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Biochemical Oxygen DemandWhat is Biochemical Oxygen Demand ?Biochemical oxygen demand or biological oxygen demand is the amount of dissolved oxygen needed by aerobic biological organisms in a body of water to break down organic material present in a given water sample at certain temperature over a specific time period.It is one of the most common measures of pollutant organic material in water. BOD indicates the amount of organic matter present in water.

The rate of oxygen consumption in a stream is affected by a number of variables:

temperature, pHpresence of certain kinds of microorganisms type of organic and inorganic material in the water.The BOD can be measured by BOD meter or by using Methylene Blue Solution

The level of water pollution can be tested by determining the biochemical oxygen demand (BOD) valueBOD values are measured as the mass of oxygen (in mg) used in 1 dm^3 of water kept at 20C for 5 days .

At high BOD levels ,organisms that are more tolerant towards low concentrations of dissolved oxygen (ex: leeches and sludge worms ) may appear and multiply .

Organisms that need higher oxygen levels (ex: freshwater shrimps and mayfly nymphs) will not be able to survive .

If oxygen levels continue to drop and the water becomes completely deoxygenated , anaerobic bacteria will multiply quickly and release toxic gases such as hydrogen sulphide Environmental Significance BOD is the principle test to give an idea of the biodegradability of any sample and strength of the waste . Hence the amount of pollution can be easily measured by it .

The determination of BOD is used in studies to measure the self-purification capacity of streams and serves regulatory authorities as a means of checking on the quality of effluents discharged to stream waters .

The BOD test is among the most important method in sanitary analysis to determine the polluting power or strength of sewage , industrial wastes or polluted water .

One form of water pollution is by organic wastes which serve as food for micro-organisms. The micro-organisms multiply on this food supply and use up oxygen in the water, which then is unavailable for other forms of life. Biological Oxygen Demand (BOD) is a measure of the rate at which oxygen is being removed from sample of water. This is the standard test used at Sewerage Treatment Plants.

Dissolved oxygen (DO - amount of dissolved oxygen in water) is consumed by bacteria when large amounts of organic matter from sewage or other discharges are present in the water.

When Organic matter such as dead plants, leaves, grass clippings, manure, sewage, or even food waste is present in a water supply, the bacteria will begin the process of breaking down this waste.

When this happens, much of the available dissolved oxygen is consumed by aerobic bacteria, robbing other aquatic organisms of the oxygen they need to live. When the DO becomes too low, the aquatic organisms in that water are unable to continue at a normal rate.

a Low BOD is an indicator of good quality water, a High BOD indicates polluted water.

Conclusion

Global Warming

Global warming is when the earth heats up and the temperature increasesMore recently, the temperatures have been rising, causing more dangers for people, animals, plants and our environment.What Is Global Warming?

Electrical pollution is a main cause for Global Warming. Mostly, fossil fuels are burned to create electricity and are made of dead plants and animals. Some examples of fossil fuels are oil and petroleum. Many pollutants (chemicals that pollute the air, water, and land) are sent into the air when fossil fuels are burned. Some of these chemicals are called greenhouse gasses.

Petroleum, one of the sources of energy, is used a lot. It is used for transportation, making electricity, and making many other things. Although this source of energy gives off a lot of pollution, it is used for 38% of the United States energy .

When we throw our garbage away, the garbage goes to landfills. They are full of garbage. The garbage is then sometimes burned. This sends an enormous amount of greenhouse gasses into the air and makes global warming even worse.Another factor that makes global warming worse is when trees are cut down. Trees and other plants collect and absorb carbon dioxide (CO2), which is a greenhouse gas .Factor of Global Warming

Results of Global WarmingGlobal warming is affecting many parts of the world, including melting glaciers, creating the sea to rise even more, and when that happens, the water covers many low land islands. Global Warming also destroys many huge forests. The pollution that causes global warming is linked to acid rain. Acid rain gradually destroys almost everything it touches. Global warming is also causing many more fires that wipe out whole forests. This happens because global warming can make the earth very hot. In forests, some plants and trees leaves can be so dry that can catch on fire.

How to overcome global warming Reduce Fossil Fuel UseBurning fossil fuels increases the levels of greenhouse gases in the atmosphere. There are two ways to reduce fossil fuel use: Use less energy, or use alternative, non-polluting energy sources like solar and wind power. At home, this translates to saving electricity by using energy-efficient appliances and compact fluorescent light bulbs, as well as reducing gasoline use and buying green power from your electricity provider, if available.

Plant TreesBecause carbon dioxide is the most important greenhouse gas, planting trees and other plants can slow or stop global warming. Plants take in carbon dioxide and release oxygen. They use carbon to build their own tissues and return some of it to the soil in a process called sequestration. Deforestation of rain forests is a large contributor to global warming and CO2 emissions, but planting new trees, even in your own backyard, can help to offset this.

Reduce WasteThe production of garbage contributes to global warming both directly and indirectly. Decomposing waste in landfills produces methane and other greenhouse gases. Waste also requires energy to manufacture in the first place. Reducing your consumption patterns and reusing items whenever possible minimizes your carbon footprint, since fewer new items need to be made. Recycling metal, plastic, glass and paper lowers greenhouse gas emissions, since recycled items take far less energy to manufacture than items produced from scratch.

Conserve WaterCities consume significant amounts of energy when purifying and distributing water, which contributes to greenhouse gas emissions. Saving water reduces the amount of energy used. At home, turn off water immediately whenever you're not using it, and repair or replace leaky faucets and toilets. In your yard, landscape with plants and grasses that require less water, and capture rainwater in barrels for irrigating.