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  • 1. Water Treatment Plants

2. Thought Of The DayWater Treatment Plants 2 3. Water FlowWater Treatment Plants 3 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. 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. 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. Water Treatment ProcessWater Treatment Plants 7 8. Drinking Water PlantWater Treatment Plants 8 9. Untreated to Treated WaterWater Treatment Plants 9 10. Conventional Surface WaterTreatmentScreeningCoagulationFlocculationSedimentationFiltrationDisinfectionStorageDistributionRaw waterAlumPolymersCl2sludgesludgesludgeWater Treatment Plants 10 11. Screening Removes large solidslogsbranchesragsfish Simple processmay incorporate a mechanized trash removal system Protects pumps and pipes in Water TreatmentPlantsWater Treatment Plants 11 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. 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. 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. 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. 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. Raw waterCoagulationAerationFlocculationSedimentation TankWater Treatment Plants 17 18. Water Treatment Plants 18 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 distributionsystem, protecting the publiconce the water leaves the plantWater Treatment Plants 19 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. 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. 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. 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. 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. US Bottled Water SalesWater Treatment Plants 25 26. Decrease in Tap Water ConsumptionWater Treatment Plants 26 27. Bottled Water vs Filtration SystemWater Treatment Plants 27 28. The Plastic PlanetWater Treatment Plants 28 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. Water Treatment Plants 30 31. Rawal LakeWater Treatment Plant 32. Water Supply Water supply in Potohar region Groundwater- major source Groundwater is supplemented with treatedsurface water DisinfectantsWater Treatment Plants 32 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. 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. 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. Main Components Screening Coagulation Aeration Flocculation Sedimentation Filtration Disinfection or Chlorination Lime DosingWater Treatment Plants 36 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. 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


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