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Exam 2 Review - CE 321, Fall 2008
Study homework, notes from class, notes from lab, 2003 Exam
Mix of short answer (30-40%) and problems (60-70%) divided into four sections: BOD/DO, Reactors, Drinking Water Treatment, Wastewater Treatment
You will be given: Equation sheet, constants, conversion factors, etc
Show your steps, write assumptions, don’t do your work in your head! Include units with conversions/calculations
Fundamental Principles (Units and Mass Balances)
A. Concentrations ( C = M/L 3 ), flow rates ( Q = L 3 /T ), mass flow rates ( Q*C )
B. Mass balance or continuity equation:
( M ) Q C Q C rxn
dt
d CV = in in − out out ±
CV = fixed volume in space through which mass flows (watershed, lake, river, reactor)
Applications at steady-state: ( LHS = 0 ) Applications with a first-order reaction: kCCV VCV
1. DO/BOD/DO Sag curve
DO in streams, Henry’s Law
BOD test: aerobic degradation under controlled conditions
BOD (^) 5 =( DOi − DOf )/ DF L t = L e −^ kt ( ) 0 ( L = BOD left) ( 1 ) kt BODt BODult e = − −
DO Sag Curve problems
2. Reactors
Design parameters: Hydraulic Retention Time (HRT) = V/Q Surface Loading Rate (overflow rate) = Q/As
Types of Reactors: Batch (no flow through, mixing, not steady-state) PFR (flow through, but no mixing of fluid, like Batch w/ t = HRT ) CSTR (flow through w/ continuous stirring, mixing of fluid)
Zero-order vs. First-order vs. Second-Order Reaction:
Rxn term: kCn dt
dC = − , n is order of reaction
Design equations derived from continuity equation with first order reaction:
Be able to apply mass balance principle to different types of reactors
3. Drinking Water Treatment
SDWA
- Primary (health-based) and. Secondary (aesthetics) standards
- Surfacewater filtration Rule
Treatment processes: coagulation, flocculation, sedimentation (settling), filtering, disinfection
- know what these are and how/why they are done
Discrete vs. flocculant settling
- Stokes Law
- Jar test
- Settling tube experiments
Chlorination
- Chicks Law
- total and fecal coliform tests
- CT approach
- chlorination by-products
