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Bioremediation for Sustainable Environmental Cleanup

12.1.1 Heavy Metals Pollution in Water and their Impacts

Heavy metals are explained as metals with high atomic weight and high density. Metallic chemicals

and metalloids (selenium, arsenic) are highly toxic to human health, while some are typically non­

toxic, like gold and silver (Tchounwou et al. 2012). While toxic metals need to be removed, precious

metals must be essentially recovered from the wastewaters. There are some essential heavy metals

likes Cu, Fe, Mg, Zn, while non-essential heavy metals are Cr, Ni, Pb, As, Hg (Kumar et al. 2020).

Heavy metal accumulation in worldwide rivers and lakes is higher than the permissible limits as per

standards of the WHO (World Health Organization) and has been increasing over the past 4–5 decades

(Zhou et al. 2020). This increased metal pollution is mainly attributed to industrial waste and mining

activities, while the geochemical origin is the natural causal factor (Zeitoun et al. 2014). Chemicals

loaded with heavy metals are used in industries like metal plating, battery production, tanneries,

petroleum refineries and mining; wastewaters from these industries include large amounts of heavy

metals. Metals are mobilized in the environment, where they alter the biogeochemical processes

and bioaccumulate in the food chain (Waldichuk 1994). Plants, animals and microorganisms are all

affected by metal polluted water and soil. Human health is adversely affected because metals tend

to get bioaccumulated in the food chain and human beings occupy higher levels in the food web.

Concentrations of various metals such as Fe, Ni, Cd and Co which are known to have serious health

implications, were found to be exceeding the permissible limits in river Yamuna flowing across the

state of Haryana (Kaushik et al. 2001) and river Ghaggar (Kaushik et al. 2000) and these metals

were mainly related to anthropogenic sources. Table 12.1 shows the health impacts of some non­

essential heavy metals and metalloids as reported by researchers.

Table 12.1. Health impacts and sources of non-essential heavy metals.

Heavy metals

Major sources

Health impacts

References

Arsenic

Industrial waste, agricultural runoff, coal

mining, fossil fuel burning, etc.

Psychological effect, decreased mental

performance, cardiovascular disease,

kidney damage, carcinogenesis, effect

on reproduction, bone demineralization

Rehman et al.

2018

Cadmium

Mine drainage water, waste from the

processing of ores, agricultural runoff

Kidney damage, osteoporosis,

cardiovascular disease, cancer, lungs

damage, obesity and diabetes

Fatima et al.

2019

Lead

Paint industry, batteries, unregulated

cosmetics and medicine

Affects brain and nervous system, high

risk of blood pressure, kidney damage,

effects pregnant woman or exposing

the fetus

Demayo et al.

1982, García-

Lestón 2010

Nickel

Batteries, paper industry, fossil fuels,

mining, volcanoes, forest fires

Cardiovascular, kidney damage, lung

fibrosis, lung and nasal cancer and

respiratory manifestations

Genchi et al.

2020

Mercury

Industrial effluents, coal combustion,

battery and fluorescent lamp production,

cement production, Hg mining, and

biofuel burning

Acute chemical bronchitis and

pneumonitis, Minamata disease

Zhang et al.

2007

12.1.2 Metal Remediation Approaches

With increasing awareness about the harmful impacts of various heavy metals on ecosystems and

organisms’ health, there is a greater emphasis on the elimination and retrieval of the metals from

polluted waters and soils by adopting various techniques (physical, chemical, biological) available,

as shown in Figure 12.1.