Ammonia oxidation, aerobic process

The biodegradation of trichloroethylene is the most studied since this is probably the most widespread halogenated solvent contaminant. Several substrates drive ttichlorethylene co-oxidation, including methane, propane, propylene, toluene, isopropylbenzene, and ammonia (25). The enzymes that metabolize these substrates have subtly different selectivities with regard to the halogenated solvents, and to date none are capable of co-oxidizing carbon tetrachloride or tetrachloroethylene. Complete mineralization of these compounds can, however, be achieved by sequential anaerobic and aerobic process. Biorem edia tion. 

Nitrification is the aerobic process by which microorganisms oxidize ammonium to nitrate and derive energy. It is the combination of two bacterial processes one group of organisms oxidizes ammonia to nitrite (e.g., Nitrosomonas), after which a different group oxidizes nitrite to... 

Terada et al. (2007) used a multipopulation model to compare co- and counter-diffusion biofilms for autotrophic nitrogen removal, which is a process that depends on coexistence between aerobic and anaerobic ammonia-oxidizers. They showed that the counter-diffusion biofilm outperformed the co-diffusion biofilm for biofilm thicknesses between 450 and 1400 pm. The counter-diffusion biofilm had a wider application range and was expected to work better for applications with fluctuations in loading rates. 

In this case, the wastewater is fed to the aerobic reactor where the remaining formaldehyde is oxidized to C02 (Equation 19.3) and urea is hydrolyzed to ammonia. This ammonia is then oxidized to nitrate (Equation 19.4). Nitrate goes to the denitrifying unit where it is reduced to dinitrogen gas in the presence of an electron donor, which is generally provided by organic matter (Equation 19.5). Because formaldehyde is oxidized in the first unit, methanol is commonly added to carry out this process, which produces an increase in operational costs. 

As bacteria die, ammonia is typically produced as a product of decomposition. Aerobic nitrifying bacteria such as Nitrosomonas and Nitrobacter can oxidize ammonia (NH3) to nitrate (N03 ). As a result of this process, the pH of the system can be reduced. 

Under aerobic conditions, ammonia is removed by a two-step biological oxidation process see reaction (10.6). Ammonia is first oxidized to nitrite... 

Under aerobic conditions, a number of specialized bacteria derive their energy needs from the oxidation of ammonia to nitrite and then further to nitrate. This process is called nitrification. Focht and Verstraete (1977),... 

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