arsenic, which are basically found as either arsenite (contains As (III) or as arsenate
(contains As (V) in the water. The metal speciation also depends upon the
oxidation-reduction conditions. As (III) species are predominate under reducing
conditions, while under oxidizing conditions, the As (V) species are more constant.
A good example of wood preservative (generally insecticide) is the lead arsenate—a
form of arsenic was widely used for many years. After the decomposition, the wood
pieces release arsenic into soil which mixes with surface water and finally makes its
way to groundwater. Another chief source of arsenic and lead is smelting operation
by which these metals are added into water directly or transported atmospherically.
Presently the arsenic poisonings are caused mainly due to the consumption of well
water where the ground water is naturally enriched in inorganic arsenic. Its overexposure may cause reduction in the production of WBC and RBC, damage blood
vessels and cause “pins and needles” sensation in hands and feet [1]. Its elongated
exposure could result in leuko-melanosis, melanosis, neuropathy, hyperkeratosis,
black foot disease, and cancer [17].
Selenium (Se) is often found in association with sulfur containing minerals in the
earth’s crust. Selenium is a metalloid component, a naturally existing trace element,
available in five oxidation states in the nature: −2, −1, 0, +4 and +6, under the
forms of elemental selenium, selenide, selenite, selenate and organic selenium
[86]. The most familiar forms of selenium in water are selenite (Se (IV), SeO 3
2− )
and selenate (Se(VI), SeO 4
2− ). It is a slow process of emergence of selenate from
selenite and both forms are found together in solution. Neither can be oxidized or
reduced easily [97]. Selenium contamination of aquatic environment could happen
due to mine drainage, agricultural drainage water, oil refineries, and sediments
produced from fossil fuel thermoelectric power industries and metal ores [63]. The
largest utilization of selenium compounds is in electronic and photocopier elements.
A key nutrient at the level of low concentration, the permissible limits for selenium
in drinking water has been set at 40 lg/L [117]. However, EPA has found that
selenium has the potential to cause a number of health issues in case people are
unmasked to it beyond MCL levels for relatively short time periods: fatigue and
irritability, damage to the peripheral nervous system; hair and fingernail changes.
A longer period exposure at levels above MCL have harmful effect on hair and
fingernail loss; kidney and liver tissue damage, and the nervous as well as circulatory systems (www.freedrinkingwater.com).
3 Emerging Water Pollutants
Although the risk of health hazardous are not yet understood, all the drinking water
supplies around the world is under contamination of chemical pollutants at least at
trace level. Such problems lack scientific research and as well as there is scarcity of
literature. But this issue is an urgent one and should be considered as emergent
issue. There are several ways to define emerging contaminants.
28
A. Ahamad et al.
(contains As (V) in the water. The metal speciation also depends upon the
oxidation-reduction conditions. As (III) species are predominate under reducing
conditions, while under oxidizing conditions, the As (V) species are more constant.
A good example of wood preservative (generally insecticide) is the lead arsenate—a
form of arsenic was widely used for many years. After the decomposition, the wood
pieces release arsenic into soil which mixes with surface water and finally makes its
way to groundwater. Another chief source of arsenic and lead is smelting operation
by which these metals are added into water directly or transported atmospherically.
Presently the arsenic poisonings are caused mainly due to the consumption of well
water where the ground water is naturally enriched in inorganic arsenic. Its overexposure may cause reduction in the production of WBC and RBC, damage blood
vessels and cause “pins and needles” sensation in hands and feet [1]. Its elongated
exposure could result in leuko-melanosis, melanosis, neuropathy, hyperkeratosis,
black foot disease, and cancer [17].
Selenium (Se) is often found in association with sulfur containing minerals in the
earth’s crust. Selenium is a metalloid component, a naturally existing trace element,
available in five oxidation states in the nature: −2, −1, 0, +4 and +6, under the
forms of elemental selenium, selenide, selenite, selenate and organic selenium
[86]. The most familiar forms of selenium in water are selenite (Se (IV), SeO 3
2− )
and selenate (Se(VI), SeO 4
2− ). It is a slow process of emergence of selenate from
selenite and both forms are found together in solution. Neither can be oxidized or
reduced easily [97]. Selenium contamination of aquatic environment could happen
due to mine drainage, agricultural drainage water, oil refineries, and sediments
produced from fossil fuel thermoelectric power industries and metal ores [63]. The
largest utilization of selenium compounds is in electronic and photocopier elements.
A key nutrient at the level of low concentration, the permissible limits for selenium
in drinking water has been set at 40 lg/L [117]. However, EPA has found that
selenium has the potential to cause a number of health issues in case people are
unmasked to it beyond MCL levels for relatively short time periods: fatigue and
irritability, damage to the peripheral nervous system; hair and fingernail changes.
A longer period exposure at levels above MCL have harmful effect on hair and
fingernail loss; kidney and liver tissue damage, and the nervous as well as circulatory systems (www.freedrinkingwater.com).
3 Emerging Water Pollutants
Although the risk of health hazardous are not yet understood, all the drinking water
supplies around the world is under contamination of chemical pollutants at least at
trace level. Such problems lack scientific research and as well as there is scarcity of
literature. But this issue is an urgent one and should be considered as emergent
issue. There are several ways to define emerging contaminants.
28
A. Ahamad et al.