Nitrification—denitrification

FIGURE 17.31 Relationship between extractable ammonium nitrogen and nitrification rates in surface soils along phosphorus gradient in the WCA-2A. (From White and Reddy, 2003.) 

Both potential nitrification and denitrification rates decreased with distance from the inflow along the entrophic gradient in WCA-2A and the rates were positively correlated to total phosphorus (White and Reddy, 2003). Higher nitrification rates in soils from entrophic areas were due to high ammonium levels, whereas higher denitrification rates were due to greater availability of bioavail-able carbon. Both nitrifiers and denitrifiers were limited by phosphorus in the oligotrophic areas of WCA-2A (White and Reddy, 1993,2003). 

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The process of nitrification—denitrification can be practiced in one of two ways. In the oxidation ditch, nitrification occurs in the vicinity of the aerators. When the dissolved oxygen is depleted as the sludge—wastewater mixture passes from the aerator, denitrification occurs. 

If the COD/N ratio of the wastewater is low, a better option is the use of a nitrification-denitrification stage without a previous anaerobic digestion in order to preserve organic matter for denitrification. 

FIGURE 19.7 Schematic representation of a nitrification-denitrification activated sludge plant. 

As wastewater from resin-producing factories contains recalcitrant compounds, the removal efficiencies achieved by means of the nitrification-denitrification systems could not reach the required disposal values and a posttreatment, such as ozonation, would be necessary to enhance the biodegradability of those compounds.2 53... 

Gupta, S.K., Raja, S.M., and Gupta, A.B., Simultaneous nitrification-denitrification in a rotating biological contactor, Environ. Technol., 15, 145-153, 1994. 

Nitrification-denitrification reactions can be carried out in suspended growth by separating the reactor into different cells. A typical arrangement would control the first cell under anoxic conditions to carry out the denitrification reactions. These reactions require organic carbon and this... 

Attached growth processes are capable of removing up to 90% of BOD5 and are thus less effective than suspended growth methods. Nitrification-denitrification reactions can also be carried out in attached growth processes. 

Bioprocesses for the removal of nitrogen oxides from polluted air are an interesting alternative [58], but current reaction rates are still too low for large-scale applications. Advanced biological processes for the removal of NO from flue gases are based on the catalytic activity of either eukaryotes or prokaryotes, e.g. nitrification, denitrification, the use of microalgae and a combined physicochemical and biological process (BioDeNO ). 

Aerobic digested sludge 0.02-0.4 0.11 1 Activated sludge + nitrification/ denitrification Australia [9]... 

Reddy KR, Patrick WH, Jr., Lindau CW. 1989. Nitrification-denitrification at the plant root-sediment interface in wetlands. Limnology and Oceanography 34 1004-1013. 

Nitrification-denitrification involves the conversion of NH " to NO , the oxidation of NOj" to N03 , and the reduction of NOj" to NO ". The gases N O and are used in the microbially mediated processes involved in the nitrification-denitrification phenomenon. 

There are also significant natural sources of oxides of nitrogen, in particular nitric oxide, which is produced by biomass burning as well as by soils where nitrification, denitrification, and the decomposition of nitrite (N02) contribute to NO production. Figure 2.4b, for example, shows the relative emission rates for biogenically produced NO in the United States in 1990 (EPA, 1995). 

Biological treatment techniques anaerobic digestion processes, aerobic digestion processes, nitrification, denitrification, and central biological wastewater treatment. 

The nitrogen supplies on land consist of the assimilable nitrogen in the soil VS2 0.19-104tkm-2, in plants (12 1091), and living organisms (0.2 1091). A diversity of nitrogen fluxes is formed here of the processes of nitrification, denitrification, ammonification, fixation, and river run-off. The intensities of these fluxes depend on climatic conditions, temperature regime, moisture, as well as the chemical and physical properties of soil. Many qualitative and quantitative characteristics of these dependences have been described in the literature (Hellebrandt et al., 2003). Let us consider some of them. 

This model assumes irreversible first-order kinetics for nitrification, denitrification, mineralization, immobilization, and plant uptake. It takes the following form, in which sinks and sources are aggregated ... 

An, S.M., and Joye, S.B. (2001) Enhancement of coupled nitrification-denitrification by benthic photosynthesis in shallow estuarine sediments. Limnol. Oceanogr. 46, 62-74. 

Risgaard-Petersen, N. (2003) Coupled nitrification-denitrification in autotrophic and heterotrophic estuarine sediments on the influence of benthic algae. Limnol. Oceanogr. 48, 93-105. 

Phosphorus Removal Nitrification-Denitrification Diminution of Global/Group/Specific Parameters... 

The total nitrogen concentration that will appear at the effluent of the nitrification-denitrification process as a result of the consumption of the residual oxygen from nitrification, destruction of nitrate, and destruction of lutrite in the denitrification step is the sum of the ammonia nitrogen in the above equation plus the nitrate nitrogen not destroyed in the denitrification step. Let [7W]n noi be the milligram moles per liter of total nitrogen in the effluent. Thus,... 

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