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<br />Table 3. Comparison of Net NP values. <br /> Net NP in kg CaCO~/t <br />Sample <br /> NAP' ABA= MOD ABA B.C.Initial' Mineralogy' <br />itKl -7,7 -5.7 0.8 -14 -8.8 <br />ItK2 5.1 8.5 18 -10 -l4 <br />RK3 -39' ~0' -40' 22' -08' <br />21C4 -103' -81' -71' -57' ~7' <br />7'1.1 0.0 ~.2 3.3 -1.8 -5 <br />17.2 -14 -29" -20 -17 -24' <br />77-3 -2.6 -26' -1.7 -20 -44' <br />1Z4 -71' ~6' -58' ~9' -55' <br />71S -86' -147' -140' -120" -131" <br />17.6 -59' -84' -78' -103' -136' <br />' Modification described in this paper. <br />= Method of Sobek et al. (1978). <br />' Method of Lawrence (1990). <br />' Method of Duncan and Bruyuesteyn (1979). <br />3 APP based on sulfide sulfur plus acid generating sulfate mineral conleat, <br />NP based on calcium carbonate plus magnesium carbonate content. <br />' values marked with an asterisk classified as acid producing <br />For the two samples on which agreement was not universal (TL-2, TL-3), all static tests <br />except the standard ABA classified the samples as "inconclusive", based on Net NP values of - <br />20 to -1.7 kg CaCO,/t. The standard ABA predicted samples TL-2 and TL-3 would produce <br />acid based on Net NP values of -29 and -26 kg CaCO;/t, respectively. The gtandard ABA <br />prediction was consistent with the mineralogic Net NP values for these two samples, which were <br />-24 and -44 kg CaCO~/t, respectively. <br />QUANTITATIVE COMPARLSON WITH OTHER STATIC TEST RIISULTS <br />Although the NAP Net NP was often higher than the other Net NP values, the disparity <br />was not generally large (Table 3 and Figure 1). Indeed, the NAP values more closely <br />approximated those from the standard ABA and Modified ABA than reported by Coastech <br />Research Inc. (1989). Modifications of the previous method, such as the greeter dosage of <br />hydrogen peroxide and longer reaction time, may have contributed to this improved agreement. <br />The modified method used sequential doses of 100 mL and SO mL of hydrogen peroxide (30% <br />strength) per gram waste, and allowed 90 minutes of reaction. The previous method used 100 <br />mL of 15`% hydrogen peroxide with a five gram sample of waste, and allowed a reaction time <br />of either five minutes or one hour after the reaction was apparently complete (Coastech Research <br />Inc., 1989). In addition, the CaCI= rinse of the solids in the modified method may have released <br />additional acid from the solids and, thereby, improved the accuracy of the technique. <br />152 <br />