HYDRAULIC HEADLOSS PREDICTIONS AS ITPREDICTIONS AS IT RELATES TO INFLUENT WASTEWATER SCREENS

Michigan Water Environment Wastewater Administrators

C f F k th MIConference Frankenmuth, MI –January 20, 2012

Presented by:Presented by:Steve Aiken

Agendag1. Background on hydraulics

2. Driving Factors why you want the hydraulics righty g

3. Hydraulic modeling and results3. Hydraulic modeling and results

FEEL FREE TO BRING UPFEEL FREE TO BRING UP QUESTIONS AS THEY ARISE

BackgroundgManual screens or comminutors used t b th lto be the only way to remove debris from the influentfrom the influent

When screens become blindedbecome blinded problems upstream canupstream can be catastrophic

Reasons for accurate headloss estimationheadloss estimation

– Allows proper selection of screening equipmentscreening equipment

– Allows proper operation of screening equipmentscreening equipment

– Required to properly size all elements associated with screening equipmentassociated with screening equipment (channel depth and width, geometry, etc.)

BerezinskiBerezinskiBernoulliDarcy WeisbachDarcy-WeisbachHazen-WilliamsKi hKirschmerManning FelleniusSpanglerp gEscandeZimmermanZimmerman

Commonly Used Equationsy

Bernoulli HL = C-1 (V2-ν2) (2g)-1

Kirschmer HL = β (w/b)1.33 h sin θ

Commonly Used Equationsy

Bernoulli HL = C-1 (V2-ν2) (2g)-1

Kirschmer HL = β (w/b)1.33 h sin θ

Driving Factorsg

Concerns or Issues to consider:

Slot VelocitSlot Velocity

• As the velocity through the screen increases the debris capture rate decreases

Concerns or Issues to consider:Hydraulic Bottleneck

• There is an increase in headloss with finer screens and the upstream water level a peak flow has to be taken into account

Concerns or Issues to consider:Blinding

Cleaning c cle times ha e to be• Cleaning cycle times have to be considered as the screen can be clean one minute and blinded off theclean one minute and blinded off the next

Headloss TestinggHeadloss vs. Approach Velocity

Measured– Measured– Calculated

Test SetupTest Channel

Storage TankPump

Slope AdjustmentSlope Adjustment

Testing Setup

Screen

Adjustable Overflow Weir

Testingg

Testing (cont.)g

Testing (cont.)Testing (cont.)

Testing (cont.)Testing (cont.)

Testing (cont.)Testing (cont.)

Testing (cont.)gOriginal coefficientsRe ised coefficientsRevised coefficients

Equation Opening, mm [in]

Bar Shape Trap Rect Tear

Original Kirschmer: 1.4 2.42 0.76g

Kirschmer β 6 [0.25] 1.3 1.2 0.7613 [0.5] 1.7 2.1 1.4

19 [0.75] 2.4 2.42 1.2[ ]Original Bernoulli: 1.42 1.42 1.42

Bernoulli C 6 [0.25] 2.2 2.5 3.513 [0.5] 2 2.1 2.213 [0.5] 2 2.1 2.2

19 [0.75] 1.4 1.5 2.5

Duperon CorporationHead Loss Vs Downstream Water Depth 25% 

Bl k dDate: 1/3/2012 Bar Width: 0.25 [In]

4014

BlockedProposal no.: P4584

Description: Missouli WWTPMachine Type: FPFS

Clear Opening: 0.25 [In]Channel Depth: 3.5 FeetChannel Width: 4 FeetMaximum Capture:15.49 [Ft^3/Hr]MontanaSite 

Address:

30

35

40

10

12

]

20

25

6

8

Upstream Level [In

Headloss [In]

5

10

15

2

4

U

000 0.5 1 1.5 2 2.5 3 3.5

Downstream Depth [FT]

Average Flow 12.54 MGD Minimum Flow 6 MGD Setteling Threshold 2

Setteling Threshold 3 Upstream level 6 MGD

In Conclusion