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Columns Representing Mound‐type Disposal Systems for Septic Tank Effluent: II. Nutrient Transformations and Bacterial Populations
Author(s) -
Magdoff F. R.,
Keeney D. R.,
Bouma J.,
Ziebell W. A.
Publication year - 1974
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/jeq1974.00472425000300030009x
Subject(s) - effluent , phosphorus , water column , chemistry , septic tank , denitrification , environmental chemistry , chemical oxygen demand , ponding , nutrient , nitrogen , environmental engineering , environmental science , wastewater , ecology , biology , organic chemistry , drainage
Abstract Carbon, nitrogen, and phosphorus transformations and bacterial populations were studied in columns representing a mound disposal system. Total‐N, total‐P, and the chemical oxygen demand (COD) of the influent (septic tank effluent) averaged 42, 21, and 257 mg/liter, respectively. The reduced‐N forms present in the influent (NH 4 ‐N and organic‐N) were oxidized to NO 3 ‐N in the aerobic fill and about 32% of the total‐N was lost by denitrification during water passage through the anaerobic silt loam at the bottom of the column. Phosphorus (mainly dissolved orthophosphate) concentrations in column effluents, increased gradually, stabilizing at about 60% of the influent P concentration. Phosphorus removal from the percolating water probably occurred by both sorption and precipitation. The COD of column effluents was very low, indicating essentially complete C removal. After crusting developed and caused permanent ponding the fill became anaerobic, and the column effluent N was mainly NH 4 ‐N. Phosphorus concentrations of the effluent increased gradually with time and reached a constant value of 2 to 6 ppm. The COD of the effluent from the totally anaerobic columns was higher than that from the uncrusted columns. Perforating column walls to more closely simulate field conditions permitted aerobic conditions in the fill after crust development caused continuous ponding. The C, N, and P transformations in the perforated crusted columns were similar to those observed in the nonperforated uncrusted (i.e., aerobic) columns. Fecal indicator bacteria were not detected in any column effluent even though the counts of fecal streptococci and fecal coliform in the influent averaged 3.8 × 10 4 and 1.7 × 10 5 /100 ml, respectively.