Biochemical oxygen demand (BOD) represents the amount of oxygen consumed by bacteria and other microorganisms while they decompose organic matter under aerobic (oxygen is present) conditions at a specified temperature.
What is BOD and why is it important?
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.
What is BOD and How Is It Measured?
The BOD test is a bioassay technique involving the measurement of oxygen consumed by the bacteria while stabilizing the organic matter in the waste as they would normally do in nature but under normal laboratory conditions. By convention, the test is conducted for a period of 5 days at 20°C (68°F).
What causes biological oxygen demand?
High biochemical oxygen demand can be caused by: high levels of organic pollution, caused usually by poorly treated wastewater; high nitrate levels, which trigger high plant growth.
What is BOD example?
Biochemical oxygen demand is a measure of the quantity of oxygen used by microorganisms (e.g., aerobic bacteria) in the oxidation of organic matter. For example, wastewater from sewage treatment plants often contains organic materials that are decomposed by microorganisms, which use oxygen in the process.
What is a good BOD level?
A BOD level of 1-2 ppm is considered very good. There will not be much organic waste present in the water supply. A water supply with a BOD level of 3-5 ppm is considered moderately clean.
What are the advantages of BOD?
The main advantages of this method compared to the dilution method are: simplicity: no dilution of sample required, no seeding, no blank sample. direct reading of BOD value. continuous display of BOD value at the current incubation time.
What happens when BOD is high?
The greater the BOD, the more rapidly oxygen is depleted in the stream. This means less oxygen is available to higher forms of aquatic life. The consequences of high BOD are the same as those for low dissolved oxygen: aquatic organisms become stressed, suffocate, and die.
Which increases BOD of water?
Organic loading is occurrence of excess organic matter inside water due to sewage disposal and eutrophication. This leads to an increase in biological oxygen demand (BOD) for putrefaction. Explosive multiplication of alga leads to algal bloom.
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.
What causes high BOD in wastewater?
Sources: BOD represents the amount of organic matter in a water supply; therefore, it increases when decaying plants, human or animal waste, and other organic compounds are added to water.
What can BOD be used to measure?
BOD provides a measure of the impact of a waste (water) on the oxygen content in a receiving water body. Wastes (organic matter, “food”) are broken down (decomposed, oxidized, metabolized) by microbial organisms (aerobic bacteria), frequently referred to as “bugs”, who require oxygen for this monumental effort.
How is BOD removed from 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.
How does COD affect water quality?
High levels of wastewater COD indicate concentrations of organics that can deplete dissolved oxygen in the water, leading to negative environmental and regulatory consequences. To help determine the impact and ultimately limit the amount of organic pollution in water, oxygen demand is an essential measurement.
How do you reduce BOD in wastewater?
- Focus on removing TSS from wastewater first.
- Get a properly sized EQ tank.
- Control the pH of the waste stream.
- Install a modern plate pack DAF made of stainless steel or plastic.
- Use a regenerative turbine air dissolution pump.
What is the BOD of drinking water?
Drinking water has a BOD level of 1 – 2 ppm. When the BOD value of water is in the range 3 – 5 ppm, the water is moderately clean. Polluted water has a BOD value in the range of 6 – 9 ppm. In polluted water, some organic waste is present.
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.
Does BOD increase with time?
Both BOD and COD is increasing with time. Join ResearchGate to ask questions, get input, and advance your work.
Does BOD affect pH?
presented in Table 2, the pH correlated negatively with the BOD (r = -0.418) and negatively with the COD (r = -0.347) … … presented in Table 2, the pH correlated negatively with the BOD (r = -0.418) and negatively with the COD (r = -0.347) …
Why are BOD samples kept in the dark?
With every mixture a duplicate of bottles is prepared. In one bottle of each pair, the concentration of dissolved oxygen is determined (e.g. by means of an oxygen probe) immediately after mixing. The other bottle is stored for n days at 20°C in the dark (to prevent photochemical reactions).
What is the BOD value of highly polluted water?
Reason: Clear water has BOD less than 5 ppm whereas highly polluted water have BOD value of 17 ppm or more.
Does BOD increase with pollution?
The higher the BOD of a water body or sample, the more polluted it is.
How do you calculate BOD of water?
For example: 1.0 mL of a full strength wastewater sample added to 9.0 mL of DI water results in a 0.1 dilution of the wastewater. The DO concentration (mg/L) reduction must then be multiplied by 10 to determine the final BOD concentration.
The more organic matter there is (e.g., in sewage and polluted bodies of water), the greater the BOD; and the greater the BOD, the lower the amount of dissolved oxygen available for higher animals such as fishes. The BOD is therefore a reliable gauge of the organic pollution of a body of water.
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.