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Modelling of nitrogen removal in the vadose zone

Ho, G.E.ORCID: 0000-0001-9190-8812, Mathew, K. and Newman, P.W.G. (1984) Modelling of nitrogen removal in the vadose zone. In: Durham, N.N. and Redefs, A.E., (eds.) Proceedings of the 2nd International Conference on Groundwater Quality Research, Tulsa, Oklahoma, 26-29 March. National Center for Ground Water Research, Stillwater, OK, pp. 112-114.



Ammonium in secondary wastewater is removed in the vadose zone when wastewater is applied to spreading basins with alternate flooding and drying. The processes involved in the removal of ammonium nitrogen are adsorption of ammonium by the soil oxidation of the adsorbed ammonium to nitrate by nitrifying bacteria in the subsequent drying period thus freeing adsorption sites in the soil for further ammonium adsorption, and reduction of nitrate to nitrogen by denitrifying bacteria during flooding.

The extent of nitrogen removal is governed by the rate of infiltration, the lengths of the flooding and drying periods, the adsorption capacity of the soil for ammonium and the rates of nitrification nod dentrification. A model incorporating these processes has been developed, which can be used to explain why nitrogen removal does not take place in some wastewater rapid-infiltration systems, why nitrogen conversion stops after the nitrification slate in some cases, and to calculate the extent of nitrogen removal as a function of soil type and operating conditions. The model shows that the approach to steady state after a change in operating conditions is reached only slowly.

The model parameters have been obtained experimentally under laboratory conditions. A case study of nitrogen removal from wastewater by rapid infiltration in Perth, Western Australia is discussed.

Item Type: Book Chapter
Murdoch Affiliation(s): School of Environmental and Life Sciences
Publisher: National Center for Ground Water Research
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