WATER POLLUTION 8 1 8 3 and 5 4 TEXTBOOK 1 Algae and sediment pollution in the Great Lakes in 2011 Image courtesy of NASA s Earth Observatory 2 Raw sewage pollutes Lake Michigan after a massive 2004 sanitary sewer overflow in Milwaukee Cheryl Nenn Milwaukee Riverkeeper 3 Farming practices have changed the chemistry of the Mississippi River and the Gulf of Mexico http www nsf gov news news images jsp cntn id 110999 org NSF 4 Hypoxia 5 Poisoned Water Clean Water Act What can we do 6 Dissolved Oxygen Every living organisms in water need dissolved oxygen DO to survive DO is consumed when biodegradable organic waste decomposes 7 Biochemical Oxygen Demand Bacterial cells Organic waste oxygen CO2 H2O new cells stable products SO4 PO4 NO3 The amount of oxygen required for bacteria to oxidize organic wastes aerobically i e in the presence of oxygen is called biochemical oxygen demand BOD It is expressed in term of mg L 8 9 Five day BOD test You start by putting a sample of waste into a bottle and measure the concentration of dissolved oxygen DO in the sample at the beginning of the test and again 5 days later The difference in DO divided by the volume of waste is called BOD5 Bottles are capped and kept in dark 10 Requirements for BOD tests 1 Presence of microorganisms that can breakdown waste 2 Constant and appropriate T 3 Adequate time usually 5 days 4 Adequate DO If the waste is too strong need to add DO by bubbling air 5 Adequate nutrients 6 Tests must be done in the dark to prevent photosynthetic production of DO 7 Appropriate pH 8 No toxic effect 11 CSI for environmental engineers Wastewater forensics A midnight dumpster flushed their waste into a gravel pit A pool of pure waste was discovered 3 days later Three factories in the vicinity generate organic waste a winery a tannery manufacture and a sugar beet factory How would you determine the source of the waste 12 table 05 08 13 Does BOD change with time A No it is a constant B Yes waste is degrading and less oxygen is required 14 BOD degrades following first order kinetics with rate constant k ultimate oxygen carbonaceous BOD amount of oxygen already consumed by the carbonaceous waste in the first t days 15 Find the amount of oxygen already consumed by the carbonaceous waste in the first t days A B C D E Lt Loe kt Lo BODt Lt BODt Loe kt BODt Lo 1 e kt BODt DOo DOt C and D 16 17 Lt Loe kt Lo BODt Lt BODt Loe kt Lo BODt 1 e kt or BODt Lo 1 e kt BODt DOo DOt 18 A waste has an ultimate BOD of 1 000 mg L and a k of 0 1 day What is its 5 day BOD t 5days BOD5 A 100 mg L B 393 mg L C 10 mg L D None of the above 19 BOD5 Lo 1 e k t mg mg 0 1 day 5 day BOD5 1000 1 e 393 L L 20 Calculate the ultimate BOD of a waste that has a measured 5 day BOD of 20 mg L assuming a BOD rate coefficient of 0 15 day A 138 mg L B 393 mg L C 38 mg L D None of the above 21 BOD5 Lo 1 e k t mg 0 15 day 5 day 20 Lo 1 e L mg Lo 38 L 22 CSI for environmental engineers Wastewater forensics A midnight dumpster discharged a tank truck full of industrial waste in a gravel pit The truck was spotted 3 days after and a pool of pure waste remains A lab technician determined that the waste has a BOD5 of 100 mg L with a rate constant of 0 1 day Three factories in the vicinity generate organic waste a winery with ultimate BOD of 343 mg L a vinegar manufacture with ultimate BOD of 80 mg L and a pharmaceutical company with ultimate BOD of 254 mg L Determine the source of the waste 23 Find the ultimate BOD of the sample COLLECTED after 3 days since the release A 2540 mg L B 10 mg L C 254 mg L D 0 1 mg L E None of the above 24 Step 1 find ultimate BOD of the sample collected after 3 days BODt Lo 1 e k t BODt Lo 1 e k t BOD5 100mg L Lo 254mg L k t 0 1 day 5 days 1 e 1 e 25 Is the ultimate BOD of samples collected after 3 days since the release the same as the remaining BOD of the original samples after 3 days A Yes B No 26 Find the ultimate BOD of the ORIGINAL sample A 3240 mg L B 343 mg L C 25 4 mg L D 0 3 mg L E None of the above 27 Step 2 find ultimate BOD of the original sample Note that the ultimate BOD of the samples collected after 3 days is the REMAINING BOD L t with t 3 days for the original sample Lt Lo e k t Lo Lt k t e winery 254 e 0 1 day 3 days 343mg L 28 Select the INCORRECT answer A 1 ultimate BOD L0 B 2 BODt consumed after t days C 3 BODt Lt L0 D 4 BOD consumed after 5 days E 3 Lt BOD remaining after t days Parameter 1 Parameter 3 Parameter 4 Parameter 2 29 A waste with a 5 day BOD BOD5 200mg L and k 0 1 day 1 is discharged to a river at a rate of 1m3 s The river has flow rate of 9 m3 s and a background BOD of 2mg L upstream of the discharge Calculate the ultimate BOD L0 of the waste A 20 mg L B 508 mg L C 32 mg L D 1000 mg L E None of the above 30 BOD5 200mg L L0 508mg L 1 1 exp kt 1 exp 0 1day 5day 31 A waste with a 5 day BOD BOD5 200mg L and k 0 1 day 1 is discharged to a river at a rate of 1m3 s The river has flow rate of 9m3 s and a background ultimate BOD of 2mg L upstream of the discharge Assuming instantaneous mixing no time for reaction after discharge calculate L0 of the river water after it has received the waste 32 What do you know and what do you need to find 33 Which of the following is correct A L0 downstreamQdownstream L0 upstreamQupstream B L0 downstreamQdownstream L0 inQin C L0 downstreamQdownstream L0 upstreamQupstream L0 inQin D L0 downstreamQdownstream L0 upstreamQupstream L0 inQin 34 A waste with a 5 day BOD BOD5 200mg L and k 0 1 day 1 is discharged to a river at a rate of 1m3 s The river has flow rate of 9m3 s and a background ultimate BOD of 2mg L upstream of the discharge Assuming instantaneous mixing after discharge calculate L0 of the …