Why should the BOD bottle be sealed during incubation?

Why should the BOD bottle be sealed during incubation?

Always put the BOD bottle in a dark incubator soon after the initial DO is measured and the bottle sealed. As a result, bubbles may form in the bottles. This can also happen with a low dilution sample, such as an effluent composite sample that was collected at 4 C and not warmed to temperature.

Why it is necessary to cover the bottle with a stopper in BOD test?

According to the EPA Standard Methods for the Examination of Water and Wastewater or the Standard Methods 5210, the BOD bottle should include a ground-glass stopper and a flared mouth which form a water seal preventing the air from the outside of the bottle coming in.

Why is it necessary to incubate the BOD bottles in dark conditions?

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.

What are the factors affecting the rate of biochemical oxidation in the BOD test?

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. The greater the value, the more rapidly oxygen is depleted in the stream.

Why is BOD bottle 300mL?

Bottles are ideal for incubating diluted samples of sewage, sewage effluents, polluted waters and industrial wastes to determine the amount of oxygen required during the stabilization of the decomposable organic matter by aerobic biochemical action. The 300mL capacity bottles are recommended for the 5-day B.O.D.

What happens if BOD is too 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 BOD5 important?

The BOD5 indicates how much dissolved oxygen (mg / l) is needed in a given time for the biological degradation of the organic wastewater constituents. This value is an important parameter for the assessment of the degree of pollution that wastewater represents for the environment (receiving water).

Why high COD is bad?

Higher COD levels mean a greater amount of oxidizable organic material in the sample, which will reduce dissolved oxygen (DO) levels. A reduction in DO can lead to anaerobic conditions, which is deleterious to higher aquatic life forms.

Why BOD is important in wastewater treatment?

BOD finds its primary importance in sewage treatment plants. It gives the respiration rate of sewage, sludge, soil, garbage. It determines the rate of respiration in living beings. Measuring BOD gives the COD or Chemical Oxygen Demand of inorganic substances.

Why a low BOD is important in wastewater treatment?

It is important to note, however, that low BOD in sewage may result in a less effective biomat forming under the leaching field. It is also important to note that BOD serves as the food source for the denitrifying bacteria which are needed in systems where bacterially-mediated nitrogen removal takes place.

How many days should the BOD bottles be incubated?

The standard oxidation (or incubation) test period for BOD is 5 days at 20 degrees Celsius (°C) (BOD5).

How to prepare blank and sample from BOD samples?

6.1 Take four 300 ml BOD bottles and add 10 ml of samples to two bottles and fill the remaining volume with dilution water. 6.2 Fill remaining two BOD bottle only with dilution water for blank. 6.3 Immediately close the bottles when filled and there should not be any air bubble in the bottle. 6.4 Mark the bottles as blank and sample.

What is the meaning of BOD in microbiology?

BOD (Biochemical oxyen demand) – The amount of oxygen required by micro-organisms to degrade the organic matter and can be calculated as BOD of diluted and Undiluted samples. The BOD values depends on the dissolved organic matter in the waste water samples.

What is the difference between BOD and CBOD?

The difference between the initial and final oxygen concentrations corrected for BOD of the seed and dilution factor is the BOD. Results can be influenced by the oxidation of ammonia, but allylthiourea can be added to prevent it. This BOD is then solely the result of carbonaceous oxidation and is identified as CBOD.

What is the difference between cod and BOD in a bioassay?

COD is the amount of oxygen required to chemically oxidize organic matter in your wastewater into inorganic matter. whereas BOD is the amount of oxygen required to biologically oxidize the organics in your sample, usually after 5 days or 21 days of incubation time, depending on the bioassay followed.