Animal Co-Products as Novel Electron Donors for In Situ Bioremediation

Chlorinated solvents account for approximately three quarters of all bioremediation sites. The vast majority of these remediation applications are predicated on a simple strategy: amend a high molecular mass electron donor into the subsurface so Dehalococcoides-like microorganisms are stimulated, and the activity is promoted over the long term. Thus far all long-term electron donors have been derivatives of soybean oil, which is problematic because of: a) limitations in the microbial populations that actually utilize strictly lipid electron donors, and b) competition with foodstuffs in US production. We have developed electron donors from rendered animal co-products, which are combinations of lipid, protein, and minimal carbohydrate. Thus far 21 co-products have been tested, and all stimulate complete dechlorination to a rate and extent, which is better than any current soybean oil-based electron donor.

Incubations were constructed using TCE-contaminated aquifer material, and each electron donor (co-product) was added as the sole electron donor. Each animal co-product was compared to 5 controls containing common electron donors (lactate, acetate + hydrogen, and one soybean oil-based electron donor) and a sterile and unamended controls.

Lactate was the fastest of the 5 controls and as a result each animal co-product was compared to it. Of the 21 animal co-products, 17 completely dechlorinated the TCE to ethene at rates faster than lactate and 4 generated ethene at the exact same rate as lactate. In general, the more proteinaceous animal co-products were able to promote dechlorination at a faster rate than the animal coproducts with a higher fat content. All materials reduced TCE to ethene (at a 1:1 stoichiometry) faster than the commercially available soybean-based electron donor (e.g. emulsified vegetable oil). This strategy introduces a new electron donor for TCE bioremediation, which thus far is faster and more cost-effective than any electron donor reported to date.