Process of Bioremediation and Types

Process of bioremediation and types post explains about what is bioremediation, factors of bioremediation, techniques of bioremediation, advantages and disadvantages

Rapid industrialization and unlimited extraction of natural resources have contributed to large scale environmental contamination and pollution. Huge amounts of toxic waste have spread in thousands of contaminated sites spread across the world. These pollutants belong to two main classes: inorganic and organic.

What is bioremediation?

Bioremediation is a method of biological interventions of biodiversity for mitigation/complete elimination of the noxious effects caused by environmental pollutants in a given site. It operates through the principles of biogeochemical cycling.

It has been successfully applied for clean-up of soil, surface water, groundwater, sediments and ecosystem restoration. It has also been unequivocally demonstrated that a number of other substances including nitro-glycerine (explosive) can be cleaned up through bioremediation technique.

Bioremediation technique is considered to include natural attenuation (little or no human action), bio-stimulation or bio-augmentation, the addition of natural or engineered micro-organisms (Bacteria, Fungi etc.) to accelerate the desired catalytic capabilities and it can definitely contribute to the removal of such hazardous wastes from the biosphere.

Factors of Bioremediation

Bioremediation depends upon various factors, such as

Bacterial bioremediation may be either Aerobic Bacteria (Pseudomonas, Alcaligenes, Sphingomonas etc.) or Anaerobic Bacteria or even Lignolytic fungi.

Natural Biological processes of bacterial bioremediation such as Catabolism and Anabolism play a very important role in Bioremediation.

Environmental Factors such as optimum Temperature (20-30 Degree Celsius), suitable pH(6.5-8.00), desirable oxygen content and Electron acceptor/donor are very essential factors.

Nutrients such as Carbon ,Nitrogen ,Oxygen etc must be present in a desirable quantity. Soil Moisture with 25-28% of water holding capacity is a prerequisite for Bioremediation. Soil with Low clay or silt content is required for bioremediation.

Techniques of Bioremediation

There are two types of Bioremediation

1. In-situ bioremediation:  If the process of Bioremediation occurs in the same place affected by pollution.

2. Ex-situ bioremediation: if the process involves deliberate relocation of the contaminated material (soil and water) to a different place.

1. In-situ bioremediation

In-situ bioremediation process is generally most desired than ex-situ bioremediation due to its lower cost and less disturbance as it provides the treatment in place avoiding transport of harmful contaminants.

In situ treatment is limited by the nature of the soil (depth) that can be effectively treated. In a lot of soils, effective rate for oxygen diffusion of bioremediation extend to only a few centimeters to about 30 cm into the soil. Different types of In-situ bioremediation techniques are

Process of bioremediation and types

In-situ bioremediation Process


Bio-venting is the most common in situ treatment and involves supplying of air and nutrients through wells to contaminated soil to stimulate the growth of microorganisms. Bio-venting provides only the amount of oxygen necessary for the bio degradation and the rate of air flow is also quite low where release of contaminants to the atmosphere is lowered significantly.

It works for simple hydrocarbons and can be used where the contamination is deep under the land surface. It involves supplying oxygen and nutrients by aqueous solutions through contaminated soils to accelerate naturally occurring microorganisms to degrade organic impurities. This technique includes circumstances like the infiltration of water-containing nutrients and oxygen for groundwater treatment.


Bio-sparging  involves the pressurised injection of air below the water table to increase the content of groundwater oxygen concentration and also increase the rate of biological degradation of wastes by naturally occurring Microorganisms.

Bio-sparging enhances the mixing in the saturated zone and causing it to increases the contact between soil and groundwater. The biggest advantage with the use of Bio-sparging technique is its handling ease and low cost of installing small-diameter air injection points.


Bioremediation process involves the continuous addition of microorganisms (indigenous or exogenous) to the contaminated sites. It is basically a process of the release of substantial quantities of microorganisms, sometimes of recombinant species, to carry out a specific remediation task in a given contaminated environment.

2. Ex-situ bioremediation

This technique involves the excavation, removal and transportation of contaminated soil from ground to a different site.

Land farming

Land farming is a simple technique in which contaminated soil is excavated and then spread over an already prepared bed and at regular intervals tilled until pollutants are degraded. The objective is to accelerate indigenous microorganisms and smooth the progress of their aerobic degradation of contaminants.

In general, the procedure is restricted to the treatment of superficial 10–35 cm of soil. Since land farming has the capability to decrease monitoring and maintenance costs, as well as clean-up liabilities, it has received much consideration as a disposal alternative.


Composting is a procedure that involves bringing together contaminated soil with non-hazardous organic materials such as manure or agricultural wastes. The presence of these organic materials maintains the growth of a rich microbial population and optimum temperature feature of composting.

Bio piles

Bio piles are a mixture of land farming and composting. Fundamentally, engineered cells are built as aerated composted piles. Characteristically used for treatment of surface contamination with petroleum hydrocarbons they are a refined version of land farming that have a propensity to control physical losses of the contaminants by leaching and volatilization. Bio piles provide an advantageous atmosphere for indigenous aerobic and anaerobic microorganisms.


Slurry bio reactors are used for ex situ treatment of polluted soil and water pumped up from a contaminated plume. Process of bioremediation in reactors includes the processing of polluted and infected solid material (soil, sediment, sludge) or water through an engineered containment system. A slurry bioreactor is a containment vessel and machinery used to create a three-phase (solid, liquid, and gas) mixing condition to expand the bioremediation rate of soil-bound and water-soluble pollutants as a water slurry of the polluted soil and biomass (usually indigenous microorganisms) capable of disintegrating target contaminants.

The rate and magnitude of biodegradation are bigger in a bioreactor system than in situ or in solid-phase systems because the contained environment is more handy and hence more controllable and foreseeable. In spite of the advantages of reactor systems, there are some disadvantages. The contaminated soil requires pre-treatment (Bioremediation example: excavation) or on the other hand the contaminant can be taking out of the soil via soil washing or physical extraction before being placed in a bioreactor.

Bioremediation Advantages

1. Process of bioremediation is a natural process and therefore Government and People perceive it as an acceptable waste treatment process for contaminated material such as soil or water. Microbes are very well able to degrade the contaminant when they increase in numbers and are degraded. The remains for the treatment are generally harmless products and include products such as carbon dioxide, water, and cell biomass.

2. Notionally, bioremediation is useful for the absolute destruction of a wide variety of contaminants. A lot of compounds that are legally considered to be hazardous can be changed to harmless products. This eradicates the chance of future liability related with treatment and disposal of contaminated material.

3. As an alternative to transferring contaminants from one environmental medium to another, for example, from land to water or air, the complete destruction of target pollutants is probable.

4. Bioremediation can over and over again be carried out on site, often without causing a major disturbance of normal activities. This also gets rid of the need to transport quantities of waste and the possible threats to human health and the environment that can take place during transportation.

5. Bioremediation is also relatively less expensive than other technologies that are used for disposal of hazardous waste.

Bioremediation Disadvantages

1. Bioremediation is restricted to those compounds that are biodegradable. Not all compounds are liable to quick and complete degradation. There are some apprehensions that the products of bio degradation may be more lasting or toxic than the parent compound.

2. Biological procedures are often extremely definite. Significant site factors required for success comprise the presence of metabolically capable microbial populations, suitable environmental growth conditions, and suitable levels of nutrients and pollutants.

3. More of research is required to develop bioremediation technologies that are suitable for sites with complicated mixtures of pollutants that are not evenly disseminated in the environment. Pollutants may be present as solids, liquids or gases.

4. Bioremediation time and again takes much more time than other treatment options, such as pyrolysis or incineration. There are also certain regulatory uncertainties regarding acceptable performance measures for bioremediation.

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