Treatment of acidic seepage employing wetland ecology and microbiology : final report

This project focuses on the treatment and amelioration of acid mine drainage (AMD) from mining wastes using natural microbial processes which occur in wetlands and sediments. Conceptually this should be possible, as acid-generation is a natural process and the stabilizing reactions which are alkalinity-generation, should also occur in nature. Since 1986, experiments have been carried out in AMD water, with the aim to determine which conditions will produce alkalinity generation. Sufficiently encouraging data had been assembled by 1988 to formulate the basis of MEND project 3.11.1: Treatment of Acidic Seepage Employing Wetland Ecology and Microbiology, funded by INCO, Environment Canada, Energy Mines and Resources and Denison Mines Limited. The main objective of this project is to determine the key design parameters for Acid Reduction Using Microbiology or the ARUM process within 4 years. This report summarizes the data obtained in various field and laboratory experiments since 1988. It describes the construction and development of the test cell system in which, through flow control, the relationships between amendment quantity, flow rates and seepage characteristics are being tested. Precipitate formation is studied and its accumulation is quantified. Cattail growth is studied under highly acidic conditions and the alkalinity-generation in severe AMD is tested. The key conclusions to date are, that microbial alkalinity-generation has been initiated in the ARUMATORS and has prevailed in the lower parts of test cells with amendment curtains at low flow conditions. Data are presented which demonstrate that acidity in AMD water has been replaced by alkalinity. The test cell system is functional. Low flow conditions of 3-5 L/min have been maintained for long periods, and the system has handled maximum flows in excess of 300 L/min. The relationship between the quantity of amendment and the onset of the ARUM process at low flow conditions is being tested during the remainder of the 1990 season. With data produced to date, it was possible to define the basic configuration which is required for a functional ARUM AMD treatment system