Measurement of Biochemical Oxygen Demand (Bod)

Topics: Biochemical oxygen demand, Oxygen, Water pollution Pages: 4 (1159 words) Published: November 20, 2012
Title: Laboratory 2: Measurement of Biochemical Oxygen Demand (BOD) Objective
To determine the amount of oxygen necessary for biological oxidation of wastewater effluent and determine the amount of oxygen required by bacteria while stabilizing decomposable organic matter.

Apparatus ; Biochemical Oxygen Demand (BOD) meter, Dissolved Oxygen bottle (DO bottle), pipette, Teflon tape, dilution water, incubator machine. Procedure; Add 300 ml dilute water then take DO reading immediately

Closed properly and keep into the incubator (200C). Take reading for the next 5 days Add 3 ml dilute water and fill up with dilute water until 300ml then take DO reading immediately

Figure 1

Samples for BOD analysis may change greatly during handling and storage. Testing should be started as quickly as possible. To reduce the changes in those samples which must be held, keep the samples at or below 4°C. Do not allow samples to freeze. Samples may be kept for no more than 48 hours before beginning the BOD test. Students assign to prevent interference from chlorine. Because chlorine is such a strong oxidizing agent, it will inhibit the growth of living bacteria in the BOD test. Any samples containing residual chlorine must be pretreated to remove chlorine before the test is run. This is done by adding sodium sulfite to the sample. Samples with extreme pH values and samples containing disinfectants such as residual chlorine must be treated prior to testing. Caustic alkalinity or acidity can prevent bacteria from growing during the course of the BOD test. To prevent this, samples which have pH values higher than pH 8.0 or lower than pH 6.0 must be neutralized to pH 7.0 before the test is performed. Result

1) 3 ml sample
Group| Sample| Result| First day (1st)| Fifth day (5th)|  |  |  | DO| Temp| DO| Temp|
| | | (mg/l)| (0C)| (mg/l)| (0C)|
1| Blank| 1st| 9.20| 25.8| 9.26| 20.3|
| | 2nd| 9.16| 25.8| 9.30|...
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