Here is your short article on Water Pollution

Water pollution is usually defined as the addition of materials to water in such quantity as to lessen its suitability for the life of aquatic organisms, for irrigation, for recreation, or for drinking. Some water pollutants are inherently toxic to one or more forms of life. While seldom intrinsically toxic, nutrients may be toxic in high concentrations or may produce so much growth of bacteria or other aquatic life as to make life impossible for other aquatic organisms.

Sources of water pollution include human wastes; runoffs of industrial processes, farmlands, feedlots, and mines, air pollutants that find their way into lakes and rivers; accidental and deliberate discharges of petroleum; and radioactive wastes. Farm runoffs include fertilizer, manure, insecticides, and herbicides.

The volume of water pollutants in the United States is huge, Runoffs into the Ohio River from mines in Pennsylvania and West Virginia, for example account for a daily outpouring of 200,000 tons of sulphuric acid.

The Detroit River alone dumps 20 million tons of miscellaneous waste into Lake Erie every day. Cleveland, Buffalo, and Toledo all add their sewage effluent and industrial discharges to the same lake. By 1980, 11 regions along the shores of the Great Lakes alone had been designated areas of major pollutions.

Several major water pollutants are considered in the sections that follow:

Biodegradable, Nontoxic Organic Wastes. The ways that sewage is usually treated in American cities tells something of the nature of the problem of pollution by biodegradable, nontoxic organic wastes.

After secondary treatment has greatly reduced biological oxygen demand (BOD); this sewage effluent is allowed to enter a river, lake, or ocean.

The BOD of water is defined as the amount of oxygen that is removed from the water by the respiration of sewage bacteria in the course of 5 days at 20°C as they decompose its organic matter; as such, it is an index of the water’s content of biodegradable organic matter. Thus, the greater the bacterial growth in a water sample, the more oxygen is used, and the greater it’s BOD.

A high BOD and consequent high depletion of oxygen will slow the process of sewage degradation. Secondary treatment usually reduces the BOD by 60 to 90 percent. The remaining organic matter in the effluent then decomposes in the lake or river into which the effluent is discharged, usually without promoting enough bacterial growth or using enough of the water’s oxygen to jeopardize its aquatic life.

BOD, however, is only one index of water quality. The bacteria that decompose the organic matter release inorganic nutrients, such as phosphates and nitrates, into the effluent. This promotes eutrophication of lakes and streams in which such nutrients have been the limiting factors in algal growth.

Lakes, especially those with weak currents or still waters, may experience growths of algae massive enough to form a heavy surface scum that reduces the penetration of light. The excess algal growth dies and decomposes, a process that depletes the water’s oxygen, thereby killing aerobic aquatic life.

The scum and its odour limit the lake’s usefulness for recreational purposes and as a community water supply. This process may initiate or accelerate ecological succession. Many communities now follow secondary treatment of sewage with tertiary treatment, a process that removes toxic metals and 90 percent or more of the phosphates, nitrates, suspended solids, and bacteria.

The burden of biodegradable organic pollution of waterways in the United States has risen steadily in the last 25 years. Only about 15 percent of this, however, can be attributed to population increase.

The rest is due partly to increased use of disposable products that end up in substance present in great dilution in the environment may thus reach lethal concentration in the top consumers. For this reason the public is often warned against eating large freshwater fish caught in polluted waters.

Much of the toxic waste that pollute water supplies does not enter lakes, rivers, or the sea. United States industries alone dispose of or store some 190 x 10⁹ 1 (50 x 10⁹ gallons) of liquid waste each year in dump sites or surface impoundments (pits, ponds, and so on).

The United States Environments Protection Agency (EPA) estimates that until the late 1970s, up to 90 percent of these wastes had been disposed of improperly. By 1981, the EPA had registered over 52,000 hazardous waste dump sites in the United States.

Over 12,000 of these were said to pose a “substantial and imminent threat to human health through contaminated groundwater, excessive radiation, or fire and explosion. Of 27,000 such impoundments inspected in 1980, 8,000 were found to be located on permeable soils above usable groundwater supplies. Over half of the groundwater thus far tested int hese areas was already contaminated in excess of acceptable health standards.