There is a formula for calculating COD. Consider the formula for COD calculation: (a – b) X C X 8,000 / the volume of the sample in mL. Let “a” represent the
How is COD and BOD calculated?
The COD test should be considered an independent measure of the organic matter in a wastewater sample rather than a substitute for the BOD test.
Can I use my COD results to predict my BOD?
| Sample 1: | COD = 2,150 mg/L | BOD = 1,100 mg/L |
|---|---|---|
| Sample 3: | COD = 1,850 mg/L | BOD = 997 mg/L |
| COD ÷ BOD = 1,850 ÷ 997 = 1.86 |
Why COD is calculated?
Chemical oxygen demand (COD) is used to determine the quantity of pollution in water after wastewater treatment. The higher value of chemical oxygen demand indicates the higher organic pollution in the water sample. Only chemically digest able matter can be determined by the COD test.
What is COD method?
COD measures how much DO is consumed by the oxidation of organic matter and inorganic compounds such as ammonia or nitrite under controlled conditions. COD testing typically involves digestion of the water sample in a sealed vial with potassium dichromate and sulfuric acid at 150C for 2 hours.
How is COD measured in water sample?
This is usually done by titration, using an indicator solution. COD is expressed in mg/L, which indicates the mass of oxygen consumed per liter of solution. The COD test only requires 2-3 hours, while the Biochemical (or Biological) Oxygen Demand (BOD) test requires 5 days.
What is the limit of COD?
The chemical oxygen demand (COD) concentration in a treated effluent, if observed to be persistently greater than 250 mg/l before disposal to any receiving body (public sewer, land for irrigation, inland surface water and marine coastal areas), such industrial units are required to identify chemicals causing the same.
How is BOD calculated?
6.1 Take four 300 ml BOD bottles and add 10 ml of samples to two bottles and fill the remaining volume with dilution water.
Biological Oxygen Demand (BOD):
| Recommended sample volume for BOD determination | ||
|---|---|---|
| BOD range (mg/liter) | Sample volume (ml) | Dilution water (ml) |
| 0-10 | 300 | |
| 11-30 | 100 | 200 |
| 31-70 | 50 | 250 |
What is a good COD level?
Greenfield CET Plant Pvt. Ltd. According to standards of Central Pollution Control Board, permissible value of BOD is 30 mg/l and COD is 250 mg/l.
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.
What is COD level in water?
COD is a measure of the oxygen equivalent of the organic matter in a water sample that is susceptible to oxidation by a strong chemical oxidant. COD is widely used as a measure of the susceptibility to oxidation of the organic and inorganic materials present in water bodies and in the municipal and industrial wastes.
How do you do the COD test?
In the titration method for determining COD, the excess dichromate is reacted with a reducing agent, ferrous ammonium sulfate. As the ferrous ammonium sulfate (FAS) is added slowly, the excess dichromate is converted into its trivalent form. As soon as all the excess dichromate reacts, an equivalence point is reached.
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.
How is COD reduction calculated?
The COD removal efficiency can be computed using ((Cin-Ceff)/Cin)*100) and expressed in %.
What is the ratio of BOD and COD?
BOD : COD (Chemical oxygen demand) ratio using the formulated seed comes in the range of 0.7-0.8 whereas that using BODSEED comes in the ratio of 0.5-0.6. The ultimate BOD (UBOD) was also performed by exceeding the 3-day dilution BOD test.
What is difference between BOD and COD?
Biochemical oxygen demand (BOD) is the amount of oxygen required by the microorganisms to break down the organic materials, whereas chemical oxygen demand (COD) is the amount of oxygen required to break down the organic material via oxidation.
What is an example of COD?
COD analysis will measure the equivalent amount of oxygen that is required to chemically oxidise organic compounds in water. Modern methods of COD testing involve the use of highly accurate scientific instruments known as environmental analysers.. A leading example of this technology is the EasyPREP COD-200.
Why BOD is calculated 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.
Does aeration reduce COD?
Aeration should help reduce the COD in 2 ways. First it may evaporate some volatiles like hexane. Second it will add oxygen to the water speeding up any biological oxidation of the less volatile organics by the bacteria (microbial growth).
What causes low COD in wastewater?
High chemical oxygen demand in water indicates greater levels of oxidizable organic matter and consequently, a lower amount of Dissolved Oxygen (DO). Critical DO depletion due to organic contamination can kill off aquatic life forms.
How do you reduce COD in wastewater?
You can reduce COD and BOD by adding hydrogen peroxide to the wastewater solution. The hydrogen peroxide will chemically attack the organics in the wastewater, degrading them and reducing the measured COD and BOD.
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.
Lorraine Wade is all about natural food. She loves to cook and bake, and she’s always experimenting with new recipes. Her friends and family are the lucky beneficiaries of her culinary skills! Lorraine also enjoys hiking and exploring nature. She’s a friendly person who loves to chat with others, and she’s always looking for ways to help out in her community.