e. Food processing waste, including oxygen-demanding substances, fats, and
grease.
f. Perchlorate—perchlorate salts are used in rocket fuels, fireworks, explosives,
road flares, inflation bags, and so on. Although these pollutants are generally
associated with military bases and construction sites when explosives are used,
natural formations in parched areas may also account for their presence in
water.
g. Trihalomethanes—these are generally the by-products of water chlorination and
may pollute groundwater and surface water via leakage through sewer lines.
Moreover, the discharge of chlorinated solvents from dry cleaners also intensifies this problem. Examples of such compounds are chloroform, bromodichloromethane, dibromochloromethane, and bromoform.
h. Pesticides/insecticides/herbicides—comprise a large number of chemicals that
enter water because of agricultural activities, directly by spraying over large
areas or indirectly with agriculture runoff. The insecticide dichlorodiphenyltrichloroethane (DDT) is a typical example of this type of water pollutant.
i. Polychlorinated biphenyls (PCBs)—in spite of a recent ban, their ubiquitous
environmental presence makes these contaminants generally associated with
urban runoffs.
j. Antibiotics and other pharmaceutical products.
2. Inorganic water pollutants:
3. Examples of water pollutants include the following:
a. Metals and their compounds—Higher health hazards are due to the organometallic
compounds, which form when metals and organic compounds in the water react.
Common examples include Hg, As, and Cr poisoning of water. As a result, if water
is polluted with both metals and organic compounds, the health risk is higher
(Figure 1).
b. Inorganic fertilizers—Some inorganic pollutants are not particularly toxic, but are
still a threat to the environment because they are used so extensively. These
include fertilizers, such as nitrates and phosphates. Nitrates and phosphates
cause algal blooms in surface water, which decrease the oxygen level in the
water. Ultimately, this results in oxygen starvation because of the uptake of
oxygen by microorganisms that break down algae. This is termed eutrophication.
c. Acidity—This is caused by industrial discharges especially sulfur dioxide from
plants, and so on.