Water Pollutants

Importance of Water

• Necessary for life• Important in industrial processes and for the reduction of

air pollution• Water means different things to different people: - meteorologists see water as the basis of clouds and

rains - biologists see water as a home for plants and animals - geologists see it as a substance that erodes rocks - engineers see water as something to be pumped,

bridged and dammed - chemists see water as the most common compound

and liquid, a stable substance, and an indispensable reagent in many chemical reactions

When Does Water Become Polluted?

• When it has become unfit for its intended purpose

• Oxygen depletion

• Turbidity or cloudiness

• Eutrophication – a process that results in oxygen deficiency in a body of water due to the presence of dissolved nutrients

Causes of Eutrophication

• Natural phase in the maturation of a body of water

• Articially due to fertilizers, pesticides and detergents

Major Sources of Water Pollution

• Increase in population and industry• Industrial wastes which do not have proper

wastewater treatment facilities• Factories discharge oxygen-demanding wastes,

and they dump dangerous and toxic chemical pollutants into the water that are difficult to detect and control

• People who live along riverbanks and who depend on overhanging latrines for their daily personal necessities, slaughterhouses, and public toilets constructed near banks of rivers

Types of Water Pollutants

1. Synthetic Organic Compounds

- many toxic organic compounds are nonbiodegradable

- some are magnified biologically in the food web

- may cause cancer in humans

- some kill fish and other aquatic organisms

- some may give water and fish an offensive odor or taste

Organism/Substance Amount of DDT (ppm)

Water 0.000003

Zooplankton 0.04

Small fish 0.5

Large fish 2

Fish-eating bird 25

2. Toxic Inorganic Chemicals – includes metals, acids and salts.

• Metals such as mercury and lead come from industrial discharges, mining, sewage effluents, and some natural sources

• Nitrates come from septic tanks, barnyards, heavily fertilized crops and sewage treatment plants. Nitrates are converted to nitrites in the intestines of humans. Scientists link them to stomach cancer

• Fertilizers like urea, ammonium nitrate and diammonium hydrogen phosphate help tiny green water plants called algae to grow and over the water surface

3. Sediments – by-products of timber cutting, agriculture, mining and construction of roads and buildings

4. Heat – changes in water temperature, rapid or gradual, can disrupt aquatic ecosystems

5. Infectious Agents – pathogenic bacteria, protozoans, fungi and viruses cause water to be polluted.

6. Organic Nutrients – formed from sewage treatment plants and some industries such as paper mills and meat-packing plants.

7. Inorganic Nutrients – nitrogen, phosporous, iron, sodium, sulfur and potassium stimulate the growth of aquatic plants.

8. Oil in the Seas. Oil contamination of the ocean comes from natural seepage from offshore deposits, well blowouts, breaks in pipelines, tanker spills and leakae from offshore wells

9. Plastics. Careless discarding of nylon fishing nets, plastic bags, plastic straps and other plastic garbage into the ocean pose dangers to marine animals.

Effects of Pollutants on Human Health and the Environment

1. Long-term exposure to toxic organic compounds may result in cancer and genetic damage. It is also detrimental to fish and other aquatic animals.

2. The signs of mercury poisoning include numbness of the limbs, lips and tongue. Muscle control is lost. Deafness, blurring of vision, clumsiness, apathy, and mental derangement may also occur. Nitrates when converted to nitrites may cause diseases in babies and stomach cancer in adults.

3. Sediments destroy spawning and feeding grounds for fish, reduce fish and shellfish populations, smother eggs and fry and decrease light penetration which may lead to the death of plants in lakes and streams

4. Thermal pollution lowers the dissolved oxygen content of water. Sharp changes in water temperature causes thermal shock and causes the death of fish and other organisms that cannot cope.

5. Effects of oils spills a. Oil kills plants and animals especially mussels and

crabs. Recovery after a major spill may take two or ten years

b. Oil spills damage beaches, shorelines, recreational areas and marine organisms

c. Oils poison algae and may disrupt major food chains and decrease the yield of edible fish.

d. It also coats birds, impairing flight or reducing the insulative property of their feathers.

6. Plastic nets entangle birds, fish, and sea mammals. They may strangle, starve to death, or drown their victims. Plastics provide breeding grounds for disease-carrying insects and rats.

7. The major infectious diseases include viral hepatitis, polio, typhoid fever, amoebic dysentery, cholera, schistosomiasis and salmonellosis

8. Organic nutrients released from industrial plants stimulate the growth of bacteria which consume dissolved oxygen. Anaerobic bacteria are responsible for breaking down the remaining substances, producing foul-smelling and toxic methane and hydrogen sulfide gases in the process

9. Excessive plant growth can impair fishing, swimming, navigation and recreational boating. Inorganic fertilizers from croplands are the major source of plant nutrients in fresh water. Laundry detergents contain synthetic phosphates called tripolyphates which stimulate the growth of aquatic algae, causing algal blooms. The natural accumulation of nutrients in lakes is called natural eutrophication.

Measures to Control Water Pollution

Pretreatment of Wastes Industries can reduce water pollution by removing

harmful chemicals from wastes before they are dumped into the water. Industrial wastes can also be reduced by using manufacturing processes that recycle polluting chemicals.

When industrial wastes contain toxic substances, the effluent water should be cleaned before it is discharged. The industrial process may also be redesigned so that the toxic substances are not discharged into the environment.

Raw sewage entering a treatment plant contains pollutants from homes, hospitals, schools, and industries. It contains human wastes, soap, detergents, dirt, food residues, and chemicals.

Purifying Water for Drinking

Filtration – removal of all suspended particles Addition of alum – collects fine solids together and

make them settle.Addition of small amounts chlorine or ozone to kill

bacteria and viruses.Aeration – removes odors and improve the taste of

waterActivated charcoal – eliminates colored and

odorous substancesDistillation – evaporation/condensation of water

Dangerous Water Pollutants

1. Mercury and Cadmium

Mercury is an exceedingly toxic metal. When absorbed by the body even in small amounts, it may cause blindness, paralysis and brain damage.

Cadmium may lead to death caused by hypertension due to kidney disorder and damaged lungs.

2. Detergents – these materials flow from sewers into streams, lakes or rivers. Detergents are nonbiodegradable; they become pollutants because they contain phosphorous which stimulates algae growth in bodies of water.

3. Sewage – contains many types of wastes including human wastes. Disease-carrying bacteria and viruses may cause epidemics when these get into drinking water. Wastes from mines, factories and refineries are dumped into rivers, thus forming sewage sludge, the solid material remaining after sewage is dumped into the sea.

Typical Water Pollutants From Some Industries

Industry Pollutants

1. Chemical Products

Acids

Explosives

Pesticides

Soaps and Detergents

Various acids

Acids, dyes, oils, soap, organic matter

Organic matter, benzene compounds, acids

Hydrolyzed fats and other dissolved and suspended organics, alkyl sulfates and sulfonates, phosphates, silicates, borates, chlorine, bromine, arsenic

2. Food products

Brewed beverages

Canned and frozen fruits and vegetables

Carbonated beverages

Dairy products

Meat and poultry

(All are high in dissolved and suspended organic matter)

Fermented starches

Dissolved particles and suspended chunks of raw plant matter, sugars, starches

Sugars, suspended solids and dissolved detergents from bottle washing

Whey solids (milk protein, milk sugar, soluble salts), fats

Fecal wastes from pens and stockyards, blood, fat, protein, and other organic matter from processing

Typical Water Pollutants From Some Industries

Industry Pollutants3. Coal Sulfuric and other acids from mine

drainage, suspended mineral particles removed as impurities during washing and sorting

4. Iron and steel Iron salts, hydrochloric acid, sulfuric acid, phenol, lime, oil

5. Leather tanning Dissolved organics, suspended animal flesh and hair particles, brine soaps, vegetable and mineral tanning chemicals, bases and acids, dyes

6. Metal plating and finishing Hydrofluoric, sulfuric and chromic acids; nickel sulfate; cyanides of copper, zinc, cadmium and silver; oils

Typical Water Pollutants From Some Industries

Industry Pollutants7. Pharmaceuticals Vitamins and other dissolved and

suspended organic compounds

8. Petroleum Organic matter, phenol, brine, oil, sulfur compounds

9. Pulp and paper Lignosulfates, wood sugars, sulfite pulping chemicals, inorganic binders and fillers, glue, dyes, acids, bases (bleaches), paper fibers, pulp, mercury

10. Rubber (natural, synthetic and reclaimed)

Organic matter, odoriferous sulfur compounds, chlorides, suspended solids

11. Textiles Strong bases, dyes, high content of dissolved matter and suspended organic matter