MINIMIZATION OF ROCK PILE LEACHATE FORMATION AND METHODS OF TREATING ROCK PILE LEACHATES
Methods of treating leachates in rock piles. Exemplary leachates include neutral aqueous leachates containing selenates and nitrates, said leachates being found in waste rock piles from coal mining operations. In certain embodiments, the method includes introducing an inert gas to the lower section of the rock pile, and allowing bacteria indigenous to the mining site to reduce the selenates and nitrates to selenium and nitrogen, respectively.
1 . A method comprising:
identifying a site having an active rock pile with a top, a bottom, an upper section, and a lower section, said lower section containing oxygen, bacteria, and an aqueous leachate, wherein the aqueous leachate comprises at least one of a selenate or a nitrate, and wherein the bacteria are indigenous to the site;
displacing the oxygen from at least a portion of the lower section of the active rock pile; and
allowing the bacteria to reduce the at least one selenate or nitrate to elemental selenium or nitrogen gas, respectively;
wherein the site comprises an active rock pile in which waste material have been added; and
wherein filler is added to the active rock pile.
2 - 4 . (canceled)
5 . The method according to claim 1 , wherein the aqueous leachate comprises a pH of about 7 to about 9.
6 . The method according to claim 1 , wherein the aqueous leachate comprises a pH of about 7.5 to about 8.8.
7 . The method according to claim 1 , wherein the indigenous bacteria are selected from at least one of Albidiferax spp., Polaromonas spp., Thiobacillus spp., or Sulfuritalea spp.
8 . The method according to claim 1 , wherein displacing the oxygen comprises injecting an inert gas into the lower section of the active rock pile.
9 . The method of claim 8 , wherein the inert gas comprises nitrogen.
10 . The method according to claim 8 , wherein the injecting comprises sparging the inert gas into perforated pipes penetrating the lower section of the active rock pile.
11 . The method of claim 10 , wherein the perforated pipes penetrate the lower section of the active rock pile horizontally.
12 . The method of claim 1 , wherein the lower section of the active rock pile extends from the bottom to a position halfway between the bottom and the top.
13 . The method of claim 12 , wherein displacing the oxygen comprises introducing an inert gas into the lower section of the active rock pile.
14 . The method of claim 13 , wherein the inert gas is introduced to the lower section of the active rock pile at a location that is closer to the bottom than the position halfway between the bottom and the top.
15 . The method of claim 8 , wherein the inert gas comprises a humidified inert gas.
16 . The method of claim 1 , wherein the method excludes the use of a cover on the top of the active rock pile.
17 . The method of claim 1 , wherein the method excludes the use of passivation or armoring.
18 - 24 . (canceled)
25 . The method of claim 23 , A method comprising:
identifying a waste rock material;
crushing the waste rock to form a rock pile, wherein the rock pile has a void volume of 5% or less;
wherein the rock pile further comprises a filler; and
wherein the filler is selected from at least one of ferrous sulfide, ferric chloride, Fe 0 , aluminum hydroxide, ferric hydroxide, calcium carbonate, magnesium carbonate, or quarry minerals.
26 . The method of claim 1 , wherein the active rock pile is derived from a process comprising:
the method of claim 25 .
27 . The method according to claim 1 , wherein the indigenous bacteria are chemolithotrophic.
28 . The method according to claim 1 , wherein the active rock pile comprises a cover on top of the active rock pile.
29 . The method according to claim 1 , wherein the the filler is selected from at least one of ferrous sulfide, ferric chloride, Fe 0 , aluminium hydroxide, ferric hydroxide, calcium carbonate, magnesium carbonate, or quarry minerals.
30 . The method according to claim 1 , wherein the active rock pile has a void volume of 5% or less.