Biostimulation

Biostimulation is an in situ bioremediation process that enhances the activity of naturally occurring microorganisms by providing the food and environmental conditions they need to biologically degrade contaminants. Rather than adding new microorganisms, biostimulation encourages the native microbial population to become more active.

Why Biostimulation Matters

Many contaminated sites already contain microorganisms capable of degrading pollutants, but they may not have enough food or the right environmental conditions to do so efficiently. Biostimulation helps overcome these limitations by providing the resources needed to support microbial growth and biological activity.

For chlorinated solvent remediation, biostimulation often involves adding an electron donor that provides food for microorganisms. As microbial activity increases, favorable anaerobic conditions develop, allowing naturally occurring biological processes to degrade contaminants. Depending on the site, biostimulation may be sufficient on its own, or it may be combined with bioaugmentation when additional specialized microorganisms are needed.

Successful biostimulation depends on understanding site conditions. Groundwater chemistry, contaminant type, soil characteristics, groundwater flow, and amendment distribution all influence treatment performance. The goal is not simply to inject a product, but to create an environment where microorganisms can effectively perform the work of remediation.

How Biostimulation Works

Biostimulation works by supplying food for microorganisms already present in contaminated soil or groundwater. As these microorganisms consume the added food source, they grow, reproduce, and become more active. Their biological activity gradually changes groundwater conditions and promotes the degradation of contaminants.

For anaerobic remediation, electron donors provide the food microorganisms need to support biological processes such as reductive dechlorination. As microbial activity increases, dissolved oxygen is depleted, oxidation-reduction potential (ORP) decreases, and the treatment zone becomes more favorable for anaerobic microorganisms.

The effectiveness of biostimulation depends on proper amendment selection and distribution. Even the most effective electron donor cannot stimulate biological activity if it is not delivered throughout the contaminated treatment zone. Every remediation site responds differently, so treatment strategies should always be based on site-specific conditions rather than a standard recipe.

Common Biostimulation Applications

Biostimulation is widely used during in situ remediation of groundwater contaminated with chlorinated solvents, petroleum hydrocarbons, and other biodegradable contaminants. It is often selected when native microbial populations are present but require additional food or improved environmental conditions to effectively degrade contaminants.

Environmental professionals commonly monitor groundwater chemistry, contaminant concentrations, dissolved oxygen, ORP, pH, and other field parameters to evaluate treatment progress and confirm that favorable biological conditions are developing throughout the remediation process.

RNAS Technical Insight

A common misconception is that biostimulation simply means adding an electron donor. In reality, successful biostimulation is about creating the right biological environment for the microorganisms already present at the site. The choice of electron donor, groundwater chemistry, amendment distribution, and site geology all influence treatment success. When these factors are properly addressed, native microorganisms often become the most effective remediation tool available.

How RNAS Supports This Process

Successful biostimulation begins with selecting the right products for the site’s conditions and delivering them where biological treatment is needed.

• Newman Zone 55 and Newman Zone HRO provide long-term food for microorganisms, supporting sustained biological activity during extended remediation projects.
• Newman Zone QR75 and Newman Zone QR90 provide soluble electron donors for applications where more rapid biological stimulation is appropriate.
• Newman Zone OS helps establish anaerobic conditions by removing dissolved oxygen that can interfere with biological treatment.
• SDC-9 bioaugmentation culture can be used when native microbial populations are insufficient to completely degrade chlorinated solvents.
• Neutral Zone helps maintain favorable pH conditions that support healthy microbial populations throughout the remediation process.