275770 Biodegradation of Carbon Tetrachloride in Laboratory Flow Channels

Thursday, November 1, 2012: 4:55 PM
331 (Convention Center )
Sathishkumar Santharam, BG Consultants, Inc., Manhattan, KS, Larry Davis, Biochemistry, Kansas State University, Manhattan, KS and Larry Erickson, Chemical Engineering, Kansas State University, Manhattan, KS

Carbon tetrachloride (CT) is a solvent used in several applications including degreasing and fumigation. CT is a common groundwater pollutant and a suspected carcinogen. Remediation feasibility studies were conducted by mesocosm experiments; a chamber was divided into six channels and filled with soil, and plants were grown on the soil surface. Each channel was fed with CT contaminated water near the bottom and collected at the outlet, simulating groundwater flow conditions. CT was introduced at a concentration of about 2 mg/L (~13 μmoles/L) in three channels, two of them with alfalfa plants and the other with grass. The other three channels were used for a different study. After the system had attained steady state, the concentrations of CT at inlet and outlet were monitored and the amount of CT disappearing in the saturated zone was studied. Since no degradation products were found at the outlet after about 100 days, anaerobic conditions were created in one channel (with alfalfa) by adding one liter of 0.2% glucose solution. The glucose solution was fed once every month starting from day 111 and continued until day 328. From day 203 to day 445, one liter of 0.1% emulsified soy oil methyl esters (SOME) was fed once a month to another channel (with alfalfa). The monthly SOME addition dates were the same as for glucose. Degradation compounds of CT were detected in the outlet liquid of the channels fed with SOME and glucose; however, the extent of degradation in the SOME fed channel was not as great as that of the glucose fed channel. No degradation compounds were observed in the outlet solution of the channel (grass grown on top) in which no carbon and energy supplements were added. The total chlorinated methanes (CMes) decreased to less than 1 μmoles/L in channels 5 and channel 6; however, the CMes remained low for a longer time in the glucose fed channel. In addition to glucose, corn starch and cheese whey were also added to channel 5, as growth substrates. Supplements such as glucose, corn starch, cheese whey and SOME stimulated the indigenous microbes and helped in the degradation of CT. In both glucose and SOME fed channels, the degradation continued several weeks after stopping the feeding of supplements. The soil matrix and the microorganisms were able to store the supplements/degradation products of supplements and provide a long-term source of carbon and hydrogen. This finding is very valuable in the design of remediation systems in field sites since it determines the frequency of supplement addition.

Extended Abstract: File Not Uploaded
See more of this Session: Fundamentals of Environmental Biotechnology
See more of this Group/Topical: Environmental Division