Lecture 7
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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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Lecture 7

Lecture 7

Introduction to Environmental Engineering


M b with multiple materials

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 materials1

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


M b with multiple materials2

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


M b with multiple materials3

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”


Materials separator

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


Materials separator1

Materials Separator

  • Recovery and Purity

x1 y1

xo yo

1

0

2

x2 y2


Materials separator2

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


Materials separator3

Materials Separator

  • Example 3.9 – Sedimentation

Qo=30m3/hr, Co = 25 mg/L

Qi=40m3/hr, Ci = 5000 mg/L

Qu=?, Cu = ?


Materials separator4

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


  • Materials separator5

    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


    Complex processes with multiple materials

    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


    Complex processes with multiple materials1

    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.


    Complex processes

    Complex Processes

    • Activated Sludge System

      • Waste Activated Sludge

    • Anaerobic Digestion

      • Volatile Solids

      • Digested sludge

      • Secondary digester

      • Supernatant

      • Gases


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