turbulence -> less vertical mixing. </li></ul></ul><ul><ul><li>Unstable atmosphere -> more turbulence -> more vertical mixing. </li></ul></ul><ul><li>Adiabatic Process </li></ul><ul><ul><li>Movement of airparcel without gaining or losing heat. </li></ul></ul><ul><ul><li>Parcel rises ,expands and cools. </li></ul></ul>
    50. 50. Box Models <ul><li>Box model is a simpler model </li></ul><ul><li>Mass balance is solved for one box </li></ul><ul><li>Not as accurate especially for regional scale </li></ul><ul><li>Used for </li></ul><ul><ul><li>Indoor air quality modeling </li></ul></ul><ul><ul><li>Modeling lab scale experiments </li></ul></ul>
    51. 51. Photochemical Grid model <ul><li>Used for regional scale </li></ul><ul><li>The atmosphere is divided into three dimensional grid that may include thousands of grid cell </li></ul><ul><li>The model moves air and pollutant into and out of cells through advection and dispersion </li></ul><ul><li>Mass balance is solved for each box at various time step </li></ul><ul><li>Concentration output of one box becomes an input to its neighboring box. </li></ul><ul><li>Inputs are </li></ul><ul><ul><li>Emission as function of time and space </li></ul></ul><ul><ul><li>Meteorological information </li></ul></ul><ul><ul><li>Deposition estimates </li></ul></ul><ul><ul><li>Chemical reaction information </li></ul></ul>
    52. 52. GAUSSIAN DISPERSION MODELING <ul><li>Gaussian dispersion modeling enables us to find the pollutant concentation with respect to x,y and z direction. </li></ul><ul><li>Q is emission rate and (1/U) is downwind distance. </li></ul><ul><li>Dispersion Parameters σ y and σ z are determined using </li></ul><ul><ul><li>Pasquill-Gifford equation </li></ul></ul><ul><ul><li>Briggs formula </li></ul></ul><ul><ul><li>Wind fluctuation measurement </li></ul></ul>
    53. 53. Methods of determining dispersion parameters σ y and σ z <ul><li>Based on Stability classes </li></ul><ul><li>RURAL AREAS </li></ul><ul><li>Pasquill Gifford Prairie Grass experiments. </li></ul><ul><li>Brookhaven National Lab Scheme. </li></ul><ul><li>Tennessee Valley Authority (TVA) scheme. </li></ul><ul><li>URBAN AREAS </li></ul><ul><li>St.Louis Urban disperion Schemes. </li></ul><ul><li>Putting Together (all the above) </li></ul><ul><li>BRIGGS Formulas </li></ul>
    54. 54. Direct measurement of dispersion parameters <ul><li>Direct measurement of Wind Fluctuations </li></ul><ul><ul><li>More accurate than other methods </li></ul></ul><ul><ul><li>Measurements can be made at the specific site . </li></ul></ul>
    55. 55. Stack tip downwash <ul><li>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. </li></ul><ul><li>HOW TO AVOID? </li></ul><ul><li> Clean Air Act recommends a safe engineering practice stack height of: </li></ul><ul><li>h s = H B + 1.5 z’. </li></ul><ul><li>H B = height of building ; hs = stack height ; </li></ul><ul><li>z’= smaller dimension of the building height or cross- wind width. </li></ul>
    56. 56. Relaxing Assumptions <ul><li>Vertical limits on dispersion due to </li></ul><ul><li>inversions. </li></ul><ul><li>Effects of topography. </li></ul><ul><li>Accounting for chemical reactions </li></ul><ul><li>Accounting for physical removal. </li></ul><ul><li>Adjusting averaging times. </li></ul>
    57. 57. CE - 5325
    58. 58. Fundamentals of Microbiology <ul><li>Classification of Microorganisms </li></ul><ul><ul><li>By carbon and energy source </li></ul></ul><ul><ul><ul><li>Chemosynthetic  energy source obtained from redox reactions </li></ul></ul></ul><ul><ul><ul><li>Photosynthetic  energy obtained from sunlight </li></ul></ul></ul><ul><ul><ul><li>Heterotrophic  Carbon source obtained from organic carbon </li></ul></ul></ul><ul><ul><ul><li>Autotrophic  carbon source obtained from CO 2 </li></ul></ul></ul><ul><ul><li>By cell structure </li></ul></ul><ul><ul><ul><li>Prokaryotic </li></ul></ul></ul><ul><ul><ul><ul><li>Small size, single DNA molecule </li></ul></ul></ul></ul><ul><ul><ul><li>Eukaryotic </li></ul></ul></ul><ul><ul><ul><ul><li>Larger size, several DNA molecules </li></ul></ul></ul></ul><ul><ul><li>Method of Reproduction </li></ul></ul><ul><ul><ul><li>Sexual, Asexual, Spore formation </li></ul></ul></ul><ul><ul><li>Environmental conditions for Growth </li></ul></ul><ul><ul><ul><li>Oxygen requirement, temperature </li></ul></ul></ul><ul><ul><li>Motility: organism free moving in water or not </li></ul></ul>
    59. 59. Fundamentals of Microbiology <ul><li>Catabolism : </li></ul><ul><ul><li>The degradative phase of metabolism in which large and complex molecules are degraded to yeild smaller, simpler molecules </li></ul></ul><ul><ul><li>Accompanied by release of chemical energy </li></ul></ul><ul><ul><li>Conversion to form energy transferring molecule Adenosine triphosphate (ATP) </li></ul></ul><ul><li>Anabolism </li></ul><ul><ul><li>Building up or biosynthetic phase of metabolism </li></ul></ul><ul><ul><li>Requires input of chemical energy, provided by Atp generated during catabolism </li></ul></ul><ul><li>Enzymes ; catalysts of biochemical reactions </li></ul><ul><ul><li>Characteristics </li></ul></ul><ul><ul><ul><li>Specific to a given reaction </li></ul></ul></ul><ul><ul><ul><li>Both intracellular and extracellular </li></ul></ul></ul><ul><ul><ul><li>Some enzymes requires cofactors </li></ul></ul></ul><ul><ul><ul><li>Most enzymes lose activity at high tempratures </li></ul></ul></ul>
    60. 60. Fundamentals of Biochemistry <ul><li>Most biological reactions are oxidation reduction reactions </li></ul><ul><li>BOD : measures DO used by microorganisms under specified conditions over specific time period </li></ul><ul><li>COD : measures the amount of organic matter that is chemically oxidized using a strong oxidant </li></ul><ul><li>TOC : Total organic Carbon  convert C  CO2 and measure </li></ul><ul><li>Yield: ratio of biomass (sludge) produced per mass of substrate removed from water. </li></ul><ul><li>Yield: depends on relative efficiencies of energy generation and utilization </li></ul>
    61. 61. Suspended Growth Systems <ul><li>Suspended growth of biological systems are estimated by using monod kinetics </li></ul><ul><li>Chemostat is a reactor used for continious growth of microbial cultures. It is a CFSTR. </li></ul><ul><li>Assumptions of Monod Kinetics </li></ul><ul><ul><li>Monod Kinetics describe degradation </li></ul></ul><ul><ul><li>Soluble substrate </li></ul></ul><ul><ul><li>Single limiting substrate </li></ul></ul><ul><ul><li>Constant Q </li></ul></ul><ul><ul><li>Completely mixed system </li></ul></ul><ul><li>Net bacterial growth rate is controlled by θ H </li></ul><ul><li>Active biomass density in the reactor depends on the inlet substrate concentration, yield and residence time </li></ul><ul><li>Effluent substrate concentration is controlled by </li></ul><ul><ul><li>Half velocity constant (Ks) </li></ul></ul><ul><ul><li>Specific growth rate ( μ m) </li></ul></ul><ul><ul><li>Endogeneous decay (Kd) </li></ul></ul><ul><ul><li>Solids Retention time ( θ H ) </li></ul></ul>
    62. 62. Suspended Growth Systems <ul><li>Cell washout : Residence time is so low that cells wash out before any reaction occur </li></ul><ul><li>If mean cell residence time is somewhat less than the growth then there would be no growth </li></ul>
    63. 63. Activated Sludge <ul><li>Components of AS system </li></ul><ul><ul><li>Aeration Basin : completely mixed aerobic reactor with aeration </li></ul></ul><ul><ul><li>Clarifier : cells are seperated by sedimentation </li></ul></ul><ul><ul><ul><li>Removes MLSS </li></ul></ul></ul><ul><ul><ul><li>Concentrates solids to return to bioreactor </li></ul></ul></ul><ul><ul><li>Solids Recycle: Return Activated Sludge: a portion of the cells are returned to the aeration basin </li></ul></ul><ul><li>Assumptions for modelling </li></ul><ul><ul><li>Aeration basin is a CFSTR </li></ul></ul><ul><ul><li>Biodegradation occurs only in the aeration basin </li></ul></ul><ul><ul><li>Monod Kinetics – single limiting soluble substrate </li></ul></ul><ul><li>Key Conept : SRT > HRT </li></ul><ul><ul><li>Low SRT  low effluent substrate concentration </li></ul></ul><ul><ul><li>Low HRT  small reactor volume, high throughput, system economy </li></ul></ul>
    64. 64. Activated Sludge <ul><li>Plug flow reactor with recycle </li></ul><ul><ul><li>More efficient than a CFSTR  higher influent concentration leads to higher reaction rates </li></ul></ul><ul><ul><li>PFR there is higher substrate and oxygen concentration in the initial or inut phase but becomes lesser as we go down </li></ul></ul><ul><ul><li>Does not handle shock loads as well as CFSTR </li></ul></ul>
    65. 65. Sludge Bulking <ul><li>Growth of filamentous organisms </li></ul><ul><li>Enough filaments to hold floc together </li></ul><ul><li>Interferes with settling and foaming problem occurs </li></ul><ul><li>Stratergies to control filamentous organisms: </li></ul><ul><ul><li>PFR : Organisms go through an area of reactor with high substrate concentration. Natural selection ofhigh growth rate under high substrate concentration </li></ul></ul><ul><ul><li>Selector : short residence time reactor with high F/M and sufficient aeration </li></ul></ul>
    66. 66. Trickling Filter <ul><li>Factors affecting Trickling Filter </li></ul><ul><ul><li>Influent cocentration : The rate at which the bacteria can remove the substrate reaches a maximum value as concentration increases </li></ul></ul><ul><ul><li>Substrate particle size and treatability : are limited to soluble substrate removal </li></ul></ul><ul><ul><li>Specific surface area and media configuration: Increase in surface area increases performance because of greater biomass as long as oxygen is not limiting </li></ul></ul><ul><ul><li>Hydraulic loading: Improved mass transfer but contact time is greatly reduced for a given coloumn height and also it affects the biofilm thickness </li></ul></ul><ul><ul><li>Effluent recycle : lowers influent concentration but decreases mass transfer resistance </li></ul></ul><ul><ul><li>Sludge Recirculation : should improve performance. </li></ul></ul><ul><ul><li>BOD loading/Aeration : BOD loading is a product of hydraulic loading and influent concentration </li></ul></ul><ul><ul><li>Dosing Period : Resting may improve aeration but the hydraulic and organic loading rates are instantaneously greater </li></ul></ul>
    67. 67. Nitrification & Denitrification <ul><li>Nitrification : biological oxidation of ammonia  Nitrite(nitrosomonas)  Nitrate (nitrobactor) </li></ul><ul><li>Denitrification </li></ul><ul><ul><li>Assimlatory : Reduction of nitrate/nitrite  Ammonia </li></ul></ul><ul><ul><li>Dissimilatory : Reduction of nitrite/Nitrate  nitrogen gas </li></ul></ul><ul><ul><li>Requires </li></ul></ul><ul><ul><ul><li>Absence of oxygen </li></ul></ul></ul><ul><ul><ul><li>Presence of BOD </li></ul></ul></ul><ul><ul><ul><li>Presence of nitrite and nitrate </li></ul></ul></ul><ul><ul><ul><li>Presence of denitrifiers </li></ul></ul></ul><ul><ul><ul><li>Sufficient time and proper environmental conditions </li></ul></ul></ul>
    68. 68. CE – 5316 Water Supply & Treatment Plant Design
    69. 69. Water Quality <ul><li>Water Quality Parameters </li></ul><ul><ul><li>Chemical Parameters </li></ul></ul><ul><ul><ul><li>Inorganic compounds (ions) </li></ul></ul></ul><ul><ul><ul><li>Organic compounds </li></ul></ul></ul><ul><ul><li>Physical Parameters </li></ul></ul><ul><ul><ul><li>Temprature </li></ul></ul></ul><ul><ul><ul><li>TSS </li></ul></ul></ul><ul><ul><ul><li>Turbidity </li></ul></ul></ul><ul><ul><ul><li>Color </li></ul></ul></ul><ul><ul><ul><li>Taste and Odor </li></ul></ul></ul><ul><ul><li>Biological Parameters </li></ul></ul>
    70. 70. Major Processes <ul><li>Screening – process to remove suspended solids through racks and screens </li></ul><ul><li>Aeration – process to increase DO concentration for taste and odor control </li></ul><ul><li>Pre-oxidations – oxidize dissolved compounds for taste and odor control, color reduction, achieving disinfection </li></ul><ul><li>Rapid mix – achieve rapid and through dispersion of chemicals required by coagulation </li></ul><ul><li>Coagulation – modify colloidal particles, stabilizing forces are reduced for efficient aggregation during flocculation </li></ul><ul><li>Flocculation – promote the growth of the floc for removal through sedimentation and filtration </li></ul><ul><li>Sedimentation – process to separate solids from water through gravity settling </li></ul>
    71. 71. Major Processes <ul><li>Filtration – process to remove fine particles and floc through bed of porous granular media </li></ul><ul><li>Activated Carbon – process to absorb dissolved organic compounds for taste & odor control and color reduction </li></ul><ul><li>Softening – process to remove hardness through chemical precipitations </li></ul><ul><li>Recarbonation – process to neutralize and restore chemical balance of water after softening </li></ul><ul><li>Disinfection – process to inactivate and remove pathogens in order meet primary drinking water standards </li></ul><ul><li>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 </li></ul>
    72. 72. Intake, Screening & Aeration <ul><li>Raw water intake : A special structure used to draw water from predetermined pool </li></ul><ul><li>Types </li></ul><ul><ul><li>Floating, Submerged, Tower, Shore intake. </li></ul></ul><ul><li>Screening : To remove objects carried in raw water, protect downstream equipments. </li></ul><ul><li>Types </li></ul><ul><ul><li>Coarse, fine screens and Micro strainers </li></ul></ul><ul><li>Aeration : Add DO, remove VOC, taste and odor causing compounds & remove CO2 and H2S by stripping </li></ul><ul><li>Types </li></ul><ul><ul><li>Gravity, Spray, Diffused & Mechanical </li></ul></ul>
    73. 73. Water Conveyance, Measurement & Pumping <ul><li>Water conveyance system : A controllable hydraulic system used to move water from one place to another </li></ul><ul><li>Flow measurement : A technique used to collect data regarding the quantity of water passing through the concerned point in the water conveyance system </li></ul><ul><li>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 </li></ul><ul><ul><ul><li>Kinetic: centrifugal and peripheral/recessed </li></ul></ul></ul><ul><ul><ul><li>Positive displacement: plunger/piston, diaphragm, rotary, screw, airlift </li></ul></ul></ul>
    74. 74. Coagulation & Flocculation <ul><li>Coagulation/Flocculation : </li></ul><ul><ul><li>- Removal of turbidity </li></ul></ul><ul><ul><li>- Removal of bacteria and virus </li></ul></ul><ul><ul><li>- Removal of color </li></ul></ul><ul><ul><li>Preparation for filterable water </li></ul></ul><ul><li>Three typically used coagulants: </li></ul><ul><ul><li>- Ferric Sulfate: Fe2(SO4)3 </li></ul></ul><ul><ul><li>- Ferric Chloride: FeCl3 </li></ul></ul><ul><ul><li>Alum (aluminum sulfate): Al2(SO4)3•14H2O </li></ul></ul><ul><li>Rapid Mix : Coagulation requires rapid dispersion of chemical throughout water and quick formation of precipitates under extremely violent agitation </li></ul><ul><li>Flocculation : Physical process used to promote the growth of the floc under slow mixing conditions. </li></ul><ul><ul><li>Agglomeration of floc after the destabilization of particles and formation of precipitates </li></ul></ul><ul><ul><li>- Flocculation requires slow and gentle agitation that will not create turbulence to break up the floc particles that already formed during coagulation process. </li></ul></ul>
    75. 75. Sedimentation <ul><li>A process used to separate the settleable solids from the water through gravity setting </li></ul><ul><li>Preconditions : </li></ul><ul><ul><li>Specific gravity of the particles should be larger than that of the fluid. </li></ul></ul><ul><li>Four types of sedimentation behaviors: </li></ul><ul><ul><li>Type I sedimentation: discrete settling </li></ul></ul><ul><ul><ul><li>individual particles settle independently, it occurs when there is a relatively low solids concentration </li></ul></ul></ul><ul><ul><li>Type II sedimentation: flocculant settling </li></ul></ul><ul><ul><ul><li>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 </li></ul></ul></ul><ul><ul><li>Type II sedimentation: hindered or zone settling </li></ul></ul><ul><ul><ul><li>particle concentration is great enough to inhibit water movement settling, water must move in spaces between particles </li></ul></ul></ul><ul><ul><li>Type IV sedimentation: compression settling </li></ul></ul><ul><ul><ul><li>occurs when particles settle by compressing the mass below </li></ul></ul></ul>
    76. 76. Filtration <ul><li>A physical process used to remove fine particles and floc through a bed of porous granular media. </li></ul><ul><li>• System Components: </li></ul><ul><ul><li>- Filters </li></ul></ul><ul><ul><li>- Backwash system </li></ul></ul><ul><ul><li>Backwash waste recovery system </li></ul></ul>
    77. 77. Backwash <ul><li>Backwash operation may be initiated by: </li></ul><ul><ul><li>Exceeding preset maximum head loss </li></ul></ul><ul><ul><li>Experiencing turbidity breakthrough </li></ul></ul><ul><ul><li>Passing pre-selected run time </li></ul></ul><ul><li>Basic design considerations include: </li></ul><ul><ul><li>Settling velocity of the media </li></ul></ul><ul><ul><li>Backwash rate </li></ul></ul><ul><ul><li>Expansion of bed </li></ul></ul><ul><ul><li>Head loss during backwash </li></ul></ul>
    78. 78. Water Treatment <ul><li>Taste and odor control </li></ul><ul><li>Residual Processing </li></ul><ul><li>Ion Exchange </li></ul><ul><ul><li>A chemical process used to exchange anions or cations on a &quot;resin&quot; bed for cations or anions of the contaminant that needs to be removed from the water </li></ul></ul><ul><li>Membrane process </li></ul><ul><ul><li>A physical process using different semipermeable membranes for removal of dissolved solids as well as colloidal particles </li></ul></ul><ul><li>Electrodyalysis </li></ul><ul><ul><li>An electrically driven dialysis demineralization process using semipermeable to remove ions </li></ul></ul>
    80. 80. Characteristics of Natural Water <ul><li>The hydrogen bonding in the water molecule is unique and very strong </li></ul><ul><li>Density </li></ul><ul><li>Density of ice < water </li></ul><ul><li>At 3.98 ̊C  max. density </li></ul><ul><li>Water cooler than 4 ̊C will float / sink (otherwise) </li></ul><ul><li>Dissolved Oxygen (DO) </li></ul><ul><li>Refers to the health of the water body </li></ul><ul><li>High value is preferred </li></ul><ul><li>No direct method to measure oxygen demand in sewage  Complexity </li></ul><ul><li>Winkler test (titration based), electrodes (modern) </li></ul><ul><li>Approximate indirect method to measure total oxygen demand is Biochemical Oxygen Demand (BOD). </li></ul>
    81. 81. Characteristics of Natural Water <ul><li>Biochemical Oxygen Demand (BOD) </li></ul><ul><li>Not direct measure but gives the feel of how much oxygen is consumed by biochemical sources present in water. </li></ul><ul><li>Actually measuring  BOD 5 = DO 0 – DO 5 </li></ul><ul><li>Test is an approximation – DO measured is strictly not biological </li></ul><ul><li>COD (Chemical Oxygen Demand) </li></ul><ul><li>Trying to calculate the refractory species (chemically active rather than biologically active) in the sample. </li></ul><ul><li>TOD = COD + BOD 5 </li></ul>
    82. 82. Characteristics of Natural Water <ul><li>Total Organic Carbon (TOC) </li></ul><ul><li>Deals with organics </li></ul><ul><li>An instrumental test </li></ul><ul><li>pH </li></ul><ul><li>pH = - log [H 3 O] + </li></ul><ul><li>Practical value = 0-14 </li></ul><ul><li>0-7  Acid, 7  Neutral, 7-14  Basic </li></ul><ul><li>pH is often called the intensity factor. </li></ul><ul><li>Alkalinity </li></ul><ul><li>The capacity of water to neutralize itself </li></ul><ul><li>Greater the alkalinity the better it resists change in a pH or buffering effects </li></ul><ul><li>Buffers are a combination of weak acid and its conjugate base </li></ul><ul><li>Carbonate system is more predominant in Natural waters </li></ul><ul><li>Alkalinity test uses phenolphthalein (pink  base , colorless  acid) </li></ul><ul><li>1 st end point – phenolphthalein – 8.3 – get the measure of Carbonate [HCO 3 ] - </li></ul><ul><li>2 nd end point – methyl orange – 4.5 – get the measure of bicarbonate [CO 3 ] 2- and [OH] - </li></ul><ul><li>Total Alkalinity = [HCO 3 ] - + 2 [CO 3 ] 2- + [OH] - </li></ul>
    83. 83. Characteristics of Natural Water <ul><li>Hardness </li></ul><ul><li>Hardness is the total concentration of divalent cations (+ve charge) in natural waters. </li></ul><ul><li>Expressed as mg CaCO 3 / L </li></ul><ul><li>Predominant ions that contribute to the hardness is Ca2+, Mg2+ </li></ul><ul><li>In ground water Fe2+ can be a contributor </li></ul><ul><li>All other is called Non-Carbonate Hardness </li></ul><ul><li>Total Dissolved Solids (TDS) </li></ul><ul><li>Measures the total dissolved solids </li></ul><ul><li>Measured in ppm </li></ul><ul><li>Increase in TDS means less desirable the water and is dangerous for aquatic life </li></ul><ul><li>Total Suspended Solids (TSS) </li></ul><ul><li>Suspended solids are a vehicle for transporting toxic materials </li></ul><ul><li>Turbidity </li></ul><ul><li>It is a measure of water clarity </li></ul><ul><li>Increase in TSS causes increase in Turbidity. </li></ul>
    84. 84. Metal Ion Co-ordination Chemistry <ul><li>Predominant dissolved metals is sodium and potassium in aquatic environment (sea) </li></ul><ul><li>Ca, Mg, K & Na can be measured in ppm or mg/L </li></ul><ul><li>All other metals are in trace concentrations in water and generally measured in ng/L or ppt, μ g/L or ppb </li></ul><ul><li>Metal ion concentration does not affect pH of water, they are of very low concentration in water. </li></ul><ul><li>A water molecule covalently bonded to a metal will be a stronger acid </li></ul><ul><li>Hydrated metal ion when behaves as an acid is called hydrolysis </li></ul><ul><li>Two species can be used to see where the Reaction is going: </li></ul><ul><ul><li>Oxidation State </li></ul></ul><ul><ul><ul><li>Increase in oxidation  more positive it becomes  stronger acidic activity </li></ul></ul></ul><ul><ul><li>pH </li></ul></ul><ul><ul><ul><li>Increase in pH  increase in degree of hydrolysis </li></ul></ul></ul><ul><li>Hydrolysis </li></ul><ul><ul><li>Increases with increasing pH </li></ul></ul><ul><ul><li>Increases with increasing dilution </li></ul></ul><ul><ul><li>Increases with increasing oxidation state. </li></ul></ul>
    85. 85. Colloidal Systems <ul><li>A colloid is a material that fall in between the homogenous and heterogeneous mixture. </li></ul><ul><li>A colloid is a homogeneous mixture of two phases. </li></ul><ul><li>One phase is called medium or bulk and the other is called the colloid </li></ul><ul><li>Colloid is pictured </li></ul><ul><ul><li>As a particle, larger than the typical solution </li></ul></ul><ul><ul><li>Which cannot dissolve in a solution </li></ul></ul><ul><ul><li>Cannot have the precipitate or the colloid to dissolve it </li></ul></ul><ul><li>Diameter of colloid is in the range of 0.0001 – 1 μ m </li></ul><ul><li>Colloids can be organic, inorganic & biological </li></ul><ul><li>They have very large surface area to volume ratio. It provides a site for chemical reaction and makes the reaction easier. </li></ul><ul><li>A colloidal particle is a transporter for materials from one place to another </li></ul><ul><li>Colloids are measure of TSS and Turbidity </li></ul>
    86. 86. Colloidal Systems <ul><li>Formation of Colloids (2 Basic models) </li></ul><ul><ul><li>Dispersion : Process involving the reduction of larger particle to smaller size </li></ul></ul><ul><ul><li>Condensation : Chemical Physical process by which particles aggregate to form a size of colloidal particles </li></ul></ul><ul><li>Types of Colloids </li></ul><ul><ul><li>Hydrophillic : affinity for water </li></ul></ul><ul><ul><li>Hydrophobic : Repels water, they will stabilize in a way that they remain suspended in water (non polar molecules) </li></ul></ul><ul><ul><li>Association : A colloid where one end is polar and the other end is non polar. </li></ul></ul><ul><li>Most colloids that are of concern in environment are either hydrophobic or association. </li></ul>
    87. 87. Aquatic Microorganisms <ul><li>Oxidation reductiom reaction is the life forming reaction of any microorganism </li></ul><ul><li>Microorganisms convert one form of chemical to another so as to recycle </li></ul><ul><li>For most digestive processes in microorganisms, they use spontaneous oxidation-reduction reaction </li></ul><ul><li>Classification of Microorganisms </li></ul><ul><ul><li>Autotrophic (Producers) : They convert inorganic materials to organic materials </li></ul></ul><ul><ul><ul><li>They depend on non-spontaneous redox process. Need a continual source of energy to keep them going </li></ul></ul></ul><ul><ul><ul><li>Sources come from two places </li></ul></ul></ul><ul><ul><ul><ul><li>Sunlight  Photosynthetic ex. Algae </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Chemicals  Chemosynthetic ex. Bacteria </li></ul></ul></ul></ul><ul><ul><li>Heterotrophic (Reducers or Decomposers) : Primary function is to convert organic  inorganic materials </li></ul></ul><ul><ul><ul><li>They depend on spontaneous redox process </li></ul></ul></ul><ul><ul><ul><ul><li>Aerobic : Requires direct oxygen </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Anaerobic : Functions in the absence of oxygen </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Facultative : can function in both presence and absence of oxygen </li></ul></ul></ul></ul>
    88. 88. <ul><li>Almost all reactions that happen in the atmosphere are photochemical </li></ul><ul><li>Scattering </li></ul><ul><ul><li>The path of the radiation is changed/redirected </li></ul></ul><ul><ul><li>Three types of scattering </li></ul></ul><ul><ul><ul><li>Rayleigh <= 1(d/ λ ) </li></ul></ul></ul><ul><ul><ul><ul><li>Characteristic of this scattering is back scattering </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Type of matter capable of doing this is the smallest of the suspended particles </li></ul></ul></ul></ul><ul><ul><ul><li>Mie Scattering = 1 </li></ul></ul></ul><ul><ul><ul><ul><li>No back scattering </li></ul></ul></ul></ul><ul><ul><ul><ul><li>Large particles in suspended air scatter light </li></ul></ul></ul></ul><ul><ul><ul><li>Optical Scattering >= 1 </li></ul></ul></ul><ul><ul><ul><ul><li>Done by Reflection, refraction and diffraction. </li></ul></ul></ul></ul>