Presentation on theme: "ACTIVATED SLUDGE PROCESS AND KINETICS OF ASP"— Presentation transcript:
1 ACTIVATED SLUDGE PROCESS AND KINETICS OF ASP PRESENTATIONONACTIVATED SLUDGE PROCESSANDKINETICS OF ASP
2 Activated Sludge Process Activated Sludge Process is thesuspended-growth biological treatmentprocess, based on providing intimate contactbetween the sewage and activated sludge.The Activated Sludge is the sludgeobtained by settling sewage in presence ofabundant O2 so as to enrich with aerobicmicro-organisms.
3 Activated sludge in sewage in presence of oxygen results into:Oxidation of organic matter present.Coagulation and flocculation ofsuspended and colloidal matterUnder the activated sludge Processbasically three processes occurs:-
4 OxidationThe organisms oxidize a portion of organicMatter present in sewage into CO2,waterand energy.Organic matter + O2+ BacteriaCO2+ H2O+ NH3+Energy + other end products
5 SynthesisIn second phase the other microbes getconverted into new bacterial cells usinga part of energy released in oxidationOrganic Matter+O2+Bacteria+EnergyNew microbial cells
6 Endogenous Respiration Finally the new microbial cells begin toconsume their own cell tissue to obtainenergy for cell maintenance.New microbial cell tissue + 5O25CO2+NH3+2H2O+Energy
7 Description of Activated sludge processes:- Conventional plug flow:- Settled water andrecycled activated sludge enter the headend of the aeration tank and are mixed bydiffused air or mechanical aeration. Duringthe aeration period adsorption, flocculationand oxidation of organic matter occurs.Modified aeration:- It is similar to conven--tional plug flow except that shorter aeration time and higher F/M ratio are used.
8 Tapered aeration:- Varying aeration rates are applied over the tank length dependingon the oxygen demand. Greater amounts ofair are supplied to the head end of theaeration tank, and the amount diminish asthe mixed liquor approaches the effluentend.
10 Step feed aerationGenerally three or more parallel channelsare used. The settled waste water is introduced at several point in the aeration tank to equalize the F/M ratio, thus lowering peak oxygen demand.
14 Flow Diagram of ASP Raw water Primary Settling tank Secondary Settling screensGritchamberaerationchlorinationReareationActivatedSludge returnActivated SludgePumpEffluentto disposalSludgeThickenerSludgeDigestionTo Sludge DryingFlow Diagram of ASP
15 Growth And Food Utilization 1)Assimilation:-The microorganisms must first becomeassimilated to their surroundings and foodprovided also called Lag Phase.2)Log Growth Phase:-In this phase the growth is rapid. Herebacterial cells reproduce binary fission.
16 3)Stationary Phase:-In this phase the production of newcells is roughly offset by death andendogenous respiration.4)Endogenous Phase:-In final phase, the cells are unableto obtain food from external sources andresult into decrease in biomassconcentrations.
17 The new cell produced undergoes an auto Cell GrowthThe new cell produced undergoes an autooxidation which involves the breakdown oforganics in cell itself to produce energy forthe maintenance of remaining cell mass.Thus, there is continuously a fractionaldecrease in cell mass with time.dX/dt = μ XdX/dt = the growth rate of biomass, mg/L tX = the concentration of biomass, mg/Lμ = the growth rate constant,1/t
18 Factors affecting the rate of biomass production and food utilization:-TemperaturepHToxicants
19 Kinetics of activated Sludge process Assumptions:Complete mixing in aeration tank.Influent substrate concentration is constant.No microbial solids in raw water.All reactions occur in reactor.No microbial activity in clarifier.No Sludge accumulation.Steady state conditions prevails.
20 ACTIVATED SLUDGE KINETIC MODEL Q(1+R)A,T,Va, X,Se(Q-Qw),Xe, SeX, SeQ, SoSecondaryClarifierQw, Xr, SeRQ, Xr, Se
21 Microorganism and Substrate Mass Balance Rate of accumulation = Biomass in + Biomassof biomass in system growth - biomass out(dX/dt)V = QXo + V [rg- kdX ] –QXrg = μ mXS /(Ks+S)(dX/dt)V = QXo + V[μ mXS/(Ks+S) - kdX ] - QXrg = Growth rate of biomassKd= Endogenous decay coefficient.