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
From 1754-1763, Britain fought the French and Indian war. Although Britain had won the war, they still had a lot of war debts to pay off. Britain turned to the colonies to pay off their debts by taxing them. The taxes angered the colonists because they believed it violated their rights. Benjamin Franklin had initially proposed the Albany plan of Union to unite the colonies, however this law was rejected by all of the colonial governments. It wasn't until after all of the British laws and taxes that the colonies would unite and write the Declaration of Independence.
Beginning of the 15th and 16th centuries, Europeans began to explore in the Atlantic Coast of Africa. They were mainly lured into the excessive trade in gold, spices and other goods without knowing about slaves in Africa. Nonetheless, Europeans had no success of taking over these African states to achieve all of these goods but later they did take over various regions in other areas. Africans seems to be willing to sell as many as 11 million people to the Atlantic slave trade to the Europeans. Thus, this makes them the first people to have slaves not the Europeans that forced them into this trade. Furthermore, at the start the Africans seems to have full control of the slave trade, but the Europeans came in and slowly dominated the trade without the Africans knowing. Later on, the trade was overturned and everything went back orderly.
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Science Experiment to Measure the Dissolved Oxygen Levels Using the HACH Method and CHEMets Test Kit
List of the tests to be conducted, material to be tested, the location of sampling, the organization’s name that will perform the test, and the frequency of testing.
Film critics widely use the Bechtel Test, which is used to analyze the roles of genders in Disney films. When the Bechtel test critiqued The Odd Life of Timothy Green, it passes. Women communicate throughout the entire film, such as Cindy, Her sister, Her Aunt and Her boss. They talk to each other throughout, at soccer games about their children’s performance, talk health and family with her aunt and talk about the nature of her job with her boss. There was not once where they spoke with each other about a man.
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