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.
Why do we use biological oxygen demand?
Biological oxygen demand is significant for water quality. Because it provides an index for determining the environmental impact of released effluent. BOD is often used to remediate wastewater. Because the breakdown of organic waste by microorganisms is a common treatment method.
What does low BOD indicate?
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.
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.
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.
Which pollution is measured by BOD?
Abstract. Biochemical oxygen demand (BOD) is the most important and widely used environmental index for monitoring organic pollutants in wastewater.
What is the range of BOD for good quality of 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.
Why a low BOD is important in wastewater treatment?
Generally, a higher BOD value indicates a higher level of water pollution, while a lower BOD value indicates less polluted, or cleaner water.
How do you reduce BOD in water?
- 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.
How does BOD determine the pollution of water?
Biological Oxygen Demand (BOD): Therefore it is used to measure the amount of certain type of organic water pollution BOD is calculated by keeping a sample of water containing a known amount of oxygen for five days at 20 °C. The oxygen content is measured again and BOD is calculated.
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 increases the 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 is BOD measured 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 is BOD value per Litre in sewage water?
The amount of oxygen required by bacteria to break down the organic matter present in a certain volume of a sample of water, is called Biochemical Oxygen Demand (BOD). It is measured in ppm. The BOD of municipal sewage is 100-4000 ppm.
What is the minimum value of BOD in polluted water?
Clean water has BOD value less than 5 ppm. Polluted water has BOD value higher than 10 ppm.
Does chlorine reduce BOD?
BOD reduction: Chlorine accomplishes BOD reduction by oxidation of organic compounds present in wastewaters. 4. Oxidation of metal ions: Metal ions which are in reduced state are oxidized by chlorine (e.g., ferrous to ferric ion and manganous to manganic ions).
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.
Does BOD increase with pollution?
The higher the BOD of a water body or sample, the more polluted it is.
How do you test BOD in wastewater?
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.
Why is BOD test run in the dark?
Bubbles in a BOD bottle also invalidate that bottle’s DO measurement. Algae in a BOD sample and left out on a lab bench exposed to sunlight can be a source of bubbles. Always put the BOD bottle in a dark incubator soon after the initial DO is measured and the bottle sealed.
Does activated carbon remove BOD?
It was found that for dosages of activated carbon in the range of 50–150 mg/l, the removal efficiencies for BOD increased from 27–70% to 76–94% while those for COD increased from 16–64% to 72–92.5% for inlet values of 45–95 mg/l and 110–200 mg/l for BOD and COD respectively.
What is BOD and COD why it is important to determine in waste water treatment?
Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) are two of the most important parameters to characterise (measure the degree of pollution) of wastewater. BOD, the biological demand for oxygen a source of water has, is the amount of oxygen used by microorganisms to break down organic substances.
What are the 7 steps of wastewater treatment?
- Step 1: Screening and Pumping.
- Step 2: Grit Removal.
- Step 3: Primary Settling.
- Step 4: Aeration / Activated Sludge.
- Step 5: Secondary Settling.
- Step 6: Filtration.
- Step 7: Disinfection.
- Step 8: Oxygen Uptake.
What is the relationship between BOD and COD?
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. COD values are almost always higher than BOD values for the same sample.
What affects BOD?
The factors affecting BOD include the type and amount of organic material present, the temperature, the pH, the dissolved oxygen concentration, and the presence of bacteria.