PASSIVE TREATMENT OF ACID MINE DRAINAGE USING COAL COMBUSTION BY- PRODUCTS AND SPENT MUSHROOM SUBSTRATE: RESULTS OF COLUMN STUDY

摘要

A column study was conducted to evaluate the feasibility of using of coal combustion byproducts (CCB) as alkaline materials in a field scale downflow constructed wetlands for acid mine drainage treatment Five columns (15.24 cm in diameter and 91.44 cm high) were constructed and filled with a combination of spent mushroom substrate (SMS) and one of three alkaline materials (limestone, hydrated fly ash, or fluidized bed ash). The five mixtures utilized were 10 percent fluidized bed ash/40 percent limestone (FBA/LS), 10 percent fluidized bed ash (FBA), 50 percent limestone (LS), 50 percent hydrated fly ash (HFA), and 50 percent sieved (>1.5 cm) hydrated fly ash (S. HFA) with the remainder as SMS on a w/w basis. Column received synthetic acid mine drainage containing, 400 mg/L iron, 59 mg/L aluminum, 11 mg/L manganese, 50 mg/L magnesium, 40 mg/L calcium, and 1200 mg/L sulfate for 5 months. Anoxic conditions in the influent reservoirs were maintained by a positive nitrogen pressure head. Flow rates of 2.0 mL/minute to each column were maintained by a miltichannel peristaltic pump. For all columns, effluent acidity concentrations were less than influent acidity concentration (877+-30, n=75). Mean effluent acidity concentrations were 241 mg/L (FBA/LS), 186 mg/L (FBA), 419 mg/L (LS), -28.5 mg/L (HFA), and 351 mg/L (S. HFA), respectivey. While all column produced measurable alkalinity, only the HFA column produced a net alkaline discharge. The results or these column studies are applicable to the design and sizing of innovative field scale systems using alkaline-rich CCB's.