Bioremediation processes can also be performed in-situ. One such process, described in U.S. Pat. No. 5,681,639, involves stimulating the growth of indigenous anaerobic Cr(VI) reducing bacteria in the contaminated soil and/or groundwater by adding a nutrient medium to the soil and maintaining a substantially anaerobic environment. Such nutrients may be carbohydrates, amino acids, organic acids or nitrogen sources. However, no reliable means of controlling the biological reaction is described.
Even in view of the above described methods, there remains a need in the art for a method of in-situ soil remediation which is workable, safe, controllable, effective, and economically feasible and which can be applied on a large scale. There is a further need for an environmentally compatible process which is able to achieve soil chromium concentration levels below the TCLP limit and groundwater chromium concentration below regulatory levels, using inexpensive, easily available reagents and without the need for excavation or mixing of enormous volumes of soil with the applicable chemical reagents.