A five-year performance review of field-scale, Slow-release permanganate candles with recommendations for second-generation improvements

Mark Christenson, Ann Kambhu, James Reece, Steve Comfort, Laurie Brunner

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

In 2009, we identified a TCE plume at an abandoned landfill that was located in a low permeable silty-clay aquifer. To treat the TCE, we manufactured slow-release potassium permanganate cylinders (oxidant candles) that had diameters of either 5.1 or 7.6 cm and were 91.4 cm long. In 2010, we compared two methods of candle installation by inserting equal masses of the oxidant candles (7.6-cm vs 5.1-cm dia). The 5.1-cm dia candles were inserted with direct-push rods while the 7.6-cm candles were housed in screens and lowered into 10 permanent wells. Since installation, the 7.6-cm oxidant candles have been refurbished approximately once per year by gently scraping off surface oxides. In 2012, we reported initial results; in this paper, we provide a 5-yr performance review since installation. Temporal sampling shows oxidant candles placed in wells have steadily reduced migrating TCE concentrations. Moreover, these candles still maintain an inner core of oxidant that has yet to contribute to the dissolution front and should provide several more years of service. Oxidant candles inserted by direct-push have stopped reducing TCE concentrations because a MnO2 scale developed on the outside of the candles. To counteract oxide scaling, we fabricated a second generation of oxidant candles that contain sodium hexametaphosphate. Laboratory experiments (batch and flow-through) show that these second-generation permanganate candles have better release characteristics and are less prone to oxide scaling. This improvement should reduce the need to perform maintenance on candles placed in wells and provide greater longevity for candles inserted by direct-push.

Original languageEnglish (US)
Pages (from-to)239-247
Number of pages9
JournalChemosphere
Volume150
DOIs
StatePublished - May 1 2016

Fingerprint

Oxidants
oxidant
trichloroethylene
Oxides
oxide
well
Potassium Permanganate
Waste Disposal Facilities
inner core
silty clay
Groundwater
recommendation
permanganic acid
Land fill
Aquifers
Potassium
landfill
Clay
Dissolution
potassium

Keywords

  • Chlorinated solvents
  • Permeable reactive barrier
  • Second-generation permanganate candles
  • Slow-release oxidants
  • TCE

ASJC Scopus subject areas

  • Environmental Engineering
  • Environmental Chemistry
  • Chemistry(all)
  • Pollution
  • Health, Toxicology and Mutagenesis

Cite this

A five-year performance review of field-scale, Slow-release permanganate candles with recommendations for second-generation improvements. / Christenson, Mark; Kambhu, Ann; Reece, James; Comfort, Steve; Brunner, Laurie.

In: Chemosphere, Vol. 150, 01.05.2016, p. 239-247.

Research output: Contribution to journalArticle

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