Abstract: CL:AIRE (Contaminated Land: Applications in Real Environments) is a public-private partnership which was established in 1999 to encourage the demonstration of remediation research and technologies on contaminated sites throughout the UK. Project proposals are submitted to CL:AIRE and reviewed and approved by the CL:AIRE Technology & Research Group. CL:AIRE provides independent verification of its projects and plays a crucial role in the dissemination of project information. During the course of the project, progress is reported through the newsletter, CL:AIRE view, which is mailed free of charge to a database of more than 4500 stakeholders with an interest in contaminated land. Progress is also tracked on the CL:AIRE website at www.claire.co.uk. On completion of the project, a project report is published and a one page summary fact sheet is prepared. The fact sheet is distributed to our database subscribers and posted on the website. The project is also presented at the CL:AIRE Annual Project Conference. In addition, aspects of the research which have practical application will be published as CL:AIRE Research Bulletins. Acid mine waters discharging from abandoned mines represent a significant environmental problem in many parts of the UK. Considerable research has been carried out to understand the geochemical process involved, and the knowledge has been used to manage groundwater discharge through physical/chemical treatment and constructed wetlands. CL:AIRE supports the development of a national site for wetland research managed by the University of Newcastle and will encourage collaborative research projects to be submitted through CL:AIRE. CL:AIRE is currently supporting two projects which demonstrate remediation of acid mine drainage and is disseminating the results of this and other research to improve confidence in the use of these techniques.

Abstract: Seven kilometres of the River Pelenna in South Wales were impacted for approximately 30 years by discharges from abandoned coal mines. Elevated iron and low pH caused significant ochreous staining and had detrimental effects on the river ecology. The River Pelenna Mine water project constructed a series of passive wetland treatment systems to treat these discharges. Monitoring of the performance and environmental benefits of these has been undertaken as part of an Environment Agency R&D project. This project has assessed the changes in water quality as well as monitoring populations of invertebrates, fish and birds between 1993 and 2001. Performance data from the wetlands show that on average the three systems are removing between 82 and 95% of the iron loading from the mine waters. In the rivers downstream, the dissolved iron concentration has dropped to below the Environmental Quality Standard (EQS) of 1 mg/L for the majority of the time. Increases in pH downstream of the discharges have also been demonstrated. Trout (Salmo trutta) recovered quickly following mine water treatment, returning the next year to areas that previously had no fish. Intermittent problems with overflows from the treatment systems temporarily depleted the numbers, but the latest data indicate a thriving population. The overflow problems and also background episodes of acidity have affected the recovery of the riverine invertebrates. However, there have been gradual improvements in the catchment, and in the summer of 2001 most sites held faunas which approached those found in unpolluted controls. Recovery of the invertebrate fauna is reflected in marked increases in the breeding success of riverine birds between 1996 and 2001. This study has shown that constructed wetlands can be an effective, low cost and sustainable solution to ecological damage caused by abandoned mine drainage.

Abstract: This paper provides a 'state of the art' overview of active mine water treatment. The paper discusses the process and reagent selection options commonly available to the designer of an active mine water treatment plant. Comparisons are made between each of these options, based on technical and financial criteria. The various different treatment technologies available are reviewed and comparisons made between conventional precipitation (using hydroxides, sulphides and carbonates), high density sludge processes and super-saturation precipitation. The selection of reagents (quick lime, slaked lime, sodium hydroxide, sodium carbonate, magnesium hydroxide, and proprietary chemicals) is considered and a comparison made on the basis of reagent cost, ease of use, final effluent quality and sludge settling criteria. The choice of oxidising agent (air, pure oxygen, peroxide, etc.) for conversion of ferrous to ferric iron is also considered. Whole life costs comparisons (capital, operational and decommissioning) are made between conventional hydroxide precipitation and the high density sludge process, based on the actual treatment requirements for four different mine waters.