Integrative Approaches for Understanding and Designing Strategies of Bioremediation
Introduction
Quality of life on Earth is solely associated with healthy environmental conditions and an abundance of natural resources. Natural resources play a vital role in life on Earth. They form the basis of everything humans need to survive. Currently, most of the world’s resources are depleting or losing their quality due to pollution, thereby affecting humans, wildlife health, and the whole ecosystem (Vidali et al. 2001, Sharma and Reddy 2004). This demonstrates our carelessness and negligence regarding the environment and natural resources. Land and water are the two fundamental pillars of natural resources on which the sustainability of agriculture and the continued existence of civilization rely. Unfortunately, both have been drastically degraded through toxic chemicals due to some natural and anthropogenic activities (Sharma and Reddy 2004, Chitra et al. 2011). These activities generate wastes and pose risks to public health, natural habitat, and all or part of the ecosystem (Yadav et al. 2018).
Currently, the contamination of water bodies and soil pollution due to toxic substances is a primary environmental concern that affects large areas worldwide. Industrial waste, domestic effluents, and agricultural practices have been the prime source of heavy metals in the soil, such as lead, chromium, arsenic, zinc, cadmium, copper, and nickel. For example, the one-sixth part of the agricultural land is affected by heavy metals in China. It is reported that 42 rivers in India are polluted with at least two toxic heavy metals (Central Water Commission 2014). The contaminated water bodies and polluted soil sites are a dormant warning to human health and the environment.
On the other hand, India is facing a considerable waste management crisis. As a developing country, this is a big setback to India. Poor waste management leads to a decline in quality of life in the aspects of health and hygiene (Yadav et al. 2018). Additionally, it is tough and increasingly expensive to find new landfill sites for the final disposal of the material. The cap and contain method are only an interim solution since the contamination remains on-site, requiring monitoring and maintenance. A healthier approach than these traditional methods is to destroy the pollutants if possible, or at least to transform them into innocuous substances (Sharma 2012). Some techniques, such as incineration, are used for decomposition of types of chemicals (e.g., base-catalyzed dechlorination). They can be very operational at reducing levels of a range of contaminants but have many drawbacks, principally their technological complexity and the lack of public acceptance (Sharma 2012, Yadav et al. 2018). Hence, considering all other methods, bioremediation is an option that offers the possibility to destroy or reduce various harmless contaminants using natural biological activity (Vidali et al. 2001, Naik et al. 2012).
Bioremediation: characterization and concepts
Bioremediatiou is a process that principally uses microorganisms, plants, or microbial or plant enzymes to detoxify contaminants in the soil and other polluted sites (Shukla et al. 2014, Sharma et al. 2018), and known efficient and eco-friendly strategies for sustainable development (Varol 2011, Sharma 2012, Rizwan et al. 2014). Bioremediation concept includes biodegradation, which refers to the partial, and sometimes total, transformation, or detoxification of contaminants by microorganisms and plants (Shukla et al. 2014, Yadav et al. 2018). In bioremediation, microorganisms must enzymatically attack the pollutants and convert them into harmless products (McCutcheon et al. 2004). As bioremediation can be practical only where environmental conditions permit microbial growth and activity, its use often involves the manipulation of environmental factors to allow microbial growth and degradation to keep at a faster rate (Sharma 2012). Bioremediation methods are naturally more cost-effective than traditional methods such as incineration, and some pollutants can be treated on-site, thus decreasing exposure risks for clean-up personnel or potentially more extensive exposure as a result of transport accidents. Since bioremediation is created based on natural attenuation, the community considers it more acceptable than other methods. Most bioremediation systems are operated under aerobic conditions. However, running a bioremediation system under anaerobic conditions may allow microbial organisms to degrade otherwise recalcitrant molecules (Colberg and Young 1995).
