What increases biological oxygen demand?


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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 causes BOD to decrease?

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.

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.

What does high BOD mean in wastewater?

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 if COD is low?

A Low concentration of Dissolved Oxygen is harmful life forms which oxygen to live. Therefore it’s best to reduce COD levels, thus increasing DO concentrations, in wastewater before releasing it.

Does BOD increase with temperature?

The BOD removal rate in the bioreactor increased when the temperature increased from 20 degrees C to 30 degrees C, 40 degrees C, and 50 degrees C, but it decreased when the temperature increased from 50 degrees C to 60 degrees C. Higher temperature enhanced the endogenous respiration of microbes in the bioreactor.

Does BOD increase with time?

Both BOD and COD is increasing with time. Join ResearchGate to ask questions, get input, and advance your work.

What causes high BOD in water?

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.

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 a good BOD number?

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 a good BOD value 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 is BOD important in water quality?

The BOD is an important parameter for assessing water quality. It deals with the amount of oxygen consumption (mg O2 Lโˆ’ 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.

Which of the following will increase the BOD of water supply?

Which of the following will increase the BOD of water supply? Solution : `CO_(2)` increase `BOD`of water .

What amount of BOD indicates low water pollution?

Clean water has BOD value less than 5 ppm. Polluted water has BOD value higher than 10 ppm.

How can we reduce BOD in waste water?

  1. Focus on removing TSS from wastewater first.
  2. Get a properly sized EQ tank.
  3. Control the pH of the waste stream.
  4. Install a modern plate pack DAF made of stainless steel or plastic.
  5. Use a regenerative turbine air dissolution pump.

What increases COD?

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.

Does aeration reduce COD?

Aeration should help reduce the COD in 2 ways. First it may evaporate some volatiles like hexane. Second it will add oxygen to the water speeding up any biological oxidation of the less volatile organics by the bacteria (microbial growth).

Why COD is higher than BOD in wastewater?

The COD test uses a chemical (potassium dichromate in a 50% sulfuric acid solution) that “oxidizes” both organic (predominate) and inorganic substances in a wastewater sample, which results in a higher COD concentration than BOD concentration for the same wastewater sample since only organic compounds are consumed …

Why is BOD done 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 the 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.

What is the relationship between BOD and DO?

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.

Why are BOD bottles kept in dark?

Incubation in the dark ensures that no additional oxygen is produced in the samples from photosynthesis. After 5 days, the dissolved oxygen is measured again. The difference between the initial and final oxygen concentrations corrected for BOD of the seed and dilution factor is the BOD.

Does chlorine increase BOD?

Chlorine dosages above 10 mg lโˆ’1 resulted in increased BOD and COD levels of the effluent, with chlorine dosages above 30 mg lโˆ’1 resulted in almost double the original BOD and COD values.

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.

Why is chlorine added to wastewater?

Chlorine is the most widely used disinfectant for municipal wastewater because it destroys target organisms by oxidizing cellular material. Chlorine can be supplied in many forms, which include chlorine gas, hypochlorite solutions, and other chlorine compounds in solid or liquid form.

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