What is Water Pollution?
Water is essential to life. Without it, the biosphere that exists on the surface of the earth wouldn't be possible. Although 70% of the earth is covered with water, only a small percentage (around 0.3%) are freshwater that can be used for human purposes. The total amount of the earth's water does not change and it is repeatedly recycled through the hydrologic cycle or also known as the water cycle. The water cycle is a natural process that collects, purifies and redistributes water, recycling all of our planet’s water. Water moves up into the atmosphere by evaporation and back down to the earth’s surface as precipitation. We rely on this system for our existence and we need to remember that it is highly sensitive to our activities and actions.
Water evaporates from the sea, lakes, reservoirs, rivers and streams (surface water) and rises into the atmosphere. As air hits the mountain side, it is forced upwards causing the water vapour to cool and condense, forming rain clouds. When clouds become heavy with liquid droplets (or ice particles in cold climates), rain (or snow) falls. The rain water will then flow over the land into rivers and streams. The sun provides energy for part of the water cycle, especially evaporation and transpiration (evaporation through the leaves). Some of the water that falls onto the land seeps through the soil and forms another store of water: groundwater.
Water pollution is the contamination of water bodies such as lakes, rivers, oceans, and groundwater caused by human activities, which can be harmful to all organisms including humans. Water pollution is a major global problem as water is important for survival and less than 3% of Earth contains water that is safe for drinking (Wikipedia, 2009). Water has the capacity to dissolve or break down many substances, especially organic compounds, which decompose during continued contact with bacteria and enzymes. Such non-biodegradable elements remain in water and can make it poisonous for most forms of life. Even biodegradable pollutants can damage a water supply for long periods of time. Thereupon, life within the water begins to suffer. Lakes are especially vulnerable to pollution because they cannot cleanse themselves as rapidly as rivers or oceans. Although a lot of factors are causing deterioration of the quality of rivers and lakes in Malaysia, these three are the main contributors which are industry, homes and farming.
a) So, how do we contaminate our freshwater supply?
i) Organic Waste
Most fresh water pollution is caused by the addition of organic material in water bodies which is mainly animal waste, human sewage, food waste or excessive soil deposits. Allowing livestock to graze near water sources often results in organic waste products being washed into the waterways, while sewage generated by houses or runoff from septic tanks may flow into water sources. This sudden introduction of organic material increases the amount of nitrogen in the water and leads to eutrophication. Oxygen is normally present in high quantities in water bodies but when bacteria and other micro-organisms feed on organic matter in the water, large populations of them quickly develop and they use up much of the oxygen dissolved in the water, thus decreasing the level of oxygen in the water. Animals have different levels of tolerance to oxygen and are considered bioindicators which reveal the condition and quality of lakes and rivers.
ii) Pesticides and Fertilizer
Farms often use large amounts of herbicides and pesticides, both of which are toxic pollutants. These substances are particularly dangerous to life in rivers, streams and lakes, where substances can build up over a period of time. Farms also frequently use large amounts of chemical fertilizers that are washed into the waterways and damage the water supply and the life within it. Fertilizers increase the amount of nitrates and phosphates in the water, which can lead to the process of eutrophication.
This sudden introduction of organic material increases the amount of nitrogen in the water and leads to eutrophication. Oxygen is normally present in high quantities in water bodies but when bacteria and other micro-organisms feed on organic matter in the water, large populations of them quickly develop and they use up much of the oxygen dissolved in the water, thus decreasing the level of oxygen in the water. Animals have different levels of tolerance to oxygen and are considered bioindicators which reveal the condition and quality of lakes and rivers.
iii) Industrial Waste
Industries and agriculture come a close second, with toxic chemical by-products being dumped into our rivers. Chemical waste products from industrial processes are sometimes accidentally discharged into rivers. Examples of such pollutants include cyanide, zinc, lead, copper, cadmium and mercury. These substances may enter the water in such high concentrations that fish and other animals are killed immediately. Sometimes the pollutants enter a food chain and accumulate until they reach toxic levels, eventually killing birds, fish and mammals.
Industry often uses water for cooling processes, sometimes discharging large quantities of warm water back into rivers. This is a form of thermal pollution where raising the temperature of the water lowers the level of dissolved oxygen and upsets the balance of life in the water. This condition can kill fish and other aquatic organisms incapable of tolerating the high temperature. Acid precipitation is caused when the burning of fossil fuels emits sulphur dioxide into the atmosphere. The sulphur dioxide reacts with the water in the atmosphere, creating rainfall which contains sulphuric acid. As acid precipitation falls into rivers, lakes and ponds it can lower the overall pH of the waterway, killing vital plant life, and thereby affecting the whole food chain. It can also leach heavy metals from the soil into the water, killing fish and other aquatic organisms. Because of this, air pollution is potentially one of the most threatening forms of pollution to aquatic ecosystems.
In mining and oil-drilling operations, corrosive acid wastes are poured into the water. Decaying tanks and cesspools, used where sewers are not available, may also pollute the groundwater and adjacent streams, sometimes with disease-causing organisms.
iv) Siltation and Sedimentation
Clearing of land for farming or any other development near riverbanks and water bodies can lead to erosion of soil into the rivers or lakes. The silting of streams is a kind of water contamination. A heavy load of silt kills fish indirectly by decreasing the quantity of oxygen and other nutrients in water. Then, as the following water slows, silt is deposited on streambeds. Reservoirs behind dams also will be filled with silt unless erosion is stopped in the watershed above. Sedimentation also taints water. It is the result of poor conservation practices. Sediment fills water supply reservoirs and fouls power turbines and irrigation pumps. It also diminishes the amount of sunlight that can penetrate the water. In the absence of sufficient sunlight, the aquatic plants that normally furnish the water with oxygen fail to grow.
v) Solid Waste
Many waterways are utilized as dumps for household and industrial wastes. Some communities dump rubbish and untreated sewage into the nearest streams. Industries contaminate the waterways when they discharge acids, chemicals, greases, oils, and organic matter into them. They destroy commercial fisheries when they block the sunlight from coming through to the organisms. They also cause streams to become unusable for recreational purposes.
vi) Oil Pollution
If oil leaks enter a slow-moving river, it forms a rainbow-coloured film over the entire surface preventing oxygen from entering the water and cause suffocation and later lead to death of the animals there.
b) Effects And Impacts Of Water Pollution :
i) Effect on Lakes and Water Organisms
As mentioned previously, water pollution from different kinds of sources will eventually lead into water bodies. Since water ecosystems are fragile, the slightest change of temperature or condition will prove disastrous to the living organisms. For example, if oil leaks into rivers or lakes, the ecosystem will face dire consequences. Snails may lose their ability to attach themselves to a rock for stability, and be swept away and killed. Fish may ingest oil and depending on how the compounds react with their individual cells, clog their gills. Crustaceans and fish eggs may be affected by toxic materials found in even a thin layer of oil on the surface of the water. In contrast, if the oil sinks into the water's sandy sediment, or covers its beaches, some species (oysters, clams, mussels, smelt, and herring) may not generate offspring. If they do, the
offspring may be affected.
ii) Effects on Human health
The effects will depend on the source of pollution itself because different sources have different impacts. Nitrates in drinking water can cause a disease in infants that sometimes results in death. Metals like lead (from batteries paint and petrol) and mercury (from batteries, plastics) can cause untold damage to the nervous system and brain functions. It can also have an effect on reproductive systems and organs. Crops can absorb cadmium in sludge-derived fertilizer; if ingested in adequate quantities, the metal can cause acute diarrhoea and liver and kidney damage.