2SCOPE AND APPLICATIONS A. The biochemical oxygen demand (BOD) test is used for determining the relative oxygen requirements of municipal and industrial wastewaters.
3SCOPE AND APPLICATIONS Application of the test to organic waste discharges allows calculation of the effect of the discharges on the oxygen resources of the receiving water.
4SCOPE AND APPLICATIONS Data from BOD tests are used for the development of engineering criteria for the design of wastewater treatment plants.
5DETECTION AND REPORTING LIMITS THE REPORTING LIMITS FOR THE BOD TEST IS <2.
6PRECISION AND BIASEighty-six analysts in fifty-eight laboratories analyzed natural water samples plus an exact increment of biodegradable organic compounds. At a mean value of 2.1 and 175 mg/l BOD, the standard deviation was + or and + or - 26 mg/l, respectively.
7WORKING RANGEA. The working range is equal to the difference between the maximum initial DO and minimum DO residual of 1 mg/l.
8SUMMARY OF METHODA. The sample of waste, or an appropriate dilution, is incubated for 5 days at 20 deg. C in the dark. The reduction in dissolved oxygen concentration during the incubation period yields a measure of the biochemical oxygen demand.
9SAMPLE COLLECTION,PRESERVATION AND HOLDING TIMES A. Samples for BOD analysis may degrade significantly during storage between collection and analysis, resulting in low BOD values. Minimize reduction of BOD by analyzing sample promptly or by cooling it to near freezing temperature during storage.
10SAMPLE COLLECTION,PRESERVATION AND HOLDING TIMES B. Sample collection for BOD can be done in a glass or plastic container. The maximum holding time for BOD is 48 hrs.
11HELPFUL COMMENTSB. 24 hours before BOD is to be set up, measure out the required number of liters of water for the test into a glass carboy and aerate for 2 hours.
12HELPFUL COMMENTSD. Always dechlorinate samples which contain chlorine.
13HELPFUL COMMENTSC. Place the carboy into the BOD incubator for 24 hours to bring to 20 C.
14HELPFUL COMMENTSE. To measure less than 25 ml, use a wide-tipped pipette; for volumes greater than 25 ml, a graduated cylinder may be used.
15HELPFUL COMMENTSF. Samples containing large solids should be homogenized or blend the samples to increase precision and allow the use of a more consistent solution.
16HELPFUL COMMENTS G. Liters to use = Number of anticipated samples + 5 (example: if 5 samples are anticipated for the BOD test measure out 10 liters.)
17SAFETY ISSUESA. Use caution when lifting heavy BOD carboy.
18SAFETY ISSUESB. Use latex gloves when handling sewage samples and when filling BOD bottles. This test represents a biohazard.
19INSTRUMENT/EQUIPMENT A. Operating instructions and service manuals for DO meters are kept in the right hand drawer of the BOD station.
20INSTRUMENT/EQUIPMENT B. Change the membrane on the DO probes on a monthly basis.
21INSTRUMENT/EQUIPMENT C. Check lab checklist for maintenance to meters or BOD probe.
22REAGENTS, STANDARDS, AND SUPPLIES A. Hach BOD Nutrient pillows (0.5 mL)B. Hach BOD Nutrient pillows (3mL)C. Hach BOD Nutrient pillows (6mL)
23REAGENTS, STANDARDS, AND SUPPLIES G. BOD Seed: order through NCLH. GGA: Order through NCL
24QA/QC REQUIREMENTSA. Run a GGA STANDARD with every BOD run. Plot the points on the QA/QC graph, daily.
25QA/QC REQUIREMENTSB. Run a duplicate on 5% of all samples run through the lab, or one sample per week.
26QA/QC REQUIREMENTSC. Unknown samples are ordered through ERA once a year.
27QA/QC REQUIREMENTSD. At least 24 hours before the test, bubble or aerate BOD water for 2 hours.
28TEST PROCEDUREA. On the day of the test remove carboy from the BOD incubator and add 1 ml per each liter (10 ml for 10 liters) of Hach Nutrient BOD pillows.
29TEST PROCEDUREB. Set up BOD Bottles in numerical order.
35TEST PROCEDUREH. Prepare Seed according to manufacturers instructions.
36TEST PROCEDUREI. Calculate % concentration for each bottle and record.(Volume of sample/300)
37TEST PROCEDUREJ. Line up BOD bottles corresponding to each page of workbook, keep numbers on bottles sequential in ascending order, and also try to keep numbers for each day sequential as well.
38TEST PROCEDUREThis will facilitate reading out BOD. Carefully record in workbook the number of the bottle each sample will go in.
39TEST PROCEDUREK. For samples with very high BOD values, it may be difficult to accurately, measure small volumes or to get a truly representative sample. In such a case, initial dilution should first be made on the sample.
40TEST PROCEDUREK. For samples that are supersaturated, bring the DO down to a range of 7 to 9 mg/L. Never set up a set of bottles, above or below this range.
41TEST PROCEDUREL. Check the chlorine residual on samples, before checking pH. Samples containing large amounts of chlorine, will destroy the pH probe.
42TEST PROCEDUREL. Check Cl2 residual and determine the amount of Na2SO3 that will be needed. ( add one ml of Na2SO3 per liter of sample for each mg of Cl2 residual.
43TEST PROCEDUREM. Check the pH of the sample. It must be between 6.5 and Use 1N H2SO4 or 1N NaOH to lower or raise pH. Record initial pH and final pH in the workbook.
44TEST PROCEDUREN. Add seed to the BOD bottles. Fill BLANK bottle with water from the distilled water carboy, and nothing else, place in the BOD incubator.
45TEST PROCEDUREAfter seed is added you have 5 minutes to have bottles filled and read, do not allow sample aliquots and seed to sit more than 5 minutes.
46TEST PROCEDUREO. Measure aliquots required for each sample. Add well- mixed samples to clean BOD bottles. For the unseeded bottles use only dilution water.
47TEST PROCEDUREP. Place the dilution water carboy on the top counter above the DO meters. (Stir gently.) Connect the vacuum line to the compressed air and gently add air to start siphon.
48TEST PROCEDUREDiscard the first 100 ml. Fill all BOD bottles to the half way point of the ground glass neck, do not place hose inside bottles.
49TEST PROCEDUREQ. Check the initial DO in each bottle by inserting the probe into the neck of the bottle and turning on the stirrer.
50TEST PROCEDUREDo not force the probe all the way in, as this displaces to much sample. Check for bubbles at the membranes. Let reading stabilize and then record reading.
51TEST PROCEDUREBottles must be read within 3 to 5 min. after being filled, as oxygen depletion begins immediately.
52TEST PROCEDURER. Stopper the bottle, making sure there are absolutely no bubbles inside. Water-seal the bottle by adding water above the stopper and use a plastic cap to inhibit evaporation.
53TEST PROCEDUREPlace BOD bottles in a 20 deg. C. incubator. Be sure and place bottles on shelves that are labeled with the day of the week that they are to come out on.
54TEST PROCEDURES. After bottles have been incubated for 5 days, determine final DO. Record the time off.
55CalculationsA. Calculate for each bottle the BOD as below and then average the results for three bottles to obtain the final value.
56CALCULATIONSFor any samples which deplete less than 2 mg/L throw out the results. And do not use them.
57CALCULATIONSFor any samples which deplete to less than 1 mg/L DO throw out the value and do not use in the average.
58CALCULATIONS Get the average for the seed bottles. Example:
59CALCULATIONSDivide the seed bottles by the amount of seed used per bottle.example:2.3 / 9=0.26*3=0.78 (0.8)
60CALCULATIONSCalculation when seeding BOD Bottles: (B-C)/(A) = BOD mg/LA= Percent sample concentrationB= Initial- Final DOC= Seed depletion