HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Rötting, T. S. Articles by Carrera, J. Search for Related Content PubMed PubMed Citation Articles by Rötting, T. S. Articles by Carrera, J. Agricola Articles by Rötting, T. S. Articles by Carrera, J. Related Collections Water Quality Heavy Metals Water Pollution

TECHNICAL REPORTS

Heavy Metals in the Environment

Passive Treatment of Acid Mine Drainage with High Metal Concentrations Using Dispersed Alkaline Substrate

^a Hydrogeochemical Engineering Res. and Outreach Group, Sir Joseph Swan Inst. for Energy Res., 3rd Floor, Devonshire Bldg., Devonshire Terrace, Newcastle Univ., Newcastle on Tyne, NE1 7RU, UK
^b Inst. of Earth Sciences Jaume Almera, CSIC, Lluis Solé i Sabarís s/n, 08028 Barcelona, Spain
^c CH2M Hill, Northpark 400, 1000 Abernathy Rd., Suite 1600, Atlanta, GA 30328

^* Corresponding author (Tobias.Roetting{at}newcastle.ac.uk).

Received for publication October 1, 2007. Passive treatment systems based on the dissolution of coarse calcite grains are widely used to remediate acid mine drainage (AMD). Unfortunately, they tolerate only low metal concentrations or acidity loads, because they are prone to passivation (loss of reactivity due to coating) and/or clogging (loss of permeability) by precipitates. To overcome these problems, a dispersed alkaline substrate (DAS) composed of a fine-grained alkaline reagent (calcite sand) mixed with a coarse inert matrix (wood chips) was developed. The small grains provide a large reactive surface and dissolve almost completely before the growing layer of precipitates passivates the substrate, whereas the dispersion of nuclei for precipitation on the inert surfaces retards clogging. Chemical and hydraulic performance of DAS was investigated in two laboratory columns fed at different flow rates with natural AMD of pH 2.3 to 3.5 and inflow net acidity 1350 to 2300 mg/L as CaCO₃. The DAS columns removed 900 to 1600 mg/L net acidity, 3 to 4.5 times more than conventional passive treatment systems. Regardless of the flow rate employed, Al, Fe(III), Cu, and Pb were virtually eliminated. Minor Zn, Ni, and Cd were removed at low flow rates. High acidity removal is possible because these metals accumulate intentionally in DAS, and their precipitation promotes further calcite dissolution. During 15 mo, DAS operated without clogging at 120 g acidity/m²·d, four times the loading rate recommended for conventional passive systems; DAS may therefore be capable of treating AMD at sites where influent chemistry precludes the use of other passive systems.

Abbreviations: ALD, Anoxic Limestone Drains • AMD, acid mine drainage • DAS, dispersed alkaline substrate • EDS, energy dispersive system • ICP-AES, inductively coupled plasma atomic emission spectroscopy • ICP-MS, inductively coupled plasma mass spectroscopy • LBOS, limestone-buffered organic substrate • RAPS, Reducing and Alkalinity Producing Systems • SEM, scanning electron microscope • TIC, total inorganic carbon