1.0 TITLEDetermination of Biochemical Oxygen Demand (BOD5) In Water and Wastewater2.0 OBJECTIVETo determine the amount of organic pollutant in water and wastewater3.0 INTRODUCTIONBiochemical oxygen demand (BOD) test measures the ability of naturally occurringmicroorganisms to digest organic matter, usually in 5 days incubation at 20°C byanalyzing the depletion of oxygen. BOD is the most commonly used parameter fordetermining the oxygen demand on the receiving water of a municipal or industrialdischarge. BOD can also be used to evaluate the efficiency of treatment processes, and isan indirect measure of biodegradable organic compounds in water. The BOD test isnormally required by a regulatory program. For this experiment, BOD 5 will be examinedby dilution method (Standard Method 5210B).4.0 MATERIALS & METHODOLOGYIncubation bottles: 300 mL bottlesBOD incubatorVolumetric flask, 1L.Beaker, 500mL.Dissolved oxygen meter.Prepare reagents in advanced but discard if there is any sign of precipitation or biologicalgrowth in the stock bottles. Use reagents grade or better for all chemicals and use distilledor equivalent water.
a. Phosphate buffer solution Dissolve 8.5 g KH2PO4, 21.75 g K2HPO4, 33.4 g Na2HPO4·7H2O, and 1.7 g NH4CI in about 500 mL distilled water and dilute to 1L. The pH should be 7.2 without further adjustment. b. Magnesium sulfate solution Dissolve 22.5 g MgSO4·7H2O in distilled water and dilute to 1L. c. Calcium chloride solution Dissolve 27.5 g CaCI2 in distilled water and dilute to 1L. d. Ferric chloride solution Dissolve 0.25 g FeCI3·6H2O in distilled water and dilute to 1L. e. Acid and alkali solutions, 1N for neutralization of caustic or acidic waste samples. i. Acid-Slowly and while stirring, add 28 mL concentrated sulfuric acid to distilled water. Dilute to 1L. ii. Alkali-Dissolve 40 g sodium hydroxide in distilled water. Dilute to 1L.1. Preparation of dilution water: Add 1mL each of phosphate buffer, magnesium sulfate, calcium chloride, ferric chloride solution into 1L volumetric flask. Add distilled water to 1L.2. Add 10mL wastewater sample (refer Appendix) into a 500mL beaker.3. Add dilution water up to 300mL into the same beaker.4. Adjust pH value to 6.5 to 7.5 by adding acid/alkali.5. Prepare 300mL dilution water as control in another 500mL beaker.6. Put all prepared samples and control in 300mL-incubation bottle each.7. Measure and record dissolved oxygen (DO) concentration for each sample using Dissolved Oxygen Meter.8. Add water to the flared mouth of bottle and cover with an aluminum foil.9. Put all the bottles in BOD Incubator for five days. Set the temperature at 20°C.
10. Measure final DO value after five days.11. Calculate BOD5 according to the formula below; BOD5, mg/L = (D1 – D2) / P Where; D1 = DO value in initial sample D2 = DO value in final sample P = Decimal volumetric fraction of sample used Or; BOD5, mg/L = (D1 – D2) x Dilution factor Dilution factor = Bottle volume (300mL) / Sample volume5.0 RESULTS & DISCUSSIONS DO1, mg/L DO2, mg/L BOD5, mg/L Control SampleYou discussion may include the following questions: 1. Discuss your results by comparing with Standard A or Standard B as stated in Environmental Quality Act 1974. 2. What is the purpose of adding water to the flared mouth of bottle? Why the flared mouth of bottle should be covered? 3. Why the light must be excluding from air incubator? 4. Samples of BOD analysis may degrade significantly during storage between collection and analysis, resulting in low BOD values. Suggest one step to minimize the reduction of BOD.
6.0 REFERENCESAndrew, D. E., Lenore, S.C., Eugene, W. R. & Arnold, E. G. 2005. Standard MethodsFor The Examination Of Water & Wastewater. 21 st Edition. APHA. AWWA. WEF.United States of AmericaHoward, S. P., Donald, R. R. & George, T. 1985. Environmental Engineering. McGrawHill. SingaporeFahid, R. Biological Wastewater Treatment-Lecture Notes in Advanced SanitaryEngineering. Faculty of Engineering. Islamic University of Gaza. 2005-2006.APPENDIXEstimate the BOD of the sample and select suitable dilutions from the following tables: Estimated BOD5 (mg/L) Suggested sample volumes (mL) <5 200, 250, 300 <10 100, 150, 200 10-30 25, 50, 100 30-60 15, 25, 50 60-90 10, 15, 25 90-150 5, 10, 15 150-300 3, 5, 10 300-700 1, 3, 5 700-1500 0.5, 1, 3 1500-2500 0.25, 0.5, 1 Standard methods provide additional guidance as follows: use less than 3mL for strong industrial wastes, 3-15mL for raw and settled wastewater, and 15-75mL for biologically treated effluent.