A bench case study was performed on Acid Mine Drainage (AMD) waste from a mine site located near Charleston, WV. The client supplied approximately four (4) gallons of iron bearing AMD waste to LES’ facility on August 5, 1994. The waste sample was clear with a slight yellow tint and contained some suspended solids of a brown-red color. The pH of the raw sample was 7.1. A portion of the feed sample was collected and submitted for iron analysis; the results are presented in Table 1.
The balance of the iron waste was processed through the ENVIRO-CLEAN PROCESS pilot carbon unit. The system consisted of a feed pump, pH controller and two (2) carbon columns. Each column contained about 180 grams of Filtrasorb 400 granular activated carbon, manufactured by Calgon Carbon. Effluent samples were collected and analyzed for total iron. This validation study was conducted to verify the system’s capability to remove iron to acceptable levels. The effluent iron results are presented in Table 1, with the time periods marked in parenthesis, designating when the sample was collected during the test run.
TABLE 1. ENVIRO-CLEAN EFFLUENT ANALYSIS
|Sample #1 (3 hrs)||<0.1|
|Sample #2 (6 hrs)||<0.1|
|Sample #3 (9 hrs)||<0.1|
|Sample #4 (12 hrs)||<0.1|
|Sample #5 (18 hrs)||<0.1|
The processing of the iron waste sample was completed without any mechanical or process difficulties. The effluent was crystal clear with no visible trace of solids or color.
The ENVIRO-CLEAN PROCESS produced an AMD effluent well below the client’s current iron discharge levels (3 mg/l). The activated carbon system’s capability to remove iron from the mining waste stream was demonstrated with removal levels of 99.1%. The feed contained 11.5 mg/l of iron. The average total iron concentration in the effluent was <0.1 mg/l. The effluent was crystal clear and exhibited no trace of color or suspended solids. A capital cost estimate showed a pay back period of less than 12 months, based on current site operating cost.