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

Certain plants, including some with bulbs, are known for their ability to bind and accumulate toxic metals from the soil. This process is called phytoremediation. Plants like sunflowers, Indian mustard, and brassicas 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.

Mechanism of Toxic Metal Uptake and Transport in Plants | SpringerLink

Frontiers | Plants’ molecular behavior to heavy metals: from criticality to toxicity

Several species of brassicas are known for their phytoremediation properties. Some of the common types include:

Brassica juncea (Indian mustard): Known for its ability to accumulate heavy metals like lead, cadmium, and chromium.
Brassica oleracea (Cabbage family): This includes varieties such as broccoli, kale, cauliflower, and Brussels sprouts. They are effective at absorbing metals like selenium and cadmium.
Brassica rapa (Field mustard): Often used for phytoremediation of soils contaminated with heavy metals.

Other plants known for their phytoremediation function include: Telegraph Weed (Heterotheca grandiflora) and California Buckwheat (Eriogonum fasciculatum). Both California Buckwheat and Telegraph Weed are native to California. They are well-adapted to the state's climate and ecosystems, making them valuable for landscaping, habitat restoration, and erosion control in the region.

And still others that are native to California include:

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.
Sunflowers (Helianthus annuus)**: Capable of absorbing heavy metals such as lead and arsenic.
Cattails (Typha species)**: Useful for filtering and stabilizing contaminants in wetland areas.

These plants are not only effective in cleaning up soils but also contribute to restoring ecosystems.

Composting metal-laden plants can help reduce the concentration of heavy metals, but it doesn't completely detoxify them. During composting, organic matter and microbial activity can stabilize heavy metals, reducing their bioavailability and mobility in the soil1. However, the effectiveness of this process depends on several factors, including the type of metal, the composting conditions, and the duration of the composting process.

While composting can be a useful step in managing contaminated plants, it's important to monitor the levels of heavy metals in the compost to ensure they are within safe limits for use in agriculture or landscaping.

A review of research studies document the role of microbial enzymes in breaking down pesticide-contaminated soil.

Another article explores the biochemical characteristics of microbial enzymes and their industrial significance. The article emphasizes the potential of microbial enzymes in revolutionizing industrial bioprocesses.

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.