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NITRATE REDUCTION AND TRANSFORMATION IN ORGANIC COMPOST MEDIA: LABORATORY BATCH STUDIES
Citation:
Su, C. AND R W. Puls*. NITRATE REDUCTION AND TRANSFORMATION IN ORGANIC COMPOST MEDIA: LABORATORY BATCH STUDIES. Battelle In-Situ & On-Site Bioremediation 7th Int'l. Symp, Orlando, FL, 06/2/5/2003.
Description:
We studied the effectiveness of three organic solid reactive media (cotton burr compost, mulch compost, and Canadian sphagnum peat) that may be potentially used in permeable reactive barriers (PRBs) for groundwater nitrate removal. We aimed at answering the question about the nature of nitrate reduction and transformation, i.e., whether this is a biotic or abiotic process by comparing the sterile and non-sterile systems. A rigorous autoclaving protocol for the cotton burr compost (steam autoclaving at 121oC for 2 h each day for 3 consecutive days) and autoclaving of all labware and the nitrate working solutions resulted in drastically different results compared to the non-autoclaved treatment. In the non-autoclaved cotton burr compost, added nitrate at 20 mg N L-1 decreased rapidly and was not detected in 3 days; whereas, the autoclaved cotton burr compost showed persistent nitrate at concentration levels above 15.5 mg N L-1 even after 10 days. Treatment using NaN3 at 1000 mg L-1 did not significantly decrease added nitrate concentration and produced results comparable with the steam autoclave sterilization of the compost. Dewaxed cotton burr compost showed decreased nitrate reduction kinetics compared to the pristine cotton burr compost, implying a biotic nature of nitrate reduction. No nitrate reduction was detected in the dewaxed Canadian Sphagnum peat, further supporting the role of microorganisms in nitrogen dynamics in these systems. It is concluded that nitrate reduction and transformation in the solid organic media are controlled by microbiologically mediated processes.