Constructed Wetlands for Minewater Treatment: Environmental Benefits and Ecological Recovery

Abstract

The ecology of the River Pelenna (in South Wales) was impoverished by polluted discharges from abandoned coal mines. A series of passive constructed wetlands was created in order to treat these discharges and to improve the ecology of the river. A three‐year Environment Agency R&D project investigated the performance, environmental benefits and sustainability of the constructed wetlands. It showed that the treatment systems were removing most of the iron contamination. In the reaches downstream from the minewaters, the dissolved‐iron concentration quickly dropped below the target level. Invertebrate abundance, trout and riverine bird populations increased in following years. However, occasional overflows from the systems have significantly affected the ecology of one stretch of river. The research work has provided an insight into the potential for ecological recovery associated with future minewater treatment.

Natural Wetlands Are Efficient at Providing Long-Term Metal Remediation of Freshwater Systems Polluted by Acid Mine Drainage

“…In this study, downstream (sites S3–S5) benthic invertebrate diversity showed a 3-fold improvement over a 7-year period following 2003, although it has not yet reached the diversity present in the non-AMD polluted tributary. Previous assessments of AMD recovery using benthic invertebrates showed a similar improvement; however, those systems were less severely impacted than the Afon Goch, with a pre- and post- remediation pH of 5.5 and 7.5 respectively, and lower metal concentrations. , This study on the Afon Goch therefore shows that even in severely polluted and acidic systems the benthic fauna can show relatively rapid and substantial recovery once efficient remediation measures are implemented.…”

“…Although a number of studies have detailed the negative impact of AMD on river biota, only a few have looked at biotic recovery following remediation. 37 In this study, downstream (sites S3−S5) benthic invertebrate diversity showed a 3-fold improvement over a 7-year period following 2003, although it has not yet reached the diversity present in the non-AMD polluted tributary. Previous assessments of AMD recovery using benthic invertebrates showed a similar improvement; however, those systems were less severely impacted than the Afon Goch, with a pre-and post-pH of 5.5 and 7.5 respectively, and lower metal concentrations.…”

“…In addition to quantifying efficiency of AMD remediation, it is essential that improvement is validated by assessment of chemical and biological quality of the downstream water course. Although a number of studies have detailed the negative impact of AMD on river biota, only a few have looked at biotic recovery following remediation . In this study, downstream (sites S3–S5) benthic invertebrate diversity showed a 3-fold improvement over a 7-year period following 2003, although it has not yet reached the diversity present in the non-AMD polluted tributary.…”

“…Previous assessments of AMD recovery using benthic invertebrates showed a similar improvement; however, those systems were less severely impacted than the Afon Goch, with a pre-and post-pH of 5.5 and 7.5 respectively, and lower metal concentrations. 37,38 This study on the Afon Goch therefore shows that even in severely polluted and acidic systems the benthic fauna can show relatively rapid and substantial recovery once efficient remediation measures are implemented.…”