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09/02 '00 WED 16 52 FAX 18259469968 ERMST QFC IR 014 <br /> ,V <br /> ` A G E 2 <br /> ERM used sample analytical data from the monitoring events completed <br /> prior to implementation of enhanced in situ bioremediation with igen <br /> Releasing Compounds (ORC) )BRM applied First Order Kinetics to <br /> estimate the rate constant for natural biodegradation,as described below <br /> The purpose of these calculations was to predict the time for COCl <br /> attenuating under natural biodegradation to attain their respeLtwe <br /> MCL/Target Concentration To do this,a natural biodegradation constant <br /> was needed. It is well documented that natural degradation processes can <br /> be modeled using the First Order Kinetics equatron(EPA Technical Protocol <br /> for Enaluatzng NabonzI AMnuatzon of Chlonnated Solvents in Ground Water, <br /> Appendix C-Data Inkrpraebrhon and C4culaftons, EPA/600/R-98/12$, <br /> September 1998) The mathematical equation representing First Order <br /> Kinetics is the following <br /> Cti =COB-i, <br /> Where n =number of samples ui the data set <br /> t =time an days <br /> Co -initial concentration of constituent, mg/L <br /> C. =constituent concentration taken after"t" days_ <br /> The equation can be rewritten as <br /> Ia = " <br /> �n <br /> Using this form of the First Order Kinetics equation, a plot was <br /> constructed Nrith"in(Co/Cn)"+ on the y-axis and`{t' on the x-axis. A <br /> straight large equation was fitted to the plotted points using linear <br /> regression to estimate the slope of the equation of the line,which is k,the <br /> natural biodegradation constant The k estimates are presented in Table 1 <br /> (Site#1)and Table 2(Site#2)and summarized in Table 3. p'igt m I ` <br /> through 3 show the platted values and the regression line <br /> Well MW-5('rite#1) and.MW-IA (Site#2)have Iustorically had lugh <br /> concentrations of CDCs and currently (as of 22 July 1999)have the hrghest <br /> site-specific reported values for benzene and'1C P -g(Tables I and 2) <br /> Therefore,the natural(biodegradation constants estimated for MW-5 and <br /> MW-IA were used,in the predictive calculations for TPH-g and benzene at <br /> Site#1 and Site RZ respectively <br />