In recent decades, environmental pollution has increased due to human activities such as population growth, deforestation, unplanned urbanization, industrialization and commodification. Pollutants pose a great threat to the environment and public health. These include chemical fertilizers, heavy metals, nuclear waste, pesticides, herbicides, greenhouse gases, etc. These wastes have been carelessly and illegally dumped into the environment. It is alarming to be able to spot and identify thousands of these hazardous waste sites, and it is estimated that more will be discovered in the coming decades.
It is a huge task to clean all pollutants. Many techniques have been used for site cleanup in the past, such as using landfills or incineration, these are prohibitively expensive and only temporary solutions. But rather than covering or burning waste, what if you could use microbes to eat and neutralize pollution? Bioremediation scientists do just that by engineering microbes to take care of the human mess.
A branch of biotechnology, bioremediation is a process that makes use of biological systems to restore or clean up contaminated sites and involves the treatment of pollutants and toxins from soil, land and water by using microbes and bacteria. In other words, it is a waste management process in which microorganisms such as fungi, algae, and bacteria are used to remove or neutralize environmental pollutants through metabolic processes. Microorganisms are found extensively in the earth’s biosphere. They grow in soil, water, plants, animals, deep seas and frozen environments. Their quantity and demand for various chemicals make microorganisms the perfect candidate to act as stewards of our environment.
Bioremediation is not an isolated treatment option, though. To effectively deal with the ever-growing variety of contaminants, bioremediation can also be used in tandem with other physical and chemical treatment options. Bioremediation technology is widely used and continues to grow at an exponential rate. Due to its eco-friendly characteristics, remediation of contaminated sites through microbial processes (bioremediation) has proven to be effective and reliable. Bioremediation is both environmentally friendly and cost-effective compared to chemical and physical remediation methods.
In the past two decades, there have been substantial developments in bioremediation technology. This has brought the goals to successfully restore polluted environments in an economic, eco-friendly approach. The micro-organisms used in bioremediation can be either indigenous (i.e., produced, growing, living or occurring naturally in a particular environment) or non-indigenous (i.e., added or brought from elsewhere). Indigenous microorganisms present in the contaminated environment are the key to solving most of the challenges related to the biodegradation and bioremediation of pollutants.
The mechanism of bioremediation is to reduce, detoxify, degrade, mineralize or convert more toxic pollutants such as chemical wastes and physical hazards into less toxic pollutants through the action of microorganisms such as bacteria, algae, fungi, yeast and so on. The enzymatic metabolic routes of the microorganisms promote the progression of biochemical reactions that help in the decomposition of contaminants. The pollutant removal process mainly depends on the nature of the pollutants, including pesticides, agrochemicals, chlorine compounds, heavy metals, xenobiotic compounds, organic halogens, greenhouse gases, hydrocarbons, nuclear waste, plastic dyes and sludge.
Microorganisms play an important role in the nutritional chains that are an important part of the ecological balance in life. Microorganisms like bacteria, fungi, algae etc., can grow at freezing temperatures as well as extremely high temperatures even in the presence of hazardous compounds or any waste stream. Their adaptability to such extreme conditions makes them suitable for the remediation process. Carbon is the main requirement for microbial activities. Bioremediation revolves around stimulating the growth of certain microorganisms that use contaminants such as oils, solvents, and pesticides as a source of food and energy. These contaminants are converted into small amounts of water and gases such as carbon dioxide.
Microorganisms act on the pollutants only when they come into contact with the compounds that provide nutrients to the microbes. The factors are mainly microbial population for degrading the pollutants, the accessibility of contaminants to the microbial population, the chemical nature and concentration of pollutants and environmental factors like the type of soils, pH, temperature, oxygen, food and nutrients. The lack of any of these elements can extend the pollutant removal time. Conditions that are not conducive to bioremediation can be improved by adding “amendments” to the environment, such as molasses, vegetable oil, or simply air.
The bioremediation process may take anywhere from several months to years to complete, depending on the size of the contaminated area, pollutant concentration, temperature, soil density, and whether the bioremediation is performed in-situ or ex-situ. Bioremediation can be performed “in-situ”, which is at the contaminated site, or “ex-situ”, which is far away from the site. If the climate is too cold to sustain microbial activity, or the soil is too dense to distribute nutrients evenly, ex-situ bioremediation may be required. Ex-situ bioremediation, however, may entail excavation and cleaning of the ground soil, which can significantly increase the cost of the process.
Compared to other purification methods, bioremediation has many advantages. By relying entirely on natural processes, it minimizes damage to the ecosystems. Bioremediation generally takes place underground, where amendments and microorganisms can be pumped to remove contaminants in groundwater and soil. Therefore, bioremediation will not harm nearby communities like other cleanup methods. It produces relatively few harmful by-products (primarily because pollutants and pollutants are turned into harmless gases like water and carbon dioxide). Finally, bioremediation is cheaper than most traditional cleaning methods because it does not require huge labour or equipment. Therefore, it is becoming a very effective and attractive option for repairing, cleaning, managing and restoring polluted environments.