Nitrification light

Conventional wastewater treatment techniques consist of physical/chemical treatments, including oil separation, dissolved gas flotation, and ammonia distillation (for removal of free cyanides, free sulfides, and ammonia) followed by biological treatment (for organics removal) and residual ammonia nitrification. Almost all residuals from coke-making operations are either recovered as crude byproducts (e.g., as crude coal tar, crude light oil, ammonium sulfate, or other sulfur compounds)... 

Nitrification rates are often low in the well lit surface waters of the ocean, probably due to light inhibition and competition for NH4 with phytoplankton and heterotrophic bacteria. 

Lipschultz et al. (1985) documented the light inhibition of NH3 oxidation in the Delaware River and concluded that this effect influenced the spatial distribution of nitrification in the estuary. Depending on their depth, light is not usually a problem for nitrification in sediments. In shallow sediments, light may have an indirect positive effect on nitrification rates by increasing photosynthesis, and thus increasing oxygen supply to the sediments (Lorenzen et al., 1998). 

Horrigan, S. G., Carlucci, A. F., and Williams, P. M. (1981). Light inhibition of nitrification in sea-surface films. Journal of Marine Research 39, 557-565. 

VanzeUa, A., Guerrero, M. A., and Jones, R. D. (1990). Recovery of nitrification in marine bacteria following exposure to carbon monoxide or light. Mar. Ecol. Prog. Ser. 60, 91—95. 

Recall from Section 2.4.2 that nitrification is a multistep process in which ammonium (NUt ) is oxidized to nitrate using O2. Nitrification is carried out by various nitrifiers, chemoautotrophic bacteria that occur in oxic environments where ammonia is present (Ha)mes, 1986). Nitrifiers use chemical energy released by ammonium oxidation to reduce CO2 to organic matter, much as green plants use energy captured from light to reduce CO2. The intermediate species of nitrification are shown in Eq. (4.55). Note that N2O can be produced by side reactions from either of two intermediates by chemical rearrangement of the short-lived nitroxyl molecule (HNO) or by the reduction of nitrite (N02 ) within the cells of the nitrifiers. 

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