Pesticides and insecticides: The pesticides, insecticides, and herbicides percolate
in and become a part of soil and water. Pesticides like aldrin/dieldrin,
hexachlorobenzene, DDT, chlordane, and benzopyrene produce persistent and recalcitrant dioxin and chlorinated hydrocarbon that tend to persist and accumulate in
water bodies and damage beneficial microorganisms. Dioxins generally are
unwanted by-products from organochlorine compounds, such as paper production
(chlorine bleaching of cellulose) and chlorine alkali electrolysis.
(d) Pharmaceutical and Radioactive Wastes
The pharmaceutical wastes such as chemicals, medicine waste, plastic wastes,
and glass vials expired, contaminated, or spilled in water sources and radionuclidecontaminated solid, liquid and gaseous waste in larger quantity are a major source of
wastewater.
(e) Other Biological Wastes
This waste includes living organisms majorly the microorganisms generated from
hospital waste, e.g., patient excreta. It constitutes of various bacteria, fungi, protozoa, and viruses.
Septic tank leakage: Septic systems that are damaged or improperly constructed,
designed, sited, and maintained can cause contamination with detergents, bacteria,
viruses, oils, nitrates, and organic and synthetic chemicals like trichloroethane or
methylene chloride.
3 Toxic Metals in Wastewater Environment
“Heavy metals” or trace elements are basically defined as the elements with specific
gravity >5 g cm_3 (density five times greater to water) in standard state (Holleman
and Wiberg 1985). These comprise of a heterogeneous group of elements with
varying chemical and biological properties (Mukesh et al. 2008). Their wide application (batteries, chemical compounds, dyes, cosmetic products, alloys, and pharmaceutical) and toxicity effects on plants and human beings increase the pollution
risk. Some common heavy metals present in wastewater are arsenic, cadmium,
copper, chromium, zinc, nickel, and lead that enter the environment by natural and
anthropogenic activities like soil erosion, earth’s crust weathering, mining, urban
runoff, sewage discharge, industrial effluents, etc. (Morais et al. 2012). Heavy metals
can be classified in four major groups on basis of their requirement and toxicity:
(1) essential heavy metals, Cu, Zn, CO, Cr, Mn, and Fe essential for good health and
growth in small quantities; (2) nonessential metals, Ba, Al, Li, and Zr; (3) less toxic,
Sn and Al; and (4) highly toxic, Hg and Cd even in low quantities. Major heavy
metals have been described:
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M. Rastogi and M. Nandal
in and become a part of soil and water. Pesticides like aldrin/dieldrin,
hexachlorobenzene, DDT, chlordane, and benzopyrene produce persistent and recalcitrant dioxin and chlorinated hydrocarbon that tend to persist and accumulate in
water bodies and damage beneficial microorganisms. Dioxins generally are
unwanted by-products from organochlorine compounds, such as paper production
(chlorine bleaching of cellulose) and chlorine alkali electrolysis.
(d) Pharmaceutical and Radioactive Wastes
The pharmaceutical wastes such as chemicals, medicine waste, plastic wastes,
and glass vials expired, contaminated, or spilled in water sources and radionuclidecontaminated solid, liquid and gaseous waste in larger quantity are a major source of
wastewater.
(e) Other Biological Wastes
This waste includes living organisms majorly the microorganisms generated from
hospital waste, e.g., patient excreta. It constitutes of various bacteria, fungi, protozoa, and viruses.
Septic tank leakage: Septic systems that are damaged or improperly constructed,
designed, sited, and maintained can cause contamination with detergents, bacteria,
viruses, oils, nitrates, and organic and synthetic chemicals like trichloroethane or
methylene chloride.
3 Toxic Metals in Wastewater Environment
“Heavy metals” or trace elements are basically defined as the elements with specific
gravity >5 g cm_3 (density five times greater to water) in standard state (Holleman
and Wiberg 1985). These comprise of a heterogeneous group of elements with
varying chemical and biological properties (Mukesh et al. 2008). Their wide application (batteries, chemical compounds, dyes, cosmetic products, alloys, and pharmaceutical) and toxicity effects on plants and human beings increase the pollution
risk. Some common heavy metals present in wastewater are arsenic, cadmium,
copper, chromium, zinc, nickel, and lead that enter the environment by natural and
anthropogenic activities like soil erosion, earth’s crust weathering, mining, urban
runoff, sewage discharge, industrial effluents, etc. (Morais et al. 2012). Heavy metals
can be classified in four major groups on basis of their requirement and toxicity:
(1) essential heavy metals, Cu, Zn, CO, Cr, Mn, and Fe essential for good health and
growth in small quantities; (2) nonessential metals, Ba, Al, Li, and Zr; (3) less toxic,
Sn and Al; and (4) highly toxic, Hg and Cd even in low quantities. Major heavy
metals have been described:
262
M. Rastogi and M. Nandal