Comparative Study for ZVI/Peroxide vs Ferric Iron Oxide Persulfate Activation Followed by Intrinsic Facultative, Biologically Mediated Processes
Michael Scalzi, President, Innovative Environmental Technologies, Inc.
An In-Situ Chemical Oxidation (ISCO) remedial process involves injecting an oxidizing agent, such as activated sodium persulfate (Na2S2O8), or other oxidant into the subsurface to destroy organic compounds. The persulfate anion (S2O82-) has a high redox potential and can be chemically activated to form the sulfate radical (SO42-•), which is a stronger oxidant. The sulfate free radical is a very potent oxidizing agent roughly equivalent to the hydroxyl radical generated using ozone or peroxide. 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 and facultative biological attenuation. The potential combination of these processes extends oxidant and free radical residuals while enhancing the in-situ environment for biologically based attenuation of the constituents of interest (COI). 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 COIs. 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 evolved heat is of value in situations where there is a high sorbed mass of the hydrophobic compounds of concern. Furthermore, as mentioned above, the decomposition products of the oxidation process are utilized in the subsurface to stimulate facultative biological degradation of the targeted compounds. After dissolved oxygen has been depleted in the treatment area following the oxidation process, sulfate (the by-product of the persulfate oxidation) may be used as an electron acceptor for co-metabolic progressions, a process termed sulfanogenesis. The use of ferric iron to activate persulfate for the purpose of degrading organic compounds presents the additional advantage of quickly generating sulfate and ferrate radicals for ISCO treatment. Moreover, it also supports long-term, sustained, secondary bioremediation processes to manage residuals and prevent contaminant rebound. 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.
Mr. Scalzi, President and founder of Innovative Environmental Technologies, Inc. (IET), has been performing biologically and chemically based remediation since the late 1980’s. Mr. Scalzi has designed and implemented projects ranging in scope from large scale, such as a 136,000 cubic yard in-situ soil remediation in New Jersey, to small scale, such as a 2,000 cubic yard in-situ injection program at a strip mall dry-cleaner in Tennessee. In the nearly 28 years he has been performing remedial projects, he has designed, implemented, and patented chemical, biological and mechanical processes.
Mr. Scalzi has been integral in expanding the application of in-situ remedial processes. His unique perspective relating to the integration of mixed technologies and delivery processes has allowed Mr. Scalzi to apply chemical oxidation, aerobic processes, anaerobic processes along with more traditional remedial approaches. IET was formed in 1998 as a resource for environmental consulting engineers. Since its inception, IET has applied a variety of remedial technologies to over 2,000 sites across the country. Included in these projects are over 250 dry cleaning facilities in Illinois, Indiana, Tennessee, New Jersey, New York, California and Pennsylvania; 30 oil terminals and distribution facilities; hundreds of closed chemical manufacturing facilities and landfills
Mr. Scalzi and IET approach each site with the experience and the resources to recommend and implement the most appropriate remedial solution. IET owns and operates its own fleet of specially designed equipment capable of implementing nearly all types of in-situ remediation processes. Since 1998, IET has grown into the largest and oldest in-situ remedial contractor/technology vendor in the United States.
Mr. Scalzi holds a Master’s degree in microbiology from the State University of New York. He has also participated in the curriculum development for environmental professional programs, sat on numerous state and federal roundtables and advisory boards, developed curriculum for college programs in New York and Pennsylvania, holds patents in delivery and remedial processes, and has published numerous articles relating to his experiences and expertise.