Bioremediation PDF

Bioremidiation  What is bioremediation? Bioremediation can be defined as a branch of biotechnology. It makes use of living organisms, such as bacteria, to remove pollutants and toxins from water, soil, and land. This can take the form of removing oil spills or heavy metals. Bioremediation...

Bioremidiation  What is bioremediation? Bioremediation can be defined as a branch of biotechnology. It makes use of living organisms, such as bacteria, to remove pollutants and toxins from water, soil, and land. This can take the form of removing oil spills or heavy metals. Bioremediation not only uses microorganisms for various beneficial purposes to maintain our environments, but it also stimulates their growth.  If there’s a microbe or bacteria that consumes contaminants such as pesticides or oil, the process of bioremediation will use them in order to mop up these contaminants in a natural way, which then become sources of energy or food for those microorganisms. The benefit of this is that it’s a win-win: the bacteria get “food” and we get a cleaner environment! In order to successfully eliminate contaminants, the process of bioremediation needs to be finely-tuned. The correct nutrients and temperatures are required, for example.  Incontrast to different hydrocarbons, metals cannot be destroyed by microorganisms. Metalscan be modified like immobilization , change in valency by these means microorganisms can remediate metals. Their removal and recovery is done by following methods : 1. Bioremediation 2. Bioleaching 3. Biosorption  1. Bioremediation : It is a process in which living microorganisms are used to remove the environmental pollutants or prevent pollution. Microbialbioremediation uses microorganisms to break down contaminants by using them as a food source. Phytoremediation uses plants to bind, extract, and clean up pollutants such as pesticides, petroleum hydrocarbons, metals, and chlorinated solvents. Mycoremediation uses fungi’s digestive enzymes to break down contaminants such as pesticides, hydrocarbons, and heavy metals.  Techniques : Contaminants can be removed or reduced with varying bioremediation techniques that are in-situ or ex-situ. Bioremediation techniques are classified based on the treatment locality. I. In-situ techniques: treats polluted sites in a non- destructive manner and cost-effective. II. Ex-situ techniques: commonly require the contaminated site to be excavated which increases costs.  In-situ techniques are of two types: Intrinsic In-situ Bioremediation This type of bioremediation technique uses naturally available microorganism in the surroundings and converts the environmental pollutants into non-toxic substances. Engineered/Accelerated In-situ Bioremediation This is a specific technique that accelerates the process by optimum growth of microbes under their optimum condition and Physio-chemical conditions of growth. Nutrients supply, Oxygen supply, and electron acceptors can increase the growth of microorganisms on the surface. This also includes Biostimulation and Bioaugmentation processes. In situ bioremediation: These techniques are generally the most desirable options due to lower cost and less disturbance since they provide the treatment in place avoiding excavation and transport of contaminants. In situ treatment is limited by the depth of the soil that can be effectively treated. In many soils effective oxygen diffusion for desirable rates of bioremediation extend to a range of only a few cms to about 30 cm into the soil, although depths of 60 cm and greater have been effectively treated in some cases. I. In situ techniques : a)-Biostimulation b)-bioventing c)-biosparging d)-bioaugmantation  Types of Bioremediation based on the source of microorganisms used : Biostimulation, which involves the addition of nutrients, electron acceptors or electron donors, and sometimes auxiliary substrate to stimulate the growth and activity of specific indigenous microbial populations. (eg. Bioventing, biobarriers). carried out by bacteria that is naturally present in the environment or adding nutrients Stimulation of growth of microorganism by mixing the contaminants with nutrients with vital components in gas or liquid form which results in quick contaminants removal using microbial population and this is the efficient process for removal of pollutants. While nutrients or food is supplied to that contaminated site, the parent microorganism population can survive and grow more of their intended work. A) Biostimulation: specific nutrients are injected at the site in soil/ground water to stimulate the activity of indigenous microorganisms. The focus here is the stimulation of indigenous or naturally existing bacteria and fungus community. The first step is by supplying fertilizers, growth supplements and trace minerals. Then, environmental requirements like pH, temperature and oxygen are provided to speed up their metabolism rate and pathway. The presence of small amount of pollutant can also act as stimulant by turning on the operons for bioremediation enzymes. This protocol is most of the time continued in the addition of nutrients and oxygen to help indigenous microorganisms. These nutrients are the basic building blocks of life and allow microbes to create the basic requirement for example, energy, cell biomass and enzymes to degrade the pollutant. Nitrogen, phosphorous and carbon is required by all of these. b) Bioventing : Bioventing is a process that increases the oxygen or air flow into the unsaturated zone of the soil, this in turn increases the rate of natural in-situ degradation of the targeted hydrocarbon contaminant An aerobic bioremediation, is the most common form of oxidative bioremediation process where oxygen is provided as the electron acceptor for oxidation of petroleum, polyaromatic hydrocarbons (PAHs), phenols, and other reduced pollutants Oxygen is generally the preferred electron acceptor because of the higher energy yield and because oxygen is required for some enzyme systems to initiate the degradation process. Stimulation of in-situ bioremediation process of aerobically degradable pollutants presents in the soil by providing them more oxygen to an existing microorganism that enhances the process is called bioventing. c) Biosparging: Biospargingis the process of groundwater remediation as oxygen, and possible nutrients, is injected. When oxygen is injected, indigenous bacteria are stimulated to increase rate of degradation. Themass removal of the contaminated saturated zone can be enhanced by the In-situ air sparging technique. This method is processed by injecting the air into the targeted contaminated zone. This technique is an exception for the removal of volatile and semi-volatile contaminants that may undergo mass transfer from the groundwater to bubbles.  Bioaugmantation: addition of exogenous, specialized microorganisms with enhanced capabilities to degrade the target pollutant. Thistechnique is used in special cases where the microorganisms are required to extract the contaminants like municipal wastewater and the major disadvantage of Bioaugmentation is impossible to control microorganism growth in process of removing the specific contaminants or pollutants Here,additional microorganisms are added to the contaminated site with pesticide so that this can be reinforced by the natural bioprocess