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Lecture 7

Lecture 7. Introduction to Environmental Engineering. M.B. with Multiple Materials . Multiple compounds into and out of our “black box” Remember: you must have strong fundamentals and organizational skills to keep track of all components. M.B. with Multiple Materials.

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Lecture 7

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  1. Lecture 7 Introduction to Environmental Engineering

  2. M.B. with Multiple Materials • Multiple compounds into and out of our “black box” • Remember: you must have strong fundamentals and organizational skills to keep track of all components

  3. M.B. with Multiple Materials • Great Examples in this section • Allegheny and Monongahela Rivers form the Ohio River in Pittsburgh, PA Allegheny, 340 cfs, 250 mg/L Ohio River, ?, ? Monongahela, 460 cfs, 1500 mg/L

  4. M.B. with Multiple Materials • Accum. = In – Out + Prod. – Consum. 0 = [(340 cfs)(250 mg/L) + (460 cfs)(1500 mg/L)] – (800 cfs)(C) C = 969 mg/L

  5. M.B. with Multiple Materials • Sometimes the “black box” • Is an actual box, like a rectangular reactor in WWTP’s or WTP • Is a theoretical representation of space, like the “box model” in air pollution • Width, length, and a theoretical mixing depth over a city • Wind blows through mixing with the pollutants • Example 3.7 is a good example of SO2 pollution of the air • Donora, PA, 27 deaths, “Donora Episode”

  6. Materials Separator • Goal • To split a mixed feed material into the individual components by exploiting some difference in the material properties • Example: clarifiers in wastewater treatment

  7. Materials Separator • Recovery and Purity x1 y1 xo yo 1 0 2 x2 y2

  8. Materials Separator • Recovery and Purity • If Rx and Ry equal 100%, then the separator is perfect • Purity • We want to make sure only a small portion of y1 is ending up in product stream 1

  9. Materials Separator • Example 3.9 – Sedimentation Qo=30m3/hr, Co = 25 mg/L Qi=40m3/hr, Ci = 5000 mg/L Qu=?, Cu = ?

  10. Materials Separator • Qu = 40 m3/hr –30 m3/hr = 10 m3/hr • 0 = CiQi – (CuQu + QoCo) + 0 – 0 • 0 = (5000 mg/L)(40 m3/hr) – [(Cu(10 m3/hr)+ (30 m3/hr)(25 mg/L) • Cu = 19,900 mg/L

  11. Materials Separator • In some situations, purity and recovery will not give you the information you need to choose between two alternatives • Worrell-Stessel Effectiveness • Rietema Effectiveness

  12. Complex Processes with Multiple Materials Most Env. Eng. Processes involve a series of unit operations, with different individual functions • M.B.’s can solve internal processes • M.B.’s can help determine the order of unit processes

  13. Complex Processes with Multiple Materials • General Rules for process train Placement • Decide what material property to exploit, this becomes the code. • Decide how the code is to activate the switch. • Try to separate easiest materials first. • Try to separate the highest quantity material first. • If possible do not add anything to promote separation.

  14. Complex Processes • Activated Sludge System • Waste Activated Sludge • Anaerobic Digestion • Volatile Solids • Digested sludge • Secondary digester • Supernatant • Gases

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