Nitrification oxygen concentration

Example 15.3 After ending off the aeration to a nitrification plant, the dissolved oxygen concentration is 2.0 mg/L. How mnch sewage is needed for the carbonaceous reaction in this last stage of aerobic reaction before denitrification sets in How much NH4-N is produced from this carbonaceous reaction ... 

Jorgensen, K.S., Jensen, H.B. and Sorensen, J., 1984. Nitrous oxide production from nitrification and denitrification in marine sediment at low oxygen concentrations. Can. J. Microbiol., 30, 1073-1078. 

D. J. Greenwood, "Nitrification and Nitrate Dissimilation in Soil. Part 2. Effect of Oxygen Concentration," Plant and Soil, J7 365-378 (1962). 

There are other such examples. Many unsaturated soils are known to convert to N2(g> via NO3 (i.e., nitrification then denitrification). They achieve this because there are local oxic and anoxic environments in the soil waters that, respectively, allow nitrification and denitrification to proceed. In stratified lakes, nitrification may occur in the oxygenated epilimnion (upper layer) and denitrification in the hypolimnion (bottom water) and in the sediment pore water where dissolved oxygen concentrations fall to zero. The nitrification and denitrification process is important in preserving the fishery in Indian Creek Reservoir in the Sierra Nevada mountains. This reservoir is fed by the tertiary effluent from the City of South Lake Tahoe sewage treatment plant. The effluent has at times contained 15 to 20 mg NH4 N/liter. Levels of ammonia of this magnitude are toxic to fish, yet in the reservoir there is a thriving fishery. This is achieved because the top waters of the lake nitrify the ammonia to nitrate and this is reduced to N2(g) by the anoxic bottom waters. The summer concentrations of nitrogen species of the reservoir are approximately 4 mg NOa -N/Iiter and 4 mg NH4-N/liter. 

Martin and Reddy, 1997). These values are lower than the values reported for mineralization, suggesting that oxygen and ammonium availability limits nitrification. Measurement of oxygen concentration in the water column or Eh values in soils can provide a reliable indication of potential nitrification. Measurement of nitrate in aerobic zones of wetlands may underestimate overall nitrification, as some of the nitrate can diffuse into anaerobic zones and is lost through denitrification. However, in well-aerated soils, nitrification potentials are determined by measuring accumulation of nitrate over time. 

The fraction of ammonium converted to nitrous oxide during nitrification is typically less than 1%, and is strongly influenced by pH and oxygen concentration. Maximum N2O production by nitrification tends to occur at... 

Both steps are influenced by dissolved oxygen and the corresponding substrate concentration. The nitrification as a wastewater treatment process benefits greatly from biomass retention, owing to the relatively slow growth rates of the nitrifiers. 

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