Removing nitrogen biologically

WW from refineriea, and generally from petrochemical plants as well, has a N concent lower than 100 mg-T and so does not warrant stripping. Instead, a biological purification process that is frequently used for MWW can lower (N.NH.j) nitrogen levels to 10 or 5 mg r depending on regulations in different countries. 

This purification process is completely carried out in two main stages nitrification and denitrification. 

Ammonification of organic N into ammonia N must be performed before nitrification of NH4, which in cum occurs in two stages  

These bacteria are autotrophic, i.e. they grow by oxidation of inorganic compounds. Nitrosomonas bacteria reproduce much more slowly than Nitrobacter, so die first reaction is determining. 

The overall reaction is acidifying and therefore consumes the alkalinity of the water which must be offset  

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Nitrification has been extensively investigated as a very useful process in the first step of nitrogen removal in biological wastewater treatment. The oxidation of ammonia and nitrite by nitrifying processes generates nitrate for denitrifying processes where nitrate is converted to molecular nitrogen. 

Cobalt compounds have been in use for centuries, notably as pigments ( cobalt blue ) in glass and porcelain (a double silicate of cobalt and potassium) the metal itself has been produced on an industrial scale only during the twentieth century. Cobalt is relatively uncommon but widely distributed it occurs biologically in vitamin B12 (a complex of cobalt(III) in which the cobalt is bonded octahedrally to nitrogen atoms and the carbon atom of a CN group). In its ores, it is usually in combination with sulphur or arsenic, and other metals, notably copper and silver, are often present. Extraction is carried out by a process essentially similar to that used for iron, but is complicate because of the need to remove arsenic and other metals. 

Reactions. The chemistry of the /V-nitrosamines is extensive and will be only summarized here (8,35,42). Most of the reactions of the nitrosamines, with respect to thek biological or environmental behavior, involve one of two main reactive centers, either the nitroso group itself or the C—H bonds adjacent (a) to the amine nitrogen. The nitroso group can be removed readily by a reaction which is essentially the reverse of the nitrosation reaction, or by oxidation or reduction (68,69). 

While many industrial wastes are so low in nitrogen and phosphorus that these must be added if biologically based treatment is to be used, others contain very high levels ofthese nutrients. For example, paint-production wastes are high in nitrogen, and detergent production wastes are high in phosphorus. Treatment for removal of these nutrients is required in areas where eutrophication is a problem. 

Acylation of a sulfonamide on the amide nitrogen serves to remove the sometimes objectionable taste of these drugs. Reac-I ion of intermediate, 154, with acetic anhydride followed by reduction of the nitro group affords acetyl methoxyprazine (156). The last, which has much the same biologic action as Mie parent compound, is used for oral administration in syrups. 

Eiroa, M., Biological Removal of Organic and Nitrogen Compounds Present in the Effluents of a Resin Factory (in Spanish), PhD thesis, University of A Coruna, 2004. 

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