Iron removal in three Pennsylvania wetlands constructed to treat acid mine drainage was evaluated by the U.S. Bureau of Mines. All wetlands were constructed with a mushroom compost substrate and were planted with typha spp. Performance was evaluated by calculating area-adjusted iron loadings and removals as fe g day-1m-2(gdm). An initial model of the iron removal capabilities of constructed wetlands was also evaluated. Relationships between ph, concentration, flow, loading, and removal were considered. At the Somerset site (av. Influent ph = 4.0), Influent iron loading, which was primarily a function of concentration, was considerably more variable than iron removal. The relationship between the two appeared asymptotic, with removal being independent at loadings above 15 gdm (av. Removal = 10.6 Gdm) and averaging 54 pct of loading at loadings less than 15 gdm. At the latrobe site (av. Influent ph = 3.0), Removal averaged 2.7 Gdm at flows > 100 l min-1 and 4.3 Gdm when flow < 100 l min-1. The overall average removal was 3.6 Gdm. At the Friendship Hill Wetland, influent ph was 2.7, and iron removal averaged 3.3 Gdm. Overall, these data were used to develop preliminary wetland-sizing criteria based upon iron loadings. In situations where mine drainage has flow > 50 l min-1 and iron concentration > 50 mg l-1, loading-based criteria result in significantly larger wetlands than conventional flow-based criteria.
Proceeds, 1990 Mng. & Reclamation Conf. & Exhibition. West Virginia Univ. Pub. Serv., V.2, PP. 385-392