Tracer Testing to Investigate Hydraulic Performance of a RAPS Treating Mine Water in South Wales

摘要

The Coal Authority commissioned a Reducing and Alkalinity Producing System (RAPS) at Tan y Garn abandoned coal mine, South Wales, UK, in 2006 to treat the acidic mine water discharge. Monitoring of the full-scale, operational scheme over 21/2 years has demonstrated the RAPS has performed well in terms of sustained alkalinity production and also iron removal, despite a progressive decrease in permeability of the vertical flow bed. In order to understand the residence time of mine water within the system a series of ten tracer tests using lithium bromide and sodium chloride were conducted. Analysis of the salt tracer tests yielded a quantitative relationship between the naturally varying flow and the resulting residence time. The measured hydraulic performance is compared with the design expectations. This improved understanding of RAPS hydraulic and chemical performance confirms the appropriateness of published design for this passive mine water treatment method. As a result, The Coal Authority will continue applying the technology to other priority mine water discharges across the UK.