Stimulated biodegradation

When aquifers were amended with nitrate in order to stimulate biodegradation, the results were generally consistent with those obtained in laboratory investigations. In a field injection experiment at Seal Beach, California, Ball et al. (1994) demonstrated complete removal of w-xylene and the m-,/-xylene fraction decreased significantly in parallel bioreactor experiments. A Canadian study showed a decrease in m- and /-xylene of 14% and 15%, respectively, over aim flowpath in the Borden aquifer (Barbara et al., 1992). Very little degradation was observed beyond that point, presumably due to the availability of preferred electron donors in the landfill leachate impacted aquifer. 

Atlas, R. M. Bartha, R. (1973a). Stimulated biodegradation of oil slicks using oleophilic fertilizers. Environmental Science Technology, 7, 538—41. 

U.S. Patent Office (1990). Method For Stimulating Biodegradation of Halogenated Aliphatic Hydrocarbons. Nelson, M.J.K. Bourguin, A. US Patent No. 4925 802. 

Refer to Exercise 36.) To deal with residual saturation, you propose to stimulate biodegradation by supplying mineral nutrients and an oxidant (electron acceptor). You receive permission to make an experimental injection of sodium nitrate (NaN03). The hydrocarbon contaminants will be oxidized as the nitrate is reduced to N2 (denitribcation is expected to occur). 

Figure 19. Nutrient-limited and -stimulated biodegradation of contaminants (BTEX, PAH) in groundwater [from Schulze (2004)].

Figure 19.9. Electrochemically enhanced microbial reductive dechlorination of perchloro-ethene (PCE) and oxidative degradation of vinyl chloride (VC). Stimulated biodegradation is indicated by a chloride increase during electrochemical treatment.

Figure 19.10. (a) Principle of electrolytical stimulation of chloroethene biodegradation, (b) Electrochemical prodnction of hydrogen and oxygen down-gradient the electrodes in a model aquifer, (c) ElectrolyticaUy stimulated biodegradation of PCE in a flow-through column system. DC, direct current C, cathodic colnmn A, anodic column in, influent out, effluent n.d., not detected. 

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