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1 tb 132 Page 1 of 1 lie ORC TECHNICAL BULLETIN # 1 . 3 . 2 pH Levels ' Moderate pH levels are maintained when ORC is used in bioremediation In relation to the insoluble nature of ORC,the pH increase remains highly localized The elevated pH levels control btofouling and they do not migrate downgradrent The following field data from the North Carolina site suggests that such nugration is minimal or very slow ' North Carolina Site Oxygen Barrier pH Measurements Day 50' UG ORC 10' DG 2S' DG 5d' DG SS' DG ' EE 113 59 61 62 21 59 105 61 65 61 G2 ' 49 10 1 6 1 63 7010 59 88 57 59 �� 137 59 111 61 59 == Note The pH of ORC is on the order of 9 0 and the hydroxide reaction products approach pH 10 in this experiment the ORC was delivered in a concrete matrix which provides a higher pH as observed in the ORC well - even at these levels there was virtually no migration UG = Upgradient; DG = Downgradient ' ORC(as Mg02) and Ca02 are both feasible as chemical oxygen sources, however, ORC has a pH which stays more highly localized at the source Both oxides are converted to the respective hydroxides over time (as oxtigeii is released) and even larger pH differences are observed The pH of Ca02 reaction products can approach 13 while those of ORC stay below 10 Furthermore, since the solubility product of Ca02 is much higher(KSp= 5 5 X 10-6) than Mg02 as ORC(Ksp= 18 X 10-11), the pH will not remain as localized ' These differences would be even more pronounced in systems more highly buffered than aquifer water In buffered soil systems the pH is quite benign with ORC which stays below 8 at concentrations of more than 1%wt hvt Ca02, however, is difficult to use above 25%wt/wt and generates a pH of close to 11 by the time it is present at 1%wt/wt ' Technical Bulletin ltidexIlRegeiiesis Home Page ' http //www regenesls tom/ORCtech/Tb 132 htm 6/20/01