design optimization for water / wastewater … optimization for water / wastewater treatment and...

Design Optimization for Water / Wastewater Treatment and Conveyance Systems using

CFD Modeling

Ferdous Mahmood, P.E. (VA)Malcolm Pirnie / ARCADIS-USDallas, Texas

Computational Fluid Dynamics Modeling

3-D visualization of liquids and gases in motion

Calculates details of flow regime (such as velocity, pressures, flow streamlines, forces, turbulence)

Cost effective evaluation of design and operation• Reduces extensive experimentation and

operational changes • Optimizes design and shortens design cycle• Validates impact of proposed design

Tank Operational (Flow) Analysis

Lower Inflow Rate

Dark blue color implies near zero velocity

Higher Inflow Rate

Lower flow produced poor mixing near the top of tankHigher flow achieves better mixing throughout the tank

Seasonal (Temperature) Analysis

478.0

79.0

80.0

81.0

82.0

83.0

84.0

85.0

86.0

87.0

88.0

Tem

pera

ture

(deg

. F.)

0102030405060708090100110120130140150

Wat

er D

epth

(ft)

-20

0

20

40

60

80

100

120

140

Y

-25025 Z

-20 0 20

X

-20

0

20

40

60

80

100

120

140

Y

-25025 Z

-20 0 20

X

Isothermal Condition

Conc0.80.60.40.20.10.01

Inflow 1 0C Less than Tank Bulk Water

78.0

79.080.0

81.0

82.083.0

84.085.0

86.0

87.088.0

89.0

Tem

pera

ture

(deg

. F.)

0102030405060708090100110120130140150

Wat

er D

epth

(ft)

Time5' below w ater surface 40' below w ater surface 75' below w ater surface140' below w ater surface Tank Level (ft)

Mixed tank

Stratified tank

Design Analysis - Radial Inlet

300

300

300

300

6” dia perforations

Outer sleeve

36” dia inlet pipe

outlet pipe

Velocity Contours

WWTP Clarifier AnalysisVelocity

Contours (m/s)

Velocity Contours

(m/s)

WTP Rapid Mix System Analysis

WTP/ WWTP Filter Flow Distribution Analysis

Dead zone

Lower flow at this filter inlet

Baffle Design and CT Analysis for Rectangular Tanks

9

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0Mas

s Fr

actio

n of

Tra

cer (

Cou

t/Cin

)

Time (hours)

Tracer Curve from CFDVelocity

Contours

Inlet

Outlet

Baffle Walls

Tracer Contours

Clearwell Tracer Movement

1

2

3

4

Tracer Concentration

(0-1 mg/L)

Baffle Design and CT Analysis for Circular Tanks

0

0.5

1

1.5

2

2.5

0 5 10 15 20 25 30 35

Con

c (p

pm)

Time (hours)

Comparisons of Breakthrough Curves

Modeled

Modeled+Cb

Measured

0.02

0.018

0.016

0.014

0.012

0.01

0.008

0.006

0.004

0.002

0

Z

Y

X

X

Close agreement between model results and field data

Clearwell Baffles

Chemical Injection and Mixing Analysis

Chemical Injection

Plates added

72” Pipe

Poor mixing of chemicalChemical only in 2nd pipe branch

Good mixing of chemicalChemical in both branches

Reservoir Short-Circuiting and Water Age Analysis

Water Residence Time

Velocity Vectors

Water Residence Time Distribution

Pump Station Design Evaluation

Velocity Contours

(ft/s)

Pipe Valve Analysis

Velocity Contours

(m/s)

Velocity Contours

(m/s)

Valve location

Large Pipe Connection Evaluation

Velocity Contours

(ft/s)

Velocity Contours

(ft/s)

Junction box

High velocity at pipe intersection corner mitigated by junction box

Dam Spillway and Aqueduct Inlet/Outlet Analysis

Spillway Entrance

AqueductSee attached movie for analysis

Questions?

Ferdous MahmoodPhone: 972-375-7965

Email: Ferdous.Mahmood@arcadis-us.com