9th INTERNATIONAL MINE WATER CONGRESS Construction of a novel Permeable Reactive Barrier (PRB) at Shilbottle, Northumberland, UK: engineering design considerations and preliminary performance assessment * Bowden Lawrence I. , Jarvis Adam, Orme Patrick, Moustafa M, Younger Paul L. Hydrogeochemical Engineering Research and Outreach group, Institute for Research on the Environment and Sustainability, University of Newcastle, Newcastle upon Tyne, UK. NE1 7RU. E-mail:
[email protected]; Tel: +44 (0)191 246 4896 Keywords: Permeable reactive barrier, Acid mine drainage, colliery spoil, treatment ABSTRACT A 170 m long PRB was installed, in two sections, for the treatment of acidic (ca. pH 4), metal-rich (ca. 700 mg/L Fe, 300 mg/L Al and 240 mg/L Mn) spoil heap leachate at Shilbottle, Northumberland, in summer 2002. The PRB is a compost-based system comprising 50% aggregate, 25% horse manure and 25% green waste compost. The barrier is 3 m deep and 2 m wide, with a nominal hydraulic retention time of 48 hours. Since commissioning the system has consistently improved water quality, with approximate removal efficiencies of 96% for Fe, 78% for Zn, 71% for Ni, 52% for Mn, and 59% for SO4. The extent of removal of ‘problematic’ metals such as Mn and Zn is particularly encouraging. The exact nature of the contaminant removal mechanisms is discussed. After 2½ years of operation the treatment system, although still operating effectively, is in need of some maintenance. These maintenance requirements are outlined, and their implications for future PRB system design are discussed. INTRODUCTION Acidic mine drainage (AMD) is a much documented problem afflicting mining regions (Nordstrom & Alpers, 1999; Younger et al., 2002).