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Every living thing must have water to survive, yet less than 1 percent of the earth’s water is considered drinkable. Why is this percentage so small—what’s wrong with the other 99 percent? Well, 97 percent of it is salty, and, although the other 2 percent is fresh, it is frozen into polar ice and glaciers. Since the amount of usable fresh water is so small, you can understand why everyone is so concerned about water pollution. We must have clean water, and, as our population grows and industry expands, water becomes even more valuable.
Gallons of water are used in everyday activities around the house. When you showered this morning, between five and ten gallons of water went down the drain every minute. Before the day is over you will probably drink about 1 ½ quarts, either plain or in some type of beverage, and consume another quart in your food. Add to that the amount you use each time you wash your hands, brush your teeth, flush the toilet, bathe the dog, wash the dishes, mop the floor, water the flowers, wash the car, or do any of the other water-using activities around the house.
Industry now uses over half of America’s water supply. At the beginning of the century, industry in our country used only 10 to 15 billion gallons a day; but it is estimated that more than 550 billion gallons a day are needed now. It takes as many as 16,000 gallons to produce one ton of steel. Water is also needed by the nation’s farmers to produce our food. In fact, as much as 40 percent of America’s water is used for irrigation purposes.
In addition to these direct needs, clean water plays an important role in our recreational activities. We use it for swimming, boating, water skiing, scuba diving, and fishing. Would you want to swim, boat, or ski in polluted water? How long do you think the world’s eight thousand species of fish could survive in polluted lakes, rivers, and streams?
All of the earth’s fresh water comes from rain, snow, and other types of precipitation. Water from the land and oceans evaporates (turns into water vapor that rises into the air). When this water vapor cools, the moisture it contains turns into drops of rain or frozen crystals and falls to the earth once more. This recycling of water from the oceans and land to the clouds and back again is called the hydrologic cycle. If this cycle were to stop, eventually there would be no fresh water. All water would be in the oceans, and all land would be dry.
Nature’s freshwater cycle is great, but it has its flaws. Rain seldom falls where and when man thinks it should. If it were distributed evenly, every spot on earth would get about 26 inches of rainfall each year. Instead, parts of India get as much as 400 inches, other areas go for years with almost none, and 75 percent of the rain falls in the oceans to become salty. As a result, our limited supply of fresh water must be used over and over again if there is going to be enough to meet everyone’s needs. But once it has become polluted, it must be made clean before it can be used again.
In our early history, wastes from our cities were dumped into the nearest river or stream. As the water ran downstream, nature filtered it and made it clean once again. This system was all right when our cities were small and there were long stretches of flowing water; however, our rivers are not able to keep up with the increased amounts of human wastes and industrial pollutants produced by today’s large cities and the pesticide-laden runoffs from our agricultural areas. Man must clean his own water if the quantities needed are to be available. We don’t have time to wait for it to trickle over rocks and be cleaned by nature.
Raw sewage, as it comes from our homes, cities, and industries, contains two types of waste matter—organic and inorganic. Organics include such things as grease, food scraps, and human wastes, while inorganics are sand, rubber, metal, etc. Those wastes that dissolve in water, such as sugar, are called dissolved solids. The others, such as coffee grounds, are called suspended solids.
Large cities have been
using various water-treatment
methods for a number of
years to make their polluted
sewage water reusable. However,
not all of these methods
are satisfactory. Raw sewage
can be treated in three
and tertiary. During the
primary treatment, screening
removes large floating objects
such as sticks and rags,
and then the water is allowed
to sit so the suspended
solids can settle. To complete
the primary treatment, the
water is chlorinated to
kill or reduce the number
of disease-causing bacteria
and then is discharged into
the river or stream. Chlorine
also helps reduce bad odors.
Primary treatment, although
used by 30 percent of America’s
cities, is really not enough
treatment for most reuse
Secondary treatment, which is now considered the minimum standard for the nation, goes a step further in purifying waste water by using biological methods to remove organic matter. After the primary treatment and before chlorine is added, the waste water (effluent) is allowed to trickle over a bed of stones three to ten feet deep. Bacteria growing on these stones break down and consume as much as 90 percent of the organic matter I the sewage. Another type of secondary treatment uses an aeration tank instead of the stone filter method. In this tank the waste water is mixed with air and sludge that is loaded with bacteria. It remains in this aeration tank for several hours so the bacteria can break down the organic matter. Then it moves to another tank where the solids are allowed to settle. Both methods of secondary treatment add chlorine before discharging the water into a river or stream. If chlorination is done properly, it will kill 99 percent of the harmful bacteria in the water.
Tertiary treatment goes even further and removes phosphates and nitrogen compounds from the water. There are varying degrees of tertiary treatment which produce water of varying quality; however, all types of tertiary treatment are better than secondary treatment methods.
Secondary treatment of municipal sewage has been required in Texas for some forty years. Although this is not a law, the existence of this administrative requirement has helped to keep Texas waters from becoming as polluted as those in other states. Of the almost 1,600 active municipal sewage-treatment plants in the state that report regularly to the Texas Department of Water Resources (1983), 563 use advanced or tertiary treatment and 1,025 use secondary treatment processes before discharging waste water into Texas streams. Primary treatment is still used in only 2 plants; the water from one of these is used only for irrigation, and the other plant is building new facilities. There are 366 plants that do not require permits because their effluents are used for irrigation or are allowed to evaporate.
Since the federal government passed the Water Quality Act of 1965, which established certain standards for all interstate streams, coastal waters, and lakes, and the Clean Water Restoration Act of 1966, which increased federal financial aid to cities to help build waste-treatment plants, the nation’s water treatment has improved. Thousands of new plants are being built, and existing ones are being expanded or modernized to make sure we have the clean water we need for the future. When Congress passed amendments to the Federal Water Pollution Control Act of 1972, two goals were set:
- Make America’s waters clean enough for swimming, boating, and protection of wildlife by 1983.
- Dump no more pollutants into waterways by 1985.
If you are interested in the quality of your community’s water, you might want to find out the source of your drinking water, who is in charge of your water supply, where your sewage goes, and how your city’s sewage is treated. We can all do our part in a small way by making sure we are not guilty of adding to the problem of water pollution by littering our lakes, rivers, and streams. Clean water is everyone’s concern.
1983 Water. Young Naturalist. The Louise Lindsey Merrick Texas Environment Series, No. 6, pp. 126-129. Texas A&M University Press, College Station.