BOD, or Biochemical Oxygen Demand is a characteristic that indicates the amount of dissolved oxygen required by microorganisms (usually bacteria) to break down or decompose organic matter under aerobic conditions (Umaly and Cuvin, 1988). Reaffirmed by Boyd (1990), that the organic material decomposes in BOD is ready decomposed organic material (readily decomposable organic matter).
Mays (1996) defines BOD as a measure of the amount used by the microbial population oksigenyang contained in waters in response to the influx of organic material that can be parsed. From these notions can be said that although the value of BOD stated amount of oxygen, but for convenience can also be interpreted as an illustration of the amount of organic material easily explained (biodegradable organics) in the waters.
BOD examination is needed to determine the burden of pollution due to waste water and to design biological treatment system (G. Alerts and SS Santika, 1987). The presence of organic matter is high enough (indicated by the value of BOD and COD) causing microbes become active and decompose organic matter is biologically a compound organic acids. This decomposition occurs along the channel aerobic and anaerobic.
Arising CH4, NH3 and H2S are malodorous. The BOD test can not be used to measure the amount of organic material that is actually present in the water, but only measures the relative amount of oxygen consumption is used to oxidize the organic matter. The more oxygen is consumed, the more the content of organic ingredients in it. BOD examination is necessary to determine the pollution load of waste water due to population or industry, and to design systems for the biological treatment of the water tercermar.
Decomposition of organic substances is a natural event; if anything bodies of water polluted by organic substances, bacteria can spend the oxygen dissolved in the water during the oxidation process which could lead to the death of fish in the water and the state becomes anaerobic and can cause a foul odor in the water. BOD examination based on oxidation reactions of organic substances with oxygen in the water, and the process is underway because of the aerobic bacteria.
On the basis of these reactions, which require approximately 2 days of which 50% reaction has been reached, so that 75% 5 days and 20 days in order to achieve the 100% inspection of BOD can be used to estimate the pollution load of organic substances. Chemical Oxygen Demand (COD) or the chemical oxygen demand (COD) is the amount of oxygen (mg O2) is required to oxidize substances – organic substances contained in 1 L of water samples. Figures COD is a measure of water pollution by substances – organic substances that naturally can be oxidized through mokrobiologis process, and the resulting reduction in dissolved oxygen in the water.
All living things need oxygen is no exception organisms that live in water. Aquatic life such as fish get oxygen in the form of dissolved oxygen which is largely derived from the atmosphere. In the absence of dissolved oxygen at a certain concentration level many types of aquatic organisms will not exist in the water. Many fish will die in polluted waters is not caused by contaminants toksitasi directly, but due to lack of oxygen as a result of the gas used in the process of decomposition / destruction of contaminants.
In the neighborhood there are a lot of organic material in the form of carbohydrates, proteins, and fats that make up living organisms and other compounds that are natural resources that are very important and needed by humans.
Normally, the organic material is composed by the elements C, H, O, and in some cases containing N, S, P, and Fe. Organic compounds are generally unstable and easily oxidized biologically or chemically into stable compounds, among others, to CO2 and H2O. It is this process that causes the concentration of dissolved oxygen in the water decreases and this causes problems for aquatic life.