Advantages and Disadvantages of Bioremediation

Introduction

With time, things are changing rapidly, including the environment. In ancient times, the environment was pure and healthy, in which people lived healthier and happier lives compared to now. Multiplication in population has given birth to major problems like pollution (air, noise, water, and land) that contaminate the hydrosphere, biosphere, atmosphere, or lithosphere, due to which earth resides in a hazardous condition.

Environmental pollution has contaminated our surroundings, due to which anthropogenic activities increased in the past few decades. All cancers, COVID-19, failure of organs, and other breathtaking diseases happen due to environmental pollution. We are developing a way of killing ourselves with developing diseases.

We must preserve and keep our environment safe and clean. There are excellent ways humans adopt, like preventive measures for anti-pollution, use of anti-pollutant things, cleaning the environment, etc. With the motive of cleaning, the scientist does deep research and finds a way of cleaning named "bioremediation".

"Bioremediation is a combination of two words "bio" and "remediate" that means "living" and "solving a problem" therefore bioremediation refers to a method of solving a problem with use of living organism (microorganism)."

It comes under the biotechnology used to clean the soil, groundwater, and subsurface contaminations with the help of biological organisms. Bioremediation is an eco-friendly cleaning process that treats environmental pollutants like pesticides, oils, solvents, and petroleum products. It helps in the removal of

• Contaminated groundwater
• Clean up oil spills
• Pollutants
• Toxins from soil
• Toxins from water
• Other environmental contaminants

History:

1. 1972- Commercial bioremediation application was made for the Sun oil pipeline spill in Ambler, Pennsylvania.
2. The mid-1980s - Bioengineering of the microbes is focused on by the researchers used in the bioremediation process but could be successfully reached.
3. In the mid-1990s - Scientists focused on natural organisms and bioremediation techniques to boost their functionality.

Working of bioremediation

Bioremediation involves the immobilization, degradation, eradication, or detoxification of hazardous biological material and various chemical waste from the surrounding through the all-inclusive action of microorganisms. Bioremediation is of two types based on the removal and transportation of waste of treatment:

A. In Situ bioremediation (at the site of contamination)

• In this type, the bioremediation process is applied to the contaminated waste at its origin. The point is kept from another place to purify it in this contamination. If soil is contaminated, it is treated there only instead of removing it from its origin point. The advantage of in situ treatment is that it reduces the risk of spreading contamination during displacement and transporting contaminated soil. This technique involves air sparging, percolation, bio-slurping, bioventing, pumping, and treatment.

In situ bioremediation is of two types:

• Intrinsic bioremediation-
• Engineered bioremediation

Techniques of In-Situ bioremediation

• Bioaugmentation: This application of bioremediation is used by industries for their industrial sites to add different exogenous species or microbes to it. It works in both sparging and bioventing applications but with limitations. Microorganisms like autochthonous or allochthonous (wild or genetically modified) are involved in treating harmful contaminants in the site. Bioaugmentation deals with the oil-contaminated environment to make it pollution free.
• Biostimulation: In this process, materials, nutrients, and electron acceptors (nitrogen, oxygen, carbon, and phosphorus) are added to lift the growth and activity of indigenous microorganisms in contaminated sites. It is an alternative method to Bioaugmentation.
• Bioslurping: In this process, remedial technologies of bioventing and vacuum-enhanced free products are merged to encourage the aerobic bioremediation of hydrocarbon-impacted soils. In this, soil and groundwater remediation is achieved by indirectly stimulating contaminated biodegradation and providing oxygen. Here contaminated soil is remediated by using volatile and semi-volatile organic compounds. A slurp is used in this technique and extends into a free product layer to make free product recovery.
• Bioventing: In this method, oxygen is directly added to a contamination site in the unsaturated zone. In this, oxygen is directly supplied through air injection into residual contamination in soil. It encourages aerobic decomposition that reduces pollutant volatilization and discharges into the environment. This process can be conducted in two ways: actively or passively.
• Active bioventing: With a blower, the air is driven into the ground (in connection with vacuum extraction of the gas.
• Passive bioventing: In this atmospheric pressure affect the gas exchange from the vent wells
• Phytoremediation: In this process, plants are used to remove contaminants. Plants interactions (biochemical, physical, chemical, chemical, and microbiological) are used in polluted sites to remove the toxic effects of pollutants. Several mechanisms are involved in the phytoremediation process, such as degradation, extraction or accumulation, volatilization, filtration, and stabilization, which depend on the pollutant type. In this, elemental pollutants and organic pollutants are treated where element pollutants, including highly toxic heavy metals and radionuclides, are removed by transformation, extraction, and sequestration, and organic pollutants, including chlorinated and hydrocarbons, compounds removed by stabilization, degradation, volatilization, rhizoremediation where mineralization is possible with the use of some plants like willow and alfalfa.

B. Ex Situ bioremediation (away from the site)

Ex situ bioremediation is conducted when the climate is too cold to sustain microbe activity or when nutrients are not evenly distributed in the soil due to its density. It excavates and cleans the soil above ground, adding high cost to the process. This process may take several months to several years to complete as it can take anywhere, depending on the size of the contaminated area, temperature, soil density, and concentration of contaminants.

Ex situ bioremediation techniques are:

• Biofiltration: Biofiltration relies on the biodegrading microbial population, purifying the contaminated air from volatile organic compounds. It is a biological treatment process of biodegradable waste using various materials like bio-trickling filters, conventional bio-filters, bio-scrubbers, etc. It is a layer of compost, soil, or peat media to which pollutants come into contact with microorganisms and get biodegraded.
• Biopile: A hybrid or combined method of composting and land farming, but the volatilization and leaching of water are controlled here. This method adds organic material such as agriculture waste or manure with a proper aeration system with excavated soil. The contaminated soil is excavated to enhance the aerobic degradation process by aerobic microbes.
• Bioreactor: A bioreactor is a vessel where microbes remove contaminants from wastewater or pumped groundwater. Microbes convert pollutants into environmentally friendly, less toxic compounds in bioreactor vessels. Process in bioreactor involves steps:
  1. Adding additive
  2. Mechanical preparation
  3. Preparation of slurry
  4. Addition of nutrients
  5. Draining of slurry
  6. Additional treatment
• Windrow: In this ex-situ bioremediation technique, piled polluted soil periodically turns to enhance bioremediation. In this, degradation activities of indigenous or transient hydrocarbonclastic bacteria are increased, which is present in polluted soil. In short, contaminated waste is naturally decayed here, and remediation occurs.
• Land farming: It is a simple and low-cost bioremediation technique requiring less equipment for operation. This method turns contaminated soil for aeration and shifts to remove contaminants. The exception is that it can be regarded as both in situ and ex-situ bioremediation techniques depending on the situation or the treatment site. The depth of the pollutant plays an important role in deciding the ex-situ or in-situ techniques to be used.

Factors affecting bioremediation

These factors affect the bioremediation process such as:

Advantages of bioremediation

a. Beneficial for environment

It can remove these contaminants like metals, fluoride, herbicides, insecticides, pathogens, volatile organic compounds, arsenic, nitrate, metals, saltwater intrusion, etc. these contaminants affect the land (soil) and groundwater. The residue of the bioremediation process, such as water, carbon dioxide, and cell biomass, is harmless to the environment.

b. A natural process

This is a natural process of cleaning nature by eliminating the pollutants and problems related to the processing and storage of pollutants.

c. No threat to human

The bioremediation process is conducted to eliminate the potentially harmful threat to humans and the environment due to pollutants (that contaminate everything).

d. Energy efficiency

This process consumes less energy than other refinement methods, including landfilling and incineration.

e. Various sites can be used for bioremediation intervention

This process can take on many sites to clean the environment contaminated by organic and inorganic compounds. The following are farms, industrial sites, on-site sanitation systems, petroleum stations, landfills, mine site tailings, lumber processing yards, accidental chemical spills, and underground water.

f. Fastest approval

As bioremediation is a natural, human, and environmentally friendly process, regulatory authorities accept it and hold it in high regard.

g. Cheapest way

Yes, it is a cheap process as compared to other refinement technologies performed with microorganisms. It can be a small amount of investment.

h. less turnaround time

Other cleaning methods can take lots of time, but in the bioremediation process, the water and soil are cleaned for reuse faster.

i. Minimal equipment requirement

Bioremediation uses bio-organisms to eliminate harmful pollutants, requiring minimal equipment.

Disadvantages of bioremediation

a. Conduct under specific conditions.

The bioremediation process operates under specific conditions that may or may not be present in the field where pollutants exist.

b. Complete harmless compounds are absent.

It is not mandatory that microorganism-treated toxins can be entirely turned into harmless compounds like bacteria that couldn't easily ingest heavy material like lead and cadmium.

c. Not suitable for every pollutant

It can be conducted on pollutants which can be limited as these pollutants are present in the environment in mixed form with different proportions such as solid, liquid, and gas. Therefore it needs to design specific bioremediation practices suitable for pollutant mixtures in the field.

d. Difficult to evaluate

The performance of the this process is difficult to evaluate against standardized criteria because this process depends on uncertain factors at the time of implementation. There is no criteria or standard of cleanliness which can guarantee 100% cleanup. Process performance is difficult to evaluate, and bioremediation treatments have no single goal.

e. Biodegradable substances are treated only.

Bioremediation techniques treat pollutants or contaminants like heavy metals, agrochemicals, pesticides, organic halogens, plastics, and greenhouse gases but can deal with biodegradable substances.

f. Harmful new product

As we know, hazardous pollutants, including petroleum products, are treated in the bioremediation process. Still, sometimes in biodegradation, a new product is released that can be more harmful to the environment compared with the original component.

g. Need advancement in technology.

This system is only suitable for sites with pollutants equally dispersed in the environment. Therefore, research is needed to develop and expand bioremediation systems suitable for all sites and pollutants.

h. Regularity is uncertain

This process is not time bounded, and we can't conclude that upto when we get the result as cleaning is uncertain. It depends on various factors, i.e., heavy metals and hazardous levels of an organic compound, environmental situation, soil nutrients, etc.

i. Time-consuming

Compared with other refinery methods, it is less time-consuming, but some bioremediation techniques are time-consuming as they depend on microbial action. The bioremediation ex-situ technique treats the contaminants offsite and needs large equipment with other stuff that takes time.

j. Show results in a long time.

Compared with other refinement methods, this process takes a long time to show results.

Conclusion:

It is concluded that the advantage and disadvantages of bioremediation help us in using the bioremediation process. Bioremediation helps tailor the needs of polluted sites by using specific microbes to break down the pollutant by selecting the limiting factor needed to promote their growth. This process takes more time to show results than traditional methods, but it has technical and cost advantages. In brief, the bioremediation process is designed to remove and reduce the pollution produced naturally or by humans and to produce clean water, air, a healthy environment, and soil for future generations.