Organic samples: OFMSW, digestate from the digestion of the very same OFMSW and vinasse.
Total Nitrogen (TN) is the sum of nitrate-nitrogen (NO3-N), nitrite-nitrogen (NO2-N), ammonia-nitrogen (NH3-N) and organically bonded nitrogen. Total Nitrogen (TN) should not be confused with TKN (Total Kjeldahl Nitrogen) which is the sum of ammonia-nitrogen plus organically bound nitrogen but does not include nitrate-nitrogen or nitrite-nitrogen.
Organic Nitrogen “Organically bound nitrogen in the trivalent state.” It does not include all organic nitrogen compounds, but includes such natural materials as proteins and peptides, nucleic acids, urea, and many synthetic organic materials (eg quaternary ammonium compounds, nitrogen containing pesticides, polymers, etc). Analytically, organic nitrogen and ammonium nitrogen are determined together as Total Kjeldahl Nitrogen (TKN), a term which reflects the method used rather than any specific chemical form of nitrogen.
Nitrogen in freshly polluted water is originally present in the form of organic nitrogen and ammonia. Natural biochemical processes slowly convert the organic nitrogen into ammonia, which is the form of nitrogen best able to be utilized as a nutrient by microorganisms in the treatment process. (Some waste waters may be nitrogen deficient and require supplemental ammonia for adequate reproduction
The Organic Nitrogen is then calculated as Norg = TKN - NH4N Protein concentration may be approximated from;
Protein = Total Organic N x 6.25 = [TKN – NH4N] x 6.25
TKN (Total Kjeldahl Nitrogen) this form of nitrogen is defined by the test method used (i.e. a ‘Kjeldahl’ digestion) which determines nitrogen in the trivalent state. The method does not determine nitrogen present in azide, azine, azo, cyanide, hydrazone, nitroso, oxime, or semicarbazone forms, nor as nitrate or nitrite, and also does not recover nitrogen from some industrial chemicals (eg refractory tertiary amines). TKN can be considered to comprise • Ammonium-N (NH4N) • Protein N • Non-protein N eg urea, DNA, benzalkonium salts.
Last paragraph by Prem Baboo is quite important, showing that Kjeldhal method may show lower total elemental nitrogen in organic samples
Role of TKN and elemental nitrogen in anaerobic digestion of Kitchen waste?
- Badges
- Science topic
- Similar topics
- Phytochemistry
- Extracts