BOD values range widely; generally, pristine waters have a value below 1 mg l − 1 , moderately polluted waters 2–8 mg l − 1 , and treated municipal sewage 20 mg l − 1 . Standards for the discharge of effluent from WWTPs have the range 20–30 mg l − 1 and require a minimum flow in receiving waters to ensure sufficient dilution.
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 is the BOD value of drinking water?
For drinking water BOD has to be less than 5 mg/L and for treated wastewater to be disposed of in the water bodies it is 30 mg/L, 100 mg/L if treated waste water is discharged into the sewerage system in India.
What is the acceptable range of biological oxygen demand?
Typical values. Most pristine rivers will have a 5-day carbonaceous BOD below 1 mg/L. Moderately polluted rivers may have a BOD value in the range of 2 to 8 mg/L . Rivers may be considered severely polluted when BOD values exceed 8 mg/L.
What is biological oxygen demand in water?
The decay of organic matter in water is measured as biochemical or chemical oxygen demand. ... 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 Toppr?
Biochemical oxygen demand (BOD) is the amount of dissolved oxygen needed by aerobic biological organisms in a body of water to break down organic material present in a given water sample at certain temperature over a specific time period.
What happen if 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.
Why is COD higher than 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.
Which value of BOD is correct for average sewage?
BOD values are usually reported in either ppm values or in mg/L values. Unpolluted rivers typically have a BOD below 1 mg/L. Moderately polluted rivers vary between 2 to 8 mg/L. Untreated sewage averages between 200 and 600 mg/L while efficiently treated municipal sewage would be 20 mg/L or less.
In which water BOD is maximum?
Notes: BOD is amount of dissolved oxygen needed by aerobic biological organisms in a body of water to break down organic material present in a given water sample at certain temperature over a specific time period, for running rivers, it would be minimum and for Untreated Municipal waste water it would be maximum.
What does the high biological oxygen demand indicates?
Biological Oxygen Demand (BOD) refers to the amount of dissolved oxygen that aerobic organisms need in order to break down organic material in water over time. Its high value indicates the intense level of microbial pollution .
What increases biological oxygen demand?
Urban runoff carrying pet wastes from streets and sidewalks ; nutrients from lawn fertilizers; leaves, grass clippings, and paper from residential areas, are all contributors to increase oxygen demand.
What does biological oxygen demand measure?
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). ... BOD is used, often in wastewater-treatment plants, as an index of the degree of organic pollution in water.
What causes high COD 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.
How is BOD removed from wastewater?
Some BOD is removed in the septic tank by anaerobic digestion and by solids which settle to the bottom of the septic tank, but much of the BOD present in sewage (especially detergents and oils) flows to the leaching field. ... The bacteria in a healthy biomat also digest most of the remaining BOD in the sewage.
What is the relationship between dissolved oxygen and biological oxygen demand?
The amount of dissolved oxygen used up by aerobic microorganisms to decompose the organic matters present in a sample of water is termed Biochemical Oxygen Demand or Biological Oxygen Demand (BOD). BOD and DO are inversely proportional to each other i.e a decline in DO levels reflects a high level of BOD.
