In-situ remediation of nitrate-contaminated ground water by electrokinetics iron wall processes

The feasibility of using electrokinetics coupled with a zero valent iron (F e-0) treatment wall to abiotically remediate nitrate-contaminated soils was investigated. Upon completion of each test run, the contaminated soil spec imen was sliced into five parts and analyzed for nitrate-nitrogen, ammonia- nitrogen and nitrite-nitrogen. Nitrogen mass balance was used to determine the major transformation products. In control experiments where only electr okinetics was used at various constant voltages, 25 to 37% of the nitrate-n itrogen was transformed. The amount of nitrate-nitrogen transformed improve d when a Fe-0 wall (20 g or about 8-10% by weight) was placed near the anod e. For test runs at various constant voltages, the amount of nitrate-nitrog en transformed ranged from 54 to 87%. By switching to constant currents, th e amount of nitrate-nitrogen - transformed was about 84 to 88%. The major t ransformation products were ammonia-nitrogen and nitrogen gases. Nitrite-ni trogen was less than 1% in all experimental runs. Two localized pH conditio ns exist in the system, a low pH region near the anode and a high pH region near the cathode. Placing of an iron wall near the anode increases the pH in that area as time increases. Movement of the acid front did not flush ac ross the cathode. This research has demonstrated that the electrokinetics/i ron wall process can be used to remediate nitrate-contaminated groundwater. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.