Water Resources And Environmental Engineering Flashcards
A
Area
B or b
Width
BOD
Biochemical oxygen demand
C
Rational runoff coefficient
CN
NRCS curve number
COD
Chemical oxygen demand
D
Pipe diameter
d
Flow depth
DBP
Disinfection byproduct
DO
Dissolved oxygen
E
Specific energy
EPA
Environmental protection agency
FAS
Ferrous ammonium sulfate
GPCD
Gallons per capita per day
g
Gravity
H
Total energy head
h
Energy head
HSG
Hydrologic soil group
HUC
Hydrologic unit code
I
Rainfall intensity
i
Hydraulic gradient
K
Hydraulic conductivity
L
Length
MCRT
Mean cell residence time
MLSS
Mixed liquor, suspended solids
MLVSS
Mixed liquor, volatile suspended solids
n
Manning‘s roughness coefficient
NOM
Natural organic materials
P
Precipitation
p
Pressure
Q
Flow rate
q
Discharge per unit width
R_h
Hydraulic radius
RAS
Return activated sludge
RO
Reverse osmosis
S
Slope of energy grade line or channel slope
SVI
Sludge volume index
T
Transmissivity
t
Time
T_c
Time of concentration
TDS
Total dissolved solids
TOC
Total organic carbon
TSS
Total suspended solids
UF
ultrafiltration
V
Volume
v
Flow velocity
WAS
waste activated sludge
y_c
Critical depth
z
Elevation above datum
γ
Specific weight
μ
Absolute viscosity
υ
Kinematic viscosity
ε
Specific roughness
f
Darcy friction factor
Hydrology def
A branch of earth science that deals with the occurrence movement and quality of surface and sub surface waters
Inflows
- precipitation
- water channeled into a given area (for example from surface runoff)
- ground water inflow from adjoining areas
Outflows
- surface runoff out (for example, from surface runoff)
- water channeled out of the same area
- evaporation
- transpiration
- infiltration or exfiltration
ΔS
Inflows - Outflows
Q_in - Q_out
V_full
(Q_in - Q_out)t
OR
t*ΔS
Watershed def
An area of land that captures water and drains it to an outlet such as a reservoir or a point along a stream channel
Drainage divide def
Elevated terrain that separates two watersheds
Discharge
Volume of water flowing past a location per unit time
Hydrograph and its anatomy
Rational formula
Q=CIA
Q = peak rate of discharge
Weighted C
When the drainage area contains distinctly different land cover characteristics
C_weighted
(ΣC_i * A_i)/A_total
T_c Eq
= L/v
L =[ft]
v =[ft/s]
Q Eq
(General runoff)
= ((P-0.2S)^2)/(P+0.8S)
S Eq
S = maximum basin retention (in)
= ((1000)/CN)-10
CN = Curve number
Types of floods
- flash
- River
- coastal
Frequency (F)
Avg number of years between storms or floods of a defined magnitude
Probability (p)
Inverse of F (frequency) - the chance that a storm or flood of a defined magnitude will be exceeded in any given year
p (probability Eq)
1/F
p (probability in n years)
p = 1-(1-1/F)^n
p (probability in m consecutive years)
p=p^m
p (probability of flood not occurring)
1-p
Continuity equation
Q
A_1v_1 = A_2v_2
Q’
Flow rate for multiple flows
= Q_1 + Q_2
Open channel flow
The conveyance of water with a free surface meaning it has the same pressure as the atmosphere around it
Manning equation
v = (K/n)R^(2/3)_h* S^(1/2)
Q
As related to mannings equation
Q = (K/n)A*R^(2/3)_h * S^(1/2)
K
1.486 US
1.0 metric
Hydraulic radius (R_h) Eq
R_h = A/P
P = wetted perimeter
R_h
For full or half-full pipe
D/4
RECTANGLE
Eqs
A = db
P = 2d + b
R_h = (db)/(b+2d)
TRIANGLE PIPE
equations
A = d^2/tanθ
P = 2D/tanθ
R_h = dcosθ/2
TRAPEZOID PIPE
Eq
A = (b + d/tanθ)*d
P = b + 2(d/sinθ)
R_h = (bdsinθ + d^2cosι)/(bsinθ +2d)
CIRCLE PIPE
not full or half full
Eq
A = (1/8)(θ-sinθ)D^2
P = 1/2θD
R_h = (1/4)(1-(sinθ/θ)D
θ IN RADIANS
Mannings equations
Related to D
Q = (0.463D^(8/3)*S^(1/2))/n
v = (0.591D^(2/3)*S^(1/2))/n
Diameter related to flow rate
D = 1.335(nQ/S^(1/2))^(3/8)
Solids lines when n is variable
Dotted lines when n is constant
Dashed and dotted lines if independent of n
Energy head
H = y + v^2/2g + z
y - flow depth
v - flow velocity
x - channel bottom elevation
Specific energy
E = y + v^2/2g
Critical depth
Q^2/g = A^3/T
Critical depth of rectangular channels
y_c = (q^2/g)^(1/3)
Slope vs depth
Deep flow - mild slope
Shallow flow - steep slope
Q as related to unit discharge
Q = q*B
Flow classifications
Flow > y_c = subcritical flow
Flow < y_c = supercritical flow
Normal flow
When the water surface and channel bottom slopes are the same
Froude number
The ratio of inertial forces to gravitational forces
Fr related to flows
Fr = 1, critical
Fr<1, supercritical flow
Fr>1, subcritical flow
Fr Eq
Fr = v/((g*y_h)^(1/2))
y_h = hydraulic depth [L]
Hydraulic jump def
When rapidly flowing water is abruptly slowed and a sudden rise in the water surface occur occurs
When does a hydraulic jump occur?
When super critical flow is forced to transition to sub critical flow
Conjugate depths
The flow depths immediately upstream, and downstream of the hydraulic jump
Conjugate depths Eq
y_2 = (y_1/2)[-1+(1+8Fr^2_1)]
Specific energy curve
Specific momentum curve
Momentum equation
Related to flow
M = (Q^2/(gA))+Ah
Weir
Free discharge suppressed
Q = CLH^(3/2)
Weir
Free discharge contracted
Q = C(L - 0.2H)H^(3/2)
Weir
V-notch
Q = CH^(5/2)
C values for rectangular weirs
3.33 US
1.84 SI
C values for 90° v-notch weir
2.54 US
1.40 SI
Pump head
p_head
z_1 + h_pump = z_2 + h_f
h_f = friction head
Q units
Gal/m
Liter/m
m(dot) units
(Mass flow rate)
lbm/s
kg/s
Pressure
Psi
kPa
W(dot)
Pump input power
HP
Watts
ρ
Fluid density
lbm/ft^3
kg/m^3
N units
Rotational speed
Rpm
Q
Affinity law
(Q/nD^3)_2 = (Q/nD^3)_1
m
Mass flow rate affinity law
(m/ρND^3)_2 = (m/ρND^3)_1
H
Head added by pump
Affinity law
(H/N^2D^2)_2 = (H/N^2D^2)_1
P
Pressure added by pump
Affinity law
(P/ρN^2D^2)_2 = (P/ρN^2D^2)_1
W
Pump input power
(W/ρN^3D^5)_2 = (W/ρN^3D^5)_1
Cavitation
Occurs when the pressure of the pump inlet has fallen below the waters vapor pressure
Characterized by
Loud noise, pitting damage to parts, and reduced capacity
NPSH Eq
h_atm + h_zs + Σh_Ls - h_vp
h_zs = static suction head
h_Ls = friction losses in the suction line
h_vp = vapor pressure Characterized
Static head
Discharge elevation - suction elevation
NOTE: below pump makes suction elevation positive
Total dynamic head
Static head + friction head
OR
discharge elevation - suction elevation + friction head
REMINDER: direction of water is
From high to low head
When given two parallel pipes with equal head loss, equate Darcy Weisbach
f1(L1/D1)(V1^2/2g)= f2(L2/D2)(V2^2/2g)
Water balance equation
P-E-I-R-ΔS=0
Calculate initial ultimate BOD
CMFR
Completely Mixed Flow Reactor
Something regulated by the Marine Protection and Sanctuaries Act
Ocean dumping by an vessel sailing from a US port
Molecular weight units
Mg/mmole
Convert mmole/1 to mg
Multiple by 100
How to remove trihalomethanes
Use chlorine
Problem with removing trihalomethane
Chlorine is expensive
When in doubt
Average it out
When given multiple values of the same kind and no Eqs just take an average
Superfund Act (CERCLA) covers what
The National Priority List (NPL)
What is the goal of the CERCLA (Superfund Act)
Cleanup of existing and abandoned hazardous waste sites
Total dynamic head
TOTAL Elevation head + friction head
Q_e
Effluent flow rates
Also the amount treated every day
X_A reps what
Mixed liquor VSS
