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' tb 132 Page 1 of 1 <br /> lie • <br />' .f' .� .+� � � !jj rj ;..1 ,� J" ,ice • <br /> pH Levels <br />' Moderate pH levels are maintained when ORC is used in bioremediation In relation to the insoluble nature of ORC, the <br /> pH increase remains highly localized The elevated pH levels control biofouling and they do not migrate downgradient <br /> The following field data from the North Carolina site suggests that such migration is minimal or very slow <br />' North Carolina Site Oxygen Barrier pH Measurements <br /> Day 50' UG ORC 10' DG 25' DG 50' DG 85' DG <br />' 777 ] 113 59 61 �6 62 <br /> 21 59 105 61 65 61 62 <br /> 49 63 <br /> 70 59 88 57 59 6� <br /> Note The pH of ORC is on the order of 9 0 and the hydroxide reaction products <br /> approach pH 10 in this experiment the ORC was delivered in a concrete matrix which <br /> provides a higher pH as observed in the ORC well - even at these levels there was <br /> virtually no migration UG = Upgradient; DG = Downgradient <br /> 1 ORC (as Mg02)and Ca02 are both feasible as chemical oxygen sources, however, ORC has a pH which stays more <br /> highly localized at the source Both oxides arc converted to the respective hydroxides over time (as oxygen is released) <br />' and even larger pH differences are observed The pH of Ca02 reaction products can approach 13 while those of ORC <br /> stay below 10 Furthermore, since the solubility product of Ca02 is much higher(Ksp = 5 5 X 10-6) than Mg02 as <br /> ORC(Ksp= 18 X 10.1 1), the pH will not remain as localized <br /> These differences would be even more pronounced in systems more highly buffered than aquifer water In buffered soil <br /> systems the pH is quite benign with ORC which stays below 8 at concentrations of more than 1%wt hvt Ca02, <br /> however, is difficult to use above 25%wt/wt and generates a pH of close to 1 I by the time itis present at 1%wt/wt <br />' Technical Bulletin Index I lRegenesis Home Page <br /> http //www regenesls com/ORCtech/Tb 132 htm 6120101 <br />