Typically, the average BOD result is divided by the average COD result to find a “conversion factor” between the two parameters. One would then multiply their COD results by this factor to estimate BOD.
How do you calculate BOD from COD?
Divide the COD concentration by the BOD concentration for each sample and average the results.
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 | ||
| (1.95 + 1.89 + 1.86) ÷ 3 = 1.9 COD:BOD Ratio = 1.9:1 |
What is the ratio of COD to BOD?
0.3 to 0.8
Typical values for the ratio of BOD/COD for untreated municipal wastewater are in the range from 0.3 to 0.8 (see in table 3). If the BOD/COD ratio for untreated wastewater is 0.5 or greater, the waste is considered to be easily treatable by biological means.
Is BOD and COD value same?
Hence, the value of COD is greater than BOD.
Chemical Oxygen Demand (COD) v/s Biological Oxygen Demand (BOD)
| BOD | COD |
|---|---|
| BOD value is determined by 5 days. | COD can be measured within few days. |
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 COD formula?
COD as mg/l of oxygen consumed =(A-B) x Normality of FAS x 8000 / ml.
What is COD & BOD in water?
The biochemical oxygen demand (BOD) represents the amount of dissolved oxygen (DO) consumed by biological organisms when they decompose organic matter in water. The chemical oxygen demand (COD) is the amount of oxygen consumed when the water sample is chemically oxidised.
Why is COD always higher than BOD?
As such, COD will always be higher than BOD. Because the test for COD takes only a few hours (as opposed to the test for BOD, which takes 5 days), it can be used as an operational adjustment parameter in close to real time.
Which is better BOD or COD?
BOD: BOD value is lower than the COD value. COD: COD value is always greater than the BOD value. Therefore, the more organic material can be oxidized by COD. BOD: Biological oxidation is capable of oxidizing natural organic detritus and organic waste in the water.
Is COD always higher than BOD?
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.
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.
How COD is measured?
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.
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.
What is the BOD value of pure water?
about 1 ppm value
UPLOAD PHOTO AND GET THE ANSWER NOW! Solution : A pure water would have about 1 ppm value. A water supply with BOD level of 3.5 ppm is moderately clean, and water with a BOD level of 6.9 ppm is considered as polluted water.
What is BOD level in water?
BOD is a measure of the amount of oxygen required to remove waste organic matter from water in the process of decomposition by aerobic bacteria (those bacteria that live only in an environment containing oxygen).
What is BOD value?
The BOD value is most commonly expressed in milligrams of oxygen consumed per liter of sample during 5 days of incubation at 20 °C and is often used as a surrogate of the degree of organic pollution of water (Sawyer et al., 2003). BOD can be used as a gauge of the effectiveness of wastewater treatment plants.
Can COD be lower than BOD?
Simply BOD indicates the biodegradable organic matter (OM) while COD represents both biodegradable and non-biodegradable OM in water. If all OM is your sample is biodegradable, so BOD will approximately equal COD. Therefore, COD should be higher than or equal BOD but never be lower 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.
What is the range of COD?
The COD of surface water normally ranges from 5 to 20 mg l−1. The COD as standardized method has found its way into wastewater legislation.
How do you test for BOD and COD in water?
Testing for BOD involves incubating a sealed water sample at 20C for five days, followed by measuring the difference in oxygen content before and after incubation. COD measures how much DO is consumed by the oxidation of organic matter and inorganic compounds such as ammonia or nitrite under controlled conditions.
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