The overall cost of bioremediation is generally significantly lower than other types of remedial approaches. The classic excavation, removal, and backfill option can easily cost  more...

The overall cost of bioremediation is generally significantly lower than other types of remedial approaches. The classic excavation, removal, and backfill option can easily cost over $50 per cubic yard, not including disposal tipping fees. Tipping fees can range from $20 per cubic yard to over $200 per cubic yard depending on the contaminant and concentration. If the excavated material cannot be landfilled, disposal costs can rise dramatically. In addition, an excavation option is generally not suited for saturated soils. A recent comparison of chemical oxidation options reported average costs of over $90 per cubic yard (Ground Water Monitoring & Remediation 30, no 4/Fall 2010). The installation costs of mechanical systems (soil vapor extraction, dual phase extraction, groundwater treatment, etc.) are highly variable and dependent on the size of the treatment area but can easily exceed $20 per cubic yard even for large projects with operation and maintenance adding additional costs. Aerobic bioremediation projects are generally in the $10 to $30 per cubic yard range for a single injection and anaerobic bioremediation projects are generally in the $2 to $6 per cubic yard range for a single injection. Although multiple injections can be required, most sites require less than 3 or 4 injections if the site is properly assessed.

Minimal O&M: Bioremediation of a subsurface contaminant is typically accomplished by enhancing natural processes. These enhancements usually include the addition of a material into the subsurface and then allowing naturally-occurring microbes to degrade the constituents of concern. Because this is essentially an apply-and-forget type of technology, there are little or no operating or maintenance costs after the material has been applied. Normal monitoring is usually required on quarterly or semi-annual basis to evaluate the progress of the application.

No above ground surface structures: Injection of material into the subsurface can generally be accomplished through the use of direct injection or through permanent injection points. If the application is done through direct injection, minimal disturbance of the surface is required during the injection event and the area can be put back into use immediately after the injection is completed. Injection through permanent points can require the installation of surface and near-surface utilities and some above-grade structures but these can usually be minimized through the use of technologies such as horizontal drilling to reduce impact to facility operations. less...

Remedial technologies can be divided into two basic categories, contaminant removal or contaminant destruction. To meet complete removal or destruction,  more...

Remedial technologies can be divided into two basic categories, contaminant removal or contaminant destruction. To meet complete removal or destruction, both approaches require the practitioner to continue remediation until all of the contamination has been addressed. The main cause of remedial option failure is the inability of a strategy to address sufficient contamination within a system to meet the goals of a project. Biological degradation relies upon natural processes that under ideal conditions can be capable of complete degradation of a contaminant. Ideal conditions are seldom, if ever, encountered in the field therefore the goals of bioremediation need to be commensurate with the resources available.

Complete mineralization: Mineralization, or conversion of an organic to carbon dioxide and water, can be accomplished with bioremediation. Rates of mineralization can vary from compound to compound but a significant increase in degradation kinetics can be expected for most sites.

Mass reduction: In situations with significant contamination over large areas, bioremediation can be very effective in reducing the overall mass of contaminants. It is not unusual to see contaminant concentrations in groundwater to be reduced by at least on order of magnitude after bioremediation implementation. In general, the maximum degradation level achievable is related to the resources allocated to the project. In this respect it is extremely important to understand the goals of the project before beginning design activities.

Wide range of contaminants: Bioremediation can be effective across a very wide range of organic and inorganic contaminants. Aerobic processes can be very effective on petroleum products including benzene, toluene, ethylbenzene, and xylenes, some chlorinated compounds, and some metals such as iron. Anaerobic bioremedial processes such as halorespiration are effective on a wide range of chlorinated contaminants including chlorinated ethenes and ethanes while the addition of sulfates can be effective in providing electron acceptors for the degradation of many petroleum hydrocarbons. In the process of enhancing anaerobic bioremediation through the addition of carbon to a system many microbes will reduce the concentration of electron acceptors such as nitrates and sulfates. If these electron acceptors are identified as contaminants, the process of adding carbon to a system can also be considered an effective remedy for these constituents of concern.

DNAPL source treatment: Contaminants can be found in a number of phases within a system including dissolved, sorbed, free-phase, and as a vapor. For contaminants that are more dense than water, the free-phase can be present in a significant mass, especially in the source area near the original release. The term dense, non-aqueous-phase liquid (DNAPL) is given to this type of contaminant mass. Although most biological processes require the contaminant to be in the dissolved phase to be metabolized, the remediation of DNAPL sites has been observed to be accelerated through the addition of a carbon substrate. The mechanisms associated with this accelerated DNAPL degradation process include increased dissolution of the DNAPL due to the establishment of a chemical gradient, the increased dissolution of the DNAPL due to the release of surfactants by the microbial communities, and the increase in dissolution due to the solubility characteristics of the substrate. less...

Bioremediation can be very effective as a stand-alone strategy but when the goals of a project require remedial time frames that cannot readily be met with bioremediation  more...

Bioremediation can be very effective as a stand-alone strategy but when the goals of a project require remedial time frames that cannot readily be met with bioremediation or in cases where other strategies are more cost-effective, bioremediation can be used in conjunction with other technologies.

Use after chemical oxidation: Chemical oxidation is dependent upon bringing the contaminant and the chemical oxidant into contact with each other before the oxidant is expended. This usually takes place within a relatively short period of time and requires sufficient oxidant to permeate throughout the entire treatment zone. Since this is a time-sensitive process, chemical oxidation is usually best suited to compact, very permeable areas of high contaminant concentration such as source areas. In cases where chemical oxidation is applied, bioremediation can be used as a follow-on technology. Chemical oxidation of petroleum hydrocarbons can be quickly be followed by the introduction of oxygen through mechanical means (soil vapor extraction, sparging, etc.) or solid peroxygens or other electron acceptors. The addition of a carbon substrate to enhance reductive dechlorination can be effective following chemical oxidation if the addition of the substrate is delayed to allow all of the oxidant to react. This can be a very effective means of addressing both high concentrations in small areas followed by the remediation of any remaining contaminant through biological means.

Remediation of groundwater: Although co-metabolic processes usually take place outside of the cell, generally contaminants must be in the dissolved phase in order for them to be metabolized within the cells. Strictly speaking this limits the contaminants to the dissolved phase but the overall process includes both biological and physical actions. Physically, if you only destroy contaminants in the dissolved phase you will establish a chemical gradient that will continually replace the dissolved phase contaminant with contaminant from other phases until the entire system has come to a complete equilibrium (ie. all contaminant destroyed). This is one of the principles of bioremediation of DNAPL sources.

Remediation of DNAPL sources: Anaerobic bioremediation of DNAPL sources can be accomplished successfully by adding organic substrate to enhance reductive dechlorination. The main mechanisms identified that contribute to DNAPL dissolution include increased biological activity promoting increased chemical diffusion, increased solubility of contaminant daughter products leading to an overall increase in contaminant solubility, increased contaminant solubility within specific substrates, and the biological production of surfactants. This process is the basis of US Patent 20040157317, published August 2004 and assigned in part to JRW Bioremediation, L.L.C.

Remediation of unsaturated zone: In many cases, especially with regards to aerobically degradable contaminants, it is possible to biologically degrade the contaminant in the unsaturated zone. This process requires some moisture and the addition of a source of electron acceptors. Most soils contain sufficient moisture to allow the biological process to function so the critical issue becomes the distribution of the electron acceptor. Electron acceptors such as oxygen can be readily distributed throughout the system through mechanical means such as soil vapor extraction or air sparging. In these cases, the mechanism removes contaminants both biologically and through volatilization. The remediation of anaerobically degradable contaminants such as chlorinated solvents is theoretically possible under anaerobic conditions. In these cases, thorough substrate distribution is critical and is usually only achievable in high moisture soils such as clays. The soil moisture provides both connectivity for the substrate to diffuse throughout the system and water to sustain the microbial populations and provide contaminant and substrate transport. less...