Water Pollution

Lilian Lam

For the past two thousand years, the human population has exhibited a J-shaped pattern of growth (Southwick, 159).  This exponential population proliferation has been coupled with the growth of cities and industrialization.  Together, these trends have posed increasing difficulties of water quality control.  The causes of water pollution range from all corners of industrial sectors and continue to be amplified by the dense populations concentrated in urban centers.

Domestic and Municipal Pollution: The Overpopulation Problem

Part of the water pollution problem stems from high population growth and the consequent need for expanded food production.  In order to increase crop yields, farmers rely on usage of insecticides, herbicides, and fertilizers.  Most insecticides, such as chlorinated hydrocarbon DDT, are non-biodegradable.  These materials adhere strongly to the soil, and most water contamination is due to the soil being eroded and washed into the surface bodies of water (Morton, 68).  Through the process of bioaccumulation, the fat-soluble chemicals accumulate in the fat of many organisms (such as fish), and can have damaging ecological effects.  The growing demand for food also affects the livestock industry and presents the problem of animal wastes.  Farm animal wastes are forms of organic matter, and runoff into a receiving body of water can overload it with nutrients.  The abundant nutrient loading promotes the rapid growth of algae and weed species, causing the depletion of oxygen resources of a lake or stream (Morton, 75).  This eutrophication has severe repercussions on the entire ecosystem. 

Another cause of water pollution is the continuous growth of cities, which has become a pattern of the population growth trend.  A “disproportionate share” of population growth occurs in the world’s cities (Southwick 168), which are “parasitic” to the surrounding landscape.  If cities were covered by giant plastic domes, they would suffocate in a matter of days from their own toxic products (Southwick, 169).  A growth in population, especially that of a city, increases the volume of used water carried by the urban drainage systems, which are frequently discharged into the nearest river or lakes without complete sewage treatment (United Nations, 2).  A 1976 statistic reported that of the raw domestic sewage that enters the municipal sewage treatment plant, about 99.9 percent consisted of water and only 0.1 percent consisted of impurities (Morton, 37).  Though this statistic is outdated, it is still relevant and applicable based on our unchanged ways of life.  It is common practice to let the water run, for instance, to rinse a glass before we fill a drink with it and after we take the drink.  Our daily showers, which first require we let the cold water out before it is heated, are followed by lengthy relaxation in the shower after we are already clean.  This diluted sewage makes it more difficult to remove pollutants than if the impurities were present in a small volume of water, as most treatment processes depend on differences in concentration, temperature, pressure, or density for their operation.  As a result, the water that leaves the sewage treatment plant is not as effectively or thoroughly removed of contaminants.  In addition, city sewers are unequipped to handle both storm runoffs and sanitary wastes during the rainy season.  This causes the two to mix and overflow into the nearest lake, stream, or ocean without being treated (Morton, 40).       

Non-point pollution is also a major contributor to the contamination of water sources, and can be attributed to urban runoff due to city landscape and living as well as landfill sites.  Urban runoff consists of residues, wastes, and natural products that are washed from the streets and lawns by rain into storm drains.  It includes everything from dirt, dust, leaves, fertilizer and soil from lawns, pet wastes, automobile oil and grease, to salt from the salting of roads in the winter which causes a spike in salt level in surface waters.  These potentially hazardous pollutants are emptied into a receiving body of water without being properly neutralized.  Another prominent source of non-point pollution are solid waste land disposal sites.  Precipitation falling on a site can become runoff, and the percolation of water through the pile of refuse and waste can generate leachates (Miller, 147-149).  Leachates from landfills are usually acidic with a high concentration of metal ions and can pollute open bodies of water as well as ground water sources.  The potential for water pollution through urban runoff is proportional to population growth as both increase in conjunction with one another.  As population numbers rise, so do the number of people inhabiting cities.  This inevitably corresponds to a rise in the total number of cars, pets, lawns with fertilizer, and detergent used (just to name a few)- all of which contribute to the increased presence of pollutants. 

Industrial Pollution: The Industrialization Problem

In addition to J-shaped population growth, another trend is growing industrialization.  Southwick points out that the most industrialized countries (such as Japan, the United States, and those in western Europe) have reduced birth rates and show population growth rates of 0.6 percent or less (Southwick, 163); however on a global scale, both total population size and total industrialization exhibit an upward growth.  Since the Industrial Revolution, industrialization has only grown and become more prominent in modern global society.  The mechanization of industries and technological innovations have become fixtures in our culture, but at the price of higher pollution levels.  The pollution of streams, rivers, and the seas are increasing, owing mainly to the development of industry, which uses water in its production processes (United Nations, 1).  Because of this extensive industrialization, every good and material made comes with a waste product, which in some cases literally outweigh the amount of good produced.  The following examples are but a few in the multitude of existing industries- almost every product has its own industry or is a part of another.

One of the first industries introduced by the Industrial Revolution was the metal industry, which has remained crucial to this day.  Iron and steel are common metals found throughout the world and are major components in buildings, automobiles, tools, and many other appliances.  Substantial amounts of water are required for iron and steel-making processes, whether it be for coking, pig-iron production, rolling operations, supplying wet-processes for treating gaseous mixtures, or for supplying exhaust gases.  Processing methods may have become more efficient now, but in 1964, the steel industry’s water requirement was 20.8 thousand million tons for an output of 115.5 million tons of raw steel, which represents a unit consumption of 180 tons of water for each ton of steel produced (United Nations, 3).  Water is used as a cooling agent in most of these processes and becomes heated by at least 15-25°C.  This heated water is released in a receiving stream, and waters which vary in temperature from hour to hour are extremely difficult to process (Nemerow, 5).  This often means that the water is not treated as thoroughly, and brings contaminants to the final natural receiving body of water.  Furthermore, if the water is still heated, it can stimulate bacterial growth and have eutrophication and pathogenic consequences to the ecosystem and to humans as well.  In addition, the metals themselves are strong acids, chromates, and are considered extremely toxic waste.  Heavy metals, such as lead, mercury, arsenic, barium, chromium, and cadmium, are not inert in the environment, but are converted into soluble methylated compounds that can find their way into fish and other organisms (Morton, 76-69). 

Another major industry is the chemical industry, responsible for converting raw materials (such as oil, minerals, and natural gases) into thousands of different products used in agriculture, manufacturing, construction, service industries, as well as daily consumer products.  Among the most common are polymers, plastics, textiles, and petrochemicals.  Plastics are one of the most common materials found throughout the world, and it is also a major contributor of organic-overloading to water sources with 45 percent of its waste products discharged to watercourses (Nemerow, 603).  The acids and alkalis discharged by chemical plants make streams unsuitable for recreational uses and inhibit the growth of aquatic life.  Sodium hydroxide is an example of an alkali that is highly soluble in water and capable of changing its alkalinity and pH.  Streams containing as little as 25 parts of sodium hydroxide per million have been reported deadly to fish (Nemerow, 4).  Any floating solids or liquids produced by the chemical industry are extremely toxic to aquatic ecosystems. 

The energy industry has an increasingly crucial role in the world as fuel is needed to maintain the functioning of all societies.  Steam power plants rely on fresh water to cool the steam, and this water is delivered to receiving waters at a higher temperature.  This increases bacterial and aquatic activity, which diminishes oxygen resources and increases sensitivity of aquatic life to toxic elements.  Petroleum is among the world’s most prized and coveted energy resource, and the petrochemical industry consistently seeks to increase its pumping and refining.  Petroleum refining creates an abundance of waste products from its pumping, desalting, distilling, fractionation, alkylation, and polymerization processes (Nemerow, 529).  Water is produced as one of these waste products in chemical reactions and is highly contaminated when added into stream waste.  Petrochemical compounds are inhibitory to biological treatment and have a high frequency of spillage and heavy metal contamination. They have an extraordinarily degrading effect on the environment (Nemerow, 550), and past oil spills in Alaska have wreaked havoc on entire ecosystems.  The production of nuclear energy by nuclear fission also leaves dangerous radioactive waste products.  The problem is the disposal of these radioactive waste products, which are currently stored underground.  The Department of Energy estimates that there are millions of gallons or radioactive wastes that cause huge quantities of contaminated soil and water.  If these radioactive wastes are not contained properly, or if there is an accident, they can cause groundwater contamination by leakage into shallow aquifers.  These leakages caused by faulty designs and unanticipated accidents are more than a hypothetical “what-if” threat, but have and still continue to occur.


Southwick’s models show the consequences of a continuation of historical trends, highlighting the dangers or exponential growth in population and industrial pollution (Southwick, 177).  The ongoing trend is a J-shaped pattern of population growth accompanied by the expansion of cities.  This increases food pressures, and the increase in agricultural production has the consequence of a greater quantity of pollutants introduced to rivers, lakes, and oceans.  Urban runoff, which will continue to increase with the current trends, is also a major source of water pollution.  Expanded industrialization is another current trend that begets both an increase in the amount of pollutants and the possibility of pollution.  Water sources- aquifers, streams, river, lakes, oceans- thus become laden with toxic chemical substances and suffer from the effects of thermal pollution, leading to extended damage on the entire aquatic ecosystem.

But what about a tech fix?  Dolan maintains that the two problems of population pressure and pollution are separate and distinct (Dolan, 69).  Instead, he seems to rely on a tech fix rescue from pollution.  He gives an example of a highway traveled by one million smog-free cars which does not produce any more smog than a highway traveled by one such car (Dolan, 69).  While technological advances have reduced the amount of pollution output of cars, Dolan does not seem to consider all the other possible sources of pollution.  What about the grease and other combustion waste products on the roads left behind by these cars?  What about the possibility of pollution from making the metal for the cars, or for producing fuel?  What about the production of agriculture and energy required to sustain our global society?  Though technology has advanced so that we may better treat contaminated waters, our current means do not completely remove all impurities.  Secondary treatment of waters remove about eighty to ninety percent of organic pollutants from domestic sewage, but does not remove nitrogen and phosphorus compounds that stimulates eutrophication in receiving bodies of water (Morton, 39).  This ten percent of untreated water accumulates over time and as the population continues to proliferate.  Furthermore, tech fixes do not provide a definite solution without creating the possibility of other unintended consequences.  The invention of wet scrubbers solved the air pollution problem in industrial stacks, but only converted it into a water pollution problem.  Liquid wastes are created as scrubbing liquid entraps contaminants, but these scrubbing effluents are discharged into a municipal sewer system that does not effectively treat all the contaminants before discharging the water into a receiving stream (Nemerow, 635).  However, Dolan does have a point in that population is not the only cause of pollution.  To be sure, it is also attributed to cultural attitudes and lifestyles: taking long showers and diluting water volume in treatment plants, not picking up after ourselves and leaving street litter, driving instead of walking and leaving behind more roadside grease and consuming more fuel- all these actions result in an increase in water pollution.



Dolan, Edwin G., Ch. 5 from "TANSTAAFL: The Economic Strategy for Environmental Crisis" 1974, pp. 55-72.

Miller, David W.  Waste Disposal Effects on Ground Water. Berkeley: Premier Press, 1980.

Morton, Stephen D. Water Pollution- Causes and Cures.  Madison: Mimir Publishers Inc., 1976

Nemerow, Nelson L.  Industrial Water Pollution. Reading: Addison-Wesley Publishing Company, Inc., 1971.

Problems of air and water pollution arising in the iron and steel industry. New York: United Nations, 1970.

Southwick, Charles H., Ch. 15 from "Global Ecology in Human Perspective" Oxford Univ. Press, 1996, pp. 159-182.

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last updated 4/9/07