Bio/Phytoremediation

Bioremediation is legally defined as the remediation of contaminated media by manipulating biological organisms to enhance the degradation of contaminants. This process involves using naturally occurring or deliberately introduced microorganisms to consume and detoxify environmental pollutants, thereby cleaning up polluted sites. The biological organisms used in bioremediation include living organisms such as bacteria, fungi and plants to transform or immobilize contaminants in the soil, effectively reducing their toxicity.

In California, bioremediation activities are regulated under various environmental laws and regulations. One key regulation is the California Code of Regulations (CCR), Title 22, which governs the management of hazardous waste, including bioremediation processes. The Department of Toxic Substances Control (DTSC) oversees these regulations and provides guidelines for the safe and effective use of bioremediation techniques to clean up contaminated sites.

Cleaning Groundwater with Bioremediation. It sounds almost comical – pouring molasses, vegetable oils, even cheese whey into contaminated groundwater to remove one of the nation’s most prevalent and toxic pollutants.

Yet it works. An emerging science that works with nature to destroy toxic chemicals is increasingly providing the remedy for groundwater cleanups throughout California. Food material poured into groundwater stimulates growth of bacterial microorganisms that eat the food (molasses, oils and whey), then keep eating until the contaminant is gone.

Cleanup experts say a decade of improved science increasingly makes “in situ” (in place) bioremediation more effective, cheaper and faster than pumping contaminated water above ground to filter and treat. Often, the newer method reduces the groundwater cleanup timeline from years to months, they say.

TYPES OF REMEDIATION

Phytoremediation: Is the use of plants to remove pollutants from the environment or to render them harmless, its also called Phytoextraction.

Bio-augmentation: Is the addition of microorganisms that can bio‐transform or biodegrade a particular contaminant. – This process consists in the artificially introduction of acclimated acclimated, genetically genetically altered altered or engineered engineered microbes into the soil or water, in order to degrade and metabolize hazardous organic chemicals.

Bio-stimulation: This process consists in the addition of oxygen and/or inorganic nutrients to indigenous microbial populations in soil and groundwater groundwater. Taking advantage advantage of the in situ bacteria. • Fun gal remediation. Fungal‐ based remediation is an ex situ form of bioremediation, in which hazardous organics are degraded or detoxified by fungi that are introduced introduced into the contaminated contaminated soil via a fungal inoculum, eg. Depleted Uranium, Gulf War.

PHYTOREMEDIATION

Scientists have shown that plants and soil microorganisms can help clean up soils and contribute to restoring ecosystems. Some plants are able to bind and accumulate toxic metals from the soil in a process called phytoremediation. Sunflowers and Brassicas (the Mustard family, including Kale and Broccoli) are often used for this purpose because they can absorb heavy metals like lead, cadmium, and arsenic through their roots and store them in their tissues. (Because of this, avoid eating leaves and seeds from plants harvested in the burn zones and fire-affected areas until soil tests show that it is safe to do so.) This process moves heavy metals from the subsoil into the plant roots and shoots, helping reduce soil metal concentrations on the site when these plants are harvested (pulled with roots).

After harvesting, and preferably before the plants go to seed, they can be composted on site. It is recommended that the finished compost produced on-site should then be tested for heavy metal concentrations, as well as the surrounding soil. Depending on the levels, the finished compost can be removed for safe use elsewhere, or disposal at an approved landfill.

With respect to asbestos, California has some areas where soils naturally formed with high concentrations of Asbestos and heavy metals, called Serpentine Soils. Some native plants have evolved to grow and thrive in these challenging soils. These wildflowers, including California Poppies, may be the first to grow in post-fire soils, while other plants may suffer. Research is ongoing, but asbestos minerals can be detoxified by plants, in conjunction with soil microorganisms and metabolites

Sunflowers (Helianthus annuus) are capable of absorbing many heavy metals, including lead, Arsenic, Cadmium, Copper, and other toxins. Sunflowers grow throughout much of North America, including California, and are considered locally native wildflowers. Planting legumes with Sunflowers will boost available soil nitrogen and make them even more effective extractors.

Research is ongoing, but many other California native plants have also been found to effectively reduce the levels of toxins in soil, through phytoremediation. These include:

Telegraph Weed (Heterotheca grandiflora) Used in restoration projects, but not usually planted in the garden, this tall, hairy plant has bright yellow flowers and can extract and accumulate lead from contaminated soils.
California Buckwheat (Eriogonum fasciculatum) These easy to grow small shrubs are a keystone species, supporting local pollinators with nectar and birds with seed. This plant also extracts and accumulates lead and other heavy metals.
Willows (Salix species): Known for their ability to stabilize soil and absorb contaminants like cadmium and nickel.
Poplars (Populus species): Often used for their deep root systems that can extract pollutants from soil and water
Cattails (Typha species): Useful for filtering and stabilizing contaminants in wetland areas.

HOW DO BACTERIA AND FUNGI TRANSFORM INERT OR INORGANIC MATERIAL LIKE HEAVY METALS?

Microbial enzymes can play a role in breaking down chemical compounds in soil, particularly organic pollutants like pesticides and hydrocarbons. Microbial enzymes, such as dehalogenases and laccases, are often involved in these processes, transforming toxic substances into less harmful forms.

However, when it comes to heavy metals, enzymes cannot break them down because heavy metals are elemental and cannot be chemically degraded. Instead, enzymes can assist in immobilizing or transforming heavy metals into less bioavailable forms, reducing their environmental impact

Key characteristics of enzymes:

Specificity: Each enzyme is specific to a particular reaction or type of substrate (the molecule it acts on).
Reusable: Enzymes are not consumed in the reaction; they can be used repeatedly.
Sensitivity: Their activity is influenced by factors like temperature, pH, and the presence of inhibitors or activators.

Enzymes are essential for processes like digestion, DNA replication, and even energy production within cells.

Here's how they work:

Hydrolysis: Enzymes like cellulases, proteases, and lipases break down complex molecules (e.g., cellulose, proteins, and fats) into simpler, more soluble forms by adding water molecules.
Oxidation-Reduction Reactions: Enzymes such as laccases and peroxidases catalyze reactions that break down tough, inert materials like lignin in plant cell walls or even synthetic materials like plastics.
Degradation of Polymers: Some enzymes target specific polymers, such as polyethylene terephthalate (PET), breaking them into their monomeric components, which can then be metabolized or further degraded.
Biofilm Formation: Microbes often form biofilms on inert surfaces, allowing their enzymes to work more effectively by concentrating their activity in a localized area.