Bioremediation: Definition, Types and Applications

Bioremediation: Definition, Types, and Applications

Definition of Bioremediation:

  • Bioremediation is the process of removing pollutants from the environment with the help of microorganisms such as bacteria and fungi with degrading functions.
  • Bioremediation is a branch of biotechnology that utilizes living organisms, such as microorganisms and bacteria, to remove pollutants, toxins, and contaminants from soil, water, air, and other environments.
  • Bioremediation is the process of the use of microbe’s metabolic activities to reduce the concentration of toxic and harmful substances from the polluted environment or make them harmless.
What is Bioremediation?

  • Bioremediation is a new technology that has just emerged in the field of environmental engineering. 
  • Bioremediation can be defined as the process of removing or neutralizing waste and toxic substances in the environment by using organisms such as microorganisms, small organisms, and plants. 
  • Many microorganisms and plants are capable of degrading toxic and harmful substances and reducing toxicity.
  • The bioremediation process depends on the organisms used, environmental factors and types, volume and status of contaminants, etc. 
  • Naturally occurring microorganisms decompose organic wastes in the environment through biodegradation.
  • But the natural purification process by many microorganisms that exist in most environments is very slow due to the lack of dissolved oxygen (or other electron acceptors), nutrients, and another limiting factor Effective microorganisms often grow more slowly.
  • To quickly remove pollutants, many enhancement measures are often taken, such as providing electron acceptors, adding nutrients such as N and P, and inoculating cultured high-efficiency microorganisms.
  • Surfactants are also often used to improve bioavailability.
  • One or more microorganisms are used to degrade organic poisons in soil, such as pesticides, petroleum hydrocarbons, organophosphorus, organochlorine, etc. 
  • At present, it has been successfully applied to the pollution control of soil, groundwater, river, and offshore surface. 
  • Bioremediation applies to many processes: industrial and domestic wastewater treatment, solid waste treatment, drinking water treatment, soil, and land treatment, 
  • There are two main types of Bioremediation; In-situ and Ex-situ.

Bioremediation definition types and example

How Bioremediation Works :

  • Bioremediation Enhance and stimulates the growth of certain microorganisms that use toxins, pollutants such as oils, solvents, and pesticides as a source of food and energy.

  • Now, these microbes convert pollutants into small amounts of water, as well as harmless gases like carbon dioxide.

  • Bioremediation requires the right combination of temperature, nutrition, and food. The absence of these elements may prolong the removal time of contaminants. 

  • Unfavorable Conditions for bioremediation can be improved by adding “modifiers” such as molasses, vegetable oils, or simply air. 

  • Modifiers create favorable conditions for microbial growth and speed up the completion of the bioremediation process.

  • Bioremediation can be performed at the site of the contamination or away from the site of the contamination.

  • Ex-situ bioremediation may be required if the climate is too cold to sustain microbial activity, or if the soil is too dense for even distribution of nutrients. 

  • Ex-situ bioremediation may require excavation and clearing of soil above ground, which can add significant costs to the process.

  • The bioremediation process can take anywhere from months to years to complete, depending on the size of the contaminated area, the concentration of contaminants, temperature, soil density, and whether bioremediation is performed on-site or off-site.

Types of Bioremediation:

  • Based on the type of organisms used: Bioremediation can be divided into microbial restoration and animal restoration and phytoremediation.

  • Based on the polluted environment to be restored: it can be divided into water bioremediation, soil bioremediation, and atmospheric bioremediation.

  • Based on the location of the site: It can be divided into In-situ bioremediation and Ex-situ bioremediation.
  • According to whether there is manual intervention: it can be divided into natural bioremediation and artificial bioremediation.

Techniques of Bioremediation

Generally, there are two types of Bioremediation In-situ Bioremediation and Ex-situ Bioremediation. 

In-situ bioremediation:

  • In-site bioremediation refers to the bioremediation process performed at the original site of infection. 
  • The concept of biological remediation is mainly used to deal with contaminants in soil and groundwater. 
  • However, the recovery rate and the effectiveness of the procedure depend on different factors. They are as follows:
  1. The type of pollution concerns
  2. Features for specific sites
  3. Distribution and concentration of pollutants
  4. The concentration of other pollutants
  5. Microbial community of the site
  6. Temperature
  7. a pH of the medium
  8. Moisture content
  9. Providing nutrients

  • The handling of the above factors is not very feasible on the spot bio-mediation. 
  • However, in on-site improved bioremediation, certain manipulations such as aeration, nutrient addition, control of moisture content, etc. are used to improve the activity of organisms and increase the rate of degradation. 
  • On-site examples Bioremediation technologies include aeration, improved biodegradation, biodegradation, phytotherapy, physical attenuation, etc 

There are different types of In-situ bioremediation techniques including 

1. Natural attenuation
  • Natural attenuation is a type of bioremediation technique that is used to treat contaminated/polluted environments with the help of microorganisms.
  • The Environmental Protection Agency (EPA) defines natural attenuation as “a variety of physical, chemical, or biological processes that, under favorable conditions, act without human intervention to reduce the mass, toxicity, mobility, volume, or concentration of contaminants in soil or groundwater.
  • Monitored Natural attenuation (MNA) is an in situ remediation technology that relies on naturally occurring and demonstrable processes in soil and groundwater which reduce the mass and concentration of the contaminants.
  • It can be an effective and low-cost approach for the remediation of contaminated sites. 
  • By Natural attenuation, we can reduce contaminant mass or concentration in soil or groundwater under intrinsic conditions.
2. Biostimulation:
  • Biostimulation involves changing the environment to stimulate existing bacteria capable of bioremediation.
  • During biostimulation, the environment is altered to stimulate native microorganisms.
  • This can be done by adding various forms of rate-limiting nutrients and electron acceptors such as phosphorus, nitrogen, oxygen, or carbon (eg in the form of molasses).
  • Biostimulation can be enhanced by bioaugmentation.
  • The main advantage of biostimulation is that bioremediation will be carried out by already existing natural microorganisms that are well adapted to the subsurface and spatially well distributed in the subsoil.
3. Bioaugmentation:
  • Bioaugmentation refers to the process of increasing the rate of biodegradation by adding the bacterial or archaeal culture.
  • Bioaugmentation products generally consist of a mixture of several strains of microorganisms, namely bacteria or fungi. 
  • Organisms are isolated from nature and are not genetically altered. 
  • They are selected based on their accelerated reproduction rates and their ability to perform specific functions, such as good foculation ability to improve their sedimentation or the ability to break down specific compounds.
  • Bioaugmentation has a wide range of applications including Treatment of high-concentration organic wastewater, Treatment of toxic and harmful refractory pollutants, and Groundwater bioremediation.
4. Bioventing:
  • Bioventing is an Ex-situ method of bioremediation technique that involves only the insertion of air into the medium to stimulate the aerobic activity of microorganisms to remove pollutants.
  • Bioventing is a pressurized oxidative biodegradation method, which involves drilling several deep wells into the contaminated soil, installing blowers and vacuuming machines, and forcing air into the soil. 
  • Then it is pumped out, and the volatile organic compounds in the soil are also removed. 
  • Bioventing is commonly used to remediate soil in the upper aeration layer of groundwater aquifers contaminated with volatile organic compounds.
  • With the rapid development of the petroleum, chemical industry, and agriculture, soil pollution by volatile organic compounds (VOCs) is becoming more and more serious to remove such pollutants bioventing process performed.
  • It has a wide range of applications, low operating costs, no secondary pollution, and flexible and simple operation. 
5. Landfarming:
  • Landfarming is an ex-situ type of bioremediation in which the waste treatment process is performed in the upper soil zone. 
  • Contaminated biological waste, soils, sludge, sediments are transported to the land farming site and mixed into the soil surface, and periodically turned over to aerate the mixture.
  • Here these contaminants are degraded, transformed, and immobilized with the help of biotic and abiotic reactions.
  • Landfarming is most successful in treating petroleum hydrocarbons, Pesticides, oily sludge, PCP, creosote, and coke wastes.
  • By landfarming, Inorganic contaminants will not be biodegraded. 
  • A large amount of space is required for landfarming.
6. Phytoremediation:
  • The process in which plants are used to remove or decompose pollutants such as heavy metals, organic matter, etc from the contaminated land or groundwater.
  • Phytoremediation is a very unique pollution control technology as compared with physical, chemical, and microbial treatment technologies.
  • Phytoremediation is a cheap and efficient method to remove Pollutants/Contaminants from land, air, and water.
  • Contaminants such as heavy metals, organic matter, radioactive elements, pesticides, explosives, and crude oil can remove by phytoremediation.
  • Many plants are used in phytoremediation such as mustard plants, sunflower alpine pennycress, Spinach, hemp, and pigweed to remove contaminants. 
  • There are different types of phytoremediation techniques: Rhizofiltration, Phytoextraction, Phytotransformation, Phyto-stimulation, and Phytostabilization.

Ex-situ bioremediation:

  • Ex-situ Bioremediation is a technique that treats pollutants away from the site where they were found. 
  • Pollutants are excavated or pumped from the original site and treated in controlled environments. 
  • A wide range of hydrocarbons is purified from ex-situ biodegradation. 
  • Contaminated soils are excavated and placed on the soil surface and treated using native microorganisms. 
  • Ex-situ Bioremediation can be controlled and managed by providing the required conditions. 
  • Examples of ex-situ bio-mediation processes include composting, soil biosystems, parcels, slurry reactors.
  • EX Situ Bioremediation is of the following types:
    1. Composting
    2. Bioreactors

1. Composting

  • Composting is essentially a method of humifying organic matter. 
  • Organic waste can form macromolecular humic acid through the composting process, and the structure of humic acid also changes with the type and number of functional groups formed. 
  • It can be applied to the remediation and quality improvement of different types of polluted soils according to the characteristics of different humic acids.
  • The ex-situ biological treatment process based on treated bed technology promotes the biodegradation of pollutants by optimizing the conditions within the mound. 
  • The excavated contaminated soil is stacked in long, static pairs. 
  • Necessary nutrients and water are added to the polluted mound, and an appropriate amount of surfactant is added if necessary, and pipes for spraying nutrients can also be installed on the mound.
  • Compost products can also be used as soil fertilizers or soil remediation agents to solve the dual problems of soil pollution remediation and quality improvement.

2. Bioreactor bioremediation 

  • The bioreactor is a system in which naturally occurring microorganisms or microorganisms with special biodegradation ability are used to degrade contaminants.
  • There are different types of bioreactors but the most studied reactors are the “lift-type reactor” and the “soil-slurry reactor”. 
  • The lift-type reactor provides proper nutrients, carbon sources, and oxygen through the flow of the water phase, to achieve the purpose of degrading the pollutants in the soil. 
  • As compared to solid-phase bioreactors the liquid-type reactor can effectively degrade pollutants in a shorter time. 
  • Bioreactor technology has been applied in the bioremediation of organically polluted soil.
  • The biodegrading microorganisms are originally present in soil or inoculated microorganisms. 
  • For bioreactors, bioremediation conditions should be strictly controlled to facilitate the degradation of organic pollutants in the mud. 
  • The treated mud is dewatered. 
  • The resulting water is further treated to remove contaminants and can then be recycled.
  • Bioreactor bioremediation is simple, Low cost, High efficiency, and Reduces industrial pollution.

Application of Bioremediation

  • It is a safe process that does not affect the environment 

  • It is simple, promising, and sustainable.

  • It is a low-cost process compared to other treatment techniques.
  • The bioremediation process uses plants and microorganisms to degrade toxic pollutants into non-toxic substances.
  • It does not destroy the soil environment required for plant growth, and the physical, chemical and biological properties of the soil remain unchanged.
  • The pollutants are completely degraded, and the organic pollutants can be degraded into completely harmless inorganic substances.
  • It is most widely used and can deal with various kinds of organic pollutants, such as Plastics, Pesticides petroleum, explosives, herbicides, etc. 
  • It can be applied on small or large ​​pollution areas, and can simultaneously treat contaminated soil, water, etc.

Disadvantages of Bioremediation

  • Bioremediation technique is considered slow as compared to artificial techniques.
  • If it is poorly calculated or put into practice in the wrong way, the use of microorganisms that do not inhabit the place can bring ecological imbalance.
  • It requires a lot of careful study and research before being applied, which ends up taking time.
  • Each bioremediation process involves a specific experimental design, depending on the particular conditions, type of Organisms, type of contaminated site, and type of pollutants.

Frequently Asked Questions on Bioremediation:

1. Which is an example of bioremediation?
Answer: Some examples of bioremediation technologies are landfarming, bioreactors, composting, phytoremediation,  bioaugmentation, rhizosphere filtration, biostimulation, etc.
2. What organisms are used in bioremediation?
  • Bacteria, 
  • Archaea
  • Fungi
  • Plants
  • Animals 
3. What are the different types of bioremediation?
Answer: Following are the different types of Bioremediation 
  1. Microbial bioremediation: It uses microorganisms as a food source to break down contaminants.
  2. Phytoremediation: It uses plants to bind, extract and clean up pollutants such as pesticides, petroleum hydrocarbons, metals, and chlorinated solvents.
  3. Mycoremediation: It uses the digestive enzymes of fungi to break down pollutants such as pesticides, hydrocarbons, and heavy metals.
4. What are the applications of bioremediation?
Answer: Bioremediation technology is used to degrade highly toxic metals, chemicals, wastewater, and pollutants in the environment.
5. What are the advantages and disadvantages of bioremediation?
Answer: Bioremediation is an environmentally friendly and sustainable method of destroying pollutants or converting harmful pollutants into harmless substances. The main disadvantage of bioremediation technology is that it is limited to biodegradable compounds. The effectiveness of bioremediation is limited in sites with high metal concentrations, highly chlorinated organics, and inorganic-organic salts.

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