Trichloroethene degradation in a two-step system by methylosinus trichosporium OB3b. Optimization of system performance: use of formate and methane.
The breakdown of dissolved TCE in a two-step bioremediation system is described. In the first reactor, the organism Methylosinus trichosporium OB3b is grown; in the second reactor, consisting of three 17-L column reactors in series, the cells degrade TCE. A special design allowed both for the addition of air (uG,s = 0.01-0. 04 mm s-1) in the conversion reactor to prevent oxygen limitation while minimizing stripping of TCE, and for the use of methane as exogenous electron donor. In two-step systems presented thus far, only formate was used (excess, 20 mM). We found formate additions could be reduced by 75% (15 degrees C), whereas small amounts of methane (0.02-0.04 mol CH4/g cells) could replace formate and led to equally optimal results. Example calculations show that up to 90% reduction in operating cost of chemicals can be obtained by using methane instead of formate. A model was developed to describe each of the conditions studied: excess formate and optimal methane addition, suboptimal formate addition and suboptimal methane addition. Using parameters obtained from independent batch experiments, the model gives a very good description of the overall TCE conversion in the two-step system. The system presented is flexible (oxygen/methane addition) and can easily be scaled up for field application. The model provides a tool for the design of an effective and low-cost treatment system based on methane addition in the conversion reactor.
Sipkema
E M
EM
Department of Chemical Engineering, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands. e.m.sipkema@chem.rug.nl
de Koning
W
W
Van Hylckama Vlieg
J E
JE
Ganzeveld
K J
KJ
Janssen
D B
DB
Beenackers
A A
AA
D001673:Biodegradation, Environmental; D001709:Biotechnology / Q000295:instrumentation / Q000379:methods; D004787:Environmental Pollution / Q000517:prevention & control; D005561:Formates / Q000494:pharmacology; D007700:Kinetics; D008697:Methane / Q000494:pharmacology; D008772:Methylococcaceae / Q000254:growth & development / Q000378:metabolism*; D015233:Models, Statistical; D012044:Regression Analysis; D014241:Trichloroethylene / Q000378:metabolism*
D005561:Formates; C030544:formic acid; D014241:Trichloroethylene; D008697:Methane