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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 optimum level of BOD?
Nutrient concentration, net primary productivity and diurnal variations of dissolved oxygen in the water were studied under three BOD levels; less than 10, 10–20 and 20–30 ppm ranges. The results indicated 10–20 ppm to be the optimum BOD range for fish culture in wastewater ponds.
What happens if BOD is low?
The dissolved oxygen readings are usually in parts per million (ppm). Higher BOD indicates more oxygen is required, which is less for oxygen-demanding species to feed on, and signifies lower water quality. Inversely, low BOD means less oxygen is being removed from water, so water is generally purer.
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.
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.
How do you reduce BOD levels in wastewater?
These are the best practices for reducing BOD and TSS that facility managers should know: 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 BOD limit?
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.
Why is BOD done for 5 days?
The standard oxidation (or incubation) test period for BOD is 5 days at 20 degrees Celsius (°C) (BOD5). The BOD5 value has been used and reported for many applications, most commonly to indicate the effects of sewage and other organic wastes on dissolved oxygen in surface waters (see TECHNICAL NOTE).
Why does BOD increase with time?
The biomass growth is the first reason. Second thing is the characteristics of the compounds in the water. The the activated sludge converts them to other compounds, which can be oxidized during BOD or COD measurement. The question is if the same bacteria are used in activated sludge and BOD.
What is BOD of drinking water?
water; BOD is a measure of, the amount of oxygen required for the bacteria to degrade the organic components present in water / waste water.
What is the BOD value of pure water?
The BOD of pure water is 1ppm and if it is greater than 17ppm then it is polluted water.
What is BOD COD and do?
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.
How is BOD calculated?
BOD is computed based on the difference between initial and final D.O. The test uses dilution water and a known amount of sample in a 250-300 ml incubation bottle. The initial D.O. is measured by probe and the bottle is stored at 20 °C. After five days, final D.O. is measured.
What is BOD COD ratio?
BOD (Biochemical oxygen demand) is the pollution index of any water sample. 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 BOD value?
The BOD value is most commonly expressed in milligrams of oxygen consumed per litre 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. BOD reduction is used as a gauge of the effectiveness of wastewater treatment plants.
How does BOD increase?
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.
Does BOD increase with temperature?
The amount of oxygen that can dissolve in water (DO) depends on temperature. Also, warmer water usually will have a higher BOD level than colder water. As water temperature increases, the rate of photosynthesis by algae and other plant life in the water also increases.
Do increases and BOD decreases?
The value of BOD decreases as it farther away from the point source and will increase as it approaches the source point, the BOD value is also due to natural things such as leaf blur. According to [4].
What does COD mean in wastewater?
5 Chemical oxygen demand (COD) The COD is the estimate of oxygen required for the portion of organic matter in wastewater that is subjected to oxidation and also the amount of oxygen consumed by organic matter from boiling acid potassium dichromate solution.
What affects BOD?
Biological oxygen demand directly affects the amount of dissolved oxygen in rivers and streams. The rate of oxygen consumption is affected by a number of variables: temperature, pH, the presence of certain kinds of microorganisms, and the type of organic and inorganic material in the 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.
Is BOD and do same?
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.
