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Nitrogen Transformations During Subsurface Disposal of Septic Tank Effluent in Sands: I. Soil Transformations
Author(s) -
Walker W. G.,
Bouma J.,
Keeney D. R.,
Magdoff F. R.
Publication year - 1973
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq1973.00472425000200040016x
Subject(s) - infiltration (hvac) , effluent , groundwater , crust , septic tank , nitrification , geology , nitrogen , hydrology (agriculture) , environmental science , environmental engineering , geochemistry , geotechnical engineering , chemistry , physics , organic chemistry , thermodynamics
Soil physical and chemical studies of five subsurface septic tank seepage beds were conducted to determine the biochemical transformations of N and thereby its potential for ground‐water pollution. Effluent was found to be ponded in all the seepage beds examined due to the presence of an impeding layer, a “crust”, at the boundary between the gravel bed and adjacent soil. The crust reduced infiltration rates approximately from 500 to 8 cm/day. Soil atmospheric composition 5 cm below the crust averaged 19.6% O 2 and 0.66% CO 2 . Nitrogen in the septic tank effluent occurred as NH 4 ‐N (80%) and organic N (20%) with virtually no NO 3 ‐N. Organic‐N was largely concentrated in the crust zone. Nitrification of NH 4 ‐N to NO 3 ‐N was essentially complete and commenced in the unsaturated subcrust soil within about 2 cm of the crust. Nitrification did not occur and NH 4 ‐N was absorbed by the soil below a seepage bed that was submerged in the ground water.