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Bioremediation for Sustainable Environmental Cleanup

Water and soil are now becoming polluted due to the release of garbage. Untreated wastewater

is added to water, and it contains various metals that create pollution (Rudakiya and Pawar 2013).

Heavy metals have a negative effect on the food web and food chain. They can also impact numerous

activities of cells (Vardhan et al. 2019).

13.1.1.1 Metals Sources

There are two kinds of metal sources in aquatic environments:

i. Natural sources

ii. Anthropogenic sources

i. Natural Sources

Natural sources include the weathering of magmatic, sedimentary and metamorphic rocks in the

rock cycle that add heavy metals to the atmosphere and aquatic reservoirs.

ii. Anthropogenic Sources

Heavy metals are mainly introduced into groundwater as well as surface water by agricultural and

industrial activities, landfilling, mining and transportation. Various origins of pollution are caused

by metallic contaminants. Sometimes single or in mixture form, metals are discharged into the

dumping areas. Different organic pollutants consist of various metal pollutants. The pesticides

contain a number metals such as zinc, arsenic and copper. The formation of stains or dyes, alloys,

pigments and batteries also require metals in their composition (Roane et al. 2015). The high level of

metal concentrations and their use causes various negative impacts on humans, plants and animals.

13.1.1.2 Heavy Metal Toxicity

Heavy metals generally exist in the form of carbonates, hydroxides, oxides, sulfides, sulfates,

phosphates, silicates and organic compounds. They also exist in their metallic, elemental form,

but are mobilized by the action of humans (anthropogenic activity extraction, smelting) or natural

phenomenon (weathering and leaching). The World Health Organization reported that heavy metals

including cadmium, arsenic, chromium, cobalt, copper, mercury, nickel, manganese, titanium,

lead and tin are toxic (Index 2018). Various heavy metals cause cellular toxicity through different

mechanisms as depicted in Figure 13.1.

Figure 13.1. Toxicity mechanisms of some heavy metals.