Land Farming versus Injection

Two Very Different Bioremediation Techniques for Soil

Anyone considering bioremediation should understand the two very different techniques used for soil remediation: land farming and injection. The first--land farming--is a simple surface process that requires no special engineering skills or exotic tools. The second--injection--is an engineering undertaking that requires the installation, operation, maintenance and monitoring of subterranean boring grids, piping and ventilating systems, monitoring wells and related systems and equipment. The soil remediating materials and techniques described in this Web Site relate to various sorts of land farming techniques, not injection or "in-situ" methods.

Microbe-Augmented Land Farming: Simple
Land farming involves mixing microbe-enriched bioremediation materials into excavated dirt that is spread out across a ground surface and kept moist for the duration of the petroleum degrading process. The name "Land Farming" comes from the fact that the excavated soil is laid out in low layers or banks that can generally resemble a farmer's freshly plowed field. (A modified version of land farming called the "staged pile technique" that allows soil to be land farmed in piles up to six foot high is explained later in this Web Site).

Injection Boring Bioremediation: Complicated
Injection is often called "in situ" bioremediation because it attempts to eliminate petroleum contamination from soil that remains "in place" during the process. No dirt is excavated. Instead, holes are drilled to facilitate the injection of bioremediation materials below the surface. The general idea is to mix the dry microbe materials and nutrients with water to form a slurry. Then the slurry is poured down the holes to soak out into the soil in all directions. In this way, contaminated dirt stretching down dozens of feet or more can be inoculated with a rich stew of hydrocarbon-oxidizing micro-organisms. But sustaining and managing this "in-situ" bioremediation process can be a mechanically intense procedure. It is further complicated by the inability to see what is happening below ground as well as the unpredictable nature of geological formations that may be unexpectedly encountered.

For instance, injection borings often intersect with aquifers and impermeable clay layers which can thwart effective subterranean bioremediation projects.

Conclusion
Microbe-enhanced surface land farming bioremediation is a low-tech, low-cost process that can be attempted by just about anyone. In the worst case possible--when little or no microbial degradation occurs--the land owner still has a number of options to readily dispose of the contaminated dirt by other means.

Injection, or in-situ bioremediation, on the other hand, tends to be a high-tech process that often requires very significant amounts of manpower and specialized equipment. It can also involve complicated mechanical, geological and potential liability issues that can only be competently addressed by qualified engineering specialists.

© 1995, Oettco
levins@tigger.jvnc.net