Bioremediation in Environmental Biotechnology

In this article we will discuss about Bioremediation in Environmental Biotechnology:- 1. Subject Matter of Bioremediation 2. Factors of Bioremediation.

Subject Matter of Bioremediation:

Environmental hazards and risks that occur as a result of accumulated toxic chemicals or other waste and pollutants could be reduced or eliminated through the application of bio­technology in the form of bioremediation. Bioremediation methods are almost typical processes which are applied to remove, de­grade, or detoxify pollution in environmental media, including water, air, soil, and solid waste.

Four processes can be considered as acting on the contaminant:

1. Removal:

A process that physically re­moves the contaminant or contaminated medium from the site without the need for separation from the host medium.

2. Separation:

A process that removes the contaminant from the host medium (soil or water).

3. Degradation:

A process that chemically or biologically destroys or neutralizes the contaminant to produce less toxic com­pounds.

4. Immobilization:

A process that impedes or immobilizes the surface and subsurface migration of the contaminant.

Removal, separation, and destruction are processes that reduce the concentration or remove the contaminant. Containment,on the other hand, controls the migration of a contaminant to sensitive receptors without reduc­ing or removing the contaminant.

Removal of any pollutant from the environment can take place on following two routes: degradation and immobilization by a process which causes it to be biologically unavailable for degradation and so is effectively removed.

Immobilization can be carried out by chemicals released by organ­isms or added in the adjoining environment, which catch or chelate the contaminant, mak­ing it insoluble, thus unavailable in the envi­ronment as an entity.

Sometimes, immobili­zation can be a major problem in remediation because it can lead to aged contamination and a lot of research effort needs to be applied to find methods to turn over the process.

Destruc­tion (biodegradation and biotransformation) is carried out by an organism or a combination of organisms (consortia) and is the core of en­vironmental biotechnology, since it forms the major part of applied processes for environ­mental clean-up. Biotransformation processes use natural and recombinant microorganisms (yeasts, fungi, bacteria), enzymes, whole cells.

Biotransformation plays a key role in the area of foodstuff, pharmaceutical industry, vita­mins, specialty chemicals, animal feed stock. Metabolic pathways operate within the cells or by enzymes either provided by the cell or added to the system after they are isolated and often immobilized.

Biological processes rely on useful microbial reactions including degrada­tion and detoxification of hazardous organics, inorganic nutrients, metal transformations, applied to gaseous, aqueous and solid waste.

A complete biodegradation results in detoxification by mineralizing pollutants to carbon dioxide, water and harmless inorganic salts. Incomplete biodegradation will yield breakdown products which may or may not be less toxic than the original pollutant and com­bined alternatives have to be considered, such as: dispersion, dilution, bio sorption, volatiliza­tion and the chemical or biochemical stabili­zation of contaminants.

In addition, bio augmentation involves the deliberate addi­tion of microorganisms that have been cul­tured, adapted, and enhanced for specific con­taminants and conditions at the site. Bio refining entails the use of microbes in min­eral processing systems.

It is an environment-friendly process and, in some cases, enables the recovery of minerals and use of resources that otherwise would not be possible. Current research on bioleaching of oxide and sulfide ores addresses the treatment of manganese, nickel, cobalt, and precious metal ores.

Biological treatment processes are com­monly applied to contaminants that can be used by organisms as carbon or energy sources, but also for some refractory pollutants, such as:

1. Organics (petroleum products and other carbon-based chemicals),

2. Metals (arsenic, cadmium, chromium, cop­per, lead, mercury, nickel, zinc), and

3. Radioactive materials.

Factors Affecting Bioremediation:

Two groups of factors can be identified that determine the success of bioremediation pro­cesses:

1. Nature and character of contaminant, which refers to the chemical nature of con­taminants and their physical state.

2. Environmental conditions:

This includes the temperature, pH, water/air/soil char­acteristics, presence of toxic or inhibiting substances to the microorganism, sources of energy, sources of carbon, nitrogen, trace compounds, temperature, pH, moisture content.

Also, bioremediation tends to rely on the natural abilities of microorganisms to develop their metabolism and to optimize enzymes ac­tivity. The prime controlling factors are air (oxygen) availability, moisture content, nutrient levels, matrix pH, and ambient tempera­ture.

Usually, for ensuring the greatest effi­ciency, the ideal range of temperature is 20- 30°C, a pH of 6.5-7.5 or 5.9-9.0 (dependent on the microbial species involved).

Other circum­stances, such as nutrient availability, oxygen­ation and the presence of other inhibitory con­taminants are of great importance for bioremediation suitability, for a certain type of contaminant and environmental compart­ment, the required remediation targets and the availability of required time.

The selection of a certain remediation method entails non-en­gineered solutions (natural attenuation/intrin­sic remediation) or an engineered one, based on a good initial survey and risk assessment.

A number of interconnected factors affect this choice:

1. Contaminant concentration

2. Contaminant characteristics and type

3. Scale and extent of contamination

4. The risk level posed to human health or environment

5. The possibility to be applied in situ or ex situ

6. The subsequent use of the site

7. Available resources.

Bioremediation technologies offer a num­ber of advantages even when bioremediation processes have been established for both in situ and ex situ treatment, such as:

1. Operational cost savings comparative to other technologies

2. Minimal site disturbance

3. Low capital costs

4. Destruction of pollutants, and not trans­ferring the problem elsewhere

5. Exploitation of interactions with other technologies.

These advantages are counterbalanced by some dis-remediation targets and how much time is available. The selection of a certain remediation method entails non-engineered solutions (natural attenuation/intrinsic remediation) or an engineered one, based on a good initial survey and risk assessment.

A number of interconnected factors affect this choice:

a. Contaminant concentration

b. Contaminant characteristics and type

c. Scale and extent of contamination

d. The risk level posed to human health or environment

e. The possibility to be applied in situ or ex situ

f. The subsequent use of the site

g. Available resources.

Bioremediation technologies offer a num­ber of advantages even when bioremediation processes have been established for both in situ and ex situ treatment, such as:

a. Operational cost savings comparative to other technologies

b. Minimal site disturbance

c. Low capital costs

d. Destruction of pollutants, and not trans­ferring the problem elsewhere

e. Exploitation of interactions with other technologies.

These advantages are counterbalanced by some disadvantages:

a. Influence of pollutant characteristics and local conditions on process implementation

b. Viability needs to be improved (time con­suming and expensive)

c. Community distress for safety of large-scale on-site treatment

d. Other technologies should be necessary

e. May have long time-scale.