Measurement of Biochemical Oxygen Demand (Bod)

Title Laboratory 2 Measurement of Biochemical atomic number 8 Demand ( mannequin) Objective To determine the add up of oxygen necessary for biological oxidation of sewer water effluent and determine the amount of oxygen required by bacteria while stabilizing analyzable organic fertilizer occasion. Methodology 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 old age Add 3 ml dilute water and fill up with dilute water until 300ml then take DO reading immediately shape 1 Precaution 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 essays which must be held, keep the samples at or below 4C. Do not allow samples to freeze. Samples may be kept for no to a greater extent than 48 hours before beginning the BOD test. Students assign to restrain interference from chlorine. Because chlorine is such a strong oxidizing agent, it will inhibit the growth of quick 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 primitive pH values and samples containing disinfectants such as residual chlorine must be treated prior to testing. Caustic alkalinity or acidity locoweed 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 classify Sample Result First day (1st) 5th 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 20. 4 3rd 9. 13 25. 8 9. 31 20 . 5 think up 25. 8 20. 4 shoot a line Water 1st 9. 24 26. 2 8. 73 20. 5 2nd 9. 12 26. 2 8. 77 20. 6 3rd 9. 10 26. 2 8. 79 20. 7 Mean 26. 2 20. 6 4 Blank 1st 9. 14 25. 9 9. 04 20. 5 2nd 9. 16 26 9. 02 20. 5 3rd 9. 15 26 9. 01 20. 5 Mean 25. 97 20. 5 Waste Water 1st 9. 08 26. 2 8. 31 20. 2nd 9. 05 26. 3 8. 34 20. 7 3rd 9. 02 26. 4 8. 35 20. 8 Mean 26. 3 20. 73 5 Blank 1st 9. 10 25 8. 86 20. 5 2nd 9. 11 25 8. 88 20. 5 3rd 9. 10 25 8. 86 20. 5 Mean 25 20. 5 Waste Water 1st 9. 10 25 7. 82 20. 5 2nd 9. 11 25 7. 82 20. 5 3rd 9. 11 25 7. 84 20. 5 Mean 25 20. 5 The BOD of the sample bathroom be calculates using the equations provided in the following First Equation is provided by the standard method BOD5= mgL= D1 D2P Second Equation is BOD5= mgL= D1 D2 -B1 B2 P WhereD1 DO of the thin out sample immediately after preparation, mg/L D2 DO of the diluted sample after 5-day incubation at 200c, mg/L B1 DO of the obligate before incubation B2 DO of the control after incubation P fraction of the wastewater sample volume to total combined volume Group Sample First day (1st) Fifth day (5th) BOD5 BOD5 DO Temp DO Temp (mg/l) (mg/l) (mg/l) (0C) (mg/l) (0C) (1st Equation) (2ndEquation) 1 Blank 9. 16 25. 8 9. 29 20. 4 52 Waste Water 9. 15 26. 2 8. 76 20. 6 39 4 Blank 9. 15 25. 97 9. 02 20. 5 59 Waste Water 9. 05 26. 3 8. 33 20. 73 72 Blank 9. 1 25 8. 87 20. 5 105 Waste Water 9. 11 25 7. 83 20. 5 128 Discussion From the equation, the result are totally different, it is because second (2nd) equation actually are specialist for seeded sample. Since that, it does not suitable and cant be used to calculate the BOD level. BOD test is a biological test dependent on the actions of the microorganisms found in the wastewater and, as such, is subject to a number of interpretations. These variations can be caused by a number of factors, including changes in temperature, weather, composition of incoming sewage, in plant o perations, and sample distribution points.Results can vary widely from day to day, or even hour to hour. . Form the result we found that the the BOD level in group 5 is 128mg/L, Group 4 72mg/L is quiet higher rather than Group 1 39mg/L. When BOD levels are high, dissolved oxygen (DO) levels decrease because the oxygen that is forthcoming in the water is being consumed by the bacteria. Since less dissolved oxygen is available in the water, fish and other aquatic organisms may not survive. If referred to the IWK website, BOD5 at 200C is 20mg/L for standard A and 50mg/L for standard B.Its mean only sample from group 1 is under control and can be authorise as clean. High level of result from group 4 and 5 may resulted by the input of nitrates and phosphate. Nitrates and phosphates in a body of water can contribute to high BOD levels. Nitrates and phosphates are plant nutrients and can cause plant life and algae to grow quickly. When plants grow quickly, they also die quickly. This con tributes to the organic waste in the water, which is then decomposed by bacteria. One of the major disadvantages of the BOD test is the time lag between the collection of samples and the final calculation of results.This makes the BOD test a poor test for determining whether or not operational changes are needed. In addition, the rate and degree that organic matter in wastewater is decomposed (or oxidized) by the normal bacteria present in a sample is largely dependent on the characteristics of the organic matter. For example, some organic matter (like sugars or starches) are oxidized very easily and rapidly, and will almost always result in measurable BOD. Other organic matter, however, is sometimes resistant to biological oxidation, and may require special acclimated bacteria to oxidize the material and to show a BOD.Although this is what actually happens in nature, it causes significant variation in BOD results from sample to sample. Conclusion, high level of BOD reflects to the DO which it will be decrease. Which is mean the water quality if poor. References Unknown. (n. d. ). Indah Water. Retrieved from http//www. iwk. com. my/v/knowledge-arena/effluent-standards Unknown, A. (n. d. ). Biological Oxygen Demand (BOD) Overview. 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