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Homework answers / question archive / Page 1 of 5 POLLUTION CONTROL – ASSIGNMENT PROJECT 3LAB EXPERIMENT BIOCHEMICAL OXYGEN DEMAND PURPOSE The aim of this lab is to provide you with an opportunity to experience the measurement of a common water pollution test, the Biochemical Oxygen Demand (BOD) test

Page 1 of 5 POLLUTION CONTROL – ASSIGNMENT PROJECT 3LAB EXPERIMENT BIOCHEMICAL OXYGEN DEMAND PURPOSE The aim of this lab is to provide you with an opportunity to experience the measurement of a common water pollution test, the Biochemical Oxygen Demand (BOD) test

Electrical Engineering

Page 1 of 5 POLLUTION CONTROL – ASSIGNMENT PROJECT 3LAB EXPERIMENT BIOCHEMICAL OXYGEN DEMAND PURPOSE The aim of this lab is to provide you with an opportunity to experience the measurement of a common water pollution test, the Biochemical Oxygen Demand (BOD) test. The objectives of this lab are to: 1) determine the BOD, of a standard glucose - glutamic acid sample, and 2) determine the BOD of a domestic greywater sample. BACKGROUND The Biochemical Oxygen Demand (BOD) test is one of the most common measures of organic matter in wastewater and contaminated natural waters. In the BOD test, the amount of oxygen used in the metabolism of biodegradable organics is termed the biochemical oxygen demand, or “BOD”. The BOD, as a function of time, follows a first-order rate model. Based on this model, the BOD exerted in the BOD bottle at any given time is equal to the difference between the total potential BOD existing at the initial time (equivalent to the ultimate BOD) and the BOD remaining at any given time (see Figure 1). Thus, Where: BODt = biochemical oxygen demand at time t (mg/L); Lo = oxygen equivalent of organic compounds at time, t = 0 (mg/L) = ultimate BOD; Lt = oxygen equivalent of organic compounds at time t (mg/L); k = first order rate constant (d-1); and, t = time (days) Because BOD changes with respect to time, it is important to report at what time a BOD measurement was made. The most common time interval for reporting BOD values is 5 days. BOD Experiment 2021 Page 2 of 5 BOD Procedure- General The most important concepts are the pre-treatment, dilution, seeding, and proper incubation of the sample. Pretreatment. All samples must be kept at or below 4?C until the sample is ready to be tested. Because microbes are most active between pH values of 6.5 and 7.5 all samples must be neutralized to a pH within this range. It is also important to remove any residual chlorine from the sample before running the experiment. Failing to do so would kill your valuable bacterial source. A seed source is used if the water sample does not contain enough bacteria to initiate biological degradation. The seed contains bacteria and is used to inoculate the sample with an active bacterial source. The seed is obtained from a commercial supplier or a wastewater laboratory. The bacteria function to oxidise the biodegradable organic matter in the sample. If your bacteria fail to oxidise the organic matter, then the test will not work. It is also important to run a seed control to account for any BOD in the seed material. It is necessary to dilute the samples being tested because the BOD concentration in most organic wastewaters exceeds the concentration of dissolved oxygen (DO) in air saturated samples. This is done by using properly prepared dilution water. This dilution water contains nutrients such as nitrogen, phosphorus, and other trace elements necessary for microbial growth. The dilution water is also buffered to ensure that the pH of the sample remains in a suitable range for microbial activity. In the laboratory exercise your samples will have already been pretreated and you will be provided with a seed source and dilution water. This year we are testing the BOD of two domestic (i.e. household) greywaters. One sample is the greywater from a washing machine and the second sample is the greywater from dishwashing in the kitchen sink. Your group will test one of these two samples and then from combing our results in class you should get be able to get an idea of the BOD of household greywater sources and thus the potential impact on the environment from releasing untreated greywater. Because the BOD of the greywater samples are unknown we will need to test the BOD at a range of sample volumes to determine the most appropriate. You will be provided with the results of other groups in your tutorial class. The BOD is calculated as, Where: BODt = Biochemical Oxygen Demand of the wastewater (mg/L) at time t; DO= dissolved oxygen (mg/L); DOi = initial DO of the wastewater plus seeded dilution water ; DO f = final DO of the wastewater plus seeded dilution water; Bi = initial DO in the seeded dilution water only (seed blank); Bf = final DO in the seeded dilution water only (seed blank); P = fraction of the seeded wastewater mixture that is wastewater = sample volume / total volume; 1 – P = fraction of the seeded wastewater mixture that is seed and dilution water. HEALTH AND SAFETY To ensure your safety in the laboratory you will only be admitted to each laboratory session if you: ? Wear a lab coat and safety glasses (borrow these if you don’t have one) ? Wear long pants, shoes that cover your feet and your hair is secured off your face if you have long hair (e.g. in a ponytail) BOD Experiment 2021 Page 3 of 5 In the laboratory, fill out and sign the risk assessment before commencing any lab work. Return your completed risk assessment to the teaching staff before commencing the practical. Follow teaching staff instructions on how to safely use equipment and undertake the BOD laboratory. MATERIALS AND METHODS In this laboratory, you will work in groups of 3-5 people. The following equipment is supplied. ? Glassware (300 mL Erlenmeyer bottles) ? Dilution Water ? Seed material ? BOD samples a) Standard sample of glucose and glutamic acid (GGA) b) Domestic greywater sample ? Dissolved oxygen meters ? Pipettes and pipette tips NB: each group may get a different standard and/or greywater sample. Make sure you write down ALL the information on the sample label and label your BOD bottles accordingly i.e. Session number, group number, sample type, sample number (1 or 2). PROCEDURE FOR BOD TEST IN THE LABORATORY To perform the BOD measurement, you need to prepare the following BOD bottle tests according to the procedure outlined below. You should make duplicates of each of the three types of sample (seed blank, GGA standard and greywater) for a total of 6 bottles. i. Seed sample blank ? Place 0.5 mL of seed material in a BOD bottle and fill to line with dilution water. Label the bottle Seed blank. ii. Standard sample of glucose and glutamic acid (GGA) ? Use the bottle provided for your group. Add the volume of sample stated in Table 2 for your group’s GGA sample. Then add 0.5 mL of seeding material and fill to the line with prepared dilution water. Label the bottle Standard. iii. Greywater sample ? Use the volume of river water as outlined for your group in Table 2 below. Use a pipette to transfer the required volume of sample into the BOD bottle. Write down the volume of sample your used. Add 0.5 ml seeding material and fill to the line with dilution water. Label the bottle Greywater. ?? Make sure you include your session and group number (e.g. S1 G1) on each bottle and that the duplicates are numbered (1 and 2) II. Place the lid on each bottle without spilling the sample, ensure there are no air bubbles and gently invert a few times to mix contents. Unlid and measure the initial DO concentration of the contents of each of the six BOD bottles before you relid each bottle with the same lid (ensuring no spillage or air bubbles). Write the DO values down for each bottle and keep for next week. Take note of which DO BOD Experiment 2021 Page 4 of 5 meter you used and if possible use the same meter in Week 2 to reduce errors. Store your bottles and pack up your equipment as instructed by the teaching staff. End of week 1. III. Week 2. Final DO measurement. Normally the final DO levels would be measured after 5 days but this is not possible because of the way is timetabled. You will measure your final DO reading after 7 days in your second lab session. Therefore, your results will be for BOD7. If possible, use the same DO meter as in Week 1. Write your day 7 DO measurements down for each bottle. Clean up your bottles and equipment as instructed by the teaching staff. IV. Tutorial class. In the tutorial class after your final lab session, you will be provided with the washing machine and kitchen sink greywater results of the other groups. You will also be given information to calculate your GGA ThOD and have the opportunity to ask questions regarding the report. REPORT ? ? Use professional references where appropriate in your report. Do not use this laboratory hand out, class notes or unverified, nonprofessional websites as a reference. REPORT CONTENTS Background In your own words provide a brief background on domestic greywater and why it’s important to understand the BOD of this wastewater source. DO NOT use the background provided in the lab handout. 0.5 page maximum (excluding a figure or a table that you may wish to include in this section). (4 marks) Objective(s) In your own words (1 mark) NO need to describe Procedure. Experimental results Summarise your data in one or two tables. Your raw data includes Table 1 with your data included plus your DO measurements and BOD results. (4 marks) Data analysis and discussion Answer the following questions. Include your full working out where relevant. BOD Experiment 2021 Page 5 of 5 i. ii. iv. v. vi. Determine the BOD of the seed blank, standard glucose and glutamic acid and greywater samples provided to your group. Show your full working out in your report. (6 marks) Determine the Theoretical Oxygen Demand (ThOD) value based on chemical stoichiometry for your standard glucose (C6H12O6) and glutamic acid (HO2CCH2CH2CH(NH2)CO2H) sample. Hint: include the carbonaceous ThOD and nitrogenous ThOD. Show full working out in your report. (5 marks) iii. For your standard glucose and glutamic acid sample, compare and discuss the BOD you obtained with the ThOD sample. (2 marks) Could you estimate the BOD of your greywater sample using ThOD? Explain why. (2 marks) Using the pooled data from the different groups in your laboratory stream, determine the most appropriate sample volume(s) for testing the BOD of the two greywater samples. Explain your answer. Hint: it’s a good idea to include a table with the BOD results for each group. (3 marks) For this practical class we only sampled two domestic greywater sources, once each. Design a sampling approach to get a better overall picture of the BOD-based water quality of domestic greywater across the various sources and over time. (3 marks) References Include if you have any. Minimum 2 references Pl Note: Seed volume to be added may change and will be updated during the class. Please check with the demonstrator. Pl Note: exact dilutions carried out for the grey water samples provided will be updated during the lab. Please check with the demonstrator. BOD Experiment 2021 Page 6 of 5 Wastewater Kitchen sink BOD (initial) (DOi) (mg/L) BOD (final) (DOf) (mg/L) Sample Duplicate Sample Duplicate 8.29 8.27 8.61 8.55 BOD Experiment 2021

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