Column-Based Remediation of Groundwater Nitrogen via Stimulation of Nitrification and Denitrification


ABSTRACT: A former research laboratory facility utilized a leach field for sanitary and aqueous laboratory waste. Surrounding soils and groundwater are impacted by ammonia and pH varies between 3.6 and 5. The feasibility of employing an in-situ, two-stage, nitrification/denitrification program was evaluated via a soil column study. The objectives of the study were to a) determine the efficacy of stimulating nitrification, followed by denitrification, and b) provide a scale-up implementation design and cost for the full-scale remedy. The study consisted of monitoring the inorganic nitrogen content of leachates from 7 columns with 4 conditions over six weeks. The four conditions were 1) un-amended groundwater controls, 2) pH adjusted, o-PO4-P amended groundwater tests with daily peroxide addition, 3) condition 2 augmented with a pure nitrifying consortium and, 4) condition 3 amended with catalase enzyme. During the nitrification phase, condition 1 nitrified to a very limited degree, indicating the presence of indigenous nitrifying organisms. Condition 2 confirmed the presence of indigenous nitrifiers, although nitrification performance was incomplete and sporadic. Condition 3 significantly outperformed condition 2. No benefit was observed from catalase addition. Column exhaustion required the denitrification phase to be performed as a slurry reaction. Slurries 1 and 2 were fed nitrate, glucose, phosphate, and sulfite to scavenge oxygen. Slurry 3 was treated in the same manner with the addition of a single denitrifying bacterial strain. Slurry 1 failed to denitrify. Slurries 2 and 3 reduced 100 mg/L of nitrate at rates of 14 and 59.5 mg/L/day, respectively.

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