Bio-wall Technology: Conceptual Design and Analysis

In-situ bioremediation is a process by which contaminants in subsurface environments are biologically eliminated or mineralized; however, it is often difficult to implement. Microbes sparsely distributed in deep soils are incapable of degrading a chemical rapidly; furthermore, fine-pore structures of soils tend to retard the penetration and propagation of these microbes and to hinder oxygen transfer. The latter is particularly detrimental to the aerobic growth of microbes, which is often essential for bioremediation. Measures intended to promote bioremediation, such as addition of surfactants for enhancing dissolution and application of genetically-engineered microbes for accelerating the biodegradation of the contaminants, are almost impossible to adopt. This is attributable to the fact that various facets of the bioremediation process, e.g., the distribution of dissolved contaminants, nutrients and oxygen, and the concentration of microbes, can not be readily manipulated. The present work proposes a novel technology, namely, bio-wall. This technology resorts to an in-situ constructed medium with porosity and organic content greater than those of the original soil for promoting the adsorption and retention of microbes and the biodegradation of contaminants. Moreover, oxygen and nutrients are supplied to the biowall to facilitate microbial growth. The results of a conceptual design study and simulation have revealed that the technology is indeed feasible and, under certain environmental conditions, cost-effective. Particularly noteworthy is the fact that the bio-wall can prevent contaminant migration through enhancement of the biodegradation rate and reduction of the plume-distance, both by several orders of magnitude.