COD is required to be done before BOD is most cases where the waste/water sample is from unknown source as fixing dilution is critical for BOD.
Why is COD better than BOD?
COD is always higher than BOD because chemical oxidation is easier than biological oxidation.
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.
Why COD is a better measure of organic carbon than BOD?
The COD test uses a chemical (potassium dichromate in a 50% sulfuric acid solution) that “oxidizes” both organic (predominate) and inorganic substances in a wastewater sample, which results in a higher COD concentration than BOD concentration for the same wastewater sample since only organic compounds are consumed
What are the advantages and disadvantages of the COD test compared to BOD?
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.
Which one is bigger BOD or COD?
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.
What if COD is high in water?
When the COD levels are higher, there is a greater demand for oxygen. This means that there is likely more oxidizable organic material in water with high COD levels. This also means that there are reduced Dissolved Oxygen (DO) concentrations in wastewater with high COD levels.
Why Sulphuric acid is used in COD?
Chemical Oxygen Demand (COD) 1% Silver Sulphate in Sulphuric Acid (conc.) provides the primary and secondary digestion catalysts for oxidation of carbon during chemical oxidation.
Why k2cr2o7 is used in COD measurement?
Currently, most COD tests use potassium dichromate as the oxidant. Potassium dichromate is a hexavalent chromium salt that is bright orange in color and is a very strong oxidant. Between 95-100% of organic material can be oxidized by dichromate.
What is the limitation of COD?
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 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.
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.).
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.
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.
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.
Why is BOD done for 5 days?
BOD occurs in 2 general stages. While calculating the oxygen demand, the carbonaceous stage is taken into account. This stage is almost completed in 5 days, which means that most of the organic content of the sewage is oxidized under aerobic conditions in 5 days. Hence ,BOD for 5 days is calculated.
What chemical is used in COD?
potassium dichromate
COD is measured via a laboratory assay in which a sample is incubated with a strong chemical oxidant for a specified time interval and at constant temperature (usually 2 h at 150°C). The most commonly used oxidant is potassium dichromate, which is used in combination with boiling sulphuric acid.
What is the permissible limit of BOD in wastewater?
The Significance of BOD in Wastewater Treatment
BOD is listed as a conventional pollutant under the U.S. Clean Water Act. Typical maximum values range from 10 mg/L for direct environmental disposal and 300 mg/L for disposal to sewer systems.
Why COD measurement is necessary along with BOD test for waste water?
COD is the amount of oxygen required to chemically oxidize organic matter in your wastewater into inorganic matter. whereas BOD is the amount of oxygen required to biologically oxidize the organics in your sample, usually after 5 days or 21 days of incubation time, depending on the bioassay followed.
Why is COD high in wastewater?
COD increases as the concentration of organic material increases. It also increases if inorganic compounds susceptible to oxidation by the oxidant (typically dichromate) are present. Water with high COD typically contains high levels of decaying plant matter, human waste, or industrial effluent.
Why glass beads are used in COD?
Test for Chemical Oxygen Demand:
Add some glass beads to prevent the solution from bumping into the flask while heating.
Justin Shelton is a professional cook. He’s been in the industry for over 10 years, and he loves nothing more than creating delicious dishes for others to enjoy. Justin has worked in some of the best kitchens in the country, and he’s always looking for new challenges and ways to improve his craft. When he’s not cooking, Justin enjoys spending time with his wife and son. He loves exploring new restaurants and trying out different cuisines.