Biochemical Oxygen Demand Measurement of Lake Samples
In the natural water system, most organic contaminants are degraded by bacterial metabolism. The amount of oxygen used in the metabolism of biodegradable organics is termed Biochemical Oxygen Demand (BOD). Therefore, BOD is a common indicator of the degree of contamination of natural water by organic pollutants. In this experiment, the BOD of samples taken from Lake Carnegie was compared to the BOD of sewage water taken from Stony Brook Sewage Treatment Plant. The purpose of this experiment was to determine the biological degradation activity of Lake Carnegie. Just as the sewage treatment plant, the active biodegrading organism in Lake Carnegie is bacteria. A bacteria containing seed sample was taken from the sewage treatment plant and added to the lake sample. As a basis of comparison and a control, the same was done to inflow and outflow from the sewage treatment plant, a standard C-BOD (glucose), and a standard C and N-BOD (glucose and glutamic acid).
The BOD of the samples are as follows:
BOD for influent: 716.404 mg/L
BOD for effluent: 43.589 mg/L
BOD for lake: 23.273 mg/L
In the case of the seed solution and the standard BOD solutions, there was no microbial activity. There are two possibilities that would give this result:
1. There is no bacteria that can degrade the glucose and glutamic acid.
2. There was no bacteria that is adapted to glucose and glutamic acid.
However, at day 9 the bacteria started to show activity. Therefore we can conclude that the observed phenomenon was a result of the acclimation time for the bacteria.
The BOD for the lake (23.273 mg/L) implies that there is not much microbiological activity in the water. In other words, there is not enough pollution in the lake water to support a high microbial environment. Florida regulates the BOD concentration in natural water not to exceed 5 mg/L, which is the most stringent regulation in America.
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