BOD (biochemical oxygen demand)
BOD is the traditional, most widely used test to establish concentration of organic matter in wastewater samples.
BOD is based on the principle that if sufficient oxygen is available, aerobic biological decomposition (i.e., stabilization of organic waste) by microorganisms will continue until all waste is consumed.
The BOD test is also known as "BOD5" since it is based on the accurate measure of DO (dissolved oxygen) at the beginning and end of a five-day period in which the sample is held in dark, incubated conditions (i.e., 20°C or 68°F).
The change in DO concentration over five days represents the "oxygen demand" for respiration by the aerobic biological microorganisms in the sample.
The five-day completion
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Must be free of chlorine. If chlorine is present in the sample, a dechlorination chemical (e.g, sodium sulfite) must be added prior to testing.
b. Needs to be in the pH range of 6.5 - 7.5 S.U. If the sample is outside this range, then acid or base must be added as needed.
c. Needs to have an existing adequate microbiological population. If the microbial population is inadequate or unknown, a "seed" solution of bacteria is added along with an essential nutrient buffer solution that ensures bacteria population vitality.
Specialized 300 mL BOD bottles designed to allow full filling with no air space and provide an airtight seal are used. The bottles are filled with the sample to be tested or dilution (distilled or deionized) water and various amounts of the wastewater sample are added to reflect different dilutions. At least one bottle is filled only with dilution water as a control or "blank."
A DO meter is used to measure the initial dissolved oxygen concentration (mg/L) in each bottle, which should be a least 8.0 mg/L. Each bottle in then placed into a dark incubator at 20°C for five
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The final DO reading is then subtracted from the initial DO reading and the result is the BOD concentration (mg/L). If the wastewater sample required dilution, the BOD concentration reading is multiplied by the dilution factor.
What is DO (dissolved oxygen)?
As the name implies, a DO test measures the concentration of oxygen dissolved in a water or wastewater sample.
DO measurement most often takes place using an electronic meter fitted with a specialized DO probe.
The concentration of DO in a water sample is significantly influenced by:
Temperature: As water temperature increases, DO decreases (i.e., as water gets warmer, it holds less oxygen) (Table 2).
Salinity: As water salinity increases, DO decreases (i.e., as water gets saltier, it holds less oxygen).
Atmospheric Pressure: As pressure increases, DO also increases (i.e., water holds less oxygen as you increase
How am I going to make it a fair test I will use a clean flask for
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Science Experiment to Measure the Dissolved Oxygen Levels Using the HACH Method and CHEMets Test Kit
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From looking at the results I can conclude that when the pH was 3 and
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I decided to experiment with pHs within the range pH 2 to pH7, as I
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Oxygen (O) is one of the most important ions present in the body, making up 61% of the body’s mass. It aids in the destruction of harmful bacteria, while preserving the bacteria that is beneficial for the body. Oxygen takes on its role, and transfers the bacteria absorbed into the lungs, to the cells, allowing for cell respiration. Oxygen allows for the replacement of old cells, protection of the new ones, production of energy from the food, and decomposition of other foods (“Oxygen and Human Body,” n.d.). Oxygen is also vital to produce an activity known as metabolism, which is ‘the sum of the physical and chemical processes in an organism by which its material substance is ...