There are six major types of water pollutants:
Biodegradable wastes
Plant nutrients
Heat
Sediments
Hazardous and toxic chemicals
Radioactive wastes
Sewage Disposal
The Sewage disposal process starts with:
Screening-Wire nets strain out dirt.
Grit Tanks- Screened sewage passes into a large tank where grit, stones and other heavy objects sink to the bottom.
Sedimentation tanks- Faeces settles at the bottom and makes a sewage, which is used as a fertiliser, the liquid moves to the top.
Aeration- air is pumped through to encourage growth of bacteria, they digest wastes and change them into harmful substances such as Carbon Dioxide.
Biological Filter- the liquor is sprinkled into tanks filled with stones, these stones are covered with microbes which digest more waste this leaves a clean liquid called effluent.
Air Pollution
The layer of air which supports life extends about 8 km above the Earth's surface and is known as troposphere. The composition of air remains remarkably constant except there may be small localised variations. Air pollution has existed since humans first used fire. The problem becomes significant since the industrial revolution in the 19th century. Almost all air pollutants are the result of burning fossil fuels, either in the home, by industry or in internal combustion engine.
Carbon monoxide occurs in exhaust emissions from cars and other vehicles. Carbon Monoxide is a poisonous gas on account of having an affinity of haemoglobin, the red pigment that carries oxygen in blood, some 250 times greater than oxygen itself. The combination, carboxyhaemoglobin, is not released and prevents oxygen from combining with it. Continued inhalation leads to death as all haemoglobin become attached to Carbon Monoxide.
The artificial generation of carbon dioxide is the burning of fossil fuels. The additional carbon dioxide in the atmosphere from such raises the atmospheric carbon dioxide concentration.
The change in carbon dioxide concentration in the air has triggered the greenhouse effect. More heat from the sun is prevented to escape from the Earth, rather like the mechanism of a greenhouse.
Sulphur dioxide causes irritation of the respiratory system. It can attach to particles forming acidic coatings that damage the epithelial lining of the alveoli. It may also aggravate asthma.
The gas reduces the growth of many plants, e.g. barley, wheat, lettuce, while others such as lichens may be killed. So the tolerance of lichen and moss species to sulphur dioxide is very valuable and they serve as the indicator species for measuring sulphur dioxide pollution. Most of the gas readily combines with water and ammonia that deposits in the soil to increase soil fertility.
It acts as a fungicide to help controlling diseases like blackspot of roses.
Nitrogen dioxide is acidic in nature. Therefore, besides sulphur dioxide, it is another gas that will cause acid rain.
The gas, together with hydrocarbons and particulates, forms photochemical smog under sunlight. Its brown coloration obscures the sky with a yellow haze that lowers the visibility. This drives away tourists from coming.
Ozone layer in the stratosphere filters out 99% of dangerous ultraviolet radiation from the sun. The thinning of the ozone layer may lead to an increase of skin cancer and eye cataract. The presence of 'ozone hole' over Antarctica and the southern hemisphere has introduced incidence of increasing victims of skin cancer. The yield of crops may also decrease. The expanse in medical cure and economical loss in food is uncountable.
Smoke, ash and soot become deposited on clothes, cars and buildings. They are costly to clean. The visibility reduces when there is smoke. This highly affects the safety of navigation and aviation. It is a reduction of appeal on tourists to come to a smoky, choky place.
Chlorofluorocarbons: Due to their inert behaviour, the once emitted CFCs can stay in the atmosphere for a long time (a few tens of years). They will not be broken down by rainwater. The prolonged effect of CFCs is the depletion of ozone layer.
The Greenhouse Effect
The greenhouse effect is the rise in temperature that the Earth experiences because certain gases in the atmosphere (water vapour, carbon dioxide, nitrous oxide, and methane, for example) trap energy from the sun. Without these gases, heat would escape back into space and Earth’s average temperature would be about 60ºF colder. Because of how they warm our world, these gases are referred to as greenhouse gases.
Most greenhouses look like a small glasshouse. Greenhouses are used to grow plants, especially in the winter. Greenhouses work by trapping heat from the sun. The glass panels of the greenhouse let in light but keep heat from escaping. This causes the greenhouse to heat up, much like the inside of a car parked in sunlight, and keeps the plants warm enough to live in the winter.
The Earth’s atmosphere is all around us. It is the air that we breathe. Greenhouse gases in the atmosphere behave much like the glass panes in a greenhouse. Sunlight enters the Earth's atmosphere, passing through the blanket of greenhouse gases. As it reaches the Earth's surface, land, water, and biosphere absorb the sunlight’s energy. Once absorbed, this energy is sent back into the atmosphere. Some of the energy passes back into space, but much of it remains trapped in the atmosphere by the greenhouse gases, causing our world to heat up.
The greenhouse effect is important. Without the greenhouse effect, the Earth would not be warm enough for humans to live. But if the greenhouse effect becomes stronger, it could make the Earth warmer than usual. Even a little extra warming may cause problems for humans, plants, and animals.
Acid Rain
"Acid rain" is a broad term used to describe several ways that acids fall out of the atmosphere. A more precise term is acid deposition, which has two parts: wet and dry.
Wet deposition refers to acidic rain, fog, and snow. As this acidic water flows over and through the ground, it affects a variety of plants and animals. The strength of the effects depend on many factors, including how acidic the water is, the chemistry and of the soils involved, and the types of fish, trees, and other living things that rely on the water.
Dry deposition refers to acidic gases and particles. About half of the acidity in the atmosphere falls back to earth through dry deposition. The wind blows these acidic particles and gases onto buildings, cars, homes, and trees. Dry deposited gases and particles can also be washed from trees and other surfaces by rainstorms. When that happens, the runoff water adds those acids to the acid rain, making the combination more acidic than the falling rain alone.
Acid rain causes acidification of lakes and streams and contributes to damage of trees at high elevations (for example, red spruce trees above 2,000 feet) and many sensitive forest soils. In addition, acid rain accelerates the decay of building materials and paints, including irreplaceable buildings, statues, and sculptures that are part of our nation's cultural heritage. Prior to falling to the earth, SO2 and NOx gases and their particulate matter derivatives, sulphates and nitrates, contribute to visibility degradation and harm public health.
The ecological effects of acid rain are most clearly seen in the aquatic, or water, environments, such as streams, lakes, and marshes. Acid rain flows to streams, lakes, and marshes after falling on forests, fields, buildings, and roads. Acid rain also falls directly on aquatic habitats. Most lakes and streams have a between 6 and 8, although some lakes are naturally acidic even without the effects of acid rain. Acid rain primarily affects sensitive bodies of water, which are located in watersheds whose soils have a limited ability to neutralize acidic compounds (called "buffering capacity").
Researchers now know that acid rain causes slower growth, injury, or death of forests. Acid rain has been implicated in forest and soil degradation in many areas of the eastern United States, particularly high elevation forests of the Appalachian Mountains from Maine to Georgia that include areas such as the Shenandoah and Great Smoky Mountain National Parks.
Acid rain looks, feels, and tastes just like clean rain. The harm to people from acid rain is not direct. Walking in acid rain, or even swimming in an acid lake, is no more dangerous than walking or swimming in clean water. However, the pollutants that cause acid rain (sulphur dioxide (SO2) and nitrogen oxides (NOx)) also damage human health. These gases interact in the atmosphere to form fine sulphate and nitrate particles that can be transported long distances by winds and inhaled deep into people's lungs. Fine particles can also penetrate indoors. Many scientific studies have identified a relationship between elevated levels of fine particles and increased illness and premature death from heart and lung disorders, such as asthma and bronchitis.
Building and Quarrying
Illegal quarrying has been an issue of concern, particularly among local authorities in Lusaka. But the business continues, causing dangerous environmental degradation.
Those engaged in stone quarrying collect sand and stones from areas not been designated for that purpose. As a result, it is common to find ditches in several outskirts of Lusaka from where stones were extracted.
Minerals extraction is broadly divided into three basic methods: open-pit or surface, underground, and solution mining. The mining method used depends on the particular mineral, the nature of the deposit, and the location of the deposit. For this industry, most mining is open-pit or surface mining.
Surface or open-pit mining requires extensive blasting, as well as rock, soil, and vegetation removal to reach mineral deposits. Waste rock, or overburden, is piled away from the mine. Benches are cut into the walls of the mine to provide access to progressively deeper ore, as upper-level ore is depleted. Ore is removed from the mine and transported to processing plants for concentration
The source of crushed stone is usually a deposit of relatively solid rock such as limestone, dolomite, trap rock, granite or sandstone. Dust emissions occur from many operations in stone quarrying and processing. Dust is released when rock and crushed stone products are loosened by drilling or blasting them from their deposit beds. Dust is also released when the loosened rock is loaded into trucks by power shovels or front-end loaders. Transporting the quarried material to the processing plant generates dust from the rock inside the truck and from the road. Sources of dust at the processing plant include the dumping of rock into primary crushers; primary, secondary, and tertiary crushing; screening; transferring rock by belt conveyor; loading rock onto storage piles from conveyors; and wind blowing dust from storage piles and open conveyors.
