Nitrification and Denitrification

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Nitrification and Denitrification. Prepared by Michigan Department of Environmental Quality Operator Training and Certification Unit. Nitrogen. Environmental And Public Health Concerns. N. Forms of Nitrogen in Wastewater. Ammonia – NH 3 Nitrite – NO 2 - Nitrate – NO 3 -. All Are - PowerPoint PPT Presentation

Text of Nitrification and Denitrification

  • NitrificationandDenitrificationPrepared byMichigan Department of Environmental QualityOperator Training and Certification Unit

  • NitrogenEnvironmentalAndPublic HealthConcerns

  • Ammonia NH3

    Nitrite NO2-

    Nitrate NO3-

    NForms of Nitrogen in WastewaterToxicOxygen DemandChlorine DemandHealth ConcernAll AreNutrients(fertilizer)

  • NOrganic NitrogenForms of Nitrogen in WastewaterComplex CompoundsProtein (plant & animal)Amino Acidsetc.Oxygen DemandNutrient Source

  • NForms of Nitrogen in WastewaterTotal Kjeldahl Nitrogen - TKN

    Total Inorganic Nitrogen - TIN

    Sum ofOrganic N + Ammonia

    Sum of Ammonia + Nitrite + Nitrate

  • NAmmonia NH3Nitrite NO2-Nitrate NO3-OrganicForms of Nitrogen in WastewaterTransformInEnvironmentAndTreatment PlantsTKNTIN?

  • Total Kjeldahl Nitrogen(TKN) NITROGEN CYCLE

  • NWASTEWATER TREATMENTOfNitrogen

  • NRaw SewageOrganic Nitrogen & AmmoniaNo Nitrite or NitrateWASTEWATER TREATMENTOfNitrogen

  • NPrimary ClarificationSome Organic Nitrogen Removed(settled solids)No Ammonia RemovedMay Increase(Solids Handling)WASTEWATER TREATMENTOfNitrogen

  • NPrimary Effluent(Secondary Influent)Organic Nitrogen (Less) AmmoniaWASTEWATER TREATMENTOfNitrogen

  • NSecondary Treatment(Biological)WASTEWATER TREATMENTOfNitrogen

  • Some Nitrogen Will be Removed By the Biomass(assimilation) Heterotrophic Bacteria Breakdown Organics (Proteins, etc.)

    To AmmoniaNBacteria Also Take Up Ammonia

  • NTo Meet an Ammonia Limit or a Total Inorganic Nitrogen (TIN) Limitthe Process Must be Capable ofNitrificationSome Nitrogen Will be Removed By the Biomass(assimilation) Biological Oxidationof Ammonia to Nitrite to Nitrate

  • Nitrification*Heterotrophic Bacteria Break Down OrganicsGenerate NH3, CO2, and H2O*Autotrophic Bacteria Utilize Inorganic Compounds(and CO2 as a Carbon Source)

  • NitrificationNitrosomonasNitrobacterNitrification of Ammonia Occurs inTwo Steps*Autotrophic Bacteria Utilize Inorganic Compounds(and CO2 as a Carbon Source)

  • Operational Controls for NitrificationAir Requirements1.5 lbs O2 / lb BOD4.6 lbs O2 / lb TKNIncrease D.O. in Aeration Tankto 3 - 5 mg/L

  • Nitrification VS D.O.NH3-N Removal, %Dissolved Oxygen, mg/L0 1 2 3 4 5 6 7 8 9100908070605040

  • Aerobic React Time Must Be Long Enough(> 5 hrs.)F:M Ratio Must Be Low Enough(< 0.25) (BOD Removal Must Occur First)Operational Controls for Nitrification

  • Effluent BOD Vs % NH3-N RemovalEffluent BOD, mg/L0 10 20 30 40 50 60 70 80NH4-N Removal, %1009080 706050403020100

  • Control Solids HandlingIn-plant Return Flows High in BOD and AmmoniaReturn SlowlyLow QuantitiesAt Low Loading TimesInhibit NitrificationExceed Nitrification CapabilityOperational Controls for Nitrification

  • Nitrifiers Grow SlowlyCRT Must Be Long Enough > 5 Days (minimum)Best > 8 DaysOperational Controls for Nitrification

  • Nitrogen, mg/LCRT, Days25201510500 5 10 15 20 25 30Effluent NH3-NTotal Nitrogen NitrifiedNitrification VS CRT

  • Effect of Temperature on NitrificationLower Temperatures CauseSlower Nitrifier Growth Rate

  • Nitrifier Growth Rate0 5 10 15 20 25 30 35 404.03.53.02.52.01.51.00.50.0Temperature, oCEffect of Temperature on Nitrification

  • Minimum of 59 Degrees F. (15 oC)for 90 % NitrificationLower Temperatures CauseSlower Nitrifier Growth RateBelow 50 Degrees F. (10 oC)Expect Maximum of 50 % NitrificationEffect of Temperature on Nitrification

  • Lower Temperatures CauseSlower Nitrifier Growth RateHigher MLSS ConcentrationMay Compensate for Lower TemperatureLimited By: Oxygen Transfer Maximum MLSS Controllable High CRT ProblemsEffect of Temperature on Nitrification

  • Importance of Alkalinity in NitrificationNH4HCO3 + O2 HNO3 + H2O + CO2 7 mg Alkalinity Destroyed Per mg NH3-N OxidizedChemicals Added For Phosphorus Removal AlsoDestroy Alkalinity

    5.3 - 13.5 lbs Alkalinity per lb Fe Added6.0 - 9.0 lbs Alkalinity per lb Al AddedpH May Become Depressed If Not Enough Alkalinity is PresentNitrifiers are pH SensitiveMost Efficient at pH 8.0 - 8.5

  • pH VS Nitrification Rate at 68 oFpH6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.01009080706050403020100% of Max Nitrification Rate

  • Importance of Alkalinity in NitrificationNH4HCO3 + O2 HNO3 + H2O + CO2 7 mg Alkalinity Destroyed Per mg NH3-N OxidizedAssure Adequate AlkalinityEffluent Above 50 mg/LInfluent Above 150 mg/L

  • Importance of Alkalinity in NitrificationNH4HCO3 + O2 HNO3 + H2O + CO2 7 mg Alkalinity Destroyed Per mg NH3-N OxidizedAssure Adequate AlkalinityEffluent Above 50 mg/LInfluent Above 150 mg/L

  • Importance of Alkalinity in NitrificationNH4HCO3 + O2 HNO3 + H2O + CO2 7 mg Alkalinity Destroyed Per mg NH3-N OxidizedAssure Adequate AlkalinityEffluent Above 50 mg/LInfluent Above 150 mg/LSodium Bicarbonate

  • Dissolved OxygenCRT, F/M TemperatureAlkalinityReturn Flows From Solids HandlingpH Swings*Toxics in InfluentNitrification Problems

  • DENITRIFICATIONWhy Denitrify ???Groundwater Discharge Permits Limit Total Inorganic Nitrogen (5 mg/L NO3-N + NO2-N + NH3-N)Biological Phosphorus Removal Depends on Removal of Nitrate

  • DefinitionsAerobic Dissolved (Free) Oxygen Present O2

    Oxic Dissolved (Free) Oxygen Present O2

    Anoxic No Free Oxygen (Combined Oxygen Nitrates NO2 and Nitrites NO3)

    Anaerobic Oxygen Absent

  • DENITRIFICATIONNO3heterotrophic bacteria + BODAnoxic environmentN2In an anoxic environment, heterotrophicbacteria will use the oxygen from nitrates as they assimilate BOD, producing nitrogen gas.

  • Added BenefitsMinimizes Rising SludgeHelps Recover OxygenMay Help Control Filamentous BacteriaRecovers Alkalinity3.57 mg Alkalinityper mg NO3ReducedDENITRIFICATION

  • Nitrite and DisinfectionNitrite is a Chlorine SpongeChlorine reacts with NitriteInstead of DisinfectingCant Meet Fecal ColiformLimits Even With IncreasedChlorine Dosage

  • Nitrite and DisinfectionCl2 + H20 HCl + HOClHOCl H+ + OCl-OCl- + NO2- NO3- + Cl-NO2

  • Nitrite and DisinfectionAbove 63 oF (17 oC) First step is slowest Nitrification(results in < 1 2 mg/L NO2)

  • At 54 to 57 oF (12 to 14 oC) Second step becomes slowest NH3 NO2 NO3Nitrite and DisinfectionDisinfection with Chlorine Becomes Very DifficultCold Water NO2 ProblemNitrificationNO2 can reach 15 mg/L

  • Nitrite and DisinfectionWarm Water NO2 ProblemDenitrificationNO3 NO2 N2Second step is slowerWorst when carbon (BOD) is limited

  • Nitrite and DisinfectionWarm Water NO2 ProblemDenitrificationNO3 NO2 N2Second step is slowerKeep System AerobicDenitrification Not Needed

  • Nitrite and DisinfectionWarm Water NO2 ProblemDenitrificationNO3 NO2 N2Second step is slowerTo Intentionally DenitrifyMake Sure BOD is AvailableDuring Denitrification

  • Nitrite and DisinfectionToxicityNitrifiers are more affectedthan other bacteriaSome toxins affect the Nitrobacter more than the NitrosomonasResults in a build-up of NO2

  • Nitrite and DisinfectionEffect of AmmoniaNH3 NO2 NO3If ammonia is not present,Free Cl reacts quickly with NO2 Cl =+DisinfectionProblemsIf enough NH3 is present,Cl reacts to form Chloramines.Chloramines disinfect,but dont react quickly with NO2

  • ORPOxidation-Reduction PotentialThe electrical potential (mv) required to transfer electrons from one compound to another.Used as a qualitative measure of the state of oxidation.

  • ORPOxidation-Reduction Potential

  • ORP

  • ORP

  • NitrificationandDenitrificationPrepared byMichigan Department of Environmental QualityOperator Training and Certification Unit

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