The Problem of Water Pollution Essay Example

and channel stabilization help reduce water erosion by reducing the channel gradient and reducing a deposit sites where sediments are deposited. Stabilization circuits can be constructed to divert water or to reduce its velocity which consequently leads to reduced soil erosion.

Self-purification takes place when a stream balances restoration of the aquatic environment through the simultaneous participation of the chemical and physical factors. For example, changes in hydraulic, biological and morphological characteristics of a river may significantly lead to “Self-purify” (Laws, 2000).

From figure 5-8, the dissolved oxygen (DO) “sag” with time is due to biological and chemical processes taking place in the water source. For example, biodegradable organic pollutants lead to a temperature increase of the water thus lowering its DO. With time, the dissolved organic compounds are gradually utilized by the aquatic organisms such as fish. This results in a gradual increase of the DO as the temperature of the water decreases.
Seasonal stratification of lakes is the separation of the lake water into three namely; hypolimnion (bottom layer), metalimnion (middle layer) and epilimnion (Top layer). The stratification occurs due to changes in temperatures at different depths and is caused by changes in water’s density. Fall overturn when summer-warmed surface layer cools to the same temperatures as the lower waters allowing the water to mix from top to bottom. On the other hand, spring overturn take place during spring and leads to accumulated nutrients brought up from the lake bottom. The nutrients provide an ideal environment for the growth of algae in the epilimnion (Laws, 2000).

Hydraulic fracturing has been determined to cause groundwater pollution significantly because the process involves the release of fluids such as proppants

which may be toxic chemicals. Ground water is also polluted if the hydraulic fluids escape during fracking (Laws, 2000).

Water is obtained from two sources. It is estimated that about 75% of drinking water is obtained from surface water sources such as river, lakes, and oceans whereas 25% is obtained from ground water sources. Different treatment processes are used to turn raw water into safe drinking water. Surface water treatment is usually more contaminated compared to ground water and therefore involves more and active steps. While surface water treatment works on water from above earth surface, ground water treatment is performed on water from below soil surfaces such as springs and aquifers. Surface water treatment may involve simple techniques such as removal of floating sentiments and filtration. On the other hand, ground water treatment involves a complicated process of removing dissolved salts and other inorganic compounds (Laws, 2000).

Too much exposure to nitrate leads to “blue baby syndrome” health condition which results due to lack of oxygen in infants. Excessive exposure to selenium has been associated with adverse effects on the endocrine function which affects the synthesis of thyroid hormones. It also leads to impairment of natural killer cells activity, gastrointestinal disturbances, and hepatotoxicity. Excessive exposure to benzene causes bone marrow not to produce sufficient red blood cells which consequently lead to anemia. Benzene also damages the immune system by causing loss of blood cells and changing blood levels of antibodies.
A sedimentation tank for water treatment is designed to have a detention time of four hours. If the flow rate entering the tank is 20 ft3/s, the tank volume required in cubic feet can be calculated as:

Coagulation-flocculation

process involves chemical treatment of water usually applied before filtration and sedimentation. The purpose of coagulation is usually to enhance water treatment process through the removal of a particle. Flocculation means agitation or gentle stirring of water so that the particles can agglomerate into large masses which can be filtered out. Therefore, coagulation- flocculation is the process of separating suspended and dissolved particles from water during water treatment process. Studies indicate that the process is straightforward and cost-effective and can be adopted by most households (Calderon, 2000).
If a rapid sand filter is to be operated at 2gpm/ft2 (gallons per minute per square foot of surface area), the screen size (in square feet) is required to treat 200,000 gpd (gallons per day) is calculated as:

Chlorination process is usually used to treat water through the addition of chlorine or hypochlorite to the water. The method is well known and widely used to kill microbes and bacteria in water because chlorine is highly toxic. Chlorination is an effective way of preventing the spread of water-borne diseases such as typhoid, dysentery, and cholera. When chlorine is dissolved in water, it converts to hydrochloric acid (HCL) and hypochlorous (HOCL). Chlorination is also applied in swimming pools, springs, water wells and other water sources with a view of reducing algal residue and bacteria. This process is known as shock chlorination and is applied by mixing the relatively large amount of hypochlorite into water (Hodges, 1977).

Lime-soda method is one of the precipitation water softening techniques used to reduce water alkalinity, silica, hardness and other constituents. The process prepares water for direct use as a first-stage treatment or cooling tower and followed by

ion exchange for process use or boiler makeup. During this process, lime or a combination of soda ash and lime (carbonate ion) chemicals react with natural alkalinity and hardness in the water to form insoluble compounds. The formed compounds precipitate allowing for sedimentation and filtration(Hodges, 1977).

References

• Moss, B. (2008). Water Pollution by Agriculture. Phil. Trans. Royal Society.
• Laws, E. A. (2000). Aquatic Pollution: An Introductory Text. New York: John Wiley and Sons.
• Hodges, L. (1977). Environmental Pollution (2nd ed.). New York: Rinehart and Winston.
• Calderon, R. L. (2000). The Epidemiology of Chemical Contaminants of Drinking Water. Food and Chemical Toxicology, 38 (1): 13–20.