Determination of Total Nitrogen in Wastewater by Steam Distillation

Determination of Total Nitrogen in Wastewaterby Steam DistillationDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Bill IckesProduct Manager Kjeldahl and ExtractionBuchi CorporationBrad MillerRegional Sales ManagerBuchi CorporationDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Who is Buchi Corporation?Determination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Buchi HeadquartersFlawilSwitzerlandDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Buchi Corporation• Rotavapor®• Parallel Evaporation• Industrial Evaporation• Kjeldahl Solutions• Extraction Solutions (Soxhlet, Hot, Pressurized)• Spray Drying• Melting Point Determination• Flash and Preparative Chromatography• Near Infrared Spectroscopy• Vacuum Pumps• ChillersDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Buchi Corporation USA• Direct Affiliate• New Castle, DE• 37 Employees Representing Sales, Marketing, TechnicalSupport, Service, and Warehouse ActivitiesDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Content• Introduction to Total Nitrogen Analysis• Introduction to the Kjeldahl Method• Step I: Digestion• Step II: Distillation• Step III: Titration• Calculation of Total Nitrogen• Other Steam Distillation Analysis• SummaryDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Introduction to Analysis of Total NitrogenDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

What is Total Nitrogen?• Ammonia (Volatile Gas)• Ammonium Salts (Ex. Ammonium Sulfate)• Organic Nitrogen (Derived from Protein, Urea, NucleicAcids, etc.)• Nitrates• NitritesDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Why Analyze for Total Nitrogen?• Good Indicator of Water Quality• Clues to Nitrogen Source• Comparison Between Influent and Effluent Waste Water• Determines Waste Water Treatment EfficiencyDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Differences in Analysis• Ammonia – Direct steam distillation of sample with noaddition of NaOH• Ammonium Salts – Direct steam distillation of samplewith addition of NaOH• Organic Nitrogen – Digestion, Distillation, and Titration byKjeldahl Method• Nitrates/Nitrites – Digestion, Distillation, and Titration byKjeldahl Method with the addition of Devarda’s Alloy priorto distillationDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Introduction to the Kjeldahl MethodDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Who was Kjeldahl?Johan Kjeldahl 1849 – 19001849 born in Denmark1867 graduation from university1876 Scientist at Carlsberg Breweries Fermentation studies Development of a method for exact determnationof nitrogen in animal and vegetablematerial Research on carbohydrates in barley and malt1883 Publication of the Kjeldahl methodDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Principle Kjeldahl Method1.DigestionConversion ofProtein-Nitrogen toNH 4+2.3.Distillation TitrationSeparation of Measure ofNH the Amount of3Acid that wasneutralised byNH 3Determination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Step 1: DigestionDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

DigestionTarget of digestion: Breakage of organic bonds Conversion of Nitrogen to AmmoniumOrganic N NH 4+H 2 SO 4 conc.Digestion MixtureDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Digestion Mixture Digestion mixture is a mixture of- a salt (i.g. potassium or sodium sulphate)- and a catalyst (Hg, Se, Cu or Ti) Reason for addition of digestion mixtureIncreasing of the digestion temperature→ faster and more efficient digestionImportant for reproducible results:Ratio of sulphuric acid and digestion mixtureIdeal proportion: 20ml/10gDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

RatioSulphuric Acid – Digestion MixtureThe ratio sulphuric acid – digestion mixture definesthe boiling point of the sulphuric acidIdeal digestion temperature: 370°CQuantityH 2 SO 4QuantityK 2 SO 4BoillingpointRemarks20 ml -- 330 °C pure H 2 SO 420 ml 5 g 350 °C20 ml 10 g 370 °C20 ml 15 g 390 °Coptimaldigestion temp.already firstnitrogen lossDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Summary Digestion (I)Sample Homogenisation, Weighingand Addition of ReagentsSample2 tabs ofCatalystSulphuric acidDigestion1.072BlankWeigh sample• 1 g of dry organic material(homogeneous)Add reagents• 10 g or 2 tabs of Kjeldahlcatalyst mixture• 20 ml of H 2 SO 4Sample Blank• add everything exceptsampleDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Summary Digestion (II)Digestionvapours toScrubberDigestion• digest at 370 °C for 90 minor until the mixture is clear(green / blue color) + 30 minDigestionDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Step 2: DistillationStep 3: TitrationDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Pre-Distillation Steps1) CoolingDigested sample is cooled down to RT2) DilutionDigested sample is diluted with deionised water3) Preparation of receiving vesselReceiving solution necessary to capture volatileammoniaDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Preparation of Receiving Vessel (I) Reason for receiving vessel:Ammonia is volatile -> has to be captured inreceiving solution Possibilities for receiving solutions:Boric acid solution (2% or 4%)Mineral acid standard solution (HCl or H 2 SO 4 )Determination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Preparation of Receiving Vessel (II)Recommendation for Kjeldahl determination:Boric Acid 4% Easier handling No risk of too low capacity to capture all NH 3 Method of most official methodsSteam DistillationNH 3Receiving AcidNH 4 [B(OH) 4 ](Boric Acid)Determination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Distillation: Addition of NaOHTarget of addition of NaOH:Release of ammonia in the form of NH 3NaOH(NH 4 ) 2 SO 4 NH 3Determination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Titration Possibilities of titration methods- potentiometric titration (pH)- visual titration (colour)- colorimetric titration (absorbance)Recommendation for Kjeldahl determination:Potentiometric titration Advantages potentiometric titration:- more precise than visual and colorimetric titration- more robust than colorimetric titration(colorimetric titration is very susceptible)Determination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Potentiometric TitrationPoints to consider: Initial pH of the boric acid should be 4.65 Endpoint of the titration should be pH 4.65Reason: pH 4.65 is turning point of the titration curvemLEnd point pH 4.65Warning pointpH3.0 4.0 5.0 6.0 7.0 8.0Determination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Summary Distillation / Titration (I)DilutionmanuallyorautomatedDilution• dilute the cooled digestionsolution with 50 ml deionisedwaterDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Summary Distillation / Titration (II)Preparation of ReceiverBoric acid titration• add 60 ml of Boric acid 4%• add 2 to 3 drops of indicatoraccording to SherDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Summary Distillation / Titration (III)Neutralisation and DistillationSodium hydroxide• add 90 ml of NaOH 32% tothe diluted digestion solutionDistillation• distill for 4 min.Determination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Summary Distillation / Titration (IV)Titration7.15Boric acid titration• titrate the condensate withsulphuric acid standard solution(0.5 N or equivalent) to the endpoint of pH 4.65Determination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

CalculationDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Calculation% N =% P =(Consumption-Blank) x 1.4007 x n x 100Sample Size(Consumption-Blank) x 1.4007 x n x PF x 100Sample Size1.4007: 1 ml 0.1 N Volumetric Solution = 1.4007 mg Nn: Normality AcidPF:Protein factor N Protein(e.g. 6.25; Milk Sample 6.38; Nuts 5.4)Determination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Other Methods of Analysis w/ Steam DistillationDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Analysis Using Steam Distillation• Cyanides• Phenols• Volatile AcidsDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Cyanide DeterminationDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Method Reference: EPA Method 9010 C/335.2Determination of Free Cyanide and Weak AcidDissociable Cyanide In Waste WaterDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Why Analyze For Cyanide?• One of Natures Toxic SubstancesDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Sources of Cyanide?• Metal Finishing• Photographic Bleaching• Galvanic Industry Waste WaterDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

How is Cyanide Analyzed?• Steam distillation with strong acid• Collected in a receiving solution of NaOH• Cyanide concentration determined colorimetrically at578nmDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Phenol DeterminationDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Method Reference: EPA Method 9065Determination of Phenolic Material bySpectrophotometric 4-aminoantipyrine MethodDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Why Analyze for Phenols?• Phenolic compounds are commonly found in sludge• Phenolic compounds can be traced to differentcontamination sourcesDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Sources of Phenols?• Plant Material• Chemical Industry Processes• Wood Processing• Plastic ProcessingDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

How are Phenols Analyzed?• Steam distillation in the presence of acid• Collected in water in the receiving solution• Photometric measurement of the receiving solutionDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Volatile Acids DeterminationDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Method Reference: Buchi Application Note K-355.004 Version ADetermination of Volatile Acids in SludgeDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Why Analyze for Volatile Acids?• Ratio of volatile acids -> total alkalinity content in sludgesubmitted to anaerobic conditions is a good index ofprocess performance inhibitionDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Source of Volatile Acids?• Acetic AcidDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

How are Volatile Acids Analyzed?• Steam Distillation• TitrationDetermination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes

Questions?Determination of Total Nitrogen in Wastewater 10/19/10 William H. Ickes