Water Pollution

Water is one of the most important natural resources for all living organisms. It is essential for the survival of any form of life in the biosphere. Water covers about three-fourths (75%) of the earth’s surface. But freshwater constitutes only about 1.998% of the earth’s total water supply. The quality of water is of vital concern for mankind, since it is directly linked with human welfare. Water pollution disturbs the normal uses of water for irrigation, agriculture, industries, public water supply and aquatic life. The word pollution is derived from the Latin word ‘pollutionem’ meaning ‘to make dirty’. Pollution is an undesirable change in the physical, chemical and biological characteristics of the environment. Water pollution is the deterioration in physical, chemical and biological properties of water brought about mainly by human activities and natural sources.

Types of water pollution

·         Surface water  pollution - pollution of lakes, rivers and oceans

·         Groundwater pollution - pollution of aquifers below soil.

·         Microbial   pollution – pollution by bacteria, viruses, protozoa and parasitic worms.

·         Oxygen depletion pollution – pollution by biodegradable organics.

·         Nutrient pollution – pollution by plant nutrients (nitrates, phosphates)

·         Suspended matter pollution – pollution by soil, silt

·         Chemical pollution -  pollution by pesticides, fertilizers, industrial solvents, oil

·         Thermal pollution- pollution by warm water, waste heat

Sources of water pollutants

Point Sources
A single definable source of the pollution, e.g. a factory, a sewage plant, etc.- pollution is easy to monitor and control.

Non-point sources 
No one single source, but a wide range of sources, e.g. runoff from urban areas, or farmland. Pollution is more difficult to monitor and control.

Non-persistent (degradable) water pollutants

Some wastes can be broken down by natural chemical reactions or by natural bacteria into simple, non-polluting substances such as carbon dioxide and nitrogen. e.g. wood, paper, biological wastes. More pollution load can lead to low oxygen levels and eutrophication.This damage is reversible.

Persistent Water pollutants

This is the most rapidly growing type of pollution. Organic chemical  substances that degrade very slowly or cannot be broken down at all; They  may remain in the aquatic environment for  longer periods of time. The damage  is  irreversible.

·         Pesticides - DDT, dieldrin

·         Leachate components from landfill sites (municipal, industrial)

·         Petroleum  and petroleum products

·         PCBs, dioxins, polycyclic aromatic hydrocarbons (PAHs)

·         Radioactive  materials- strontium-90, cesium-137, radium-226, and uranium

·         Metals  - lead, mercury, cadmium

kinds of  Water pollutants

·         Pathogens - bacteria, viruses, parasites.

·         Oxygen demanding wastes – animal manure, human wastes, plant residues.

·         Water soluble inorganic chemicals- acids, salts, toxic metal compounds like mercury and lead.

·         Inorganic plant nutrients – water soluble phosphates, nitrates, ammonium.

·         Organic chemicals - petrochemicals, plastics, pesticides, cleaning  solvents, detergents and industrial wastes. 

·         Sediment & Suspended Matter – dirt, soil, silt . –reduce water clarity.

·         Radioactive materials- uranium, thorium,  iodine and radon.

·         Thermal Water – heat From power plants, industrial cooling.

·         Alien Species - Zebra Mussels, Asiatic Catfish, Sea Lamprey, etc. 

Impact of  Microbial water pollution

The number of people lack access to safe drinking water is over 1 billion. The number of people lack adequate sanitation is 2.6 billion . This has led to widespread microbial contamination of drinking water. Deaths due to water-associated infectious diseases may go up to 3.2 million people per year. (approx. 6% of all deaths globally). Deaths due to diseases caused by inadequate water, sanitation, and hygiene are 1.8 million people.

Eutrophication (nutrient pollution)

Excessive amounts of plant nutrients like P,N,C cause excessive growth or ‘blooms of algae’. Algal blooms leads to oxygen depletion. Hypoxia leads to mass fish kills, degradation of water and habitat quality.

Oceans - A global dumping ground  

Around 50% of the world’s population lives on or within 160 miles of shore. Fourteen billion pounds of garbage, mostly plastic, is dumped into the ocean every year. For every 1 million tons of oil that is shipped, about 1 ton is spilled. More oil is seeped into the ocean each year as a result of leaking cars and other non-point sources.

River pollution

Asian rivers are the most polluted in the world. River Ganges in India is one of the most polluted rivers in the world. Approximately 46% of the lakes in America are too polluted for fishing, aquatic life, or swimming.

      Plastic waste in water

The amount of plastic waste has been increasing about 10% each year for the past 20 years. Over 1 million seabirds are killed by plastic waste per year. Over 100,000 sea mammals and countless fish are killed per year due to pollution.

Health impacts of dissolved chemicals in water

·         Pesticides  - damage nervous system and also cause cancer.

·         Lead – affects central nervous system .

·         Fluorides – damage teeth and the skeleton.

·         Nitrates – cause blue – baby syndrome in infants.

·         Petrochemicals – cause cancer.

·         Arsenic – damage liver and nervous system, skin cancer.

·         Heavy metals – damage nervous system and kidneys.