sources of platinum involve laboratories, glass manufacturing, jewelry shops, and
petroleum/ammonia processing activities.
• Silver is generated mainly from small-scale household products such as polishes,
domestic water treatment devices, etc. (Shafer et al. 1998; Adams and Kramer
1999). Studies in Spain showed the presence of elevated concentrations of Cd,
Cu, Hg, Pb, and Zn in urban wastewater and in the coastal environment, with high
concentrations of copper and zinc possibly due to the use of fungicides in glass
houses.
7.3 Sewage Sludge
Sewage sludge is known to be rich in nutrients (nitrogen and phosphorus), organic
matter, and trace elements that are beneficial for plant growth and better yield
(Kauthale et al. 2005). Sewage sludge is also considered a suitable substitute for
commercial fertilizers, and the use of sewage sludge as a fertilizer decreases the
requirement for commercial fertilizers (Richards et al. 1998). Commercial fertilizers
require large amount of phosphorus, whereas phosphorus is known to be a limited
resource. Even though the nitrogen available in commercial fertilizers may not be a
limited resource, the production of nitrogen fertilizers demands significant amount of
energy. The organic carbon in sludge-amended soil can increase as far as threefold
compared to inorganic fertilizer-amended soils (Seaker et al. 1988; Nyamangara and
Mzezewa 2001). Inorganic fertilizers usually reduce soil pH and increase the rate of
soil acidification as well as increase the percentage of aluminum saturation (Porta
et al. 1999). The decrease in pH of soils is traced possibly to the ammonium in the
fertilizer. Sludge needs to be treated before releasing it into environment because it
contains potentially toxic elements such as zinc (Zn), copper (Cu), lead (Pb),
chromium (Cr), and cadmium (Cd).
7.4 Environmental Consequences of Effluents and Sludge
Due to rapid establishment of industries during the last two decades, the disposal of
industrial effluents has become a serious problem. The effluents and sludge are often
discharged to nearby land or mainly in water bodies. The composition of effluents
and sludge differs from industries to industries. Untreated water causes bad odor and
foul smell near the point of disposal. It is known that organisms inhabiting areas
influenced by effluent discharges can suffer deleterious somatic effects or genetic
damage and that people using polluted water could be at higher risk of genotoxic
effects and cancer development (Rajaguru et al. 2002). However, industrial wastewater and sludge could be used safely and effectively with proper precautions to
increase soil productivity. The utilization of industrial wastes for agricultural purposes could also provide a solution to the disposal problems (Chhonkar et al. 2000).
110
D. Angmo et al.
petroleum/ammonia processing activities.
• Silver is generated mainly from small-scale household products such as polishes,
domestic water treatment devices, etc. (Shafer et al. 1998; Adams and Kramer
1999). Studies in Spain showed the presence of elevated concentrations of Cd,
Cu, Hg, Pb, and Zn in urban wastewater and in the coastal environment, with high
concentrations of copper and zinc possibly due to the use of fungicides in glass
houses.
7.3 Sewage Sludge
Sewage sludge is known to be rich in nutrients (nitrogen and phosphorus), organic
matter, and trace elements that are beneficial for plant growth and better yield
(Kauthale et al. 2005). Sewage sludge is also considered a suitable substitute for
commercial fertilizers, and the use of sewage sludge as a fertilizer decreases the
requirement for commercial fertilizers (Richards et al. 1998). Commercial fertilizers
require large amount of phosphorus, whereas phosphorus is known to be a limited
resource. Even though the nitrogen available in commercial fertilizers may not be a
limited resource, the production of nitrogen fertilizers demands significant amount of
energy. The organic carbon in sludge-amended soil can increase as far as threefold
compared to inorganic fertilizer-amended soils (Seaker et al. 1988; Nyamangara and
Mzezewa 2001). Inorganic fertilizers usually reduce soil pH and increase the rate of
soil acidification as well as increase the percentage of aluminum saturation (Porta
et al. 1999). The decrease in pH of soils is traced possibly to the ammonium in the
fertilizer. Sludge needs to be treated before releasing it into environment because it
contains potentially toxic elements such as zinc (Zn), copper (Cu), lead (Pb),
chromium (Cr), and cadmium (Cd).
7.4 Environmental Consequences of Effluents and Sludge
Due to rapid establishment of industries during the last two decades, the disposal of
industrial effluents has become a serious problem. The effluents and sludge are often
discharged to nearby land or mainly in water bodies. The composition of effluents
and sludge differs from industries to industries. Untreated water causes bad odor and
foul smell near the point of disposal. It is known that organisms inhabiting areas
influenced by effluent discharges can suffer deleterious somatic effects or genetic
damage and that people using polluted water could be at higher risk of genotoxic
effects and cancer development (Rajaguru et al. 2002). However, industrial wastewater and sludge could be used safely and effectively with proper precautions to
increase soil productivity. The utilization of industrial wastes for agricultural purposes could also provide a solution to the disposal problems (Chhonkar et al. 2000).
110
D. Angmo et al.