Document VG57JkRM4O6npoyrnRQ94a684

C-8 BIODEGRADATION IN GROUNDWATER ctg. Xn y: > Cr7SH 6SS0003G Andrew Hartten Dave Ellis May 7, 1'998 h IS4H 6IWW2 3I3NidelO :'l 'i WHY STUDY C-8 DEGRADATION IN GROUND WATER? .... rr t^ Cqng exposure to C-8 Long residence times * Available Relatively simple 09S000HG THE THREE LINES OF EVIDENCE Reduction in concentration along the flow path downgradient Documented loss of contaminant mass by chemical and geochemical data biological decay rate data Microbiological laboratory data supporting degradation and decay rates c O '1 s i 19S0007IG SITE CONCEPTUAL MODEL *:y Source Areas * Former anaerobic digestion ponds m (sludges removed) C-8 up to 614 mg/kg @ 8 -10 foot depth 'v 5# Ground water at 30' SITE CONCEPTUAL MODEL - 2 ( '. -V,<* Hydrogeology '.5W- -.. 'f . Sand and gravel 65 - 100 feet deep Yields up to 300 GPM Production wells influence GW flow paths Linear velocity 1 ft/day K= loo ft/day -V: ' ' illi'f.e 9soooaa LUBECK WELL FIELD lia Travel time from anaerobic ponds is about 5 years 2 ppb discharge concentration o wsoooaa USEPA 7810 4 L-5 \ V\ L_ 2 A * ^A\\^ WELL LOCATION MAP C o ip o fM # Rw m KSatksn Cfrw p JmJIMmt* k itm m * # m < aw l JW B -CM aw aa 9 m m Boday MB n o m . Buldkvj 27 WSmlnqton, Datooora 19880-0027 WASHINGTON WORKS WASHINGTON. WEST VIRGINIA war a-------- B SmVaa USEPA781^C02:?1 LEGEND: l!/ 653 tZ2 <*v Stolte Motor Lm L Dk . m i Lm L Mono* now BncHo S orta Motor How Oiroctkm ^ tw foco Motor now DlrwcHon IB IIT ld 71TWC3 SITE CONCEPTUAL MODEL C R O SS SECTION C ^ - Q^ E. I. du Pont de Nemours At Compony, hie. WASHINGTON WORKS PLANT, WEST WtGIMA Qoomn USEPA7812 Converting Biodegradation Rate Constants to Half-lives && * C = C 0e"kt, where k is the rate constant If you solve the equation C - C e kt, for k and t when C = 0.5Cothan t = -0.693/k where *' t is half-life in days and k is the rate constant For example: k = 0.0019 = a half-life of 365 days or 1 year os p ;> X V 00 950003(1 'I METHOD REQUIREMENTS GW velocity and direction Wells along a single flow line Analyses of parent and daughters Sorption information cin _ ffl . i> I t) 00 V , I--* . 89soooaa 0.051 w 0.0255 We use the MDL if concentration is below method detection limit MiVi C-8 IN GROUNDWATER * 0S000HQ Distance ~L- MW-l MW-2 MW-3 MW-4 MW-5 MW-6 at Lubeck 0 220 520 800* 1770 , 2440 2900 c-8 ppm 5.64 0.234 0.487 .0842 0.05 0.02 0.002 USEPA 7816 onccntration APPARENT LOSS RATE usoooaa INTERPRETATION V/ Y = 1.2344e--002X SLOPE = ,,0.002 = k R2 = 0.8401 zsoooaa USEPA 7818 INTERPRETATION tV 0.693/(k*v) However, k must be corrected for GW velocity using the "retardation factor". ' -i t = 0.693/(k*v*Rf) 3oo ^ Co iiirraT ii r < ""lr R f = 1 + (Pb/n) *F ) * (IC S For C-8, K =5000 Foi = 0.0005 pb = 1.8 Rr= 13.8 wsoooaci IMPACT OF RETARDATION Velocity 365 ft/yr 100 ft/vr 365 ft/vr 100 ft/yr 0.73 Retarded 0.0145 0.053 $$00030 USEPA 7821 SENS1T1V1TES {' Aquifer organic carbon content determines retardation factor - big impact on Tl/2 GW velocity - big impact on T l/2 '' % Intermediate source appears to exist. Changes ability to fit data. 3M was not able to find either fluoride or C-7 daughter products. 9S000Ha CONCLUSIONS C-8 half life appears to be slow: half life from 13 to 48 years is No biodegradation products found by 3\1 Rate estimate sensitive to TOC and V Rate estimate very sensitive to Koc soooaa