With the increasing pace of development in the agriculture and manufacturing industries, there is a release of a large amount of biomass waste into the environment. Excess load of this hazardous waste has led to environmental pollution (Kamaludeen et al., 2003). Bioremediation is a process which uses biological agents i.e. microorganisms like bacteria, yeast, and fungi, to make the soil and water sources free from contaminants of the biomass (Strong and Burgess, 2008). The consortium of specific microorganisms grows on the contaminated sites to perform their action to eliminate the waste. These microorganisms utilize the contaminants as nutrients or energy sources (Tang et al., 2007).
Microbial populations bioremediation of biomass
Carbon source from the biomass is the main source of energy for the microorganisms involved in the process of bioremediation (Mary Kensa, 2011). The microorganisms degrade or remediate the environmental waste due to their adaptability in this environment. Some of the group of microbes responsible for bioremediation of biomass are given below-
- Aerobic bacteria- They have the ability to degrade the pesticides and hydrocarbons (both alkanes and polyaromatic compounds). They use the biomass as the sole source of carbon and energy. Example- Pseudomonas, Alcaligenes, Sphingomonas, Rhodococcus, and Mycobacterium.
- Anaerobic bacteria- They are primarily used for the bioremediation of polychlorinated biphenyls in river sediments, dechlorination of the solvent trichloroethylene and chloroform.
- Ligninolytic fungi- They degrades toxic environmental pollutants. A common substrate used includes straw, sawdust or corn cobs. Examples- white rot fungus.
- Methylotrophs- they are used for the degradation of chlorinated aliphatic trichloroethylene and 1,2-dichloroethane.
Types of bioremediation processes
On the basis of removal and transportation of wastes for treatment, there are basically two methods
1. In situ bioremediation
In- situ bioremediation do not involve removal of soil or water from the biomass in order to accomplish remediation. In this process, there is a constant supply of oxygen and nutrients by circulating aqueous solutions through the contaminated soil to stimulate naturally occurring bacteria to degrade organic contaminants. It is used for soil and groundwater remediation (Mary Kensa, 2011). This method is cheaper and uses harmless microbial organisms to degrade the chemical. The chemotactic ability of the bacteria can move into an area containing the contaminants. So by enhancing cell’s chemotactic abilities, in situ bioremediation will become a safer method in degrading harmful compounds. In-situ bioremediation process is of two types-
Intrinsic bioremediation- This approach deals with stimulation of indigenous or naturally occurring microbial populations by feeding them nutrients and oxygen to increase their metabolic activity.
Engineered in situ bioremediation- When the site conditions are not suitable, engineered systems have to be introduced to that site. Engineered in situ bioremediation accelerates the degradation process by enhancing the physiochemical conditions to encourage the growth of microorganisms.
2. Ex situ bioremediation
This process involves excavation of the biomass from its site for the remediation process to take place. It is of two types-
Solid phase system (including land treatment and soil piles).
Solid phase system involves organic waste like leaves, manures and agricultural waste. This treatment includes processes like land farming, soil bio-piles and composting.
Slurry phase systems (including solid liquid suspensions in bioreactors).
This technique is more rapid than the solid phase treatment. Water is mixed with contaminated soil in a large tank called bioreactor and mixed to keep the microorganisms, which are already present in the soil, in contact with the contaminants in the soil. Optimum conditions are maintained in the bioreactor for the microorganisms by adding nutrients and oxygen. After the treatment is completed the water is removed from the solids and it is disposed of.
Summary of the bioremediation process
Factors to consider
|Ex-situ||Solid phase- Land farming, soil biopiles and composting.
Slurry phase- Bioreactors, Bioventing, Biosparging, Bioaugmentation.
Optimized environmental parameter.
Effective use of inoculants.
Need to control abiotic loss.
Mass transfer problems.
Toxicity of amendments.
Toxic concentration of contaminants.
Natural attenuation processes.
Treat soil and water.
Extended treatment time.
|Presence of metals and other inorganics.
Distribution of pollutants.
- The residue from the bioremediation are harmless and include mostly carbon dioxide, water and cell biomass.
- Complete destruction of the target pollutant is possible.
- It is mainly carried out on site so there is less disruption to the environment.
- It is less expensive than other technologies to clean up waste.
Disadvantages of bioremediation
- Not all compounds are susceptible to rapid and complete biodegradation.
- For the sites with complex mixtures of contaminants that are not evenly dispersed in the environment, there is a special need to develop and engineer bioremediation technologies.
- Bioremediation often takes longer than other treatment options, such as excavation and removal of soil or incineration.
Bioremediation provides a technique for cleaning up pollution by enhancing the natural biodegradation processes. So by developing an understanding of microbial communities and their response to the natural environment and pollutants, expanding the knowledge of the genetics of the microbes to increase capabilities to degrade pollutants, conducting field trials of new bioremediation techniques which are cost-effective, and dedicating sites which are set aside for long-term research, these opportunities offer potential for significant advances. This technology offers an efficient and cost-effective way to treat contaminated groundwater and soil. Its advantages generally outweigh the disadvantages, which is evident by the number of sites that choose to use this technology and its increasing popularity.
- Kamaludeen, S. P. B. et al. (2003) ‘Bioremediation of chromium contaminated environments’, Indian Journal of Experimental Biology, 41(9), pp. 972–985. doi: 10.3184/095422909X12578511366924.
- Mary Kensa, V. (2011) ‘Bioremediation – An overview’, Journal of Industrial Pollution Control, 27(2), pp. 161–168. doi: 10.1351/pac200173071163.
- Strong, P. J. and Burgess, J. E. (2008) ‘Treatment Methods for Wine-Related and Distillery Wastewaters: A Review’, Bioremediation Journal. Taylor & Francis, 12(2), pp. 70–87. doi: 10.1080/10889860802060063.
- Tang, C. Y. et al. (2007) ‘Effect of Flux (Transmembrane Pressure) and Membrane Properties on Fouling and Rejection of Reverse Osmosis and Nanofiltration Membranes Treating Perfluorooctane Sulfonate Containing Wastewater’, Environmental Science & Technology. American Chemical Society, 41(6), pp. 2008–2014. doi: 10.1021/es062052f.