Permeable Reactive Barriers
(Proceedings of the International Symposium held at Belfast, Northern Ireland, March 2004). IAHS Publ. 298, 2005, 117-122.Remediation of acidic colliery spoil leachate in a hybrid passive treatment system comprising a permeable reactive barrier, ponds and a reedbed (Shilbottle, Northumberland, UK)
PAUL L. YOUNGER & MAHMOUD MOUSTAFA
School of Civil Engineering and Geosciences, Drummond Building, University of Newcastle, Newcastle upon Tyne NE1 7RU, UK
Abstract Highly acidic spoil leachates at the former Shilbottle Grange Colliery site (Northumberland, UK) have been constrained to flow through a permeable reactive barrier (PRB) containing a mixture of limestone gravel, horse manure and composted green waste. Leachates leave the PRB through a seepage face, draining into ponds and a reedbed. Iron concentrations decrease across the system from >800 mg l-1 to ~ 10 mg l-1. Iron loading reduction is about 98%. While pH rises from 4 to 6 in the PRB, subsequent precipitation of metals as hydroxides and hydroxysulphates leads to the apparent paradox of simultaneous decreases in both total acidity and pH. The PRB removes about 30% of the sulphate (by reductive precipitation of metal sulphides), while the lagoons and reed bed together remove another 20% (as hydroxy-sulphate precipitates). The system as a whole reduces the sulphate content of the raw water by 50%.
Key words
acidic mine drainage; geochemistry; groundwater; mining; permeable reactive barrier; pollution; remediation; treatment; spoil; UK; wetlands