tool:
– Wardrobe BOD incubator with a temperature range of -10 to 50 0 C and was stabilized at 20 0 C at the test temperature
– BOD Bottle 300 ml
– Aerator
– Measuring cup 100 ml
– The glass cup 100 ml
– Equipment for testing dissolved oxygen in accordance with the scale of SNI M-10-1990-F
Material :
– Solution diluent
– Solution of sodium hydroxide, NaOH, 0.1 N
– Sulphuric acid solution, H2SO4, 0.1 N
– Sodium Sulfite Na2SO3 solution, 0.025
Ways of working:
– Provide the test sample has been taken in accordance with the sampling method of water quality testing SNI 06-2412-1991
– Measure 100 ml of sample in duplicate and input into the beaker 200 ml
– If the test sample is acidic or alkaline, neutralize with 0.1 N NaOH or H2SO4 to between pH 6.5 – 7.5
– If the sample contains residual chlorine, Cl 2, add 0.025 N Na2SO3 solution until all missing
– If the sample contains no micro organisms additional 1000 ml diluent solution so pengencaran 2 times.
– If the test sample is estimated to have a BOD of more than 6 mg / l, dilute the test sample with diluent solution so that BOD levels between 3-6 mg / l
– Aeration with Aerator for 10 minutes until dissolved oxygen 7-8 mg / l
– Put into 2 pieces BOD bottles of 300 ml overflow
– Then close the BOD bottle, avoid turbulence of air bubbles during filling
– Samples are ready to test
Preparation of the test:
Prepare test equipment and supporting material for testing dissolved oxygen in accordance with SNI 06-2424-1991 Test method:
– Check the levels of dissolved oxygen zero days of one BOD bottle containing the specimen in accordance with the testing method of oxygen dissolved in the water, ISO-2424-1991
– Put BOD bottle containing the specimen into the closet incubating temperature of 20 0 C
– Eramkan for 5 days
– Check the level of oxygen dissolved five days in accordance with the testing methods of dissolved oxygen in water SNI 06-2424-1991
– If the sample was diluted, do step 1 to 4 of the diluent solution to pengencaran blank
Calculation:
Calculate the BOD levels by using the formula:
(1) Samples undiluted BOD = C0 – C5
(2) Samples were diluted BOD = C0 – C5 – k (AP0 – AP5) xp
Information:
C0: OT Levels mg / l zero day test object
C5: OT Levels mg / l five day test object
Ap0: OT Levels zero day diluent solution
AP5: OT Levels five days diluent solution
K: Correction of (P-1) / P
Q: dilution factor
Difference in maximum allowable BOD levels between the two testers Duplo is 10% and average the results.