Nitrogen Presentation By Douglas Rittmann, Ph.D., P.E Water/Wastewater Consultant Presented to CE 4153 On April 11, 2006

Nitrogen

General Considerations * Atmosphere serves as a reservoir which nitrogen is removed by * Action of Electrical Discharge oxidized to N 2 O 5 + H2O HNO 3 * Action of Bacteria * Action of Algae * Animals and Humans are incapable of utilizing nitrogen from air but obtain it from plant & other animals in the form of proteins * Urine contains the nitrogen from metabolic breakdown of proteins C =O + 2 H2O (NH4)2CO3 NH2 Nitrogen exists in urine as urea Which is hydrolyzed by ammonium carbonate

* Nitrosomonas group are nitrite formers bacteria 2NH3 + 3O2 2NO2 + 2H+ + 2H2O * Nitrobacter group are the nitrate formers bacteria 2NO2 + O2 2NO3 General Considerations * Under anaerobic conditions, nitrates and nitrites are reduced by process of denitrification. NO3 to NO2 to N2.

Sanitary Significance of Nitrogen Data Org N & NH3-N are recent pollution & Pose most danger NO2 & NO3 are Examples of pollution a long time ago & pose the least threat to public health. Bacti tests replaced significance of N as pollution indicator NO3-N MCL is 10 mg/L Because it causes Methemoglobinemia “Blue Baby” syndrone

Oxidation in Rivers and Estuaries * Since Nitrogen is essential to Algae growth, it may cause adverse effect of excessive loss of dissolved oxygen on the receiving stream from over stimulation of the algae & subsequent die-off of the algae * Also, discharge of ammonia nitrogen can seriously reduce the dissolved Oxygen levels in rivers and estuaries * Sometimes it is desirable in wastewater treatment to carry the oxidation of nitrogen to nitrate form in order to minimize oxygen uptake in the receiving stream

Cadmium Reduction Method General Discussion Principle: Cadmium reduces nitrates in the sample to nitrite. The Nitrite ion reacts in an acidic medium with sulfanilic acid to form an Intermediate diazonium salt. The salt couples with gentisic acid to form An amber colored solution. Interferences Iron, copper, or other metals lowers reduction efficiency. EDTA can Eliminate this interference. Color in sample can interfere with spectro Analysis. Chloride >100 mg/L will cause low results. Nitrite interference but bromine and phenol can eliminate interference. Strong oxidizing And reducing substances interfere. Highly buffered samples or extreme pH may exceed the buffering capacity of reagents.

Persulfate Method 1. General Discussion The persulfate method determines nitrogen by oxidation of all Nitrogenous compounds to nitrate. a. Principle: Alkaline oxidation at 100 to 110C converts organic And inorganic N to nitrate. 2. Apparatus a. Autoclave, or hotplate, and pressure cooker b. Glass culture tubes c. Apparatus for nitrate determination

Persulfate Method 3. Reagents A. Ammonia free and nitrate free water. b. Stock Nitrate solution c. Intermediate nitrate solution d. Stock glutamic acid solution

Nessler Method of Analysis All nitrogen that exists as ammonium ion or in the equilibrium is Considered to be ammonia nitrogen NH 4 + NH 3 + H + By Direct Nesslerization: After sample clarification using zinc sulfate and Sodium hydroxide, the amount of ammonia is determined with Nessler’s reagent, potassium mercuric iodine. It combines with NH3 in alkaline Solution to form a yellowish-brown colloidal suspension whose intensity of Color is directly proportional to the amount of NH3. The color is easily matched by eye or by photometric method.

Distillation Method of Analysis * Distillation procedure separates ammonia from interfering substances such as color and turbidity. * At pH levels of 7.2 to 7.4, ammonia and hydrogen ion is liberated as a gas along with steam produced when sample is boiled. * Since hydrogen is combined ammonia, a phosphate buffer is used to prevent pH drop * Experience has shown that all free ammonia is expelled after 200 ml of water has been distilled from solutions whose pH is between

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