Remediation of Metal Contaminated Simulated Acid Mine Drainage Using a Lab-Scale Spent Mushroom Substrate Wetland

The performance of an innovative pilot-scale spent mushroom substrate wetland for the attenuation of simulated acid mine drainage (SAMD) similar in composition to wastewater from the Irish mining region in Avoca, Co. Wicklow was investigated. The small-scale surface flow wetland, consisting of four cells in triplicate, measuring 0.46 m in width, 0.622 m in length and 0.489 m in depth, received approximately 4.32 l/day of simulated acid mine drainage. Over a period of 800 days, average removal efficiencies of Al (99%), Zn (99%), Cu (99%), Fe (97%) and Pb (97%) were recorded, with no removal noted for Mn. These high removal rates were found to be comparable with other published results and in most cases surpassed removal rates of published results. Despite the reduction in pH and alkalinity over the duration of the trial, the rise in sulphate concentrations and the production of ammonia within the system were of concern, especially if a similar treatment system was utilised on a large-scale basis. Temperature was also found to have an effect on metal removal rates, with poor removal rates recorded at low-temperature events (< 1°C). The high metal removal rates of the system still make it a very attractive and environmentally sustainable remediation technology, which could be further expanded to include other passive treatment technologies, to enhance and increase the longevity of the system.