Use of successive alkalinity-producing systems (SAPS) for treatment of acidic mine drainage (AMD) has grown in recent years. However, inconsistent performance has hampered widespread acceptance of this technology. This research was conducted to determine the influence of system design and influent AMD chemistry on net alkalinity generation by SAPS. Monthly observations were obtained from eight SAPS cells in southern West Virginia and southwestern Virginia. Analysis of these data revealed strong, positive correlations between net alkalinity generation and three variables: the natural log of limestone residence time, influent dissolved Fe concentration, and influent non-Mn acidity. A statistical model was constructed to describe SAPS performance. Subsequent analysis of data obtained from five systems in western Pennsylvania (calibration data set) was used to reevaluate the model form, and the statistical model was adjusted using the combined data sets. Limestone residence time exhibited a strong, positive logarithmic correlation with net alkalinity generation, indicating net alkalinity generation occurs most rapidly within the first few hours of AMD-limestone contact and additional residence time yields diminishing gains in treatment. Influent Fe and non-Mn acidity concentrations both show strong positive linear relationships with net alkalinity generation, reflecting the increased solubility of limestone under acidic conditions. These relationships were present in the original and the calibration data sets, separately, and in the statistical model derived from the combined data set. In the combined data set, these three factors accounted for 68% of the variability in SAPS systems performance.

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Successive Alkalinity-Producing Systems (SAPS) have proven to be a successful technology for renovating acidic mine drainage (AMO). This study was conducted to serve as a basis for development of guidelines to aid in the design of future systems. Performance of field systems and laboratory columns were monitored and modeled. The field study examined eight SAPS systems located in Virginia and West Virginia. Monthly performance data were collected on each system for periods of2 to 5 years. The laboratory SAPS columns were operated for 13 months to measure the water chemistry changes as the AMO flowed down through the columns. All SAPS systems demonstrated an ability to generate alkalinity and/or neutralize acidity. Analysis of water-chemistry data collected from the field systems revealed significant correlations between alkalinity production and the natural log of residence time, influent total iron, and influent non-Mn acidity. The laboratory column study revealed seasonal variations in dissolved oxygen removal below the organic compost layer of these systems. During the colder months, sub-compost dissolved oxygen levels did not reach the I mg/I maximum concentration that is recommended to prevent limestone armoring. These studies revealed several concepts that can be used to guide SAPS system design: Alkalinity production appears to increase in response to residence time as a log-normal function; alkalinity production tends to vary in response to influent acidity; and a compost-residence time may be an important design element in order to achieve oxygen removal necessary for optimizing SAPS system performance.