Use of Polymer Mats in Series for Sequential Reactive Barrier Remediation of Ammonium-Contaminated Groundwater: Field Evaluation

B.M. Patterson, M.E. Grassi, B.S. Robertson, G.B. Davis, A.J. Smith, Allan Mckinley

Research output: Contribution to journalArticle

22 Citations (Scopus)

Abstract

A pilot-scale field trial was undertaken to evaluate the potential of in situ polymer mats (installed in series) as permeable reactive barriers within a treatment wall remediation system to induce sequential bioremediation of ammonium-contaminated groundwater. The treatment wall consisted of 10 m wide impermeable wings on either side of a 0.75 m wide permeable reactive zone flow-through box. Two polymer mats were positioned in the flow-through box. The upgradient polymer mat within the flow-through box was used to deliver oxygen to induce bacterial nitrification of the ammonium to nitrite/nitrate as the groundwater moved past. The downgradient polymer mat delivered ethanol to induce bacterial denitrification of the nitrite/nitrate to produce nitrogen gas. The field trial was carried out at a near-shore location. Initially the flow-through box was left open; however, this resulted in substantial groundwater mixing, which inhibited sequential remediation. Once the flow-through box was in-filled with gravel, groundwater mixing was reduced, achieving a greater than 90% reduction in total N. Estimated first-order half-lives for nitrification and denitrification rates were 1.2 and 0.4 d, respectively. Field nitrification half-lives were approximately an order of magnitude greater than rates determined in large-scale columns using soil and groundwater from the site, while denitrification half-lives were similar. The results of this pilot-scale field trial indicate that sequential bioremediation of ammonium-contaminated groundwater at field scale is feasible using in situ polymer mats as permeable reactive barriers, although hydraulic conditions can be complex in such barrier systems.
Original languageEnglish
Pages (from-to)6846-6854
JournalEnvironmental Science & Technology
Volume38
Issue number24
DOIs
Publication statusPublished - 2004

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