For prediction of BOD result, must be multiply the COD result with dilution factor. e.g. Dilution factor is 0.2 and COD result is 1355 mg/L, Predict BOD result will be 1355 * 0.2 = 271 mg/L.
Is there any correlation between COD and BOD?
COD typically correlates to BOD, which is one of the reasons the method was initially developed. It has been found to be a very useful tool in municipal wastewater treatment process monitoring and modeling, and to aid in process control.
What is the relationship between the COD and BOD values in waste water?
The only relation between COD & BOD is – COD > BOD. For most industrial process waste water, community sewage, drains and even some hetrogeneous sources, COD/BOD ratio has been found to be in a defined range and hence, COD result gives more or less BOD value range for such identifiable waste water.
How does COD compare to BOD?
The main difference between BOD and COD is that BOD is the amount of oxygen which is consumed by bacteria while decomposing organic matter under aerobic conditions whereas COD is the amount of oxygen required for the chemical oxidation of total organic matter in water.
Why is COD value higher than BOD value in polluted water?
COD is always higher than BOD because chemical oxidation is easier than biological oxidation.
Why is COD preferred BOD?
COD is normally higher than BOD because more organic compounds can be chemically oxidised than biologically oxidised. This includes the chemical toxics to biological life, which can make COD tests very useful when testing industrial sewage as they will not be captured by BOD testing. Hence, COD is preferred over BOD.
What are the advantages of COD determination over BOD determination?
The COD test has the advantage of not being subject to interference from toxic materials, as well as requiring only two or three hours for test completion, as opposed to five days for the BOD test.
Is COD always higher than BOD?
COD stands for Chemical Oxygen Demand, and it is the amount of oxygen that will be consumed by the chemical break down of both organic and inorganic compounds. As such, COD will always be higher than BOD.
What is the significance of COD?
COD, the chemical demand for oxygen a source of water has, is the amount of oxygen required to break down organic substances chemically and convert them to CO2 and H2O. It is also expressed in mgO2/L, and the higher the COD, the more polluted the water is.
Why are BOD values lesser than COD values?
No, BOD is always less or equal to COD, since BOD gives you only the biodegradable organic content of a aquatic sample, while COD gives you the biodegradable and the non-biodegradable organic content, thus the total organic content.
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 is the difference between BOD and COD which one is better and why?
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.
How do you measure BOD of water?
BOD measurement requires taking two samples at each site. One is tested immediately for dissolved oxygen, and the second is incubated in the dark at 20 C for 5 days and then tested for the amount of dissolved oxygen remaining.
What are the advantages and disadvantages of the COD test compared to 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.
What happens if COD is high?
Higher COD levels mean a greater amount of oxidizable organic material in the sample, which will reduce dissolved oxygen (DO) levels. A reduction in DO can lead to anaerobic conditions, which is deleterious to higher aquatic life forms.
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.
Why is it important to perform COD test in wastewater treatment?
In wastewater treatment, the Chemical Oxygen Demand (COD) is an important measurement for the amount of oxygen that is required to break down pollutants (organic substances) in water. The chemical oxygen demand can be measured using different methods, direct or indirect.
Which indicator is used for the estimation of COD?
Using potassium dichromate
. Most commonly, a 0.25 N solution of potassium dichromate is used for COD determination, although for samples with COD below 50 mg/L, a lower concentration of potassium dichromate is preferred.
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