Nitrate removal by denitrification using 'captor' media

Abstract

In many areas throughout the U.S. groundwater supplies are contaminated by nitrates in excess of the standard of 10 mg/L (as N)mandated by the Safe Drinking Water Act of 1974 and its subsequent amendments. The nitrate standard is based on the fact that nitrates can cause infant methemoglobinemia and it also may lead to the possible formation of nitrosoamines, which are known carcinogens. Economic methods for the removal of nitrates from water supplies are needed to mitigate the problems caused by this pollutant. The research results presented herein used an attached growth biological denitrification process using a new media called 'captor'. 'Captor' media denitrification was determined in a packed column and compared with a conventional packing media; e.g., 1" flexiring. The synthetic feed simulating ground water quality had nitrate levels varying from 10-30 mg/L. Methanol was added as a carbon source with NO3:methanol ratio of 1:4. At all loading rates (0.2 to 1.2 Kg/m3/d) the "Captor" media performed better than the flexiring media. The percent NO3^--N removal decreased exponentially for both systems as the loading rates were increased. Even at NO3^--N loading rate of up to 0.7 Kg/m^3/d, the "Captor" column removed greater than 80 percent of the incoming NO3^--N . The reduction of empty bed contact time (EBCT) from 60+ minutes to 20+ minutes reduced the NO3^--N removal efficiency markedly, even though the loading rate was reduced from 0.7 to 0.4 Kg/m^3/d. Thus, it seems that EBCT is a very important parameter for evaluating the removal efficiency of attached growth denitrification process.

This material is based upon work supported by the U.S. Geological Survey and the Missouri Water Center under the Grant/Cooperative Agreement.

The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the opinions or policies of the U.S. Geological Survey or Missouri Water Center. Mention of trade names or commercial products does not constitute their endorsement by the U.S. Geological Survey or Missouri Water Center.