Community Relations and Stakeholder Management on Third-Party Owned Site during MGP Site Remediation Activities
Community Relations and Stakeholder Management on Third-Party Owned Site
During MGP Site Remediation Activities
Presenter: Douglas Kier (AECOM)
Authors: Douglas Kier and Crystal Shadle (AECOM), Peter Farrand (PECO Energy Company)
There are various methods of activating persulfate; heat, peroxide, divalent transition metals, trivalent transition metals and caustic, however, several of the activation mechanisms involve the use of potentially hazardous chemicals under extreme conditions (e.g., pH >11) while others are simply not conducive to sustained biological processes. The two activation methods presented below have the advantage of utilizing both biotic and abiotic processes that include the use of free radical chemistry, oxidation chemistry, while also enhancing the in-situ environment for biologically based attenuation of the constituents of interest. The abiotic portion of the ZVI/Peroxide activated persulfate method uses a unique blend of peroxyl, hydroxyl, evolved heat and sulfate free radicals which results to the oxidation of the contaminants of concern. This mixture allows Fenton-like reactions with long-lived sulfate free radical oxidation to occur, while the presence of zero valent iron acts as a catalyst for both reactions. The decomposition products of the oxidation process are utilized in the subsurface to stimulate facultative biological degradation of the targeted compounds. The use of ferric iron to activate persulfate presents the additional advantage of quickly generating sulfate and ferrate radicals for ISCO treatment. Similar to the ZVI/Peroxide activation method described above, that process is achieved by enhancing the subsequent utilization of sulfate and iron as terminal electron acceptors for facultative redox reactions in order to improve biodegradation of any residual COIs. The ferric activated method, similar in its chemistry to the peroxide, ZVI persulfate, differs in that it is an endothermic process while still providing no extreme pH conditions that can mobilize heavy metals causing secondary impact issues, while the presence of iron will sequester sulfur liberation during sulfate reduction reactions to minimize H2S formation. Moreover, the remedy combines treatment mechanisms thereby allowing for more cost-efficient dosing of the product.