Stocks Tech Stocks. What Is Bioremediation? Key Takeaways Bioremediation is a branch of biotechnology that employs the use of living organisms, like microbes and bacteria, in the removal of contaminants, pollutants, and toxins from soil, water, and other environments.
Bioremediation is used to clean up oil spills or contaminated groundwater. Bioremediation may be done "in situ"—at the site of the contamination—or "ex situ"—away from the site. Compare Accounts. The offers that appear in this table are from partnerships from which Investopedia receives compensation. This compensation may impact how and where listings appear. Investopedia does not include all offers available in the marketplace.
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Partner Links. Bioremediation, a biological process mediated by microorganisms, is now considered to be one of the most sustainable approaches to degrade and detoxify environmental contaminants.
This approach is often successful but practically admiration of less result as desirable, i. The key to successful bioremediation is to trap up the naturally occurring catabolic potential of microorganisms to effectively catalyze transformations of environmental pollutants. Small scale experiments using distinct microbial consortia in the laboratory is an immense starting point in providing crucial initial indication of the bioremediation process within definite control condition.
However In situ bioremediation in real execution is a complex phenomenon involving more than one contaminant and simultaneously mediated by different microorganisms involving different metabolic pathways, across geochemical gradients, geophysical and hydrological complexities Purohit, Proteomics : Proteomics is the large-scale study of proteins, particularly their structures and functions.
Microbial Degradation : Interest in the microbial biodegradation of pollutants has intensified in recent years as humanity strives to find sustainable ways to clean up contaminated environments. Metabolomic : Metabolomics is the scientific study of chemical processes involving metabolites. Genetic Engineering : Genetic engineering, also called genetic modification, is the direct manipulation of an organism's genome using biotechnology.
MetaRouter : It is a system for maintaining heterogeneous information related to Biodegradation in a framework that allows its administration and mining.
Metagenomic : Metagenomics is the study of genetic material recovered directly from environmental samples. Bioreactor technologies may offer effective means for treatment of many contaminants in groundwater, soil and air [ 4 , 5 , 7 , 12 ].
The bioreactor type of choice for any application should be easy to operate and maintain for the selected purpose and application. Table 1 presents some of the studies that involved the use of bioreactors in bioremediation.
Flexibility to design bioreactor tailor made for different processes and remediation applications makes the use of bioreactors in bioremediation attractive [ 9 ].
The design should accommodate high biomass from cell growth, supply of necessary nutrients and also removal of waste components from the system. A description of some bioreactor types and their application is given in Sections 3.
Slurry phase bioreactors, as the name implies treats polluted media that is within a slurry phase. Alternative names are bio-slurry reactors and slurry phase biological treatment. Slurry bioreactors offer an ex situ environmentally friendly way for remediating mostly soils and sediments from petrochemical hydrocarbons, tars, creosotes, chlorinated solvents, herbicides, pesticides and explosives or when a solid substrate that is formulated into a slurry is used [ 4 , 6 , 25 , 26 ].
Hydrophobic nature of most persistent chemicals makes them sorb to soil or sediments and not easily accessible for biodegradation. Operation of the slurry reactor can be in batch, semi-continuous and continuous mode, with the batch process being the most common one [ 6 , 26 ]. Figure 1 shows an illustration of a simplified slurry reactor. Water is mixed with the contaminated solid matrix in suitable ratios and this enhances contact between microorganisms, pollutant, media and oxygen.
Pollutants that are solubilized become more bioavailable. Table 2 shows some of the studies that have involved the use of slurry phase bioreactors in bioremediation.
Simplified slurry reactor [ 26 ]. Partitioning bioreactors are used in bioremediation when two phases need to be achieved, e. Reactors are designed with the aqueous and organic phase, and can be single or multiphased [ 24 ].
With toxic hazardous waste, toxicity to degrading microorganisms is a problem. In partitioning bioreactors, there is a two-phase system where a water immiscible and biocompatible organic solvent is allowed to float on the surface of a cell containing aqueous phase [ 45 ]. This means that high amounts of hazardous waste dissolved in a solvent can be added to the reactor without the microorganism experiencing inhibitory concentrations of the pollutant [ 24 , 45 , 46 ].
A rigorous process involving selection of the solvent, taking into consideration the biological, physical, operational, environmental and economic factors is necessary in developing an efficient partitioning biotreatment system.
Partitioning reactors find application in the remediation of toxic compounds from petrochemical industry such as benzene as well as VOC in waste gases of many industrial processes [ 45 , 47 , 48 ].
Angelucci et al. Several other studies involving phase partitioning bioreactors are described [ 24 , 45 , 46 , 47 , 48 , 49 , 50 ]. A continuous stirred tank bioreactor consists of a cylindrical vessel with motor driven central shaft that supports one or more agitators impellers. Stirred tank bioreactors are the predominantly used design for submerged cultures. Stirred tank bioreactors are mechanically agitated where the stirrers are the main gas-dispersing tools and provide high values of mass transfer rates coupled with excellent mixing.
Advantages of the STR include the efficient gas transfer to growing cells, good mixing of the contents and flexible operating conditions, besides the commercial availability of the bioreactors. The main shortcoming of the stirred tank bioreactor is its mechanical agitation which requires energy and stirring can cause shear strain on microbial cells.
Gargouri et al. The reactor used is shown in Figure 2. Bi [ 51 ], applied a continuously stirred tank reactor for bioremediation of ethanol, toluene and benzyl alcohol by P. Schematic diagram of the aerobic continuously stirred tank bioreactor CSTR used for continuous experiments [ 7 ].
A basic biofilter bioreactor consist of a large media bed where pollutants are passed through and get degraded by the microorganisms. Biofilters are amongst the oldest environmental bioremediation techniques. Biofilters are used mostly in waste water treatment as well as in the control of air pollution [ 34 , 52 , 53 ]. A number of materials are used for bed media such as peat, composted yard waste, bark, coarse soil, gravel or plastic shapes.
A typical example of a biofilter is the trickling filter which finds extensive application in the treatment of different liquid effluents or waste waters or waste that is constituted into liquid. A trickling filter is usually a round, vertical tank that contains a support rack and is filled with aggregate, ceramic or plastic media and in the middle of the tank is a vertical pipe that has a rotary connection with spray nozzles on the top end [ 34 ].
A spray arm is attached to the rotary connection and has spray nozzles installed along its length for distribution of the waste water. Microorganisms grow in biofilm forms on the packing material surface and are responsible for the degradation of the pollutants from the effluent. Schmidt and Anderson [ 34 ] described the use of a trickling biofilter in the removal of high concentrations of 1-butanol from contaminated air.
The laboratory-scale perlite-packed biotrickling filter was operated for 60 days and demonstrated effective and efficient removal of butanol concentrations up to 4. Packed bed bioreactor systems provide for microbial growth on fixed film substrata. In order to obtain compact reactors and ensure greater treatment reliability, fixed film reactors are used.
They offer the advantage that dilute aqueous solutions can be remediated at high biomass without the need to separate biomass and the treated effluent [ 13 , 54 ]. In packed bed biofilm biotreatment processes, unlike suspension cultures there is no need to incorporate special measures such as centrifugation and membrane filters to retain the biomass.
This feature makes the use of packed bed reactors particularly appropriate in bioreactors systems where large substrate—flow through is required. While high biomass concentrations can be easily maintained, the medium to biofilm mass transfer of substrate is the rate limiting process in packed bed bioreactors [ 54 , 56 ]. Substrates such as oxygen, carbon and nitrogen sources have to cross the biofilm—liquid interface by diffusion, thus a diffusion gradient occurs.
To calculate the kinetics of conversion in the biofilm processes, two important processes that occur in the system are considered and these are i transport of solutes over the biofilm and ii combined reactions and diffusion inside the biofilm [ 54 ].
In the packed bed reactors, development of excess microbial biomass also occurs leading to hydraulic channeling or loss of interstitial fluid volume. To overcome the severe constraints of hydraulic hold up within the interior of the reactor extra-capillary space transverse flow bioreactors were developed [ 57 ].
Selection of suitable substances as packing materials is an important consideration. Materials that have been used include nylon web, polyurethane foam, silicone tubing, sintered glass, porous ceramics, propylene, stainless steel, agarose and agar gel beads [ 58 , 59 , 60 , 61 , 62 , 63 , 64 , 65 , 66 , 67 ]. The ideal support should be chemically inert in physiological growth medium, rigid and porous to facilitate mycelial attachment and re-usable after removal of the fungus.
Figure 4 shows a Simplified diagram of a laboratory based packed bed bioreactor. Examples of remediation studies in packed bed reactors are given in Table 3. Airlift bioreactors can provide an attractive treatment alternative for treatment of gaseous or volatile air pollutants. Bioremediation has been successfully used to clean up more than Superfund sites across the United States. In addition, EPA assists state and local governments with the remediation of brownfields , sites that may also contain hazardous pollutants.
Currently, more than , brownfields exist throughout the United States. The environmental impact of the remediation process has increasingly gained attention over the past two decades. In , EPA launched its Superfund Green Remediation Strategy , which recognizes the range of negative environmental impacts from contaminated site cleanups.
As a cleanup method, bioremediation offers an environmentally friendly approach compared to traditional remediation technologies. Bioremediation draws on natural processes without adding any foreign or toxic chemicals to the site, creating few, if any, waste byproducts. Furthermore, since natural organisms degrade contaminants into simple compounds that pose little or no threat to the environment, polluted soil and groundwater can be treated on site, or in situ.
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