Welcome to Lab Manual. Copywrite Lab Man Corp. Free Laboratory Manual. Biochemical oxygen demand test. National Field Manual for the Collection of Water. Lab Manual Ch 7 Bichemical Oxygen Demand. Chapter 7 BOD Biochemical Oxygen Demand return to Table of Contents. The Biochemical Oxygen Demand test measures the ability of naturally occurring microorganisms to digest organic. This measures biodegradable organic matter. This is normally expressed as O2. L. The biochemical oxygen demand analysis. The disadvantage is the 5 day time lag and the difficulty in obtaining consistent repetitive values. Many organic compounds which are dichromate. Certain inorganic substances, such as sulfides, sulfites, thiosulfates. COD, which is misleading when estimating. The BOD results also may be affected by lack of seed acclimation, giving erroneously low readings while the COD results are independent of seed acclimation. BOD values are a measure of food for naturally. When food is introduced, naturally occurring microorganisms begin to multiply rapidly. After all the food is consumed. The Biochemical Oxygen Demand test provides. There is a limited amount of oxygen which will dissolve in the sample (about. L), therefore dilutions are prepared with a buffered mineral nutrient containing water. The test does not. The BOD indicates the concentration of biodegradable organic material. Standard Analytical Procedures for Water Analysis May 1999. The BOD is then calculated on the basis of reduction of DO and the. In conducting the test, several different. For computation. of the BOD value, at least 2 mg/L of O2 should be consumed with at least 1 mg/L remaining. Two different dilutions of the same sample should generate. The BOD5 values of the two dilutions are normally averaged. Check a few old Water Pollution Studies .. Ultimate Oxygen Demand is usually expressed as (1. BOD5). + (4. 6 x NH4- N). The 1. 5 factor for. BOD5. accounts for the fact that only 6.
BOD is oxidized in 5 days. To encourage the bacteria to consume ALL. As an aside, for some samples . There are different procedures for doing that, but one of the most commonly used. Appendix B of Chapter 4. Code of Federal Regulations, Part 1. CFR 1. 36), the code (law) governing the. NPDES program. Appendix B calls for preparing a sample of known concentration that is near but higher than the. MDL mentioned in the written method. You analyze that sample seven times in one batch, calculate the standard deviation. The answer is that lab's MDL for that method. SM1. 8. 5. 21. 0B states the MDL for BOD is 2. L. That's as low as you can go because of the method requirement that a. L. If the sample analyzed was say 2. L sample and 5 m. L dilution. water (to get the needed nutrients . That doesn't mean that the lab can actually analyze accurately at that. To find out what your lab's actual MDL is, analyze a sample seven times, at a concentration of say. L, just as called for in Appendix B, 4. CFR 1. 36. Matrix spikes are performed on reagent water. Acceptable. values for the glucose- glutamic acid (G/GA) solution give 1. The obtained value will depend to a great extent on the mixed microbiological. Control charts should be maintained for accuracy on either. G/GA or KHP test solutions and for precision on real sample duplicates. Samples suitable for BOD5. When chlorinated effluent is tested it must be dechlorinated. Na. 2SO3). and seeded. If dechlorination is required, refer to the method for directions, as excess dechlorinating reagent. BOD5 result. The BOD5. DO values and the percent concentration. In the BOD test you. The actual readings themselves could be off 0. L and may not make any. The Winkler titration has. The use of a barometer is crucial to achieving the < 0. L change in the dilution water. If a lab's average. If the lab's average is considerable LOWER than 1. In the table of suggested dilutions for various. BOD samples, at the bottom of the table where the suggested volumes to be diluted are 1. Caution the analyst to remember to multiply the BOD result by that additional dilution. Source water is the single most common cause of bad blanks, and it deserves a discussion. Labs. that use their own distilled or DI, or both, often. All of these have a bad impact on BOD. Sometimes it is best to buy distilled water (NOT distilled drinking. The purpose of the biochemical oxygen demand. BOD5) test is to measure the potential of wastewater and other waters to deplete the oxygen. Wastewater treatment plant operators also use the BOD5. BOD5 of the influent. The BOD5 test may also. Oxygen is required (used up, depleted, consumed) by microorganisms as they assimilate various organic and inorganic. Some of those materials contain reduced forms of nitrogen. Collectively, these. If those nitrifying bacteria. BOD5. or CBOD5. Carbonaceous material is that consumable material which does not contain nitrogen. For example, wastewater treatment plants report . Many biological treatment plant effluents. Because nitrogenous demand has historically been considered an interference (i. BOD5 test is to measure carbonaceous material .. It would take the bacteria in a wastewater. Because it is impractical to. BOD5). Another test that measures the oxygen requirements of wastewater is chemical oxygen demand. COD, which can measure 1. One can expect. BOD5 and COD results for the same sample to be related. Also, because BOD5. CBOD5 is a measure. BOD5 and CBOD5. for a given sample. The BOD5. test is widely used to determine the degree to which a waste stream will contribute to pollution of receiving waters. The BOD5. test is of prime importance in regulatory programs and in determining the overall health of receiving waters. The BOD5. test is normally required by a regulatory program that is governed directly or indirectly by Chapter 4. Code of. Federal Regulations, Part 1. CFR 1. 36). Currently, 4. CFR 1. 36 allows the use of four analytical methods for. BOD5 and/or CBOD5. EPA Method 4. 05. Standard Methods 5. B, USGS Method I- 1. AOAC Method 9. 73. EPA Method 4. 05. Standard Methods 5. B for specifics on conducting the test. It is Standard Methods 5. B or its derivative that is most commonly used in environmental laboratories. All BOD5. methods approved by EPA are based on the determination of oxygen depleted by bacteria in samples during a 5- day. BOD5 samples are normally incubated in 3. L BOD bottles, and are diluted as necessary. L of DO (dissolved oxygen) to remain at the end of the 5- day period. To be a valid test. L of oxygen must be depleted during the incubation. If necessary, samples must be pretreated to. H, temperature, and absence of toxic materials (e. BOD- consuming bacteria. The foregoing are requirements of all EPA- approved BOD5. Sampling, Sample Preservation, Holding timesa. Discharge permits or. Care must be taken to make sure the sample is representative. Samples should be taken in. BOD bottles that will be incubated for that sampling site. Another consideration in determining sample size. Preservation and Holding Times(1) In most environmental samples, bacteria. Therefore. starting the analysis as soon after taking the sample is very important. CFR 1. 36 establishes the maximum storage. Standard. Methods 5. B recommends that. Standard Methods 5. B also says that if analysis can start on a grab sample within two hours of sampling. Composite samples must be kept at 4. After removal from the compositor, samples must be. A variance is allowed by 4. CFR 1. 36 if the permittee has data showing specific. Measurement of Dissolved Oxygen (DO). CFR 1. 36 allows measurement of DO using either an electrode and meter, or the azide modification of a Winkler titration. An oxygen- sensitive membrane. EPA- approved method requirements. The YSI 5. 0- series. Orion 8. 00- series instruments are examples of commercial meters meeting those requirements for measuring DO. If DO is routinely measured using an electrode and meter, checking calibration of the meter periodically. Winkler titration will help make sure the meter is functioning properly. Standard Methods 4. O G is a commonly- used electrode method for measuring DO.(2) Winkler. Burettes capable of measuring. L are sufficient for the Winkler titration. Standard Methods 4. O D is a commonly- used method for measurement of DO using a modified Winkler titration. Temperature in the BOD incubator. If using an air incubator, the thermometer should be immersed to the immersion. If. using a water bath, simply immerse the thermometer to the immersion line. Calibrate a less expensive thermometer. Incubator or Water Bath. Either an air. incubator or water bath may be used to incubate BOD bottles. The apparatus must be able to maintain a temperature. It must be of sufficient size to hold all BOD bottles for a given batch (i. For reasons explained later, it is also advantageous. BOD5determination. The incubator/water bath must exclude all light to prevent photosynthesis. BOD test). Incubators specifically designed for. BOD5(such as Hach Company's Incutrol. A household refrigerator can be modified to meet. BOD5 test needs. One required modification is installation. The thermometer. used to monitor temperature in the incubator should be placed in the vicinity of the majority of the BOD bottles. Dilution water container. A glass or plastic. Although not required, a convenient. BOD bottles without creating air bubbles is to siphon the water from the dilution. If this technique is used, the siphon hose should terminate with a 6- inch length of glass tube. BOD bottle from the bottom without submerging the hose. The dilution water container and all associated. Incubation (BOD) Bottles. Bottles used. should never be used for any test other than. BOD5. Just like the dilution water container. BOD bottles must be kept clean. Wash after each use with detergent, rinse with distilled water, drain, and store. If blanks unexpectedly test higher. BOD bottles need acid washing. This can be done by first washing, rinsing, and draining. Rinsing is accomplished by carefully swirling. L of the dilute acid until all inner surfaces of the bottle are wetted. Allow the bottle to sit for a. Then rinse the bottle with distilled water and drain. Acid rinsing. is not necessary every time the BOD bottles are used and might never be required as long as blanks test less than.
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