BIOREMIDIATION

BY: RAHUL ANDHARIA (MSIWM001)

Introduction:

  • Bioremediation refers to use of naturally occurring microorganisms or introducing live microorganisms to break down environmental pollutants. This method is useful in reducing environmental pollution.
  • Enzymes, plants and microorganisms are used to prevent soil contaminants and to detoxify it from the environment.
  • The rate of natural microbial degradation of contaminants by supplementing indigenous microorganisms is enhanced by the process of bioremediation.

History:

  • Older versions of bioremediation dates back to 600Bc when bioremediation was first used by the Romans. They used bioremediation for the purpose of cleaning waste water.
  • Bioremediation was officially invented by George Robinson in the year 1960. First, large clean up of oil spill was initiated by him in the year 1968.

Principle involved in Bioremediation:

  • Microbes using contaminants like oil, solvents and pesticides as a source of food and energy relies on bioremediation for stimulation of their growth.
  • Contaminants consumed by microbes get converted to small amounts of water and carbon dioxide.
  • Combination of right temperature, nutrients and food is essential for effective bioremediation otherwise much longer time will be taken to cleanup contaminants.
  • Amendments can be added such as Molasses, vegetable oil, or simply air to make favorable conditions for bioremediation to take place.
  • Optimum conditions (most favorable conditions for growth) are created by these amendments for microbes to flourish and complete the bioremediation process.
  • Bioremediation is a slow process and can take anywhere from few months to several years. The amount of time required depends on factors like; size of the contaminated area, conditions like temperature and soil density, concentration of contaminants and whether the bioremediation process is in-situ or ex-situ.

Key Features of Bioremediation:

  • Contaminants in the soil matrix are destroyed in most of the bioremediation treatment technologies.
  • Generally, technologies are designed to reduce toxicity either by destruction or by transforming toxic organic compounds into lesser toxic forms.
  • Bacteria and fungi are most commonly used. In some cases, specific bacteria or fungi are used that can degrade the contaminant. (Biodegradable). Ozone or h202 (hydrogen peroxide) are added as electron acceptors to enhance growth and reproduction of indigenous organisms.

Categories of bioremediation:

  1. Microbial Remediation:
  2. Use of microorganisms to clean up contaminants is called as microbial bioremediation.
  3. Actinomycetes, fungi, bacteria, yeasts can be used in this process.
  4. Many elements present in microorganisms can be used as nutrients and microbes are easily available, omnipresent and highly diverse which makes them ideal candidates for bioremediation.
  5. Specific Microorganisms can be used for extreme environmental conditions and can be applied in both in-situ and ex-situ conditions.
  6. Mix culture approach is more suitable than pure culture approach in bioremediation as in pure culture synergistic interactions are seen while degrading crude oil present in soil.
  7. Examples: Cyanobaacteria, Pseudomonas, Nocardia, Acenetobacter and so forth. (These are the bacteria which are capable of degrading major pollutants).
  • Phytoremediation:
  • It refers to using different types of plants to transfer, remove, and stabilize/destroy contaminants present in soil and groundwater. Different phytoremediation methods are available which are as follows:
  • Rhizosphere biodegradation: Roots releases natural plant substances and supplies nutrients to microorganisms in soil. Biological degradation is enhanced by microorganisms.
  • Phyto-stabilization: chemical substances produced by plants immobilize contaminants rather than degrading them.
  • Phyto-accumulation: roots of plants accumulates contaminants along with nutrients. This process can also be called as phytoextraction. This method is best suited for wastes containing metals.
  • Hydroponic system for treating water streams: this method can also be called as Rhizofiltration. In this technique, plants used in cleaning process are raised in green houses with their roots dipped inside the water.
  • Phyto-Volatilization: organic contaminants are taken up by plants and are released into the air through leaves.
  • Phyto-degradation: plants destroys contaminants present in tissues through this technique.
  • Hydraulic control: in this method, groundwater movement is indirectly remediated by trees. Example: Poplar tree (30 gallons of water per day).

Types of Bioremediation methods:

  1. Natural bioremediation: occurs naturally. This is also called as intrinsic bioremediation.
  2. Biostimulation: fertilizers are added in the bioremediation process to increase bioavailability within the medium.
  3. In-situ technology: on site, treating of contaminated material is called in-situ technology. Large volume of soil can be treated at once. Example: Phyto-remediation.
  4. Ex-situ technology: contaminated material is treated at a place other than the site at which the process takes place, is called ex-situ technology. Treatment has more certainty in terms of uniformity. Example: slurry, solid phase bioremediation.
  5. Common examples of bioremediation technologies:

Phyto-remediation (using plants), bioventing (biodegrading contaminants by providing air or oxygen to microorganisms), bioleaching (extracting metals using microbes), bio-augmentation (Achaea cultures are added to speed up contaminant degradation and so forth.

Advantages of bioremediation:

  • Environmental friendly it uses green methods.
  • Cheaper than most of the cleanup methods.
  • It can be created for cleaning a specific site with the help of specific microbe.
  • Bioremediation is an underground process and hence microbes can be pumped underground to clean water and soil.

Limitations/Concerns of bioremediation:

  • Bioavailability of degradation products and toxicity of products cannot be known always.
  • If harvested plants contains heavy metals, it can pose a problem for disposal.
  • Plants may die, if concentration levels are too high.
  • Larger surface area is required for Phyto-remediation.  

Bioremediation is an emerging technology and has lots of prospects for specific type of cleaning but at the same time lacks few applications.

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