BOD measures the amount of oxygen required by the aerobic organisms to decompose organic matter and COD measures the oxygen required to decompose organic and inorganic constituents present in the wastewater by chemical reaction. Hence, the value of COD is greater than BOD.
Which method is better to determine oxygen demand in sewage water?
COD (chemical oxygen demand) COD is the most popular alternative test to BOD for establishing the concentration of organic matter in wastewater samples.
Which is better BOD or COD?
COD is always higher than BOD because chemical oxidation is easier than biological oxidation.
Which method is used for measuring oxygen demand?
The two important methods used to measure oxygen demand are BOD and COD. Table 28.3 summarizes the principle, advantages, and disadvantages of BOD and COD. The BOD test measures the amount of oxygen required by microorganisms to oxidize the biodegradable organic matter present in water and wastewater.
What is the difference between BOD and COD in wastewater?
BOD measures the oxygen demand for the decomposition of organic material by the microbes in the wastewater. COD measures the oxygen demand for the decomposition of both organic and inorganic materials in wastewater. This is the main difference between BOD and COD.
What are the advantages of COD over BOD?
COD is normally higher than BOD because more organic compounds can be chemically oxidised than biologically oxidised. This includes chemicals toxic to biological life, which can make COD tests very useful when testing industrial sewage as they will not be captured by BOD testing.
Why is BOD value important in wastewater treatment?
The BOD is an important parameter for assessing water quality. It deals with the amount of oxygen consumption (mg O2 L− 1) by aerobic biological organisms to oxidize organic compounds. Sewage with high BOD can cause a decrease in oxygen of receiving waters, which in turn can cause the death of some organism.
Why is COD determination preferred over biological oxygen demand determination?
COD uses strong chemicals to oxidize organic matter. Generally, COD is preferred to BOD for process control measurements because results are more reproducible and are available in just two hours rather than five days.
Which property BOD or COD will be higher for a water sample and why?
BOD is a measurement of organics that can be oxidized (utilize as a food source) by microorganisms while COD is a measurement of organics that can be oxidized by chemicals (oxidizing agents) that why COD is higher than BOD in most of the cases.
What is importance of determining COD & BOD?
COD and BOD tests are important because they help in the determination of the amount of waste in wastewater. This is important because the organic content in wastewater needs to be reduced before the wastewater is discharged.
What are the limitations of BOD test?
Limitations Of Test
The method takes five days to perform and uses a discrete sample. The test has poor reproducibility and toxic chemicals can inhibit measurement. Short-term BOD determinations magnify errors and still require relatively long sample periods. The test is not suited for on-line, continuous measurement.
How do you measure oxygen demand in water?
Measuring biochemical oxygen demand requires taking two measurements. One is measured immediately for dissolved oxygen (initial), and the second is incubated in the lab for 5 days and then tested for the amount of dissolved oxygen remaining (final).
What is BOD What does it mean if a water sample has more BOD?
Solution : Biochemical oxygen demand (BOD) represents the amount of dissolved oxygen that would be consumed if all the organic matter in one litre of water were oxidized by microorganisms. More value of BOD means the water sample is polluted with organic matter.
What is the relationship between the COD and BOD values in waste water?
COD results are typically higher than BOD5 values, and the ratio between them will vary depending on the characteristics of the wastewater. This ratio has been commonly used as an indicator for biodegradation capacity [1]. It is called “Biodegradability index” (B.I.).
What is the difference between BOD biological oxygen demand and do dissolved oxygen )?
Biochemical oxygen demand is the amount of oxygen consumed by bacteria and other microorganisms while they decompose organic matter under aerobic conditions. The common lake or stream contains small amounts of oxygen in the form of dissolved oxygen (DO).
What is the difference between biochemical and biological oxygen demand?
Biochemical oxygen demand (BOD, also called biological oxygen demand) is the amount of dissolved oxygen needed (i.e., demanded) by aerobic biological organisms to break down organic material present in a given water sample at certain temperature over a specific time period (Kaiser, 1998).
What is the limitation of COD test?
One of the main limitations of the COD test is its inability to differentiate between biodegradable and biologically inert organic matter on its own. The use of chemicals such as chromium and strong acids produce hazardous liquid waste, which requires careful disposal.
What are the advantages of COD?
Nutrition. Cod is a low-fat source of protein, making it an excellent choice for people who would like to reduce their fat intake and improve their heart health. Cod also contains a significant amount of iodine, which is an important mineral for thyroid function.
Why is COD important in water quality?
COD is a water quality measure used not only to determine the amount of biologically active substances such as bacteria but also biologically inactive organic matter in water [8]. It is an important and rapidly measured variable for characterizing water bodies, sewage, industrial wastes, and treatment plant effluents.
Wastewater from sewage treatment plants often contains organic materials that are decomposed by microorganisms, which use oxygen in the process. (The amount of oxygen consumed by these organisms in breaking down the waste is known as the biochemical oxygen demand or BOD.
Why is COD value higher than BOD value in polluted water?
From the amount of dichromate that has been consumed the equivalent amount of oxygen in mg/L can be calculated. This test method oxidises more organic material than the BOD test and therefore the COD value is always higher than the BOD value.
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