Nitrogen RemovalSlide 2NitrificationDenitrificationImportant Reactor FactorsSolids Retention TimeLet’s Start With Color KeysSlide 8Slide 9Slide 10Slide 11Slide 12Nitrate Probe CalibrationCalibrationNitrate Probe AnalysisSlide 16Slide 17Slide 18Slide 19Slide 20ConclusionAcknowledgementsNitrogen RemovalNitrogen RemovalTim Julian Matt Fountain Matt DuffanyNitrogen RemovalNitrogen RemovalNitrogen removal is a combination of the Nitrogen removal is a combination of the nitrification and denitrification microbial nitrification and denitrification microbial processes.processes.NitrificationNitrificationWastewater carries nitrogen Wastewater carries nitrogen predominantely in its ammonium form: predominantely in its ammonium form: NHNH44++Nitrosomonas and Nitrobacter populations Nitrosomonas and Nitrobacter populations oxidize this nitrogen to provide energy for oxidize this nitrogen to provide energy for cell synthesiscell synthesis  32222242242232NOONOHOHNOONHrNitrobacteasNitrosomonDenitrificationDenitrificationA variety of facultative microorganisms A variety of facultative microorganisms now use nitrate as a terminal enow use nitrate as a terminal e- - acceptor in acceptor in respirationrespirationConditions must be anoxic to promote Conditions must be anoxic to promote denitrificationdenitrificationSufficient COD must be present for Sufficient COD must be present for denitrification reactions to occurdenitrification reactions to occurImportant Reactor FactorsImportant Reactor FactorspH must be controlled (8.3) to achieve pH must be controlled (8.3) to achieve optimal microbial activity since nitrification optimal microbial activity since nitrification decreases pHdecreases pHCOD levels must be kept high for COD levels must be kept high for denitrification (industry addition of denitrification (industry addition of methanol)methanol)Heavy metal concentrations must be kept Heavy metal concentrations must be kept low (inhibition of nitrifying bacteria)low (inhibition of nitrifying bacteria)Solids Retention TimeSolids Retention TimeToo short and nitrifying bacteria population Too short and nitrifying bacteria population will not compete with heterotrophic will not compete with heterotrophic decomposers of organic carbondecomposers of organic carbonToo long and proportion of viable microbes Too long and proportion of viable microbes in waste will decreasein waste will decreaseOptimal Industry values ~ 9 – 12 daysOptimal Industry values ~ 9 – 12 daysdayper reactor leaving sludge massreactorin sludge massSRTLet’s Start With Color KeysLet’s Start With Color Keys= waste= tap water stock= activated sludge= 20 ppm nitrate solutionExperiment to Check Probe OperationExperiment to Check Probe Operation4 hBiomassBiomassAdd tap waterAdd 20x concentrated wasteAerate for 6 hoursSettle for 1 hourDischarge Clean Supernatant leaving 1.2 L biosolidsNitrate SensorDO ProbeSetup to Examine Difference Between Anoxic and Aerobic StatesSetup to Examine Difference Between Anoxic and Aerobic StatesBOD0BOD0Add tap water and 20x concentrated wasteAerate for 4.17 hoursSettle for 1 hourDischarge Clean Supernatant4 hAnaerobic for 2.2 hoursCheck for Interference Due to Sludge and WasteCheck for Interference Due to Sludge and WasteBOD0BOD0Add tap water and 0.931 g NaNO3Aerate for 4.17 hoursSettle for 1 hourDischarge Clean Supernatant4 hAnaerobic for 2.2 hoursImpact of Sludge on Electrical InterferenceImpact of Sludge on Electrical InterferenceBOD0BOD0Add tap water and 20x concentrated wasteAerate for 4.17 hoursSettle for 1 hourDischarge Clean Supernatant4 hAnaerobic for 2.2 hoursExamination of Impact of COD on DenitrificationExamination of Impact of COD on DenitrificationBOD0BOD0Add tap waterAerate for 2.2 hours, add 0.931 g NaNO34 hAnaerobic for 2.2 hoursBOD0BOD04 hAerate for 2.2 hours, add 10 g DextroseAnaerobic for 2.2 hoursNitrate Probe CalibrationNitrate Probe CalibrationSoaked in Distilled Water for 15 minutesSoaked in Distilled Water for 15 minutesSoaked in Diluted Nitrate Solution for 2 Soaked in Diluted Nitrate Solution for 2 hourshoursWashed, Placed into Distilled Water with Washed, Placed into Distilled Water with Varying Nitrate ConcentrationsVarying Nitrate ConcentrationsCorresponding Voltages Recorded Corresponding Voltages RecordedCalibrationCalibrationwater volume 100 mlstd concentration 1000 ppmamount std (ml) test solution concentration (ppm)voltage (volts)1.0 10.0 0.152.0 20.0 0.1293.5 35.0 0.115.0 50.0 0.1Nitrate Probe Calibration Curve for use in converting raw sensor data to nitrate concentrations. Calibrated in distilled water with a known nitrate solution at 1000 ppm.Nitrate Probe AnalysisNitrate Probe AnalysisNitrate Concentration Measurements in Nitrate Concentration Measurements in Full Cycle Compared to Expected ResultsFull Cycle Compared to Expected ResultsProof Nitrate is Being MeasuredProof Nitrate is Being MeasuredSources of Possible InterferenceSources of Possible InterferenceFinal Decision on Nitrate Probe UseFinal Decision on Nitrate Probe UseNitrate Probe AnalysisNitrate Probe AnalysisActual Nitrate Vs. Predicted Nitrate Over Two Cycles00.20.40.60.811.20.160.180.20.220.240.260.270.290.310.330.350.370.390.410.420.440.460.480.50.520.540.560.570.590.610.630.650.670.690.710.720.740.760.780.8Time (day fraction)DO (mg/L)00.20.40.60.811.21.41.61.82Nitrate (10 ug/L)DO (mg/L) Expected Nitrate Actual Nitrate (10 ug/L)AerobicAerobicAnaerobicAnaerobicSettleSettleDischarge / FillDischarge / FillWhat Values Are We Getting?Nitrate Probe AnalysisNitrate Probe AnalysisNitrate and Dextrose Spikes0123456780.8450.8550.8660.8760.8870.8970.9070.9180.9280.9390.9490.9590.9700.9800.9911.0011.0121.0221.0321.0431.0531.0641.0741.0841.0951.1051.1161.1261.1371.147Time (day fraction)DO (mg/L)0123456789Nitrate (10 ug/L)DO (mg/L)Nitrate (10 ug/L)AerobicAerobicAnaerobicAnaerobicNitrate AddedDextrose AddedIs the Probe Measuring Nitrate?Nitrate Probe AnalysisNitrate Probe AnalysisDetermining Possible Sources of InterferenceNitrate Spike Added to Water / Cycle Run 0246810120.9500.9670.9851.0021.0191.0371.0541.0711.0891.1061.1241.1411.1581.1761.1931.2101.2281.2451.262Day FractionDO concentration (mg/L)012345678DO (mg/L) Nitrate (10 ug/L)AerobicNitrate SpikeAnaerobic SettleDischargeFill WaterNitrate Probe AnalysisNitrate Probe AnalysisDetermining Possible Sources of InterferenceCycle with Water and Waste