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# Lecture 7 - PowerPoint PPT Presentation

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

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
• 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 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 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
• 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 Separator
• Recovery and Purity

x1 y1

xo yo

1

0

2

x2 y2

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 Separator
• Example 3.9 – Sedimentation

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

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

Qu=?, Cu = ?

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 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

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 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
• Activated Sludge System
• Waste Activated Sludge
• Anaerobic Digestion
• Volatile Solids
• Digested sludge
• Secondary digester
• Supernatant
• Gases