Evaluation of a Sulfur-Thiobacillus denitrificans Nitrate Removal System
1976
Sikora, L. J. | Keeney, D. R.
An evaluation of sulfur-Thiobacillus denitrificans nitrate removal system as a means of denitrifying nitrified septic tank effluent was conducted. Duplicate 10 by 64 cm columns were filled with a 1/1 mixture (wt/wt) of elemental S (>2 mm) and dolomite chips (1 cm), and were pretreated by recycling an enrichment culture of T. denitrificans ATCC 23642 through the columns for 3 days. Continuous passage of the nitrified septic tank effluent (column influent) containing 40 µg NO₃⁻-N/ml through the columns resulted in nearly complete NO₃⁻ removal in 3.3 hours at steady-state conditions (23C). Statistical analyses indicated that the denitrification kinetics closely resemble first order in the range of NO₃⁻ concentrations employed. Oxidation-reduction potentials (Pt black electrodes) ranged from +160 to +300 mV. Analysis the gases produced showed that N₂ was present in highest concentration. Sulfate was the major S end product and was present at relatively high concentrations (90 µg SO₄²⁻-S/ml). A significant decrease in inorganic C occurred with depth in the columns while changes in organic C content were insignificant. A significant linear relationship was obtained between decreases in (NO₃⁻ + NO₂⁻)-N and production of S0₄²⁻-S. Passage of column effluent through 10 by 60 cm Plainfield sand columns did not significantly decrease SO₄²⁻ levels. While use of this NO₃⁻ removal system appears promising, SO₄²⁻ contamination of the ground water may limit its applicability.
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