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Activated sludge process
 

Activated sludge process

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    Activated sludge process Activated sludge process Presentation Transcript

    • Activated Sludge Process
    • Thought of the Day31-May-13 2Activated Sludge Process
    • 31-May-13 3Activated Sludge Process
    • 31-May-13 4Activated Sludge Process
    • 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)31-May-13 5Activated Sludge Process
    • Water/Wastewater Termsdecomposition: the process of breaking down into constituent parts orelementsdomestic wastewater: wastewater that comes primarily from individuals,and does not generally include industrial or agricultural wastewatereffluent: 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 plant31-May-13 6Activated Sludge Process
    • 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.31-May-13 7Activated Sludge Process
    • 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 secondary treatment,which could include filtration, nutrient removal (removal of nitrogen andphosphorus) and removal of toxic chemicals or metals; also called“advanced treatment” when nutrient removal is included31-May-13 8Activated Sludge Process
    • 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 purposes31-May-13 9Activated Sludge Process
    • Activated Sludge ProcessMixed Liquor Suspended SolidsWaste Activated SludgeReturnedActivatedSludge31-May-13 10Activated Sludge Process
    • Activated Sludge ProcessThe most common suspended growthprocess used for municipal wastewatertreatment is the activated sludge process31-May-13 11Activated Sludge Process
    • Activated Sludge PlantActivated sludge plant involves• wastewater aeration in the presence ofa microbial suspension• solid-liquid separation following aeration• discharge of clarified effluent• wasting of excess biomass• return of remaining biomass to theaeration tank31-May-13 12Activated Sludge Process
    • Activated SludgeActivated Sludge serves two purposes1. Reducing organic matter in wastewater byusing a complex biological community inthe presence of oxygen and convertingthe organic matter to new cellmass, carbon dioxide and energy2. Producing solids capable of bio-flocculating and settling out in theclarifier to produce and effluent low inBiochemical Oxygen Demand (BOD) andTotal Suspended Solids (TSS)31-May-13 13Activated Sludge Process
    • The Process• In activated sludge process wastewater containingorganic matter is aerated in an aeration basin inwhich micro-organisms metabolize the suspendedand soluble organic matter.• Part of organic matter is synthesized into new cellsand part is oxidized to CO2 and water to deriveenergy.• In activated sludge systems the new cells formed inthe reaction are removed from the liquid stream inthe form of a flocculent sludge in settling tanks.• A part of this settled biomass, described asactivated sludge is returned to the aeration tankand the remaining forms waste or excess sludge31-May-13 14Activated Sludge Process
    • Activated Sludge ProcessVariablesThe main variables of activated sludgeprocess are the• mixing regime• loading rate• flow scheme31-May-13 15Activated Sludge Process
    • Oxidation and Synthesis31-May-13 16Activated Sludge Process
    • Oxidation and Synthesis31-May-13 17Activated Sludge Process
    • 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 + NBOD531-May-13 18Activated Sludge Process
    • 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 toallow it to grow and divide.31-May-13 19Activated Sludge Process
    • 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.31-May-13 20Activated Sludge Process
    • 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 sludgeage31-May-13 21Activated Sludge Process
    • Activated SludgeThe basic activated sludge process hasseveral interrelated components. Thesecomponents are1. aeration tank2. aeration source3. clarifier4. recycle5. waste31-May-13 22Activated Sludge Process
    • 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.31-May-13 23Activated Sludge Process
    • Activated Sludge Flow Diagram31-May-13 24Activated Sludge Process
    • 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, biological andnutritional requirements) alllead to good sludge quality31-May-13 25Activated Sludge Process
    • Mixed Liquor Suspended SolidsMLSS• The combination of raw sewage and biological mass is commonlyknown as Mixed Liquor.• In all activated sludge plants, once the sewage (or industrialwastewater) has received sufficient treatment, excess mixedliquor is discharged into settling tanks and the treatedsupernatant is run off to undergo further treatment beforedischarge.• Part of the settled material, the sludge (RAS), is returned tothe head of the aeration system to re-seed the new sewageentering the tank.• Mixed Liquor is a mixture of raw or settled wastewater andactivated sludge within an aeration tank in the activated sludgeprocess• Mixed Liquor Suspended Solids (MLSS) is the concentration ofsuspended solids in the mixed liquor, usually expressed inmilligrams per litre (mg/l)31-May-13 26Activated Sludge Process
    • Why Measure MLSS• If MLSS content is too high– The process is prone to bulking and the treatment systembecomes overloaded– This can cause the dissolved oxygen content to drop with theeffect that organic matters are not fully degraded andbiological die off„– Excessive aeration required which wastes electricity• If MLSS content is too low– The process is not operating efficiently and is wastingenergy• Typcial Control band– 2,000 to 4,000 mg/l31-May-13 27Activated Sludge Process
    • 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 returnvolume to be adjusted to keep the solids level in the aerationbasin within the control parameters• Excess sludge which eventually accumulates beyond thatreturned is defined as Surplus or Waste Activated Sludge(SAS/WAS)• This is removed from the treatment process to keep the ratioof biomass to food supplied (sewage or wastewater) in balance• Typical Range– 4,000 to 6,000 mg/l31-May-13 28Activated Sludge Process
    • 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.)31-May-13 Activated Sludge Process 29
    • 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.31-May-13 Activated Sludge Process 30
    • Activated Sludge Design Parameters31-May-13 Activated Sludge Process 31
    • 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 to lb/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.31-May-13 Activated Sludge Process 32
    • Example # 131-May-13 Activated Sludge Process 33
    • Example # 231-May-13 Activated Sludge Process 34
    • Calculations in S.I. Units31-May-13 Activated Sludge Process 35
    • Example # 431-May-13 Activated Sludge Process 36
    • Example # 531-May-13 Activated Sludge Process 37
    • Example # 631-May-13 Activated Sludge Process 38
    • Example # 631-May-13 Activated Sludge Process 39
    • 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.31-May-13 40Activated Sludge Process
    • Extended Aeration31-May-13 Activated Sludge Process 41
    • Assignment # 3Due Date: Wednesday,3rd April, 2013• Each Group has to make an excel sheet in which detailed populationanalysis 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 increasein temp.• Refer to Urban Water Demand Model California31-May-13 42Activated Sludge Process
    • Dredging and Cleaning of DrainsFrom 17th May to 29th June 2012
    • 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.31-May-13 Activated Sludge Process 44
    • Javed Colony DrainBefore After31-May-13 45Activated Sludge Process
    • Muslim Town UC 28Before After31-May-13 46Activated Sludge Process
    • Dhoke MatkalBefore After31-May-13 47Activated Sludge Process
    • Javed ColonyBefore Work in progress31-May-13 48Activated Sludge Process
    • Javed Colony31-May-13 Activated Sludge Process 49
    • ShamsabadWork in progress Work in progress31-May-13 50Activated Sludge Process
    • 31-May-13Cleared51Activated Sludge Process
    • Ganda NullahWork in progress Cleaned31-May-13 52Activated Sludge Process
    • Work in ProgressBohar Bazaar Jama Masjid31-May-13 53Activated Sludge Process
    • Jama Masjid RoadWork in progress Cleaned31-May-13 54Activated Sludge Process
    • Thandi GaliBefore Work in Progress31-May-13 55Activated Sludge Process
    • Kohati BazaarBefore Work in Progress31-May-13 56Activated Sludge Process
    • Nirala Sweet DrainBefore After31-May-13 57Activated Sludge Process
    • Sharjah GroundBefore After31-May-13 58Activated Sludge Process
    • Dhoke KhabbaBefore After31-May-13 59Activated Sludge Process
    • Night Working at Bohar Bazar31-May-13 60Activated Sludge Process
    • Dhoke Illahi BukshBefore After31-May-13 61Activated Sludge Process
    • Sarfaraz Road31-May-13 62Activated Sludge Process
    • Work at Dabu Road31-May-13Bhatta Naik Allam63Activated Sludge Process
    • Pakistan Day31-May-13 64Activated Sludge Process
    • Thank You