Water treatment plants


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Water treatment plants

  1. 1. Water Treatment Plants
  2. 2. Thought Of The DayWater Treatment Plants 2
  3. 3. Water FlowWater Treatment Plants 3
  4. 4. Water ConsumptionWater provided for human consumption requirestreatment in order to make it• safe (potable)• pleasant to taste (palatable)Modern technology offers remarkable capabilitiesto accomplish these goals• introduction of new and different pollutants• cost of treating to required levels is a challengefor the water supply industryWater Treatment Plants 4
  5. 5. Water Demand• Municipal water supplies are treated tobe both palatable and potable,regardless of their intended use• If each person uses about 100 litres ofwater per day• Commercial and industrial users mayincrease that demand by more than 5timesWater Treatment Plants 5
  6. 6. Drinking Water - QualityOur water supply comesfrom two sources• surface waters i.e.rivers, lakes andreservoirs• groundwater, which isstored below theearths surfaceEach source presents its ownproblems• Surface water has elevatedlevels of soil particles and algae,making the water turbid• may contain pathogens• Groundwater has higher levelsof dissolved organic matter(yellow color) and minerals suchas iron• Both sources may have highlevels of calcium and magnesium(hardness)• both can be contaminatedby toxic chemicalsWater Treatment Plants 6
  7. 7. Water Treatment ProcessWater Treatment Plants 7
  8. 8. Drinking Water PlantWater Treatment Plants 8
  9. 9. Untreated to Treated WaterWater Treatment Plants 9
  10. 10. Conventional Surface WaterTreatmentScreeningCoagulationFlocculationSedimentationFiltrationDisinfectionStorageDistributionRaw waterAlumPolymersCl2sludgesludgesludgeWater Treatment Plants 10
  11. 11. Screening• Removes large solidslogsbranchesragsfish• Simple processmay incorporate a mechanized trash removal system• Protects pumps and pipes in Water TreatmentPlantsWater Treatment Plants 11
  12. 12. Coagulation• Small particles are notremoved efficiently bysedimentation because theysettle too slowly• they may also pass throughfilters• easier to remove if they areclumped together• Coagulated to form largerparticles, but they dontbecause they have a negativecharge• repel each other (like twonorth poles of a magnet)• In coagulation• we add a chemical suchas alum which producespositive charges toneutralize the negativecharges on the particles• particles can stick together• forming larger particles• more easily removed• process involves addition ofchemical (e.g. alum)• rapid mixing to dissolve thechemical• distribute it evenlythroughout waterWater Treatment Plants 12
  13. 13. Coagulants• Aluminum SulfateAl2(SO4)3• Ferrous Sulfate FeSO4• Ferric SulfateFe2(SO4)3• Ferric Chloride FeCl3• Lime Ca(OH)2Aluminum salts arecheaper but iron salts aremore effective over widerpH rangeFactors for choosing acoagulant?1. Easily available in alldry and liquid forms2. Economical3. Effective over widerange of pH4. Produces less sludges5. Less harmful forenvironment6. FastWater Treatment Plants 13
  14. 14. Flocculation• Now the particles have a neutralcharge• can stick together• The water flows into a tank withpaddles that provide slow mixing• bring the small particlestogether to form largerparticles called flocs• Mixing is done quite slowly andgently in the flocculation step• If the mixing is too fast, theflocs will break apart into smallparticles that are difficult toremove by sedimentation orfiltration.Water Treatment Plants 14
  15. 15. Sedimentation• water flows to a tank called asedimentation basin• gravity causes the flocs tosettle to the bottom• Large particles settle morerapidly than small particles• It would take a very long timefor all particles to settle outand that would mean we wouldneed a very large sedimentationbasin.• So the clarified water, withmost of the particles removed,moves on to the filtration stepwhere the finer particles areremovedWater Treatment Plants 15
  16. 16. Filtration• The filtration apparatus is aconcrete box which contains sand(which does the filtering), gravel(which keeps the sand from gettingout) and underdrain (where thefiltered water exits)• After the filter is operated for awhile, the sand becomes cloggedwith particles and mustbe backwashed• Flow through the filter is reversedand the sand and particles aresuspended• The particles are lighter than thesand, so they rise up and are flushedfrom the system. When backwashingis complete, the sand settles downonto the gravel, flow is reversed andthe process begins againWater Treatment Plants 16
  17. 17. Raw waterCoagulationAerationFlocculationSedimentation TankWater Treatment Plants 17
  18. 18. Water Treatment Plants 18
  19. 19. Disinfection• With particles removed, it onlyremains toprovide disinfection, so that nopathogens remain in the water• Protozoan pathogens are large insize and have been removed withother particles• Bacteria and viruses are nowdestroyed by addition ofa disinfectantChlorination• Enough chlorine is added so thatsome remains to go out in thewater distribution system,protecting the public once thewater leaves the plantWater Treatment Plants 19
  20. 20. Softening• Areas where water comes intocontact with limestone, theremay be high levels of calcium andmagnesium present• these chemicals make the water"hard"• Hardness is removed by aprocess called softening• Two chemicals (lime, CaO andsoda ash, Na2CO3 ) are added towater• causing the calcium andmagnesium to form precipitates• solid substance is then removedwith the other particles bysedimentation and filtrationWater Treatment Plants 20
  21. 21. Synthetic Organic Chemicals• Water supplies can be contaminated withsynthetic organic chemicals (SOCs) fromagricultural runoff or commercial andindustrial sources• such as the leaking underground storagetank• These chemicals are not efficientlyremoved by the simple water treatmentprocess• These chemicals can be removed bypassing the water through a layerof activated carbon in a column• The carbon granules strongly attractorganic chemicals removing them fromthe water by a process called adsorption• When the carbon is full and cant holdany more chemical, it is removed fromthe column, heated to burn offcontaminants and can then be re-used.Water Treatment Plants 21
  22. 22. Distribution• Pumping of the cleanwater produced atthe treatment plantto the community iscalled distribution• This can be donedirectly or by firstpumping the waterto reservoirs orwater storage tanksWater Treatment Plants 22
  23. 23. Onsite TreatmentColor, Taste and Odor• The activated carbontechnology used inmunicipal drinking watertreatment can be appliedin homes as well• the carbon is contained ina "household-sized"column• water passes through thecarbon removing organicmatter (which can cause ayellow color) and alsocompounds which causeunpleasant taste and odorWater Treatment Plants 23
  24. 24. Onsite TreatmentAt The Tap• Home water treatmentsystems may also beinstalled at the tap• Although thetechnologies varysomewhat amongproducts, they typicallyinclude pre-filtration• hardness and metalsremoval by ion exchange• organic matter removalwith activated carbon• post-filtrationWater Treatment Plants 24
  25. 25. US Bottled Water SalesWater Treatment Plants 25
  26. 26. Decrease in Tap Water ConsumptionWater Treatment Plants 26
  27. 27. Bottled Water vs Filtration SystemWater Treatment Plants 27
  28. 28. The Plastic PlanetWater Treatment Plants 28
  29. 29. Implement A Project (5 Marks)Due Date: Wednesday, 10th April, 2013Low Cost• Water Conservation• Water Treatment• Wastewater Treatment• Safe Drinking Waterfor Flood EffectedPeople• Rainwater HarvestingOr• Any Smart Idea relatedto Public HealthEngineeringWater Treatment Plants 29
  30. 30. Water Treatment Plants 30
  31. 31. Rawal LakeWater Treatment Plant
  32. 32. Water Supply• Water supply in Potohar region• Groundwater- major source• Groundwater is supplemented with treatedsurface water• DisinfectantsWater Treatment Plants 32
  33. 33. Sources of Drinking Water inRawalpindiTwo main sources of water in Rawalpindi.Groundwater• Groundwater with Tube wells• located throughout the city• 290 tube wells in WASA controlled area• supplying approximately 28 MGD water to the residentsof Rawalpindi.Surface water in the form of lakes• Surface water is supplied from Khanpur Dam (14.6 MGD)through Sangjani Water Treatment Plant• Rawal Lake through Rawal Lake Water Filtration Plant (23MGD).Water Treatment Plants 33
  34. 34. Ground- vs. Surface WaterGroundwater• constant composition• high mineral content• low turbidity• low color• low or no D.O.• high hardness• high Fe, MnSurface water• variable composition• low mineral content• high turbidity• colored• D.O. present• low hardness• taste and odorWater Treatment Plants 34
  35. 35. HistoryInitial Construction 1962-63Capacity 14 MGDExecuting Agency WAPDAContractor WABAG, GermanyFirst Extension (7 MGD) 1975-79Extended Capacity. 21 MGDExecuting Agency PHED, Govt. of PunjabContractor M/S Federal Const. Corp. Lahore.Second Extension (7 MGD) 2000-2002Extended Capacity. 28 MGDExecuting Agency PMU, WASA/RDAContractor VA TECH. WABAG GmbH,Austria.Water Treatment Plants 35
  36. 36. Main Components• Screening• Coagulation• Aeration• Flocculation• Sedimentation• Filtration• Disinfection or Chlorination• Lime DosingWater Treatment Plants 36
  37. 37. ComponentsScreening• 3 Bar Screens.• large pieces• form of branches of trees• leaves• clothes• plastic bags• dead animalAeration• 2 Blowers. Air flow @ 6 m3/min.• remove taste and odor problems from incoming raw water• Dissolved Oxygen (DO) level of water is enhanced by this processCoagulation• 2 geared drives• shaft mounted mixers for alum mixing• coagulant delivery pipes• alum is added and rapidly mixed with water• remove suspended particles in the form of turbidityWater Treatment Plants 37
  38. 38. Components• Flocculation• Clarifier # 1 to 3• 3 Mechanical Flocculation mounted on a central rotating fullbridge with sludge scraper rotating bridge• Clarifier Area = 475 m2• Up flow velocity = 2.55 m/hr.• Total flow = 336 L/s• Clarifier # 4• 4 flat bottom clarifiers Hydraulic flocculators (Vertical baffles)16 sludge concentrator Cones• Clarifier Area = 4 x 190 = 760 m2• Up flow velocity = 2.2 m/hr.• Total flow = 475 L/ s• Coagulant is mixed through vertical baffling arrangementsWater Treatment Plants 38
  39. 39. ComponentsSedimentation• large flocs are removed by gravity settling• clear water is collected from the surface• settled material (sludge) removed from sedimentation tank• rotating vipers and sludge valvesFiltration• removal of suspended non settleable solids from the drinking water• supernatant water after sedimentation• passed through a 1.4 meter column of silica sand• effective size of 0.95mm ( 10 %)• filtration rate of 5.4 m/hr. (average)-6.5 m/hr (Max)(110-130 glns/ft2. /hr.)Filter Backwashing• Conventional backwashing system includes• Compressed air• Air and Water• Water• Approximate time 12 to 20 minutesWater Treatment Plants 39
  40. 40. Filter Backwash• Sand is backwashed when• It becomes clogged• Turbidity of filtered water gets too high• During backwash, water is pumped upwardsthrough the sand bed• Sand becomes “fluidized”, and particles areflushed from the sand• Dirty backwash water is pumped into a settlingpond and either• Recycled back into plant or• Disposed• Backwashing can consume 1% to 5% of a plant’sproductionWater Treatment Plants 40
  41. 41. Raw waterCoagulationAerationFlocculationSedimentation TankWater Treatment Plants 41
  42. 42. Water Treatment Plants 42
  43. 43. ComponentsDisinfection or Chlorination• Liquid chlorine is used for this purpose• dosage rate varies from 1.5 to 2.0 mg chlorine perliter of water• depending upon the level of contamination, pH, andtemperature• ensuring the residual chlorine upto 0.3-0.5 mg/l.Lime Dosing• last unit process applied at Rawal Lake waterfiltration plant• lime is used to adjust the pH of waterWater Treatment Plants 43
  44. 44. Disadvantages of ChlorinationChlorine is a dangerous chemical because1. it irritates the respiratory system2. it irritates the eyes3. can form Trihalomethanes, THMs, which are possiblecarcinogensOther disinfectant chemicalsOzone gas (O3)Ultraviolet light (UV)Not as desirable becauseMore expensive than chlorineCan’t maintain a residual concentrationWater Treatment Plants 44
  45. 45. Water Quality MonitoringProgram• Water quality analysis laboratory• regularly monitor and analyze the quality ofwater supplied through plant• equipped with latest instruments and chemicals• to test all the basic physico-chemical andbiological parameters• recommended by the World Health Organization• Urban Water Supply & Sanitation Project PhaseIWater Treatment Plants 45
  46. 46. Serial No. Water Quality ParameterPHYSICAL PARAMETERS1 Appearance2 Color3 Odor4 Taste5 Temperature6 TurbidityCHEMICAL PARAMETERS7 pH8 Alkalinity9 Hardness as CaCO310 Electrical Conductivity11 Sulphate12 Calcium13 Magnesium14 Total Dissolved Solids15 Chlorides16 Residual Chlorine17 Nitrate as NO3-18 Nitrite as NO2-BACTERIOLOGICAL PARAMETERS19 Total Coliform Count20 Fecal Coliform CountTOXIC SUBSTANCES21 Arsenic as As +3/+522 Cyanide as CN-Water Treatment Plants 46
  47. 47. Treated Water Quality• Turbidity. 1-3 NTU• Color. Colorless• Odor Unobjectionable• pH 7.5 to 9.5• Residual Chlorine. 0.3 to 0.5 mg/L(at WW 1 and Topi WW)• Coliform Bacteria Nil/100 mlWater Treatment Plants 47
  48. 48. Rawal Lake Catchment AreaDiplomaticEnclaveMalpurVillageLakhwalVillageQ.A.UniversityBari ImamPoultry Waste fromMurreeBani GalaVillageNoor Pur ShahanFiltration PlantWASAKurrangRiverChatter ParkWater Treatment Plants 48
  49. 49. UpstreamWater Treatment Plants 49
  50. 50. Shahdra KassWater Treatment Plants 50
  51. 51. Bari ImamWater Treatment Plants 51
  52. 52. Bari ImamWater Treatment Plants 52
  53. 53. Bari ImamWater Treatment Plants 53
  54. 54. Bari ImamWater Treatment Plants 54
  55. 55. Human Activities at Korang RiverWater Treatment Plants 55
  56. 56. Quaid-e-Azam UniversityWater Treatment Plants 56
  57. 57. Pictorial View - Filtration PlantRAWAL LAKE FILTRATION PLANTWater Treatment Plants 57
  58. 58. Intake StructureWASA WASAWater Treatment Plants 58
  59. 59. Main BuildingWASAWater Treatment Plants 59
  60. 60. Main Electrical Control PanelWASAWater Treatment Plants 60
  61. 61. Circular and Rectangular ClarifiersRectangularClarifierCircularClarifierFiltration MediaWASAWater Treatment Plants 61
  62. 62. Filtration SystemWASA WASAWater Treatment Plants 62
  63. 63. Filtered Water Collection SystemWASAWater Treatment Plants 63
  64. 64. Lime Dosing SystemWASAWater Treatment Plants 64
  65. 65. Safe Drinking WaterHow can you ensurethat your drinkingwater is safe?a) Boilingb) Storing it safelyc) Drinking water fromsafe sourcesd) All of aboveWater Treatment Plants 65
  66. 66. Thank You