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Le~dv[le, CO, Tiiger Trannel MiW neutralization experiment. <br />Flowing MIW o~rer llimestone (CaC[]3). AK. o~ji~/as. <br />~4a <br />Lao <br />160 <br />14Q <br />~i <br />~ 12.0 <br />+• <br />c <br />a 140 <br />C <br />6 <br />N <br />'} ~_a <br />60 <br />40 <br />Z~ <br />~sno <br />:,; l,'i i <br />15 Ceti <br />1uG0 <br />J.: C' <br />Discussion and Conclusions: <br />Our goal was to neutralize synthetic Tiger Tunnel MIW in the presence of limestone <br />alone or limestone/pebble lime mixtures. Additionally, we hoped to see precipitation of <br />iron and aluminum by conversion of their sulfate forms to oxides with an increase of pH. <br />Our iiutial experiments in batch reactors where there was no change of basic rock <br />(limestone or limestone/pebble lime mixtures) or volume of water demonstrated that the <br />presence of pebble lime caused the pH to go beyond the neutral point and also caused <br />heat-generating reactions. In the batch reactor containing a 25% pebble lime/limestone <br />mixture, the reaction damaged the reaction vessel. Limestone alone did bring the <br />synthetic Tiger Tuiulel MIW's pH up to pH = 6 within 1 day. Thus, we decided to work <br />with limestone alone in order to keep the reaction stable (i.e. not heat-generating or <br />explosive) and because the pH eventually lut the neutral target mark. <br />We used limestone alone with synthetic Tiger Tunnel MIW when designing the flow <br />system based on our above-described batch reactor data. An average hydraulic residence <br />time (HRT) of 0.67 days was insufficient to increase the pH to 6 after 11 days of <br />operation. The flow-through reactor should reach steady state conditions within a time <br />period equal to 3 hydraulic residence time (2 days for a HRT of 0.67 days). <br />ICP-AES data showed that the amount of calcium concentration increased to almost <br />2000% of the influent water and the amounts of copper and aluminum dropped to almost <br />zero at day 9 but then increased again (Figure 2). The amount of iron dropped minimally, <br />to approximately 75% of the influent water. The increase of copper and alununum may <br />have resulted from the physical disturbance of the reactor vessel. <br />Frg~ter~oa EP~-re1x~rt, Jztne ?~, 200<~ 4 <br />:7 2 4 5 , LG 1:'_ <br />TYIfYfe (clays} <br />