Bioremediation PDF

Environmental pollution Environmental pollution has been on the rise in the past few decades due to increased human activities such as population explosion, unsafe agricultural practices, unplanned urbanization, deforestation, rapid industrialization and non-judicious use of energy rese...

Environmental pollution Environmental pollution has been on the rise in the past few decades due to increased human activities such as population explosion, unsafe agricultural practices, unplanned urbanization, deforestation, rapid industrialization and non-judicious use of energy reservoirs and other anthropogenic activities. Among the pollutants that are of environmental and public health concerns due to their toxicities are: chemical fertilizer, pesticides, agrochemicals, chlorinated compounds, heavy metals, xenobiotic compounds, organic halogens, greenhouse gases, hydrocarbons, nuclear waste, dyes plastics and sludge. Cleaning degradation, eradication, immobilization, or detoxification diverse chemical wastes and physical hazardous materials from the surrounding through the all-inclusive and action of microorganisms. Carbon is the main requirement for microbial activity. Bioremediation process was carried out by microbial consortium in different environments. These microorganisms comprise Achromobacter, Arthrobacter, Alcaligenes, Bacillus, Corynebacterium, Pseudomonas, Flavobacterium, Mycobacterium, Nitrosomonas, Xanthobacter, etc. There are groups of microbes which are used in bioremediation such as: Aerobic: aerobic bacteria have degradative capacities to degrade the complex compounds such as Pseudomonas, Acinetobacter, Sphingomonas, Nocardia, Flavobacterium, Rhodococcus, and Mycobacterium. These microbes have been reported to degrade pesticides, hydrocarbons, alkanes, and polyaromatic compounds. Many of these bacteria use the contaminants as carbon and energy source. Anaerobic: anaerobic bacteria are not as regularly used as aerobic bacteria. Typical Landfarming operation Typical Biopiles Scheme Windrows Through an engineered containment system, bioreactors treat contaminated solid material (soil, silt, sludge) or water with the help of microorganisms. This process might be aerobic or anaerobic in nature. These bioreactors are typically cylindrical in shape, with sizes ranging from liters to cubic meters, and are frequently composed of stainless steel. Bioreactor-based bioremediation process having excellent control of pH, temperature, agitation and aeration, substrate and inoculum concentrations efficiently reduces bioremediation time. The bioreactor approach is an ex-situ biochemical processing system that utilizes microbes to remove contaminants from wastewater or pumped groundwater, as well as the solid and liquid (slurry) stages of contaminated soil treatment.  Treatment of Aerobically Degradable Compounds: Bioreactor technology has been effectively employed in the treatment of aerobically degradable compounds such as SVOCs, refractory insecticides, explosive substances, aromatic hydrocarbons, and chlorinated organic compounds, polycyclic aromatic hydrocarbons (PAHs), on both a laboratory and commercial scale. Full Scale Device And Feasibility Studies: Slurry bioreactors have been used as full-scale devices and for feasibility studies in a wide range of bioremediation applications. Soil Treatment: This approach is used to treat soils that are difficult to treat using conventional methods, such as soils with high clay concentration (> 40%) or when a faster treatment is necessary. Membrane bioreactors The advantages of bioremediation It is a natural process; it takes a little time, as an adequate waste treatment process for contaminated material such as soil. Microbes able to degrade the contaminant, the biodegradative populations become reduced. The treatment products are commonly harmless including cell biomass, water and carbon dioxide. It needs a very less effort and can commonly carry out on site, regularly without disturbing normal microbial activities. This also eradicates the transport amount of waste off site and the possible threats to human health and the environment. It is functional in a cost effective process as comparison to other conventional methods that are used for clean- up of toxic hazardous waste regularly for the treatment of oil contaminated sites. It also supports in complete degradation of the pollutants; many of the toxic hazardous compounds can be transformed to less harmful products and disposal of contaminated material. It does not use any dangerous chemicals. Nutrients especially fertilizers added to make active and fast microbial growth. Because of bioremediation change harmful chemicals into water and harmless gases, the harmful chemicals are completely destroyed. Simple, less labor intensive and cheap due to their natural role in the environment. Contaminants are destroyed, not simply transferred to different environmental. Nonintrusive, possibly allowing for continued site use. Current way of remediating environment from large contaminates and acts as ecofriendly sustainable opportunities. The disadvantages of bioremediation It is restricted for biodegradable compounds. Not all compounds are disposed to quick and complete degradation process. There are particular new products of biodegradation may be more toxic than the initial compounds and persist in environment. Biological processes are highly specific, ecofriendly which includes the presence of metabolically active microbial populations, suitable environmental growth conditions and availability of nutrients and contaminants. It is demanding to encourage the process from bench and pilot-scale to large-scale field operations. Contaminants may be present as solids, liquids and gases. It often takes longer than other treatment preferences, such as excavation and removal of soil or incineration. Research is needed to develop and engineer bioremediation technologies that are appropriate for sites with complex mixtures of contaminants that are not evenly dispersed in the environment.  Phytoremediation Phytoremediation is defined as the treatment of pollutants or waste (as in contaminated soil or groundwater) by the use of green plants that remove, degrade, or stabilize the undesirable substances (such as toxic metals). Pollutants like heavy metals and radionuclides are commonly removed by extraction, transformation and sequestration. Organic pollutants hydrocarbons and chlorinated compounds are mostly removed by degradation, rhizoremediation, stabilization and volatilization, with mineralization being possible when some plants such as willow and alfalfa are used. Some important factors of plant as a phytoremediator include: root system, which may be fibrous or tap depending on the depth of pollutant, above ground biomass, toxicity of pollutant to plant, plant existence and its adaptability to predominant environmental conditions, plant growth rate, site monitoring and above all, time mandatory to achieve the preferred level of cleanliness. In addition, the plant must be resistant to diseases and pests. In phytoremediation removal of pollutant includes uptake, translocation from roots to shoots. Further, translocation and accumulation depends on transpiration and partitioning. The mostly plants growing in any polluted site are good phytoremediators. Therefore, the success of any phytoremediation method mainly depends on improving the remediation potentials of native plants growing in polluted sites either by bioaugmentation with endogenous or exogenous plant. One of the major advantages of using plants to remediate polluted site is that some precious metals can bioaccumulate in some plants and recovered after remediation, a process known as phytomining. The Mechanisms of phytoremediation : 1) Phyto-accumulation/Phyto-extraction Contaminant drawn in by plant roots by phyto-extraction, resulting in the translocation/accumulation of contaminants into plant shoots and leaves. 2) Phyto-degradation Plants produce enzymes such as dehalogenase and oxygenase, which help catalyse degradation. This process metabolises the contaminants within plant tissues due to the enzymes. 3) Phyto-stabilization Chemical compounds produced by plants immobilise contaminants at the interface of roots and soil. 4) Phyto-volatilization Volatile metals (such as mercury and selenium) are taken up, changed in species then transpired through the leaves.