ENVIRONMENTAL ENGINEERING

441

Lecture Time:

Class 1:

11:15 to 12:45

Monday & Wednesday

Philadelphia UniversityFaculty of Engineering

Department of Civil EngineeringFirst Semester, 2013/2014

INTERNATIONAL SYSTEM OF UNITS

The International System of Units (abbreviated SI) is the modern form of the metric system. It is the world's most widely used system of units, both in everyday commerce and in science.

The older metric system included several groupings of units. The SI was developed in 1960 from the metre-kilogram-second (mks) system, rather than the centimetre-gram-second (cgs) system which, in turn, had many variants.

The SI introduced several newly named units. The SI is not static; it is a living set of standards where units are created and definitions are modified with international agreement as measurement technology progresses.

With few exceptions, the system is used in every country in the world, and many countries do not maintain official definitions of other units. In the United States, industrial use of SI is increasing, but popular use is still limited. In the United Kingdom, conversion to metric units is official policy but not yet complete. Those countries that still recognize non-SI units (e.g. the U.S. and UK) have redefined their traditional non-SI units in terms of SI units.

SI BASE UNITS

 Type  Name Symbol 

 length  metre  m

 mass  kilogram  kg

 time  second  s

 electric current  ampere  A

 temperature  kelvin  K

 amount of substance

 mole  mol

 luminous intensity

 candela  cd

SI DERIVED UNITSType  Name Symbol 

 acceleration meter/square second 

m/s2

 angle  radian  rad

 area  square meter  m2

 capacitance  farad  F

 density kilogram/cubic meter 

kg/m3

 dynamic viscosity

 pascal second  Pa-s

 electric charge  coulomb  C

 electric conductance

 siemens  S

 electric resistance

 ohm  Ω

 energy  joule  J

 force  newton  N

 frequency  hertz  Hz

Type  Name Symbol 

 inductance  henry  H

 mass flow rate kilogram/second 

kg/s

 mole flow rate  mole/second  mol/s

 power  watt  W

 pressure  pascal  Pa

 speed  meter/second  m/s

 surface tension  newton/meter  N/m

 torque  newton meter  N-m

 voltage  volt  V

 volume  cubic meter  m3

 volume flow rate cubic meter/second 

m3/s

 amount-of-substance concentration

 mole/cubic meter 

mol/m3

SI PREFIXES Factor  Prefix Symbol 

 1024 1E24  yotta  Y

 1021 1E21  zetta  Z

 1018 1E18  exa  E

 1015 1E15  peta  P

 1012 1E12  tera  T

 109 1E9  giga  G

 106 1E6  mega  M

 103 1E3  kilo  k

 102 1E2  hecto  h

 101 1E1  deca  da

 101 1E1  deka  da

 10-1 1E-1  deci  d

 10-2 1E-2  centi  c

 10-3 1E-3  milli  m

 10-6 1E-6  micro  µ

 10-9 1E-9  nano  n

 10-12 1E-12  pico  p

 10-15 1E-15  femto  f

 10-18 1E-18  atto  a

 10-21 1E-21  zepto  z

 10-24 1E-24  yocto  y

USCS - UNITED STATES CUSTOMARY SYSTEM UNITS

USCS - United States Customary System Units: are the measuring units used in the U.S. consisting of the Mile (eq 1609.344 m) Foot (equal 0.3048 m) Inch (eq 0.0254 m) Gallon ( US eq 3.785 L) (UK eq 4.546 L) second Pound (eq 0.45359 Kg)

Commonly used USCS and SI-units

USCS unit SI unit SI symbol

Conversion factor (mutiply USCS unit with

factor )Square foot Square meter m2 0.0929Cubic foot Cubic meter m3 0.2831

Pound per square inch

Kilopascal kPa 6.894

Pound force Newton N 4.448

Foot pound torque Newton meter N·m 1.356

Kip footKilonewton

meterkN·m 1.356

Gallon per minute Liter per second L/s 0.06309

Kip per square inch Megapascal MPa 6.89

FOR ONLINE CONVERSION YOU CAN USE THE FOLLOWINGHTTP://WWW.ONLINECONVERSION.COM/

EXAMPLE #1: CONCENTRATIONS AND CONVERSIONS

Some employees at GE wash the PCB tainted floor with organic solvent (TCE) and the discharge enters a holding tank that is 25 m x 25 m x 5 ft and is full with water. The volume of solvent is 3 L and the concentration of PCBs in the solvent is 10 ppm.

What is the final concentration of PCB in mg/l in the holding tank?

MATERIAL BALANCES

MB is a key tools in achieving a quantitative understanding of the behavior of environmental systems.

Mass Balances provide us with a tool for modeling the production, transport, and fate of pollutants in the environment.

MATERIAL BALANCES / MASS BALNCE

Conservation of mass Mass is neither created nor destroyed”

Mass that comes in either stays, reacts or goes out.

“the sum of weights (masses) of substances entering into a reaction is equal to the sum of

weights (masses) of the products of the reaction

Feed In Products out

Inputs - Output = Accumulation

STEADY STATE FLOW CONSERVATIVE SYSTEM:

Steady State Flow, conservative system:

Σ CinQin = ΣCoutQout

Assumption #1: Steady‐state: no change in conc. throughout control volume

Assumption #2: Conservative system: No reaction

EXAMPLE #1

The Hudson river flows with a flow rate of300,000 cfs. GE discharges to the Hudson with

a flow rate of 10 cfs. The concentrationof PCBs in the discharge is 5 g/L. What is the

final concentration in the river?downstream from the discharge? Assume

perfect mixing. Also assume concentration of PCBs upstream

of the discharge is 0 ppm.

STRATEGY OF SOLVING MB Sketch a flow chart or figure defining the boundary

of the process Label the flow of each stream & their composition

with symbols Show all known flows and compositions on the

figure. Calculate additional compositions from the data where possible

Select the basis for calculations e.g. 1h, 1 day, 1 kg, etc

Write the MBs which includes the total balance and component balances. There must be x independent equations if there are x unknowns

Solve the equations and check the solutions

EXAMPLE #2

A wastewater treatment plant with an output of 38400m3/day discharges the liquid effluent with a BOD of 20mg/L into a river. If the BOD of the river upstream of the discharge point is 0.2mg/l, at a minimum flow of 20m3/s, compare the BOD of the river downstream of the discharge, assuming complete mixing.

Answer = 0.63mg/L

EXAMPLE #3

A slurry containing 20 percent by weight of limestone (CaCO3) is processes to separate pure dry limestone from water. If feed rate is 2000kg/h, how much CaCO3 is produced per hour?

HOME WORK

1. Each day 3780 m3 of wastewater is treated at a municipal wastewater treatment plant. The influent contains 220 mg/L of suspended solids. The clarified water has a suspended solids concentration of 5mg/L. Determine the mass of sludge produced daily from the clarifier and write down the mass balance of the clarifier.

2. As a fuel source 20kg of ethylene (C2H4) is burned with 400 kg of air. Determine the composition of the resulting mixture. What is the percentage of excess air, assuming complete conversation?

ANALYSIS PERFORMANCE OF REACTOR TYPE

influentEffluent

Qin

CAin

Q out

C Aout

V (m3)

Reactor

Input – output+ generation= accumulation

GENERAL MATERIAL BALANCE EQUATION FOR FIRST ORDER REACTION RATES:

VdC/dt =ΣCinQin − ΣCoutQout ± kCV

C = concentration in the control volume (river/stream/reactor) [=] mg/L

V = volume of control volume [=] L, m3, ft3

Qin = flowrate of inlet streams [=]m3/s, L/s, cfs, MGD

Qout = summation of all outlet streams [=]m3/s, L/s, cfs, MGD

Cin = concentration in each inlet stream [= ] mg/L

Cout = concentration in each inlet stream [= ] mg/L

k = 1st order reaction rate constant (will be given) [=] 1/s

t = time [=] sec, mi

influent Effluent

Qin

CAin

Q out

C Aout

V (m3)

Reactor