7.2 Sources of Toxic Effluents
• Cadmium primarily comes from launderettes, small electroplating and coating
shops, and plastic manufacture industries, and it can be used in alloys, pigments,
dental work, paints, photography, Ni-Cd batteries, glazes, artisanal shops, and car
repair shops (ATSDR 1999).
• Chromium are found in alloys and is released from diffuse sources and products
such as preservatives and dying and tanning activities. Chromium III is broadly
used as a tanning agent in leather operation. Chromium VI being highly toxic, its
uses are now restricted, and there are less commercial sources.
• Copper is used in electronics, plating, paper, textile, rubber, fungicides, printing,
plastic, and brass and other alloy industries, and it can also be released from
various small commercial activities and warehouses, as well as buildings with
commercial heating systems (Chikwendu et al. 1989).
• Lead is often used as a fuel additive (now greatly reduced or banned in the EU)
and in cigarettes, cosmetics, traditional medicine, and lead-glazed ceramics. Paint
and pigments contain lead in the form of lead chromates (Romieu et al. 1994).
• Mercury is used in the manufacturing of electrical equipment, and it also acts as
catalyst in chlor-alkali processes for chlorine and caustic soda production. The
main sources in effluent are from clinical thermometers, dental practices, electrical equipment, glass mirrors, and traces in disinfectant products (bleach) and
caustic soda solutions.
• Nickel. The primary sources of nickels are from corrosion of equipment from
small electroplating shops, launderettes, and small and jewelry shops and from
old pigments and paints. The mining and refining activities of nickel, burning of
residual and fuel oils, and municipal waste incineration are the main anthropogenic sources of nickel emissions in the environment (WHO-1991). These
sources account for about 90% of the total global emission, estimated to be
42.85 Â 10
6 kg/year.
• Zinc is utilized for processes such as galvanization and brass and bronze alloy
production; in products such as batteries, paints, plastics, rubber, fungicides,
paper, textiles, taxidermy (zinc chloride) and embalming fluid (zinc chloride),
building materials, and special cements (zinc oxide, zinc fluorosilicate); in dentistry (zinc oxide); and also in cosmetics and pharmaceuticals. The current trend
towards electrolytic production of zinc which, in contrast to thermally produced
zinc has virtually no cadmium contamination. This means that cadmium pollution
due to the corrosion of galvanized steel will in time become negligible (Adams
and Kramer 1999).
• Platinum and platinum group metals (PGMs) such as palladium and osmium
often come from medical and clinical practices, mainly as anti-neoplastic drugs.
The amount generated in hospital/clinical effluent has been estimated to be
between 115 and 125 ng L
À1 (Kümmerer and Helmers 1997; Kümmerer et al.
1999) giving a total emission of 84–99 kg per annum from hospitals. Other major
7 Natural Biological Treatment of Effluent and Sludges to Combat the Burden of. . .
109
• Cadmium primarily comes from launderettes, small electroplating and coating
shops, and plastic manufacture industries, and it can be used in alloys, pigments,
dental work, paints, photography, Ni-Cd batteries, glazes, artisanal shops, and car
repair shops (ATSDR 1999).
• Chromium are found in alloys and is released from diffuse sources and products
such as preservatives and dying and tanning activities. Chromium III is broadly
used as a tanning agent in leather operation. Chromium VI being highly toxic, its
uses are now restricted, and there are less commercial sources.
• Copper is used in electronics, plating, paper, textile, rubber, fungicides, printing,
plastic, and brass and other alloy industries, and it can also be released from
various small commercial activities and warehouses, as well as buildings with
commercial heating systems (Chikwendu et al. 1989).
• Lead is often used as a fuel additive (now greatly reduced or banned in the EU)
and in cigarettes, cosmetics, traditional medicine, and lead-glazed ceramics. Paint
and pigments contain lead in the form of lead chromates (Romieu et al. 1994).
• Mercury is used in the manufacturing of electrical equipment, and it also acts as
catalyst in chlor-alkali processes for chlorine and caustic soda production. The
main sources in effluent are from clinical thermometers, dental practices, electrical equipment, glass mirrors, and traces in disinfectant products (bleach) and
caustic soda solutions.
• Nickel. The primary sources of nickels are from corrosion of equipment from
small electroplating shops, launderettes, and small and jewelry shops and from
old pigments and paints. The mining and refining activities of nickel, burning of
residual and fuel oils, and municipal waste incineration are the main anthropogenic sources of nickel emissions in the environment (WHO-1991). These
sources account for about 90% of the total global emission, estimated to be
42.85 Â 10
6 kg/year.
• Zinc is utilized for processes such as galvanization and brass and bronze alloy
production; in products such as batteries, paints, plastics, rubber, fungicides,
paper, textiles, taxidermy (zinc chloride) and embalming fluid (zinc chloride),
building materials, and special cements (zinc oxide, zinc fluorosilicate); in dentistry (zinc oxide); and also in cosmetics and pharmaceuticals. The current trend
towards electrolytic production of zinc which, in contrast to thermally produced
zinc has virtually no cadmium contamination. This means that cadmium pollution
due to the corrosion of galvanized steel will in time become negligible (Adams
and Kramer 1999).
• Platinum and platinum group metals (PGMs) such as palladium and osmium
often come from medical and clinical practices, mainly as anti-neoplastic drugs.
The amount generated in hospital/clinical effluent has been estimated to be
between 115 and 125 ng L
À1 (Kümmerer and Helmers 1997; Kümmerer et al.
1999) giving a total emission of 84–99 kg per annum from hospitals. Other major
7 Natural Biological Treatment of Effluent and Sludges to Combat the Burden of. . .
109