title: New perspectives on the passive treatment of ferruginous circumneutral mine waters in the UK.
abstract: This paper examines major physico-chemical processes during the passive treatment of ferruginous circumneutral drainage from abandoned coal mines in the UK. Data collected over several years of studies on mine water treatment systems shed new light on the relative importance of hydraulics, settling velocity, Fe(II) oxidation rates and cascade aeration, which, in turn, informs the design of future systems. This paper demonstrates that (1) the complex settling behaviour of Fe(III) precipitates may be described by a first-order volumetric process and that settling rate is different for different mine waters; (2) the hydraulic efficiency (ratio of time to peak tracer concentration to nominal residence time) of the settling ponds studied was widely variable at low flow rates in comparison to constructed wetlands; (3) aeration cascades contribute dissolved oxygen and lead to a rise in pH due to CO2 degassing, which are very important in reducing the required time for iron oxidation and removal; (4) for at least 10 of the 30 sites examined, modelling of the rates of Fe(II) oxidation and particulate settling reveals that removal of iron is primarily dependent on settling rate; and (5) that substantial increases in pH can be brought about by forced aeration of mine water over several hours. Findings of this study apply to the majority of coal mine water treatment sites in the UK and may have broader application to other ferruginous waters with circumneutral pH or after treatment to increase pH.
authors: Cardiff School of Engineering, Cardiff University, Queen's Buildings, The Parade, Cardiff, CF24 3AA, UK, sapsfordDJ@cf.ac.uk.
authors: D J
authors: DJ
authors: Sapsford
mesh_terms: D052918:Environmental Restoration and Remediation; D005290:Ferric Compounds / Q000032:analysis*; D008906:Mining; D010084:Oxidation-Reduction; D006113:United Kingdom; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000032:analysis*; D018508:Water Purification / Q000379:methods*; D053833:Wetlands
chemical_list: D005290:Ferric Compounds; D014874:Water Pollutants, Chemical
references: Water Res. 2009 Feb;43(2):423-32
references: 19022469
references: Water Sci Technol. 2010;62(8):1937-46
references: 20962411