Centripetal filtration of groundwater to improve the lifetime of an MgO recycled refractory filter: observations and technical challenges
- 49 Downloads
In the context of improving permeable reactive barrier (PRB) filters, axial and a centripetal column tests were performed to compare their evolution in terms of chemical and hydraulic performances. For both tests, the MgO reactive media, made of crushed (< 10 mm) spent MgO–C refractory bricks was used to treat water contaminated with Co and Ni by raising the pH and promoting hydroxide precipitation. As opposed to the traditional cylindrical axial configuration, the centripetal column consists of an annulus of reactive media through which the water flows from the outer radius towards the inner radius. Under similar conditions (total reactive mass, porosity), the centripetal column is expected to delay the breakthrough of contaminants because of its higher cross-section and lower flow speeds at the entrance of the media. However, as we found in this study, the design of a granular radial filter poses several technical problems. Indeed, a breakthrough of the contaminants, accompanied by a decline in pH, was observed much sooner in the centripetal (100 pv) than in the axial (375 pv) filter. This lower performance was deemed to be due to a hydraulic shortcut and was supported by the results of a tracer test (average renewal volume much lower (199 ml) than the theoretical one (7530 ml)) as well as the observation of preferential clogging upon dismounting the radial filter. While the design of a filter that induces a purely radial flow still poses a technical challenge, this study contributes to advance the knowledge for centripetal radial filtration of groundwater in PRBs.
KeywordsPermeable reactive barriers Magnesium oxide Metals precipitation Radial filtration Groundwater
The authors would like to thank the Fonds de recherche du Québec – Nature et technologies, the Natural Sciences and Engineering Research Council of Canada and Blumetric Environmental Inc. for supporting this research.
- Bildstein O (1998) Modélisation géochimique des interactions eau-gaz-roche. Application à la diagenèse minérale dans les réservoirs géologiques [Geochemical modeling of water-gas-rock interactions. Application to mineral diagenesis in geological reservoirs] (Doctoral thesis). University of Strasbourg 1, Strasbourg, FranceGoogle Scholar
- Courcelles B (2012) Radial Filtration in permeable reactive barriers. IJEPR 1:107–113Google Scholar
- ITRC (2011) Permeable reactive barrier: technology update (No. PRB-5). Interstate Technology & Regulatory Council, PRB: Technology Update Team, Washington, D.C.Google Scholar
- Lowell PS, Meserole FB, Parsons TB (1977) Precipitation chemistry of magnesium sulfite hydrates in magnesium oxide scrubbing (No. EPA/600/7-77/109). U.S. Environmental Protection Agency, Office of Research and Development, Washington, D.C.Google Scholar
- Terringo J III (1987) Magnesium hydroxide reduces sludge/improves filtering. Pollut Eng 19:78–83Google Scholar
- USEPA (2008) Green remediation: incorporating environmental practices into remediation of contaminated sites (No. EOA 542-R-08-002). U.S. Environmental Protection Agency, Office of Solid Waste and Emergency ResponseGoogle Scholar