Thermal Pollution: Why it is a Problem and How to Control it
Why is thermal pollution a problem? How would you feel if, suddenly, your world became much warmer. Obviously for humans, we are much more adaptable. But for less adaptive organisms like fish, an increase in temperature can be deadly. And that is exactly what is happening across the globe, due to thermal pollution. These watery ecosystems are becoming warmer due to many issues that are taking place. Many of which, factor into or are part of the effects of other kinds of pollution. This is why it's espicially important to look at what thermal pollution is, and the steps we can take to combat it.
Information on Thermal Pollution
The thermal pollution definition is as follows. The degradation of water quality by any process that changes ambient water temperature. Usually, this happens when the activities of people or industries, suddenly cause an increase or decrease in the temperature of the bodies of water in the surrounding area. This may include lakes, rivers, oceans or ponds.
The sources and causes of thermal pollution vary, which makes it difficult to extensively calculate the problem. Also, there is a sense of neglect in this area of study because thermal pollution does not directly affect the health of humans. Of course, the first place people usually look to when it comes to pollution in any way, is power plants. Since the nuclear power industry has become tightly regulated. Therefore, the impact of nuclear power plants on the environment is much easier to document. The contribution of less regulated, but possibly more extensive thermal polluters, is difficult to ascertain. These include polluted runoff, or nonpoint source pollution. The cause of this may be rainfall or snowmelt, which washes sediment and pollutants into the surrounding waters, as well as the removal of vegetation from the river banks or coastal areas.
Water pollution has been aware of from very early on. In 1972, the EPA began a nationwide effort to reduce water pollution. This was done under the guidance of the Clean Water Act, along with the state regulatory agencies. The program's first focus was on the identifiable sources of water pollution. They did an assessment of power plants and other manufacturers and the bodies of water around them. This led to the discovery of water temperature changes in the areas in or near the facilities.
In the case of power plants, the discharge of warm water, also known as cooling water, from the facilities was found to drastically affect the marine ecosystems. In the late 1980s, the EPA and local governments turned their attention to nonpoint source pollution. Think of nonpoint source pollution as indirect pollution, while point source is direct. An example of thermal pollution that is indirect could be agricultural practices like removing trees and topsoil which can cause soil erosion. As a result, wind may blow the loose sediment to nearby bodies of water. This, in turn, can affect the water in many ways including the natural flow, temperature, and sedimentation of the water, ultimately impacting the marine environment in a negative way. Indirect pollution is much harder to detect and even harder to control.
What Are The Causes of Thermal Pollution
In today’s society, pollution of all kinds is a huge threat and power plants are one of the largest contributors to all kinds of pollution. This is no different when looking at thermal pollution. However, like other forms of pollution, there are many issues that factor into the overall problem. To answer the question, where does thermal pollution come from, here is a list of the primary causes of thermal pollution.
- Power Plants, and Industrial/ Manufacturing Facilities- Power, production and manufacturing plants are, of course, at the top for sources of thermal pollution. They discharge a lot of heat into nearby water sources. Many power plants also use the cool water from the surrounding bodies of water to cool their machinery. They then release that same water back into the area which it came from. The water they release is most of the time 10 degrees celsius higher than the normal temperature. As a result, the marine life that was thriving in the normal temperature, can not adapt to the sudden and drastic change in temperature. The discharge of higher temperature water also decreases dissolved oxygen content in the water ways. Both resulting in the death of fish and other marine life. This increase in water temperature can also affect the vegetation along the rivers and lakes.
- Industrial Effluents- This includes drainage from research institutions, hospitals, other manufacturing companies, explosives, and nuclear plants. All of those activities produce a lot of heat and traces of heat absorbing materials into the surrounding water systems.
- This is the discharge of sewage waste into lakes, rivers and streams or canals. Unfortunately, this is a common occurrence all over the world. In fact, this sewage waste is usually discharged with little to no treatment at all. And yet, people still do not see the negative effects it has on the water. This practice has many detrimental effects on the marine life as well as our own. Fishermen often get their fish from the same rivers and lakes that others dump their waste into. As a result, the quality of the fish is extremely poor and can lead to health risks in humans.
- Many other forms of pollution contribute to others. Land pollutants often end up in the water. As storms become increasingly more common and powerful, the toxins that are polluting the soil, can wash into the nearby waters. These toxins could be manure from factory farms, trash, or even materials that, by themselves, do not seem all that dangerous like the concrete or rocks from roads. During hot days and months, those stones and pieces of concrete get extremely hot. During a storm, those particles can runoff into the surrounding bodies of water. If enough is washed into the waters, it can drastically affect the temperature of that water.
- Trees and vegetation is responsible for absorbing and reflecting much of the sun’s heat. They also act as a cushion for the intense heat that is often in rivers, ponds, canals, and lakes. When that vegetation is stripped away, not only does it take nature's ability to absorb carbon from the atmosphere, it also exposes water sources completely to the sun’s heat. With atmospheric temperatures constantly rising due to the increase of carbon dioxide emissions, now is not the time to get rid of our trees.
- The continuation of soil erosion can cause siltation and sedimentation which, as a result, raises water levels, exposing more surface area to direct sunlight. The more exposure to the sun, the warmer the waters become. Streamside erosion may also remove vegetation cover along the streams further exposing the water to the sun’s thermal radiation.
Hydroelectric Power Generation-
- While using water as a sustainable source of power is a good idea, these hydroelectric dams can have damaging effects on the ecosystem. The power generation process, which is the turning of steam heated turbines, heats up the water and dumps it back into the receiving water at a much higher temperature.
- Yup, that’s right. Thermal Pollution can be natural as well. In fact, some pollution is natural. However, human activity has been increasing the amount of pollution beyond the Earth’s ability to control it. Geothermal activity and active volcanoes below the oceans can induce natural underground heating. Hot rocks and active lava have the potential of heating and raising the temperature of bodies of water.
Harmful Effects of Thermal Pollution
So, how does thermal pollution affect the environment? As part of Earth’s natural systems, water can absorb small amounts of thermal energy. However, when the temperature of an ecosystem changes drastically and suddenly, the organisms living in that ecosystem are unable to adapt properly. This is known as thermal shock. Changes in dissolved oxygen and the redistribution of organisms in the local community. A little like culture shock, when humans are thrown into a brand new culture and they can not act as they normally would. Aquatic life sees the same thing, but much more deadly. Most aquatic life have enzyme systems that operate in a fairly narrow range of temperature. These stenothermic organisms can die by sudden temperature changes, that exceed their limits of tolerance.
Even small changes in temperature can be damaging to aquatic life. It can damage the reproductive system of organisms and also make them more susceptible to disease. In addition, hot water contains less oxygen than cold water, so when the waters heat up, there is less oxygen available for the organisms. Warmer temperatures also increase the speed of decomposition of organic matter. This also depletes dissolved oxygen. These decreases in the oxygen content of the water occur around the same time that the metabolic rates of the aquatic life. These are dependent on a sufficient oxygen supply, and they are rising due to the increasing temperature.
Loss of Biodiversity
While the popular belief may be that thermal pollution affects only fish, that is not the case. Fish are vital to the entire ecosystem, hence when they are in danger, the entire system is in danger. Thermal pollution also stimulates the digestive system of aquatic animals, making them consume more food in shorter periods of time. This can cause food shortages along with slowing the fish breeding because small fish are eaten away by larger fish in a much larger quantity.
This leads to another very harmful effect on the ecosystem as a whole, loss of biodiversity. Biodiversity is the amount of diverse species in a specific ecosystem. Each species has its own role to play in the ecosystem. With the loss of one species, the whole ecosystem is off balance.
The different species in an ecosystem depend on each other. Typically, the more species within an area there are, the stronger the ecosystem will be as a whole. When the ecosystems are healthier, biodiversity will also increase. Some fish eat the plants and algae found in the oceans. Those fish will then be eaten by bigger fish and are then eaten by humans. You can see that each organism directly effects the next. Thats why it's important to make sure the area in which they live is free of pollutants and encourages their growth.
Prevention of Thermal Pollution
It is not too late to prevent thermal pollution. While other forms of pollution may take a while to reverse their adverse effects on the environment, we can avoid thermal pollution all together. Once that happens, the natural systems of the Earth will swing back into motion and marine life can continue their regular roles. Companies can take measures to reduce the water temperature before power plants and other facilities discharge the cooling water to prevent further thermal shock to the ecosystems.
Cooling ponds and cooling towers supply water needed to cool powerplants that are nearby. Cogeneration is a form of recycled energy that uses run-off heat from powerplants and other manufacturing bulidings. The exhasut normally dumped back into the atmosphere is then recyled. It can even be used to supply the heating for inside of the plant/building itself.
Methods for Cooling Water
An example from the San Onofre Nuclear Generating Station. They have two main reactors circulating a total of 2,400 million gallons of ocean water per day, at a flow rate of 830,000 gallons per minute for each unit. The cooling waters enter a station from two intake structures located 3,000 feet offshore in 32 feet deep water. The water becomes much wamer, due to the cooling process, an increase of about 19 degrees fahrenheit above the normal temperature. However, before it is thrown back into the ocean, it goes through a series of 63 exit pipes over a distance of 2,450 feet. The water is rapidly mixed with regular seawater so that the average rise in temperature when it hits the source is less than 2 degrees celsius.
The water can also be controlled with cooling ponds. These designs are man made bodies of water, meant to cool through evaporation, convection or radiation. Another controlling method is using cooling towers, which transfer waste heat to the atmosphere through evaporation or heat transfer. Lastly, cogeneration, which is the recycling of heat for other heating purposes.