Test+6+-+Biochemical+Oxygen+Demand

﻿Biochemical Oxygen Demand

Biochemical oxygen demand is the measurement of the amount of oxygen consumed by different organisms and organic matter that is breaking down in small streams and creeks. It also measures the amount of chemical oxidation in matter that is inorganic. How fast the oxygen consumed in a stream is affected by a number of things such as- temperature, pH, the kind of certian microorganisms. and the type of organic and inorganic material. The more biochemical oxygen demand in the water the quicker oxygen is taken from the stream. This causes some water organisms to suffocate and die. Sources of Biochemical oxygen demand are debris, dead animals, manure, wastewater, septic systems, and some .stormwater,runoff

BOD is important because if it is not at the right levels it can cause certain organisms in the water to die. The presence of a sufficient concentration of dissolved oxygen is critical to maintaining the aquatic life and beautifal quality of streams and lakes. Determinng how organic matter affects the concentration of dissolved oxygen (DO) in a stream or lake is a small part of water-quality management. The decay of organic matter in water is measured as biochemical or chemical oxygen demand. The BOD levels around here are expected to be high at first and then after the 5-day incubation period the levels should lower drastically. Low levels are better meaning that the ﻿re is little to no waste in the water. The scale of BOD levels are rated from 1-10mg/L showing the

quality of the water. Between 1-3mg/L is the cleanest the water can get with very few bacteria in the stream. = = =The Steps for Testing BOD= step1. Obtain an initial dissolved oxygen reading at the site you are testing for BOD. step2. Collect three water samples for BOD. step3. If the time between collection of samples and incubation of samples is greater than 30 minutes. step4. Place BOD bottles in an incubator or dark closet at about 20 degrees celcius. step5. Position the computer away from water. step6. Plug in Dissolved oxygen probe into channel 1. <span style="font-family: 'Comic Sans MS',cursive;">step7a. Remove the blue protective cap if it is still on. <span style="font-family: 'Comic Sans MS',cursive;">step7b. Unscrew the membrane cap from the probe. <span style="font-family: 'Comic Sans MS',cursive;">step8. Prepare to collect data by opening the file 06 BOD. <span style="font-family: 'Comic Sans MS',cursive;">step9. Warm up the dissolved oxygen probe for 5-10 minutes. <span style="font-family: 'Comic Sans MS',cursive;">step10. Ready to calibrate the Dissolved Oxygen Probe <span style="font-family: 'Comic Sans MS',cursive;">step10a. Choose Calibrate. <span style="font-family: 'Comic Sans MS',cursive;">step10b. Remove the probe from the water bath and place the tip of the probe into the sodium sulfate calibration solution. <span style="font-family: 'Comic Sans MS',cursive;">step10c. Type 0. <span style="font-family: 'Comic Sans MS',cursive;">step10d. When the displayed voltage for reading 1 stabilizes, click keep. <span style="font-family: 'Comic Sans MS',cursive;">step10e. Rinse the probe with distilled water. <span style="font-family: 'Comic Sans MS',cursive;">step10f. Unscrew the lid of the calibration bottle provided with the probe. <span style="font-family: 'Comic Sans MS',cursive;">step10g. Add water to bottle to a depth of 1/4 inch and screw the bottle into the cap <span style="font-family: 'Comic Sans MS',cursive;">step10h. Type the correct saturated dissolved oxygen value. <span style="font-family: 'Comic Sans MS',cursive;">step10i. Displayed voltage reading. <span style="font-family: 'Comic Sans MS',cursive;">step11. Remove the water samples from the incubator. <span style="font-family: 'Comic Sans MS',cursive;">step12a. Submerge the probe tip in the BOD bottle and move probe up and down. <span style="font-family: 'Comic Sans MS',cursive;">step12b. Click collect to begin data collection. <span style="font-family: 'Comic Sans MS',cursive;">step12c. Click keep to begin a 10 s sampling run. Leave probe submerged. <span style="font-family: 'Comic Sans MS',cursive;">step12d. When sampling run is complete, stop data collection and record the dissolved oxygen value on the Data & Calculations sheet as the final 5 day DO reading. <span style="font-family: 'Comic Sans MS',cursive;">step13. Return to step 12 to obtain a reading for the other two samples. When all readings have been taken, rinse the tip of the probe and secure it in the calibration bottle filled with water. <span style="font-family: 'Comic Sans MS',cursive;">