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complete layout of course design in Masters program :)

complete layout of course design in Masters program :)

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  • Need to explain in brief about the various properties of air.

Final Comprehensive Examination Presentation Transcript

  • 1. DEEPAK LEO JOHN
  • 2. CE 5328
  • 3. INTRODUCTION
    • 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.
    • Types of Pollutants
    • Primary Pollutants : Directly emitted from source
    • Secondary Pollutants : Not emitted dirctly but are formed in the atmosphere by chemical reactions
    • Sources
    • Point / Stationary
    • Area / Mobile
  • 4. Structure of Atmosphere
    • Atmosphere is divided into layers based on the thermal structure
    • Troposphere, 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)
  • 5. Properties of Air
    • Composition of air
    • Molecular weight of air
    • Viscosity
    • Reynolds Number
    • Ideal Gas Law (PV=nRT)
    • Concentration Measurements
  • 6. Types of Air Pollutants
    • Primary 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.
  • 7. 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 : SO 2 , No x , CO, O 3 , 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.
  • 8. Clean Air Act
    • Fedreal 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.
  • 9. Gas Flow Measurement
    • Continuity 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
  • 10. Sampling and Monitoring
    • Sampling  intermittent
    • Monitoring  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.
  • 11. Control Technologies
    • Gas control Technologies
      • Incineration
      • Adsorption
      • Absorption
      • Biological control
    • Particulate control Technologies
      • Electrostatic prcipitators
      • Fabric Filters
      • Particulate scrubbers
  • 12. CE - 5320
  • 13. Solid Waste Hierarchy
    • Solid 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 Management
      • Source Reduction in source
      • Recycling
      • Waste Transformation
      • Landfilling
  • 14. Sources, Types & Composition of MSW
    • Sources
      • Treatment plant sludge
      • Light Industrial Waste
      • Mixed waste (residential & commercial)
    • Types
      • Residential / Commercial
      • Institutional
      • Construction and demolition
      • Industrial
    • 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.,
  • 15. Properties of MSW
    • Physical Properties
      • Specific weight
      • Moisture Content
      • Particle size & size distribution
      • Field capacity
      • Degree of compaction
      • Permeability of compacted MSW
    • Chemical Properties
      • Proximate Analysis
      • Fusing point of Ash
      • Ultimate Analysis
      • Energy conent of MSW
    • Biological Properties
      • Biodegradability
      • Odor
      • Breeding of flies
  • 16. Municipal Solid Waste
    • Waste Generation (Quantitative)
      • Load count analysis – recording the no. of individual loads
      • Weight Volume analysis – directly measuring weight and volume of each load
    • Waste Handling
      • Seperation of wastes
      • Collection and Routing of MSW
      • Transfer Stations – a link between community collection and final disposal facility
  • 17. Sanitary Landfill
    • Operational Steps
      • Unload
      • Spread
      • Compact
      • Cover
    • Basic components of Sanitary Landfill
      • Cell
      • Cover layer system
      • Gas control & recovery system
      • Leachate collection system
      • Gas monitoring probes
      • Ground water monitoring wells
  • 18. Sanitary Landfill
    • Design of Landfill
      • Develop preliminary site plan of fill area
      • Compute the solid waste sorage volume, soil requirement volumes & site life
      • 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
      • Prepare cost estimates
      • Prepare environmental impact assesment
      • Prepare plans for closure and post closure care.
  • 19. CIRP 5357
  • 20. Fundamentals of GIS concepts
    • Two types of data to describe geographic features
      • Spatial 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 types
      • Bounded area, continious area, networks and points.
    • Spatial data is organized by layers, with each layer representing a common feature.
  • 21. Fundamentals of GIS concepts
    • Attribute data types
      • Categorical(character field) and Numerical(integer, floating point, decimal)
    • Data are grouped into Vector and Raster data models
    • Vector data model
      • Location referenced by x,y coordinates, which can be linked to form lines and polygons
      • Attributes referenced through unique id number to tables
      • Best used for layers with disrete boundaries
    • Raster data model (requires spatial analyst models)
      • Location is referenced by a grid cell in a rectangular array
      • Attributes reffernced through a single value for the cell
      • Best used for continious layes.
  • 22. ArcGIS Components
    • ArcCatalog
      • For organizing and managing GIS data
        • Browse
        • Search
        • Define
        • Metdata
    • ArcMap
      • Cental Application
        • Cartography
        • Analysis
        • Editing
    • ArcToolbox
      • Standalone Geoprocessing Tools
        • Analysis
        • Conversion
        • Batch Processing
  • 23. Query, Analysis and Modeling
    • Basic Spatial Opreation
      • Spatial Measurement
        • Distance
        • Area
        • Centroid
      • Spatial Aggregation
        • Redistricting
        • Classification
      • Spatial Overlays and joins
        • Spatial selection
        • Spatial assignment
        • Clipping
        • Erasing
        • Merging
    • Buffer analysis
    • Geocoding
    • Attribute operations
      • Record selection
      • Variable recoding
      • Record aggregation
      • General statistical analysis
  • 24. 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)
      • Reduce rasters to unit width by decreasing the pixels
      • Vector extraction – to identify the lines
      • Topological reconstruction – recreates topological structures
  • 25. PHYSICAL CHEMICAL PROCESSES Ι CE – 5318
  • 26. Stiochiometery & Batch Reactor Kinetics
    • Stiochiometery tells how much one chemical reacts with another to form how much of a product
    • Stoichiometric co-eff of reactant –ve (disappearing)
    • Stoichiometric co-eff of product +ve (appearing)
    • Reaction Kinetics tells how fast a reaction is occurring
    • Classes of reaction:
      • Homogeneous : single phase  reaction
      • Hetrogeneous : reaction occurs between different phases  reaction and transport
    • Mass Balance:
        • Accumulation = Inflow – Outflow + Generation
    • Batch 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
  • 27. Complete Mix and Plug Flow Reactor
    • They are continuous type reactor
    • Plug Flow reactor
      • Completely mixed laterally
      • No mixing longitudinally
      • The response of a PFR as a fn of θ H at steady state is the same as the response of a batch reactor
    • Complete 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
  • 28. Hetrogeneous System
    • Hetrogeneous : reaction occurs between different phases  reaction and transport
    • Mechanism 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
  • 29. Lake Classification
    • Lakes are classified by
      • Method of origin
      • How often lakes undergo thermal stratification and destratification
      • Trophic level
    • Trophic level clasification
      • Photosynthetic growth levels called primary production
      • Nutrient concentration
      • Measurement of biodiversity
    • Modelling of Water Quality in lakes
      • Hydraulic 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
  • 30. Lake Classification
      • Water 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 PFR
      • Equation describes DO sag as a fn of θ H
      • Actually calculates the defecit of oxygen
      • Hence can calculate DO at any point of the river
  • 31. Mixing and Flocculation
    • Perfectly mixed  CFSTR  Homogenity at all locations in the reactor
    • Mixing is a fuction of turbulence
    • Turbulence is a result of irregular flow conditions
    • The intensity of turbulence can be expressed as a fraction of time average velocity
    • Eddies are important for flocculation
    • Particles smaller than eddies will move together and not colloide
    • Large eddies arise from the interaction of mean flow with the boundaries
    • They carry most of the mixing energy
    • Under 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
  • 32. Mixing and Flocculation
    • Perikinetic (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 μ m
    • Orthokinetic (Macrofloc) Flocculation :
      • Aggregation of particles greater than 1-2 μ m
      • Can be brought about by induced velocity gradient and differential settling
  • 33. Sedimentation
    • Types of sedimentation : depends on conc of suspension& characteristics of particles
      • Discrete 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
  • 34. Sedimentation
      • Hindered (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
  • 35. Filtration
    • Characteristics
      • Filtration used for removal of suspended and colloidal particles
      • Porous media captures solids and transports water
      • Filtration is a primary physical process but chemicals can be added to improve performance
      • Two phase process : solids removals during filtration followed solids removal in backwashing
      • Filtration is typically non continious process because it has two phases
    • The effective size of filtering medium
      • It is the 10% size based on mass
      • Uniformity co-efficient Uc is d 60 /d 10
      • d 10 is used in selecting filter medium
      • Indicator of performance & Low d 10 produce better quality
  • 36. Gas Transfer
    • Gas transfer is a hetrogeneous system
    • Two 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 phase
      • The two film theory provides the resistance to the passage of gas molecules between the bulk gaseous phase
    • Oxygen transfer rate OTR
    • Standard Oxygen transfer rate SOTR
  • 37. TRANSPORTATION & AIR QUALITY CE - 5324
  • 38. The Mobile Source Problem
    • Trends of vehicle ownership
    • The upside and the downside of automobiles
    • Trends of on road transportation source emission
    • Trends of off road emissions
    • Air pollution in developing countries
  • 39. Internal Combustion Engines
    • Pollutants that result from combustion
      • Oxides of Nitrogen
      • Oxides of Sulfur
      • Particulates
      • CO
    • Otto cylce (4 stroke)
      • Intake stroke
      • Compression stroke
      • Power stroke
      • Exhaust stroke
    • Air to fuel ratio influneces the pollutant production
    • Evaporative emmisions
    • 2 stroke gasoline engines
  • 40. Clean Air Act Provisions
    • Clean air act direct provisions
    • Clean air act SIP provisions
    • Conformity
      • CAA requires confirmity that highway and transportation projects conform to the purpose of SIP
    • Fuel economy standards
      • Corprate average fuel economy (CAFÉ)
      • Cars  27.5 mpg
    • California’s Low Emission Vehicle(LEV) program
  • 41. Estimating Emissions
    • SIP requires quatitative estimates of emission reductions
    • To ensure controls are sufficient to bring the region into compilance
    • Emmisions = Emission Factor x VMT
    • Macro 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  VMT
      • Estimates the amount of transportation activity occuring in a region
      • Typical outputs : No. of transit trips, automobile occupancy, average vehicle speed for each roadway segment, VMT
  • 42. Ambient Concentration Modelling
    • Dispersion Modelling
      • uses output from emission model as input
      • Accounts metereology to predict atmospheric concentration
      • Simulates what happens to the pollutants emitted into the atmosphere
      • 3-D analysis system
      • Assumes double gaussian distribution (double bell shaped curve)
  • 43. Engine Design Changes
    • Avoiding 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
  • 44. Alternate Fuels
    • Natural gas, propane, methanol, ethanol and biodiesel
    • Reformulated gasoline
    • Hybrids
    • Fuel cells, hydrogen
    • Add on tailpipe emission control
      • Catalytic converters
      • On board vapour recovery system
  • 45. Transportation System Management (TSM)
    • Reducing emissions due to vehicle operations
    • Improve traffic flow by better management of existing transportation facilities
    • Cheaper than capital improvements
    • Travel time is decreased (mobility increased)
    • Good management can increase roadway capacity by 30%
    • TSM Measures
      • Speed Limit Reduction
      • Intelligent transportation system
      • Driver behaviour education
  • 46. AIR DISPERSION MODELLING CE - 5323
  • 47. INTRODUCTION TO AIR QUALITY MODELING
    • Air Quality Model simulates mathematically pollutants concentration between source and receptor
    • It includes Pollutants transport, dispersion ,chemical and physical removal along with the removal process
    • Thus the above factor makes it to fit into the field of air pollution
    • Types of air pollution modeling:
      • Gaussian dispersion modeling
      • Photochemical Modeling
      • Box Modeling
      • Receptor modeling
      • Statistical modeling
  • 48. REVIEW OF AIR POLLUTION METEOROLOGY
    • Causes of wind :
      • ∆ T-> ∆ ρ -> ∆P -> wind
    • 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.
    • 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
      • U 2 = u 1 *(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
  • 49. 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 turbulence
    • Causes 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.
  • 50. Box Models
    • Box model is a simpler model
    • Mass balance is solved for one box
    • Not as accurate especially for regional scale
    • Used for
      • Indoor air quality modeling
      • Modeling lab scale experiments
  • 51. Photochemical Grid model
    • Used for regional scale
    • The atmosphere is divided into three dimensional grid that may include thousands of grid cell
    • The model moves air and pollutant into and out of cells through advection and dispersion
    • Mass balance is solved for each box at various time step
    • Concentration 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
  • 52. GAUSSIAN DISPERSION MODELING
    • Gaussian 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 σ y and σ z are determined using
      • Pasquill-Gifford equation
      • Briggs formula
      • Wind fluctuation measurement
  • 53. Methods of determining dispersion parameters σ y and σ z
    • 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
  • 54. Direct measurement of dispersion parameters
    • Direct measurement of Wind Fluctuations
      • More accurate than other methods
      • Measurements can be made at the specific site .
  • 55. 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:
    • h s = H B + 1.5 z’.
    • H B = height of building ; hs = stack height ;
    • z’= smaller dimension of the building height or cross- wind width.
  • 56. Relaxing Assumptions
    • Vertical limits on dispersion due to
    • inversions.
    • Effects of topography.
    • Accounting for chemical reactions
    • Accounting for physical removal.
    • Adjusting averaging times.
  • 57. CE - 5325
  • 58. Fundamentals of Microbiology
    • Classification 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 CO 2
      • 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
  • 59. Fundamentals of Microbiology
    • Catabolism :
      • 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
  • 60. 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
  • 61. 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 θ H
    • 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 ( μ m)
      • Endogeneous decay (Kd)
      • Solids Retention time ( θ H )
  • 62. Suspended Growth Systems
    • Cell washout : Residence time is so low that cells wash out before any reaction occur
    • If mean cell residence time is somewhat less than the growth then there would be no growth
  • 63. 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
  • 64. Activated Sludge
    • Plug 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
  • 65. Sludge Bulking
    • Growth of filamentous organisms
    • Enough filaments to hold floc together
    • Interferes with settling and foaming problem occurs
    • Stratergies 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
  • 66. Trickling Filter
    • Factors 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
  • 67. Nitrification & Denitrification
    • Nitrification : biological oxidation of ammonia  Nitrite(nitrosomonas)  Nitrate (nitrobactor)
    • Denitrification
      • Assimlatory : Reduction of nitrate/nitrite  Ammonia
      • Dissimilatory : Reduction of nitrite/Nitrate  nitrogen gas
      • Requires
        • Absence of oxygen
        • Presence of BOD
        • Presence of nitrite and nitrate
        • Presence of denitrifiers
        • Sufficient time and proper environmental conditions
  • 68. CE – 5316 Water Supply & Treatment Plant Design
  • 69. Water Quality
    • Water Quality Parameters
      • Chemical Parameters
        • Inorganic compounds (ions)
        • Organic compounds
      • Physical Parameters
        • Temprature
        • TSS
        • Turbidity
        • Color
        • Taste and Odor
      • Biological Parameters
  • 70. Major Processes
    • Screening – 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
  • 71. Major Processes
    • Filtration – 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
  • 72. Intake, Screening & Aeration
    • Raw water intake : A special structure used to draw water from predetermined pool
    • Types
      • Floating, Submerged, Tower, Shore intake.
    • Screening : To remove objects carried in raw water, protect downstream equipments.
    • Types
      • Coarse, fine screens and Micro strainers
    • Aeration : Add DO, remove VOC, taste and odor causing compounds & remove CO2 and H2S by stripping
    • Types
      • Gravity, Spray, Diffused & Mechanical
  • 73. Water Conveyance, Measurement & Pumping
    • Water 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
  • 74. 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.
  • 75. 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
  • 76. Filtration
    • A 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
  • 77. Backwash
    • Backwash 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
  • 78. Water Treatment
    • Taste and odor control
    • Residual Processing
    • Ion 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
  • 79. ENVIRONMENTAL SYSTEMS A CHEMICAL ASPECT EVSE - 5310
  • 80. Characteristics of Natural Water
    • The hydrogen bonding in the water molecule is unique and very strong
    • Density
    • Density of ice < water
    • At 3.98 ̊C  max. density
    • Water cooler than 4 ̊C will float / sink (otherwise)
    • Dissolved Oxygen (DO)
    • Refers to the health of the water body
    • High value is preferred
    • No direct method to measure oxygen demand in sewage  Complexity
    • Winkler test (titration based), electrodes (modern)
    • Approximate indirect method to measure total oxygen demand is Biochemical Oxygen Demand (BOD).
  • 81. Characteristics of Natural Water
    • Biochemical Oxygen Demand (BOD)
    • Not direct measure but gives the feel of how much oxygen is consumed by biochemical sources present in water.
    • Actually measuring  BOD 5 = DO 0 – DO 5
    • 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 + BOD 5
  • 82. Characteristics of Natural Water
    • Total Organic Carbon (TOC)
    • Deals with organics
    • An instrumental test
    • pH
    • pH = - log [H 3 O] +
    • Practical value = 0-14
    • 0-7  Acid, 7  Neutral, 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)
    • 1 st end point – phenolphthalein – 8.3 – get the measure of Carbonate [HCO 3 ] -
    • 2 nd end point – methyl orange – 4.5 – get the measure of bicarbonate [CO 3 ] 2- and [OH] -
    • Total Alkalinity = [HCO 3 ] - + 2 [CO 3 ] 2- + [OH] -
  • 83. Characteristics of Natural Water
    • Hardness
    • Hardness is the total concentration of divalent cations (+ve charge) in natural waters.
    • Expressed as mg CaCO 3 / 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.
  • 84. 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, μ g/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.
  • 85. 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
      • As a particle, larger than the typical solution
      • Which cannot dissolve in a solution
      • Cannot have the precipitate or the colloid to dissolve it
    • Diameter of colloid is in the range of 0.0001 – 1 μ m
    • 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
  • 86. Colloidal Systems
    • Formation 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 Colloids
      • Hydrophillic : affinity for water
      • Hydrophobic : 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.
  • 87. Aquatic Microorganisms
    • Oxidation reductiom reaction is the life forming reaction of any microorganism
    • Microorganisms convert one form of chemical to another so as to recycle
    • For most digestive processes in microorganisms, they use spontaneous oxidation-reduction reaction
    • Classification 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
  • 88.
    • Almost all reactions that happen in the atmosphere are photochemical
    • Scattering
      • The path of the radiation is changed/redirected
      • Three 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.