What is COD and BOD in waste water treatment plant?

Five-Day Biochemical Oxygen Demand (BOD5): BOD5 is defined as the amount of oxygen required by bacteria to decompose organic matter for a specified time (usually5 days) under aerobic conditions. The amount of oxygen reported with this method represents only the carbonaceous oxygen demand (CBOD) or the easily decomposed organic matter. BOD5 is commonly used to measure natural organic pollution

Chemical Oxygen Demand (COD): COD is defined as the oxygen equivalent of the organic portion of the sample that is susceptible to oxidation by a strong chemical oxidant potassium dichromate K2Cr2O7,

Biochemical Oxygen Demand (BOD) is a chemical procedure for determining how fast biological organisms use up oxygen in a body of water. It is usually performed over a5-day period at20° Celsius. It is used in water quality management and assessment, ecology and environmental science. BOD is not an accurate quantitative test, although it could be considered as an indication of the quality of a water source.

In environmental chemistry, the chemical oxygen demand (COD) test is commonly used to indirectly measure the amount of organic compounds in water. Most applications of COD determine the amount of organic pollutants found in surface water (e.g. lakes and rivers), making COD a useful measure of water quality. It is expressed in milligrams per liter (mg/L), which indicates the mass of oxygen consumed per liter of solution. Older references may express the units as parts per million (ppm).

Its the parameter that determines the pollution in water i.e. production waste,stream etc. These parameters also helps in process seletion of the polluted water and safely discharge to nature.

BOD is a measure of, the amount of oxygen that requires for the bacteria to degrade the organic components present in waste water.

COD or Chemical Oxygen Demand is the total measurement of all chemicals (organics & in-organics) in the waste water.

ther is arelationship between BOD&COD ,COD is higher than that of BOD; maximum of up to3 times Aprox COD=2.5BOD

*Biochemical oxygen demand or B.O.D5 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(as normal5 days). The term also refers to a chemical procedure for determining this amount. This is not a precise quantitative test, although it is widely used as an indication of the organic quality of water. The BOD5 value is most commonly expressed in milligrams of oxygen consumed per liter of sample during5 days of incubation at20 °C and is often used as a robust surrogate of the degree of organic pollution of water.

**BOD can be used as a gauge of the effectiveness of wastewater treatment plants. It is listed as a conventional pollutant .

BOD is similar in function to chemical oxygen demand (COD), in that both measure the amount of organic compounds in water. However, COD is less specific, since it measures everything that can be chemically oxidized, rather than just levels of biologically active organic matte

*** chemical oxygen demand (COD), in that both measure the amount of organic compounds in water. However, COD is less specific, since it measures everything that can be chemically oxidized, rather than just levels of biologically active organic matter.

***In environmental chemistry, the chemical oxygen demand (COD) test is commonly used to indirectly measure the amount of organic compounds in water. Most applications of COD determine the amount of organic pollutants found in surface water (e.g. lakes and rivers) or wastewater, making COD a useful measure of water quality. It is expressed in milligrams per liter (mg/L) also referred to as ppm (parts per million), which indicates the mass .

The method covers determination of COD in waste water treatment (influent- aeration tank-

Effluent most type off organic matter are oxidized by boiling mixer of chromic and sulfuric acids sample is refluxed in strongly acid with known excess of potassium dichromate after digestion the remaining un reduced C2Cr2O7 IS titrated with ferrous ammonium sulfate to determine the amount of C2Cr2O7 consumed and oxidizable matter is calculated in terms of oxygen equivalent

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Ahmad kamal

) الأوكسجين المستهلك كيميائياً : COD

 هو كمية الأوكسجين المستهلكة كيميائياً مقدرة بالميليغرام / اللتر و اللازمة لأكسدة المواد العضوية إلى مواد لاعضوية في شروط محددة من الزمن و درجة الحرارة و بوجود عامل مؤكسد

) الأوكسجين المستهلك حيوياً BOD

 هو كمية الأوكسجين المستهلكة حيوياً من قبل الكائنات الحية الدقيقة خلال نشاطها الحيوي في درجة حرارة ثابتة و خلال فترة زمنية محددة يطلق عليها فترة الحضانة

 و كلما كانت كمية الأوكسجين المستهلكة حيوياً كبيرة كلما كانت المياه ملوثة بدرجة أكبر

BOD is biological oxygen demand and COD means Chemical oxygen demand. These two will determine how much air supply is required into the bio reactor. It is mainly required when a treatment plant is designed.

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