Bioremediation Technology

Environmental pollution has become a major global concern due to rapid growth of industrialization, urbanization and modern agricultural development. Energy generation which have exploited natural resources for fulfilling human desires and needs, resulted in disturbing the ecological balance on which the quality of environment depends. Technological innovations and advancements in products and processes in industries have given rise to new products and new pollutants in abundant level which are above the self cleaning capacity of the environment. It is the industrial revolution that gave birth to environmental pollution.

Amongst the knowledge-based technologies, biotechnology is a frontier technology, which has the potential to provide substantial benefits to society in a wide range of sectors such as agriculture, medical and health, forestry, animal husbandry, environment protection, and improving the quality of products and services. Industrialization in developing countries is causing considerable environmental damage, as the conventional responses of end-of- pipe pollution controls are inefficient and expensive. The social and economic costs of environmental damage caused by the prevailing industrial growth in India have been estimated to be much higher than the required expenditure of 0.5-1.0 percent of GNP for pollution control. The clean up of xenobiotics and anthropogenic contaminants, which are introduced in the environment following rapid industrialization, is one of the environment related problems currently being encountered globally. The least cost clean-up technology involving bioremediation originates in environmental biotechnology, which warrants interdisciplinary approach involving such disciplines as environmental and chemical engineering, earth sciences, chemistry, toxicology, ecology, microbiology and biochemistry. In addition, the demographic compulsions and declining per capita natural resources necessitate the developing countries to optimize land and water use and restore environmental quality but, at the same

The harmful effects of organic and inorganic pollutants on ecosystems and on human health are well known and much expenditure is devoted to industrial treatment methods to prevent or limit discharges (Gadd, 2009).

Bioremediation by definition is concerned with the fate and, if necessary, removal of unwanted organic chemicals from soil and/or water. At present, bioremediation is considered as a less expensive alternative to physical and chemical means of degradation of organic pollutants. It deals with substances that are anthropogenic, distributed in nature and recalcitrant. At the same time, it is not lacked of interest to involve the bioremediation to improve some properties of the soils. The lignins are biosynthesized in plants to carry out different functions, such as storage of energy, bonding agent between plant cells, protection agent against microorganisms, antioxidant, and hydrophobic agent. Lignin is an important precursor for stabilized soil organic carbon. Terrestrial ecosystems that produce large amounts of lignin are thought to have high potential for sequestering carbon which can decrease global warming by reducing atmospheric CO₂. After the death of the plants, their compounds are transformed at the soil level with humus formation. Based on biological transformation some utilization of lignins could be developed among other things such as crop cultivation and bioremediation (Abaecherli and Popa, 2005).

Hazardous waste: A substance which has no further economic use and is disposed off on to land, water or air which might be potentially harmful to man and his environment, by reason of its physico-chemical, biological properties. Environment (Protection) Act 1986 under the Hazardous Waste (Management and Handling) Rule (1989) describes about the hazardous waste and state to ensure that hazardous waste are managed in a manner which will protect human health and environment against the adverse effects which may result from such wastes.

Pesticides usages are intensive all over the world to control insect pests even a commitment to the rapid adoption of integrated pest management techniques. Pesticides are ranked as the most widely distributed chemical contaminants of the environment in the twentieth century. According to data compiled by the United States Environmental Protection Agency and the World Health Organization, over 1000 compounds are used as pesticides, representing many different chemical classes: carbamates, thiocarbamates, organophoshates, dipyridyls, triazines, phenoxyacetates, coumarins, nitrophenols, pyrazoles, pyrethroids, and organic compounds containing chlorine, phosphorus, tin, mercury, arsenic, copper, etc. Millions of tons of pesticides are produced and used annually in close association with agriculture. Many articles, reviews and books are devoted to pesticides.

A range of pollutants are being added to the environment by human activities. Majority of these contaminants are chemically synthesized compounds also termed as xenobiotics. Some of these persist in the environment for longer periods due to presence of structural elements or constituents that do not occur naturally in nature and therefore are resistant to attack by degradative enzymes. Pollutants like nitro aromatics, polycyclic aromatics and biphenyls are degraded relatively within a short period of time or transformed into non-toxic end products owing to microbial degradation. However, highly nitrated and halogenated compounds as well as pesticides and explosives are chemically inert with longer half-lives under native conditions making them recalcitrant. Due to their poor water solubility they tend to enter the food web and are subsequently biomagnified. In addition, many of these pollutants are often metabolized in the mammalian cells resulting in intermediates that are potentially mutagenic or carcinogenic agents (Henschler et al., 2001; Galloway and Handy, 2003). This has led to imposition of prohibition on use of several of these compounds. Apart from this, large quantity of radioactive waste is also generated as a byproduct from nuclear plants generating atomic energy. This bio-hazardous waste is disposed in multiple waste dumping sites worldwide. Currently there is no efficient technology to store this waste safely. Radio nuclides need to be detoxified or effectively immobilized to prevent leaking from the contaminated sites. Ecological disasters resulting from accidental spills of the accumulated toxic waste, not only affects terrestrial ecosystem and marine life but also influences the economy of the area (Samanta et al., 2002; Brim et al., 2003; Regueiro et al., 2007).

Pollutants are artificially generated by-products of modern human world and most of them are known to have little to severe ecotoxicological impact on nature. The growing awareness of environmental pollution and its direct or indirect impact on ecosystem warrants development of cost effective, efficient and environmentally safe methods. The excessive use of chemicals in every walk of life due to unabated industrialization of modern society and growing market of cheap but harmful products due to globalization are disturbing the homeostatic balance of nature and its environment. Being the most intelligent creature of the universe, it is the prime duty of human beings to keep nature free of pollutants and provide environmentally safe ambience not only to the society but also to those innocent creatures who cannot express their discomfort.

The strategy for increasing and improving the efficiency of remediation techniques is to increase the bioaccumulation and biotransformation potential of plant and microbes for detoxification of toxic metals. With an increase in anthropological practices, more and more toxic metal ions are being added to the natural environment disrupting the ecosystem. Metals like Cd, Pb, Cr, As etc. when present in high concentrations in soil show potential toxic effects on overall growth and metabolism of plants and microbes (Yadav et al., 2009; Juwarkar et al., 2008). Bioaccumulation of such toxic metals in the plants poses a risk to human and animal health. Removal of excess of metal ions from the contaminated site is brought about by chemical as well as biological means. However, the existence of many classes and type of chemical species make the removal of the toxic metals from the environment very complicated.

The amount of hazardous waste generated by manufacturing industries increased tremendously due to industrialization worldwide. This waste is generated at every stage in the production process, use and disposal of manufactured products. Thus, the introduction of many new products for the home and office—computers, drugs, textiles, paints and dyes, plastics—also introduced hazardous waste, including toxic chemicals, into the environment. These, too, must be managed with extreme care to avoid adverse environmental or human health impacts.

Waste, by definition, is any material (solid materials such as process residues as well as liquid and gaseous effluents) that has been or will be discarded as being of no further use. Radioactive waste is a waste product containing radioactive material. It is usually the product of a nuclear process such as nuclear fission. However, industries not directly connected to the nuclear industry may also produce radioactive waste. The majority of radioactive waste is "low-level waste", meaning it contains low levels of radioactivity per mass or volume. The radiation from this type of waste is protected by use of protective clothing, but still dangerous radioactive contamination occurs in a human body through ingestion, inhalation, absorption, or injection.

Plants require essential metals for their growth and development and uptake of mineral elements from soil is a part of mineral nutrition. The plant roots are in direct contact with soil and are involved in uptake of metal ions which are later translocated to different aerial parts, where they are subsequently used for growth, development and reproduction. Concentration of metal ions in soil and their chemical speciation change with the location and environment and plants have tightly regulated mechanisms for uptake, transport and sequestration of metals (Kramer et al., 2007). Essential metals at elevated levels and contaminant non-essential metals can be toxic to plant cells and a highly regulated network of metal homeostasis mechanisms operate for control of metal uptake, trafficking and storage (Clemens, 2001).

The size dependent behaviour of any particle relates to some of its unique properties. This gave rise to rapidly growing field of Nanosciences. Nanotechnology has attracted considerable interest of both scientific and industrial community in the past few years. Nanotechnology inter-relates various research areas and applied sciences like physics, chemistry, biology, electronics and material sciences. It is often described as an emerging technology which is truly capable of revolutionizing our approaches to common problems. Nanotechnology involves the design, characterization, production and application of structures/particles by controlling their size and shape at nanoscale. An important challenge in nanotechnology is to engineer particles with desired optical and electronic properties by controlling their size and shape. This can be achieved by chemical processes and also by biological agents. Utilization of microorganisms for intracellular/extracellular synthesis of nanoparticles with different chemical composition, size, shapes and controlled monodispersity (of similar size and shape) can be a novel biological, economically viable and eco-friendly means for biosynthesis of nanoparticles. Nanotechnology holds promise in improving various aspects of life ranging from medicine to industrial materials. Also, Nanotechnology has much more to offer to environmental protection, reduction and clean-up of pollution, energy production and conservation. This chapter is an attempt to introduce the readers to the nanoworld and its use for bioremediation of toxic pollutants in the environment. This discussion also raises some of the important questions like what will be the fate of nanomaterials released in the environment and their consequent impact on the ecosystem.