· Lot of people around the world depend on ground water for drinking, domestic, industrial and agricultural uses.
· Generally groundwater is a clean source of water.
· However, human activities such as improper sewage disposal, dumping of farm yard manures and agricultural chemicals, industrial effluents are causing pollution of ground water.
· ‘Eu’ maens well or healthy and ‘trophy’ means nutrition.
· The enrichment of water bodies with nutrients causes entrophication of the water body.
· Discharge of domestic waste, agricultural surface runoff, land drainage and industrial effluents in a water body leads to rapid nutrients enrichment in a water body.
· The excessive nutrient enrichment in a water body encourages the growth of algae duckweed, water hyacinth, phytoplankton and other aquatic plants.
· The biological demand for oxygen (BOD) increases with the increase in aquatic organisms.
· As more plants grow and die, the dead and decaying plants and organic matter acted upon by heterotrophic prtozoans and bacteria, deplete the water of dissolved oxygen (DO).
· Decrease in DO result in sudden death of large population of fish and other aquatic organisms including plants, releasing offensive smell and makes the water unfit for human use.
· The sudden and explosive growth of phytoplankton and algae impart green colour to the water is known as water bloom, or “algal blooms”.
· These phytoplankton release toxic substances in water that causes sudden death of large population of fishes.
· This phenomenon of nutrient enrichment of a water body is called eutrophication.
· Human activities are mainly responsible for the eutrophication of a growing number of lakes and water bodies in the country.
Methods for control of water pollution and water recycling
Control water pollution
· Waste water from domestic or industrial sources or from garbage dumps is generally known as sewage.
· It may also contain rain water and surface runoff.
· The sewage water can be treated to make it safe for disposal into water bodies like rivers, lakes etc.
The treatment involves three stages: primary, secondary and tertiary.
This includes :
· The first four steps are of primary treatment.
· The first three steps are involved in primary treatment remove suspended particulate matter.
· Secondary treatment removes organic solids, left out after primary treatment, through their microbial decomposition.
· Effluents after secondary treatment may be clean but contain large amounts of nitrogen, in form of ammonia, nitrates and phosphorous which can cause problem of eutrophication upon their discharge into a receiving water body such as river, lake or pond.
· The tertiary treatment is meant to remove nutrients, disinfect for removing pathogenic bacteria, and
· aeration removes hydrogen sulphide and reduce the amount of carbon dioxide and make water healthy and fit for aquatic organisms.
· This treatment of waste water or sewage is carried out in effluent treatment plants especially built for this purpose.
· The residue obtained from primary treatment one known as sludge.
Water recycling :
· It is essential to utilize the available water with maximum economy.
· This involves recycling of waste water for certain uses with or without treatment.
· Recycling refers to the use of waste-water by the original user prior to the discharge either to a treatment system or to a receiving water body.
Control of water pollution :
The following measures can be adopted to control water pollution:
(a) The water requirement should be minimized by altering the techniques involved.
(b) Water should be reused with or without treatment.
(c) Recycling of water after treatment should be practiced to the maximum extent possible.
(d) The quantity of waste water discharge should be minimized.
SOIL POLLUTION :
· Addition of substances which adversely affect the quality of soil or its fertility is known as soil pollution. Generally polluted water also pollute soil.
· Solid waste is a mixture of plastics, cloth, glass, metal and organic matter, sewage, sewage sludge, building debris, generated from households, commercial and industries establishments add to soil pollution.
· Fly ash, iron and steel slag, medical and industrial wastes disposed on land are important sources of soil pollution.
· In addition, fertilizers and pesticides from agricultural use which reach soil
as run-off and land filling by municipal waste are growing cause of soil pollution.
· Acid rain and dry deposition of pollutants on land surface also contribute to soil pollution.
Sources of soil pollution :
Plastic bags :
· Plastic bags made from low density polyethylene (LDPE), is virtually indestructible, create colossal environmental hazard.
· The discarded bags block drains and sewage systems.
· Leftover food, vegetable waste etc. on which cows and dogs feed may die due to the choking by plastic bags.
· Plastic is non biodegradable and burning of plastic in garbage dumps release highly toxic and poisonous gases like carbon monoxide, carbon dioxide, phosgene, dioxine and other poisonous chlorinated compounds.
Industrial sources :
· It includes fly ash, chemical residues, metallic and nuclear wastes.
· Large number of industrial chemicals, dyes, acids, etc. find their way into the soil and are known to create many health hazards including cancer.
Agricultural sources :
· Agricultural chemicals especially fertilizers and pesticides pollute the soil.
· Fertilizers in the run off water from these fields can cause eutrophication in water
· Pesticides are highly toxic chemicals which affect humans and other animals adversely causing respiratory problems, cancer and death.
Control of soil pollution
· Indiscriminate disposal of solid waste should be avoided.
· To control soil pollution, it is essential to stop the use of plastic bags and instead use bags of degradable materials like paper and cloth.
· Sewage should be treated properly before using as fertilizer and as landfills.
· The organic matter from domestic, agricultural and other waste should be segregated and subjected to vermicomposting which generates useful manure as a by product.
· The industrial wastes prior to disposal should be properly treated for removing hazardous materials.
· Biomedical waste should be separately collected and incinerated in proper incinerators.
RADIATION POLLUTION: SOURCES AND HAZARDS
· Radiation pollution is the increase in over the natural background radiation.
· There are many sources of radiation pollution such as nuclear wastes from nuclear power plants, mining and processing of nuclear material etc.
· The worse case of nuclear pollution was the chernboyl disaster in Russia occured in 1986 but the effects still longer today.
· Radiation is a form of energy travelling through space.
· The radiation emanating from the decay of radioactive nuclides are a major sources of radiation pollution.
· Radiations can be categorized into two groups namely the non-ionizing radiations and the ionizing radiations.
· Non-ionizing radiations are constituted by the electromagnetic waves at the longer wavelength of the spectrum ranging from near infra-red rays to radio waves.
· These waves have energies enough to excite the atoms and molecules of the medium through which they pass, causing them to vibrate faster but not strong enough to ionize them.
· In a microwave oven the radiation causes water molecules in the cooking medium to vibrate faster and thus raising its temperature.
Ionizing radiations :
· Ionizing radiations cause ionization of atoms and molecules of the medium through which they pass.
· Electromagnetic radiations such as short wavelength ultra violet radiations (UV), X-rays and gamma rays and energetic particles produced in nuclear processes, electrically charged particles like alpha and beta particles produced in radioactive decay and neutrons produced in nuclear fission, are highly damaging to living organisms.
· Electrically charged particles produced in the nuclear processes can have sufficient energy to knock electrons out of the atoms or molecules of the medium, thereby producing ions.
· The ions produced in water molecules, for example, can induce reactions that can break bonds in proteins and other important molecules.
· An example of this would be when a gamma ray passes through a cell, the water molecules near the DNA might be ionized and the ions might react with the DNA causing it to break.
· They can also cause chemical changes by breaking the chemical bonds, which can damage living tissues.
· The ionizing radiations cause damage to biological systems and are, therefore, pollutants.
Radiation damage :
The biological damage resulting from ionizing radiations is generally termed as radiation damage.
· Large amounts of radiation can kill cells that can dramatically affect the exposed
organism as well as possibly its offspring.
· Affected cells can mutate and result in cancer.
· A large enough dose of radiation can kill the organism.
· Radiation damage can be divided into two types:
(a) somatic damage- (also called radiation sickness)
· Somatic damage refers to damage to cells that are not associated with reproduction.
· Effects of somatic radiation damage include reddening of the skin, loss of hair, ulceration, fibrosis of the lungs, the formation of holes in tissue, a reduction of white blood cells, and the induction of cataract in the eyes.
· This damage can also result in cancer and death.
(b) genetic damage-
· Genetic damage refers to damage to cells associated with reproduction.
· This damage can subsequently cause genetic damage from gene mutation
resulting in abnormalities.
· Genetic damages are passed on to next generation.
Radiation dose :
· The biological damage caused by the radiation is determined by the intensity of radiation and duration of the exposure.
· It depends on the amount of energy deposited by the radiation in the biological system.
· In studying the effects of radiation exposure in humans, it is important to realize that the biological damage caused by a particle depends not only on the total energy deposited but also on the rate of energy loss per unit distance traversed by the particle (or “linear energy transfer”).
· For example, alpha particles do much more damage per unit energy deposited than do electrons.
Radiation effects and radiation doses :
· A traditional unit of human-equivalent dose is the rem, which stands for radiation equivalent in man.
· At low doses, such as what we receive every day from background radiation (< 1 m rem), the cells repair the damage rapidly.
· At higher doses (up to 100 rem), the cells might not be able to repair the damage, and the cells may either be changed permanently or die.
· Cells changed permanently may go on to produce abnormal cells when
they divide and may become cancerous.
· At even higher doses, the cells cannot be replaced fast enough and tissues fail to function.
· An example of this would be “radiation sickness.” This is a condition that results after high doses is given to the whole body (>100 rem).
· Nuclear explosions and accidents in nuclear reactors are a serious source of radiation hazard.
· The effects of atomic explosions in Nagasaki and Hiroshima are still not forgotten.
· The nuclear reactor accident at Chernobyl in 1986 led to deaths of many reactor personnel and a very large release of radionuclide to the environment causing a long term radiation damage to the people living in the neighboring regions.
Accidents at nuclear power plants :
· Nuclear fission in the reactor core produces lot of heat which if not controlled can
lead to a meltdown of fuel rods in the reactor core.
· If a meltdown happens by accident, it will release large quantities of highly dangerous radioactive materials in the environment with disastrous consequences to the humans, animals and plants.
· To prevent this type of accidents and reactor blow up, the reactors are designed to have a number of safety features.
· Inspite of these safety measures two disasters in the nuclear power plants are
noteworthy- namely at ‘Three Mile Island’ in Middletown (U.S.A.) in 1979, at Chernobyl (U.S.S.R.) in 1986.
· In both these cases a series of mishaps and errors resulted in over heating of the reactor core and lot of radiation was released into the environment.
· The leakage from Three Mile Island reactor was apparently low and no one was injured immediately. However, in case of Chernobyl the leakage was very heavy causing death of some workers and radiation spread over large areas scattered all over Europe.
· People of the city had to be evacuated to safer places and the plant had to be closed down.
· These two disasters are a reminder that nuclear power reactors require a constant up gradation of safety measures.
· Accidents with nuclear submarines also points to the same.