BIOCHEMICAL REDUCTION OF NITRATE LEVELS IN WATER SYSTEMS BY BACTERIA IN DECOMPOSING ORGANIC MATTER

  Tim Schramm, Jacob Becker, and Duane Bartak

   The capability of denitrifying bacteria to reduce nitrate levels in water was tested using wood chips as the organic matter needed to sustain respiration.  Both distilled water and water taken from a natural lake were spiked to 100 parts per million nitrate (22.58 ppm nitrogen) and were introduced to aged oak wood chips in 1liter flasks.  The effects of stirring were examined.  The nitrate levels were monitored over various time intervals via ion chromatography.  Over the first 25 hours of contact with the wood chips, the nitrate concentration was decreased by 50% and was depleted by 98% over the course of five days. The same wood chips used were then introduced to more nitrate spiked water and the nitrate levels were depleted even faster.  A seven-foot drainage tile packed with wood chips was also set up in order for spiked water to percolate through the wood chips.  Preliminary tests show the nitrate concentration is reduced by 40% after four passes through the tile and it is reduced by 80% after seven.  Nitrite analysis was also carried out in order to demonstrate that the nitrate ions were being reduced to nitrite ions.  The data suggested the nitrite was further reduced to nitrogen gas by the bacteria on the wood chips.

This research was funded in part by the Roy J. Carver Charitable Trust and the Iowa Space Grant Consortium.