Up-Scaling from Trial to Operation: Practicalities of Construction and Permitting, Force Crag Mine

摘要

Following successful small-scale compost-based bioreactor (tank size 3.75 m~3; flow rate 1.1 L/min) metal mine treatability trials undertaken by Newcastle University, a full-scale vertical flow pond treatment system was constructed in 2014 at the abandoned Force Crag Mine (Cumbria, UK). Metal concentrations in the mine water are sufficiently high to cause the receiving water course, the Coledale Beck, to fail UK environmental quality standards. The innovative system remediates the baseflow of mine water (6 L/s), which contains elevated concentrations of zinc (3.8 mg/L) in a treatment area of 1250 m~2 with a target residence time of -14 hours.Force Crag is a remote site located within a National Park that is popular with tourists and walkers. The mine site, including the underground workings, buildings and mine surface, are owned and managed by the National Trust (a UK historical conservation charity). Construction of a treatment system in this isolated, open access, rugged area resulted in challenges that needed to be considered in the design process. The novel nature of the treatment technology deployed at the site required any scheme to be designed to enable rigorous scientific investigation of the system to prove the design concept. Furthermore, operational issues (e.g. quantities of gas release) that could result from the full-scale system also needed to be addressed.All of these challenges were overcome, resulting in the successful delivery of a new treatment technology. This paper highlights the engineering and permitting aspects of up-scaling from a trial system to a full-scale novel treatment methodology.