Activated Sludge Process


Published on

1 Comment
  • Dr. Masjid. Your presentation is good
    Are you sure you want to  Yes  No
    Your message goes here
No Downloads
Total views
On SlideShare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

Activated Sludge Process

  1. 1. Activated Sludge Process
  2. 2. Thought of the Day26-Mar-13 Activated Sludge Process 2
  3. 3. 26-Mar-13 Activated Sludge Process 3
  4. 4. 26-Mar-13 Activated Sludge Process 4
  5. 5. Water/Wastewater Termsactivated sludge: sludge particles produced by the growth ofmicroorganisms in aerated tanks as a part of the activated sludge processto treat wastewateraeration: exposing to circulating air; adds oxygen to the wastewater andallows other gases trapped in the wastewater to escape (the first step insecondary treatment via activated sludge process)biochemical oxygen demand (BOD): a laboratory measurement ofwastewater that is one of the main indicators of the quantity of pollutantspresent; a parameter used to measure the amount of oxygen that will beconsumed by microorganisms during the biological reaction of oxygen withorganic materialbiosolids: sludge that is intended for beneficial use. Biosolids must meetcertain government specified criteria depending on its use (e.g., fertilizeror soil amendment)26-Mar-13 Activated Sludge Process 5
  6. 6. Water/Wastewater Termsdecomposition: the process of breaking down into constituent parts orelementsdomestic wastewater: wastewater that comes primarily fromindividuals, and does not generally include industrial or agriculturalwastewatereffluent: treated wastewater, flowing from a lagoon, tank, treatmentprocess, or treatment plantgrit chamber: a chamber or tank used in primary treatment wherewastewater slows down and heavy, large solids (grit) settle out and areremovedinfluent: wastewater flowing into a treatment plant26-Mar-13 Activated Sludge Process 6
  7. 7. Water/Wastewater Termslagoons (oxidation ponds or stabilization ponds): a wastewater treatment methodthat uses ponds to treat wastewater. Algae grow within the lagoons and utilizesunlight to produce oxygen, which is in turn used by microorganisms in the lagoon tobreak down organic material in the wastewater. Wastewater solids settle in thelagoon, resulting in effluent that is relatively well treated, although it does containalgaemunicipal: of or relating to a municipality (city, town, etc.). Municipal wastewater isprimarily domestic wastewater.primary treatment: the first stage of wastewater treatment that removessettleable or floating solids only; generally removes 40% of the suspended solids and30-40% of the BOD in the wastewatersecondary treatment: a type of wastewater treatment used to convert dissolvedand suspended pollutants into a form that can be removed, producing a relativelyhighly treated effluent. Secondary treatment normally utilizes biological treatmentprocesses (activated sludge, trickling filters, etc.) followed by settling tanks and willremove approximately 85% of the BOD and TSS in wastewater. Secondarytreatment for municipal wastewater is the minimum level of treatment required bythe EPA.26-Mar-13 Activated Sludge Process 7
  8. 8. Water/Wastewater Termssedimentation: the process used in both primary and secondarywastewater treatment, that takes place when gravity pulls particles to thebottom of a tank (also called settling).settling tank (sedimentation tank or clarifier): a vessel in which solidssettle out of water by gravity during wastewater or drinking watertreatment processes.sludge: any solid, semisolid, or liquid waste that settles to the bottom ofsedimentation tanks (in wastewater treatment plants or drinking watertreatment plants) or septic tankstertiary treatment: any level of treatment beyond secondarytreatment, which could include filtration, nutrient removal (removal ofnitrogen and phosphorus) and removal of toxic chemicals or metals; alsocalled “advanced treatment” when nutrient removal is included26-Mar-13 Activated Sludge Process 8
  9. 9. Water/Wastewater Termstotal suspended solids (TSS): a laboratory measurement of the quantityof suspended solids present in wastewater that is one of the mainindicators of the quantity of pollutants presenttrickling filter process: a biological treatment process that uses coarsemedia (usually rock or plastic) contained in a tank that serves as a surfaceon which microbiological growth occurs. Wastewater trickles over themedia and microorganisms remove the pollutants (BOD and TSS). Tricklingfilters are followed by settling tanks to remove microorganisms that washoff or pass through the trickling filter media.turbidity: the cloudy or muddy appearance of a naturally clear liquidcaused by the suspension of particulate matterwastewater: water that has been used for domestic or industrial purposes26-Mar-13 Activated Sludge Process 9
  10. 10. Activated Sludge Process Mixed Liquor Suspended Solids Returned Activated Sludge Waste Activated Sludge26-Mar-13 Activated Sludge Process 10
  11. 11. Activated Sludge ProcessThe most common suspended growthprocess used for municipal wastewatertreatment is the activated sludge process26-Mar-13 Activated Sludge Process 11
  12. 12. Activated Sludge PlantActivated sludge plant involves• wastewater aeration in the presence of a microbial suspension• solid-liquid separation following aeration• discharge of clarified effluent• wasting of excess biomass• return of remaining biomass to the aeration tank26-Mar-13 Activated Sludge Process 12
  13. 13. Activated SludgeActivated Sludge serves two purposes1. Reducing organic matter in wastewater by using a complex biological community in the presence of oxygen and converting the organic matter to new cell mass, carbon dioxide and energy2. Producing solids capable of bio- flocculating and settling out in the clarifier to produce and effluent low in Biochemical Oxygen Demand (BOD) and Total Suspended Solids (TSS)26-Mar-13 Activated Sludge Process 13
  14. 14. The Process• In activated sludge process wastewater containing organic matter is aerated in an aeration basin in which micro-organisms metabolize the suspended and soluble organic matter.• Part of organic matter is synthesized into new cells and part is oxidized to CO2 and water to derive energy.• In activated sludge systems the new cells formed in the reaction are removed from the liquid stream in the form of a flocculent sludge in settling tanks.• A part of this settled biomass, described as activated sludge is returned to the aeration tank and the remaining forms waste or excess sludge26-Mar-13 Activated Sludge Process 14
  15. 15. Activated Sludge Process VariablesThe main variables of activated sludgeprocess are the• mixing regime• loading rate• flow scheme26-Mar-13 Activated Sludge Process 15
  16. 16. Oxidation and Synthesis26-Mar-13 Activated Sludge Process 16
  17. 17. Oxidation and Synthesis26-Mar-13 Activated Sludge Process 17
  18. 18. The BOD CurveThe BOD determination involvesthe measurement of thedissolved oxygen used bymicroorganisms in thebiochemical oxidation of organicmatter. The BOD test bottle isincubated for 5 days at 20oC. Atypical BOD curve is shown inFigure. The BOD5 of secondaryeffluents consists of two majorcomponents – a carbonaceousdemand resulting from theoxidation of carbon and anitrogenous demand resultingfrom the oxidation of nitrogen.That is,BOD5 = CBOD5 + NBOD526-Mar-13 Activated Sludge Process 18
  19. 19. The Growth CurveThe growth curve has five distinct phasesThese are:1. Adaptation (Lag) Phase – This portion of thecurve represents the time required for theorganisms to acclimate themselves to theorganic material present in the wastewater.The numbers of bacteria are notincreasing, however, a shift in the populationof the different species of bacteria in thewastewater is occurring so that the bacteriathat can best utilize these organic materialsbecome predominate.2. Log Growth Phase – Once the bacteria have“adapted”, only the number of organismspresent limit the rate of growth. Becausebacterial cells reproduce by binary fission(i.e., cell division – one cell divides andbecomes two, these two divide and becomefour, then eight, sixteen … ), this is known aslogarithmic growth. Food is not a limitingfactor for growth in this phase, that is, foreach cell formed enough food is present to26-Mar-13 Activated Sludge Process 19allow it to grow and divide.
  20. 20. The Growth Curve3. Declining Growth Phase – In thisphase food becomes a limiting factor tothe growth of the bacterial cell massbecause not every bacterium that isformed has the food required to grow.4. Maximum Stationary Phase – Herethe available food is just sufficient tokeep the cell mass at a constant levelwith a rate of growth equal to zero.5. Endogenous (Cell Death) Phase –When the supply of food becomesinsufficient to maintain the bacterialmass at a constant level, themicroorganisms are forced tometabolize their own protoplasm.26-Mar-13 Activated Sludge Process 20
  21. 21. Sludge AgeTherefore, an optimum“sludge age” existswhich provide anadequate separation ofthe cell mass from theliquid. For a specificsystem the optimumsludge age can bedetermined by plottingthe sludge volume index(SVI) versus the sludgeage26-Mar-13 Activated Sludge Process 21
  22. 22. Activated SludgeThe basic activated sludge process hasseveral interrelated components. Thesecomponents are1. aeration tank2. aeration source3. clarifier4. recycle5. waste26-Mar-13 Activated Sludge Process 22
  23. 23. Activated SludgeAeration tank. A single tank or multiple tanks designed generally for eithercomplete mix or plug flow with a detention time of as little as 2 hours andup to over 24 hours. The contents of the aeration tank are referred to asmixed liquor.Aeration source. Generally either diffused air or surface mechanicalaeration used to supply oxygen and mix the aeration tank contents.Clarifier. A settling tank where the mixed liquor solids are separated fromthe treated wastewater. Most treatment plants employ several secondaryclarifiers.Recycle. Solids that settle in the clarifier and are returned to the aerationtank.Waste. Excess solids that must be removed from the system.26-Mar-13 Activated Sludge Process 23
  24. 24. Activated Sludge Flow Diagram26-Mar-13 Activated Sludge Process 24
  25. 25. Activated SludgeA typical activated sludgeplant identifies the threemajor control mechanism forthe activated sludgetreatment process1. aeration rate2. return sludge rate3. waste sludge rateControl of three variables inaddition to providing theproper environment(physical, chemical, biologicaland nutritional requirements)all lead to good sludge quality26-Mar-13 Activated Sludge Process 25
  26. 26. Mixed Liquor Suspended Solids MLSS• The combination of raw sewage and biological mass is commonly known as Mixed Liquor.• In all activated sludge plants, once the sewage (or industrial wastewater) has received sufficient treatment, excess mixed liquor is discharged into settling tanks and the treated supernatant is run off to undergo further treatment before discharge.• Part of the settled material, the sludge (RAS), is returned to the head of the aeration system to re-seed the new sewage entering the tank.• Mixed Liquor is a mixture of raw or settled wastewater and activated sludge within an aeration tank in the activated sludge process• Mixed Liquor Suspended Solids (MLSS) is the concentration of suspended solids in the mixed liquor, usually expressed in milligrams per litre (mg/l)26-Mar-13 Activated Sludge Process 26
  27. 27. Why Measure MLSS• If MLSS content is too high – The process is prone to bulking and the treatment system becomes overloaded – This can cause the dissolved oxygen content to drop with the effect that organic matters are not fully degraded and biological die off„ – Excessive aeration required which wastes electricity• If MLSS content is too low – The process is not operating efficiently and is wasting energy• Typcial Control band – 2,000 to 4,000 mg/l26-Mar-13 Activated Sludge Process 27
  28. 28. RAS and WAS• A proportion of the floc is called Return Activated Sludge (R.A.S.) and is used to re-seed the process.• Measuring the solids concentration of RAS allows the return volume to be adjusted to keep the solids level in the aeration basin within the control parameters• Excess sludge which eventually accumulates beyond that returned is defined as Surplus or Waste Activated Sludge (SAS/WAS)• This is removed from the treatment process to keep the ratio of biomass to food supplied (sewage or wastewater) in balance• Typical Range – 4,000 to 6,000 mg/l26-Mar-13 Activated Sludge Process 28
  29. 29. Activated Sludge ParametersThe parameters in the diagram and a fewothers that will be used for the activatedsludge calculations are summarized in thelist below.• primary effluent flow rate, Qo, MGD(m/day for S.I.)• primary effluent biochemical oxygendemand (BOD) concentration, So, mg/L(g/m3 for S.I.)• primary effluent suspended solidsconc., Xo, mg/L (g/m3 for S.I.)• aeration tank volume, V, ft3 (m3 for S.I.)• aeration tank MLSS (suspended solidsconc.), X, mg/L (g/m3 for S.I.)• secondary effluent flowrate, Qe, MGD, (m3/day for S.I.)• secondary effluent susp.solidsconc., Xe, mg/L (g/m3 for S.I.)26-Mar-13 Activated Sludge Process 29
  30. 30. Activated Sludge Parameters• secondary effluent biochemical oxygendemand (BOD) concentration, Se, mg/L (g/m3for S.I.)• waste activated sludge flow rate, Qw, MGD(m3/day for S.I.)• waste activated sludge biochemical oxygendemand (BOD) conc., Sw, mg/L (g/m3 for S.I.)• waste activated sludge susp. solids conc., Xwmg/L (g/m3 for S.I.)• recycle activated sludge flow rate, Qr, MGD(m3/day for S.I.)• Food to Microorganism ratio, F:M, lbBOD/day/lb MLVSS (kg BOD/day/kg MLVSS)• Hydraulic retention time, HRT, hours (hoursfor S.I.)• Sludge retention time (also called sludgeage), SRT, days (days for S.I.)• Volumetric loading, VL, lb BOD/day/1000 ft3(kg BOD/day/m3 for S.I.)• % volatile solids in the aeration tank mixedliquor suspended solids, %Vol.26-Mar-13 Activated Sludge Process 30
  31. 31. Activated Sludge Design Parameters 26-Mar-13 Activated Sludge Process 31
  32. 32. CalculationsNOTE: F:M values will be the same for units of lb BOD/day/lb MLVSS.Calculations with these design parameters can be made in U.S. units usingthe following equations:• V = [ (8.34*So*Qo)/VL ] (1000)• VMG = V*7.48/1,000,000• HRT = 24*VMG/Qo• F:M = (8.34*So*Qo)/(8.34%Vol*X*VMG) = (So*Qo)/(%Vol*X*VMG)VMG is the tank volume in millions of gallons.It is introduced for convenience in calculations, since the primary effluentflow rate is given in MGD.The 8.34 factor in the equations above is used to convert mg/L tolb/MG, and the 7.48 is for conversion of ft3 to gallons.Also, note that the primary sludge flow rate is typically very small incomparison with the influent wastewater flow rate, so the primary effluentflow rate, Qo, is typically taken to be equal to the plant influent flow rate.26-Mar-13 Activated Sludge Process 32
  33. 33. Example # 126-Mar-13 Activated Sludge Process 33
  34. 34. Example # 226-Mar-13 Activated Sludge Process 34
  35. 35. Calculations in S.I. Units26-Mar-13 Activated Sludge Process 35
  36. 36. Example # 426-Mar-13 Activated Sludge Process 36
  37. 37. Example # 526-Mar-13 Activated Sludge Process 37
  38. 38. Example # 626-Mar-13 Activated Sludge Process 38
  39. 39. Example # 626-Mar-13 Activated Sludge Process 39
  40. 40. Other Aerobic Treatment UnitsStabilization ponds: The stabilization ponds are open flowthrough basins specifically designed and constructed to treatsewage and biodegradable industrial wastes. They providelong detention periods extending from a few to several days.Aerated lagoons: Pond systems, in which oxygen is providedthrough mechanical aeration rather than algal photosynthesisare called aerated lagoons.Oxidation ditch: The oxidation ditch is a modified form of"extended aeration" of activated sludge process. The ditchconsists of a long continuous channel oval in shape with twosurface rotors placed across the channel.26-Mar-13 Activated Sludge Process 40
  41. 41. Extended Aeration26-Mar-13 Activated Sludge Process 41
  42. 42. Assignment # 3 Due Date: Friday, 5rd April, 2013• Each Group has to make an excel sheet in which detailed population analysis for every decade will be done for one city from 2000-2100• Based on that population, the water demand for the same city• Assuming 100 gallons per capita per day• Also incorporating temp change/climate change scenario• Assuming additional 10 gallons per capita per day per 0.20 C increase in temp.• Refer to Urban Water Demand Model California26-Mar-13 Activated Sludge Process 42
  43. 43. Dredging and Cleaning of Drains From 17th May to 29th June 2012
  44. 44. DredgingDredging is an excavation activity oroperation usually carried out at leastpartly underwater, in shallow seasor fresh water areas with the purpose ofgathering up bottom sediments anddisposing of them at a different location.26-Mar-13 Activated Sludge Process 44
  45. 45. Javed Colony DrainBefore After26-Mar-13 Activated Sludge Process 45
  46. 46. Muslim Town UC 28Before After26-Mar-13 Activated Sludge Process 46
  47. 47. Dhoke MatkalBefore After26-Mar-13 Activated Sludge Process 47
  48. 48. Javed ColonyBefore Work in progress26-Mar-13 Activated Sludge Process 48
  49. 49. Javed Colony26-Mar-13 Activated Sludge Process 49
  50. 50. ShamsabadWork in progress Work in progress26-Mar-13 Activated Sludge Process 50
  51. 51. Cleared26-Mar-13 Activated Sludge Process 51
  52. 52. Ganda NullahWork in progress Cleaned26-Mar-13 Activated Sludge Process 52
  53. 53. Work in ProgressBohar Bazaar Jama Masjid26-Mar-13 Activated Sludge Process 53
  54. 54. Jama Masjid RoadWork in progress Cleaned26-Mar-13 Activated Sludge Process 54
  55. 55. Thandi GaliBefore Work in Progress26-Mar-13 Activated Sludge Process 55
  56. 56. Kohati BazaarBefore Work in Progress26-Mar-13 Activated Sludge Process 56
  57. 57. Nirala Sweet DrainBefore After26-Mar-13 Activated Sludge Process 57
  58. 58. Sharjah GroundBefore After26-Mar-13 Activated Sludge Process 58
  59. 59. Dhoke KhabbaBefore After26-Mar-13 Activated Sludge Process 59
  60. 60. Night Working at Bohar Bazar26-Mar-13 Activated Sludge Process 60
  61. 61. Dhoke Illahi BukshBefore After26-Mar-13 Activated Sludge Process 61
  62. 62. Sarfaraz Road26-Mar-13 Activated Sludge Process 62
  63. 63. Bhatta Naik AllamWork at Dabu Road26-Mar-13 Activated Sludge Process 63
  64. 64. Pakistan Day26-Mar-13 Activated Sludge Process 64
  65. 65. Thank You