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ENVIRONMENTAL ENGINEERING II

ENVIRONMENTAL ENGINEERING II. Mr. Shree Kamble DEPARTMENT OF CIVIL ENGINEERING Dr. D Y PATIL INSTITUTE OF ENGINEERING MANAGEMENT & RESEARCH. UNIT 1: Introduction. Air , water & food essential for human existence

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ENVIRONMENTAL ENGINEERING II

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  1. ENVIRONMENTAL ENGINEERING II Mr. Shree Kamble DEPARTMENT OF CIVIL ENGINEERING Dr. D Y PATIL INSTITUTE OF ENGINEERING MANAGEMENT & RESEARCH

  2. UNIT 1: Introduction • Air , water & food essential for human existence • If polluted creates problems: air- respiratory deceases, water - water borne deceases & food- food poisoning • Therefore essential to protect them • Productivity of nation dependents on these factors

  3. Objectives of EE • To supply water safe in quality & adequate in quantity • To collect treat and dispose WW generated in community • Domestic waste contributes 60 % of total water pollution • To put in place, the methods on pollution prevention in industries • I.e. Solid waste, liquid waste and air pollutants • To control air pollution • To control solid waste ( Community & industry)

  4. Quantity & Quality • History: • Civilization development on banks of river • Importance of quantity was realized very earlier but not the quality • Storage of water in copper vessels: Bactericidal property to water (Indian literature) • First recorded incident: 1854- Central London, Dr. John Snow • Handled Broad Street hand pump: Colara decease • Removed handle of hand pump and got punished

  5. Attributes of Drinking Water: • Aesthetics : Free from colour, taste, odour & pleasing (physical perception) Hence, subjective test. • Safety : • Bacteriological ( Free from pathogens disease causing micro-organisms) Analytical test. • Chemical: Free from toxicants like heavy metals. • Anthropogenic activities (Mercury- Biomagnification) • Natural (Arsenic – geological formations) • Economics

  6. Quantity of Water: • ¾ surface is covered with water • 0.62% of the total water is available as fresh water for supplies • Sources of water: • Groundwater (Fe & Mn – causes stains) • Shallow <30m ( Bactriological contamination) • Deep >300m ( Inorganic contaminants ) • Surfacewater ( Pathogens, organic inorganic pollutants) • Lakewater ( Algal growth, taste & odour) • Seawater ( Salinity, TDS) • Treated Effluents ( Pathogens, nutrients) – ZLD Concept

  7. Basic concepts: • Pollution : Foreign organic or inorganic material • Sources of pollution: Point / Nonpoint • Contamination : Micro-organisms, pathogens • Pollution caused by Anthropogenic activities : • Suspended load • Colloidal/ Coarse • Chemical • Organic – Biodegradable / Non-biodegradable • Inorganic - Pesticides • Microbiological - Pathogens

  8. System Model • Water Quality Graph

  9. Design Period • Collection system i.e. Sewer Network : 30 yrs • Pumping station (Civil Work) : 30 yrs • Pumping machinery : 15 yrs • Sewage Treatment Plant (STP) : 30 yrs • Effluent disposal & utilization : 30 yrs

  10. Collection of Sewage • Separate system: Municipal wastewater • Combined system : Municipal wastewater + Storm water

  11. Flow Quantity Estimation • Design period • Population forecasting • Per capita sewage flow • For dry weather : 40 % • For well developed areas : 90 % due to industrial wastewater • Generally, 80 % of water supply is expected to reach sewers • Minimum of 100 lpcd is considered for design of sewers • Variations • Peak factors are adopted for hydraulic design of sewers • Peak factor : (2-3) based on contributory population

  12. Water Requirements • Per capita water demand – 135 lpcd and a minimum of 70 to 100 lpcd • Bathing – 55 • Washing of cloths – 20 • Flushing of WC – 30 • Washing of house – 10 • Washing of utensils – 10 • Cooking – 5 • Drinking – 5 Total – 135

  13. Water Requirements • Institutional use • Hospital • Bed < 100 ---- 450 per bed • Bed > 100 ---- 340 per bed • Hotels - 180 • Hostels, Boarding schools colleges - 135 • Restaurants, Airports / Sea ports - 70 • Day schools, colleges & offices – 45 • Cinema, concert halls - 15

  14. Design of circular sanitary Sewer • The sewage in sewer should flow under gravity with 0.5 to 0.8 full at designed discharge • The sewers should be laid at least 2 to 3 m deep to carry sewage from basement. • Calculation of design peak flow from given data • Minimum daily flow = 1/3 to 2/3 of Avg daily flow • While designing the sewers the flow velocity at full depth is generally kept at about 0.8m/sec • It is necessary to check the sewer for minimum velocity of about 0.45 m/sec at the time of minimum flow (1/3 of average flow) and the velocity of about 0.9 to 1.2 m/sec should be developed at a time of average flow.

  15. Design of circular sanitary Sewer • Hydraulic Formulae for Determining Flow Velocities • Manning’s Formula V = 1/n r^2/3 s^1/2 n = 0.011 to 0.015 • Chezy’s Formula V = C r^0.5 s^0.5 • Hazen Williams Formula V = 0.849 C r^0.63 s^ 0.54 C = 120 • Minimum velocity : Self cleansing velocity • Vs = (8K/f’ * (Ss-1)g.d’)^1/2 • K = 0.04 for inorganic solids and 0.06 for organic solids • F = 0.03 Darcy Weisbatch friction factor • Ss = Specific gravity of sediments • d’ = Diameter of grain , m

  16. Pumping of Sewage • Necessity & Location • Pumping of sewage from localized low lying pockets • To prevent excavation to lay down sewers • Pumping of sewage from basements of structures • Transfer of sewage across high ridge (i.e. instead of tunnel ) • Effect of change of lifestyle on sewage quality

  17. Effluent Discharge Standards

  18. Stream Sanitation • Self purification of natural streams • Rive classification as per MoEF & CC

  19. Self purification of natural streams • Physical Forces • Dilution & Dispersion : CsQs + CRQR = C (Qs+QR) • Sedimentation • Sunlight : stabilizing bacteria & photosynthesis) • Bio-Chemical Forces • Oxidation • Reduction : Hydrolysis of settled OM ---- ultimate oxidation

  20. Self purification of natural streams • Factors affecting : • Temperature : High rate of reaction & low solubility of DO • Turbulence : Maintenance of aerobic conditions • Hydrography ( flow parameters ) • Available DO • Amount and type of OM • Rate of Re-aeration

  21. Self purification of natural streams • Zones of pollution in river stream • Zone of degradation / Zone of pollution • Water is charatceried with colour and turbidity • DO reduced to 40% of its saturation value (7.6 mg/l at 30 degree c. ) • Sludge deposits • High CO2 concentrations • De-oxygenation is more than Re-oxygenation

  22. Self purification of natural streams • Zones of pollution in river stream • Zone of Recovery • River tries to regain its normal position • Cleaner water with algae formations • BOD falls down, DO conc. Rises above 40%

  23. Stream Sanitation • Oxygen Sag Curve • Streeter Phelps Equation

  24. Wastewater • Two types : Domestic & Industrial • Constituents / Components: • Solids • Suspended & Dissolved • Organic ( C,H,O, sometimes N,P,S) • Inorganic (Other than C,H,O like Ca, Mg, Heavy metals) • Nutrients (N & P) • Micro-organisms

  25. Characteristics of Sewage • Physical : (Colour, Turbidity, Solids, Conductivity) • Chemical : (pH, Acidity, Alkalinity, Chlorides etc.) • Biological: (Organic matter) • OM: • BOD5 at 20 deg. C– Biochemical Oxygen Demand (UBOD) • COD – Chemical Oxygen Demand • Th. OD = COD + NOD • TOC – Total Organic Carbon

  26. Characteristics of Sewage • Physical Characteristics • Solids • Turbidity • Colour • pH • Conductivity

  27. Characteristics of Sewage • Solids • Classified depending upon size • Very very small (Nanometer) – Dissolved Solids • 0.01 µm to 1 µm – Colloidal solids (Stable so cant settle, in Brownian movement) • Suspended solids can be removed by Settling • Settlable solids - 60 % of Total OM – Imhoff cone (ml/l) • Total Solids (TS) – Evaporate all water at 105 C (mg/l) • Total Suspended solids (TSS) - Glassfiber filter (2µm) filtration • Volatile Suspended Solids (VSS) – Muffel Furnace at 500 +- 50 C • TSS – FSS ( Left over) = VSS • Volatile Dissolved Solids (VDS) & Fixed Dissolved Solids (FDS) • Silica crucible – TDS – FDS = VDS • TVS = VSS + VDS • TFS = FSS + FDS • TS = TVS + TFS

  28. Characteristics of Sewage • Colour • Apparent colour - Due to TSS • True colour – Due to TDS • Measured with the help of colorimeter • Colour of wastewater • Grey – Non-septic • Black – Septic sewage • Grey Water – Other than toilet • Black water – From toilet

  29. Characteristics of Sewage • Physical Characteristics • pH • Conductivity • Indirect measure of measuring TDS • Conductivity = 2.5 x 10^-5 (TDS) – Applicable in case of water due to IOM solids • Wastewater mainly consists OM

  30. Characteristics of Sewage • Chemical Characteristics • Biochemical Oxygen Demand - BOD • Chemical Oxygen Demand – COD • Total Organic Carbon - TOC • Theoretical Oxygen Demand - ThOD • Nutrients • Toxic Compounds • Alkalinity • Hardness

  31. Characteristics of Sewage • Chemical Characteristics • Biochemical Oxygen Demand (BOD) – Gives pollution status of water • Oxygen demand by microbs during degradation of organic matter to CO2 & H2O under aerobic conditions at a particular temperature & incubation period • Three things are important – Micro-organisms, nutrients and DO • For valid test, DO consumption should be minimum 2 mg/l and final DO of >1 mg/l • MO seed - 10^6 to 10^7 MO per ml of domestic wastewater

  32. UBOD • Oxidation CHONS + O2 + Bacteria CO2 + H2O + NH3 + Other end products + Energy • Synthesis CHONS + O2 + Bacteria + Energy C5H7NO2 (New cell ) • Endogenous Respiration C5H7NO2 + 5O2 5CO2 + 2H2O + NH3 UBOD = O2 required for ( Oxidation + Synthesis + Endogenous Respiration )

  33. Characteristics of Sewage • Biochemical Oxygen Demand - BOD • Microbes consumes OM as a function of time (Not instantaneous consumption of OD) • BOD exertion – OM consumption : First order reaction • dL/dtα L • Where, L= OM present at any time • dL/dt = -K L • Where, K = BOD rate constant , Doubles for rvery 10 degree rise in temp • Property of OM present in wastewater • Integrating we get, L = L0 e^-Kt

  34. Characteristics of Sewage • BOD

  35. Characteristics of Sewage • BOD

  36. Characteristics of Sewage • Chemical Oxygen Demand - COD • To reduce time required for BOD (to assess pollution strength) • Microbes and DO in BOD are replaced by strong oxidizing chemicals • Potassium dichromate (Cr+6) : At high temp & low pH (Initially added – Remaining = Consumed for oxidation of OM) • Titrated with the help of FAS & Ferroin indicator • BOD/COD > 0.5 Go for biological treatment. For, Sewage it is > 0.7

  37. Characteristics of Sewage • Total Organic Carbon – TOC OM+ UV + High Temp ------------- CO2 ( detected IR analyser ) • ThOD • Used when exact composition of OM is known. ( By stoichiometric calculations) • E.g. Glucose solution C6H12O6 + 6O2 6CO2 + 6H2O One mole of glucose (180gm) = 6 Moles of O2 (192gm) ThOD = 192/180 = 1.06 gm of O2 / gm of glucose

  38. Characteristics of Sewage • Nutrients • Causes Eutrophication • Nitrates & Phosphates • Nitrates • Organic Nitrogen • Ammonical Nitrogen Org. N & NH3 NO2- (Nitrites) NO3– (Nitrates) NitrosomonasNitrobacter

  39. Characteristics of Sewage • Toxic chemicals (Difficult to degrade) • Phenols – From cleaning • Detergents & surfactants • Pesticides (DDT, BHC) • Volatile Organic Compounds - VOC - From Industries • Heavy metals – Accumulative chemicals • Copper, Cadmium, Nickel, Zinc, Mercury • Enters food chain and get Biomagnified – (Max Permissible Body Burden, MPBB)

  40. Characteristics of Sewage • Biological Characteristics • Virus • Bactria • Fungus • Yeast • Protozoa

  41. Unit Processes & Unit Operation • Unit operations are the physical operations to remove the impurities present in the water and waste water • Whereas the unit processes are the chemical and biological conversion on the status of the impurities that they will be converted to a form that can be easily separated.

  42. UNIT 2: Unit Processes & Unit Operation • Unit Operations • Screening • Skimming • Settling • Filtration • Unit Processes • Biological processes • Aerobic. An-aerobic, Anoxic etc • Chemical Processes

  43. Unit Processes & Unit Operation

  44. Introduction to Sewage Treatment • Preliminary • Screening, O&G Chamber, Grit Chamber / Detritus tank • Primary • Settling Basins • 15 to 30% BOD removal • Secondary • Filters, Aeration tanks, Oxidation ponds, Aerated Lagoon, Anaerobic Digesters etc. • Along with Secondary Settling Basins • Tertiary • Disinfection (Chlorination) • Filtration – If reuse of treated water is desired

  45. Introduction to Sewage Treatment

  46. Classification of Sewage Treatment Processes • Based On Bacterial Growth • Suspended Growth • Attached Growth • Based on mode of operation • Continuous • Batch • Based on Ecnomics • Standard (High Cost) • Low cost Treatments

  47. Sewage Treatment • Chemical • Biological • Aerobic – In presence of Oxygen • ASP, Aerated Lagoon, Oxidation Ditch, SBR, Extended Aeration, Aerated Wetland etc. • Anaerobic – In absence of Oxygen • UASB, Anaerobic Lagoon, Trickling Filters, Septic Tank etc. • Anoxic – In presence as well as absence of Oxygen • Nitrification etc.

  48. Design of Process Flow Sheets • Activated Sludge Process (ASP)

  49. Design of Process Flow Sheets • Oxidation Ditch

  50. Design of Process Flow Sheets • Aerated Lagoon & Waste Stabilization Pond

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