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Bod Lab Report

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Biochemical oxygen demand is the amount of oxygen needed by aerobic organisms (need oxygen) to break down organic matter in a given water sample at a certain temperature. Organism require oxygen, and in water bodies, they get that oxygen in the form of dissolved oxygen. As the name implies, Dissolved oxygen (DO) is oxygen that has dissolved in water. Like plants and animals living on land, aquatic organisms and microorganisms also need oxygen to breathe. For aquatic organisms, they get their oxygen from dissolved oxygen. Therefore, it is important that there is enough dissolved oxygen in a water sample to ensure a healthy community. However, there are many factors that may cause DO levels to decrease. An increase in light/sun light will result …show more content…

The most common way to calculate BOD is through a method called BOD5. Firstly, the water sample you want to measure is brought into a science lab where a dissolved oxygen probe is used to measure it’s DO. The water sample must be kept in a air tight beaker filled to the the top. The sample is than kept in a dark incubator at 20. This is done to ensure that it doesn’t undergo photosynthesis and only respiration. The bottles are than kept in the incubator for a total of 5 days. At the end of the 5 days, using the same oxygen probe, measure the new DO concentration. The new levels must be less than the original as this shows that in the 5 days, bacteria/ microorganism consumed oxygen in order to break down organic matter. I speculate that an increase in the concentration of fertilizers will cause a greater BOD value as there would be more organic matter for the bacteria to consume. However, if there is so much organic matter, the bacteria may consume all the oxygen before it is able to break down all the organic matter. I currently reside in Vancouver Canada and have been living here for the past 9 years. I live near a golf course and every time I pass by it, I see the river right beside it filled with with plankton. I’ve always wondered what caused this phenomenon to occur. It was only after doing a lot of research that I learnt that golf courses use a tremendous amount of fertilizers, and when …show more content…

Because the conditions necessary to these algal blooms are sometimes temporary or because the algae exceed the threshold level of some other limiting factor, the blooms are only temporary. They often last only a few days. What happens when the bloom is over? The algal cells don't have enough nutrients and most of them die. At this point, the aerobic bacteria become important and start to decompose the algae. Because there is so much food for them, they also experience a sort of bloom, and they literally suck the oxygen out of the water. When the oxygen is gone, the bacteria and most other aerobic creatures in the aquatic system start to

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