Algae and sediment pollution in the Great Lakes in 2011 WATER POLLUTION 8 1 8 3 and 5 4 TEXTBOOK 1 Raw sewage pollutes Lake Michigan after a massive 2004 sanitary sewer overflow in Milwaukee Image courtesy of NASA s Earth Observatory 2 Farming practices have changed the chemistry of the Mississippi River and the Gulf of Mexico Cheryl Nenn Milwaukee Riverkeeper http www nsf gov news news images jsp cntn id 110999 org NSF 3 Hypoxia 4 Poisoned Water Clean Water Act What can we do 5 6 EPA 1 Dissolved Oxygen Biochemical Oxygen Demand Every living organisms in water need dissolved oxygen DO to survive DO is consumed when biodegradable organic waste decomposes 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 7 8 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 9 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 10 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 2 Does BOD change with time table 05 08 A No it is a constant B Yes waste is degrading and less oxygen is required 13 BOD degrades following first order kinetics with rate constant k 14 Find the amount of oxygen already consumed by the carbonaceous waste in the first t days A B C D E ultimate oxygen carbonaceous BOD amount of oxygen already consumed by the carbonaceous waste in the first t days Lt Loe kt Lo BODt Lt BODt Loe kt BODt Lo 1 e kt BODt DOo DOt Both C and D 15 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 3 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 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 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 22 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 4 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 25 26 27 28 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 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 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 Parameter 1 Parameter 3 A 20 mg L B 508 mg L C 32 mg L D 1000 mg L E None of the above Parameter 4 Parameter 2 29 30 5 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 31 32 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 What do you know and what do you need to find 33 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 river water after it has received the waste A 20 6 mg L B 508 mg L C 52 6 mg L D 1000 mg L E None of the above 35 36 6 What is ultimate BOD at a distance 50 km downstream Lo A 20 6 mg L B 2 mg L C 200 mg L D 29 5 mg L E None of the above Assumption the river is uniformly mixed at any cross section W 20m and H 5 m and flows as 37 a plug 38 Dissolved oxygen and BOD in Rivers DO is required to maintain balanced community of organisms in water When DO drops below 4 5 mg L fish starts dying The episode in King Harbor follows unusually heavy rainfall in Southern California which washed lawn fertilizer dog droppings and similar nutrients into coastal waters Algae have …