Nitrogen Presentation

By

Douglas Rittmann, Ph.D., P.EWater/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 N2O5 + H2O HNO3

* 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)2CO3NH2

NH2

Nitrogen exists in urine as ureaWhich is hydrolyzed by ammoniumcarbonate

* Nitrosomonas group are nitrite formers bacteria2NH3 + 3O2 2NO2 + 2H+ + 2H2O

* Nitrobacter group are the nitrate formers bacteria2NO2 + 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 arerecent pollution &Pose most danger

NO2 & NO3 areExamples of pollutiona long time ago & pose the least threatto public health.

Bacti tests replacedsignificance of Nas pollution indicator

NO3-N MCL is 10 mg/LBecause it causesMethemoglobinemia“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. TheNitrite ion reacts in an acidic medium with sulfanilic acid to form anIntermediate diazonium salt. The salt couples with gentisic acid to formAn amber colored solution.

Interferences

Iron, copper, or other metals lowers reduction efficiency. EDTA can Eliminate this interference. Color in sample can interfere with spectroAnalysis. Chloride >100 mg/L will cause low results. Nitrite interferencebut bromine and phenol can eliminate interference. Strong oxidizingAnd reducing substances interfere. Highly buffered samples or extremepH may exceed the buffering capacity of reagents.

Persulfate Method

1. General Discussion

The persulfate method determines nitrogen by oxidation of allNitrogenous compounds to nitrate.

a. Principle: Alkaline oxidation at 100 to 110C converts organicAnd 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

NH4 + NH3 + H+

By Direct Nesslerization: After sample clarification using zinc sulfate andSodium hydroxide, the amount of ammonia is determined with Nessler’sreagent, potassium mercuric iodine. It combines with NH3 in alkaline Solution to form a yellowish-brown colloidal suspension whose intensity ofColor 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 7.2-7.4

Questions?