basics on screening and hydraulics...basics on screening and hydraulics mwea lagoon committee may...

Basics on Screening

and Hydraulics

MWEA Lagoon Committee

May 2018

Presented by:

Steve Aiken

BS Civil Engineering – Wayne State Univ.

20 years in Design, O&M Assistance and Commissioning

Michigan Class A Wastewater Operator

20 years in Plant Operation, Maintenance and Supervision

Steve Aiken

Regional Sales Manager – Duperon Corp

7 years in Sales

Agenda: 1. General overview of different screening technology

2. Primer on Hydraulics

3. Wrap Up and Final Questions

Screening Overview

BackgroundManual screens or

comminutors used

to be the only way

to remove debris

from the influent

Different Screening

Technologies use different

types of bars, plates or screens

Bars Come In All Different

Shapes

Perforated Plate

Wedge Wire Screen

Different Types of Technology

Step Screen

Band Screen

Drum Screen

Climber

Helical Screw

Multi Rake

FlexRake – Sentinel FSP

Technology

Step / Stair

Screen

DEFINED: Utilizes individual

screening elements mounted

vertically which travels up from

the channel floor – similar

operation to an up escalator

STEP SCREEN Advantages

1. Can clean channels with smaller openings

(channel depth)

3. Able to remove non-bulky debris—excellent as

secondary screen for smaller opening

Technology Step Screen

Technology

Band Screen

Screens that move

around tracks or

sprockets that utilize

woven wire mesh or

perforated plate, either

in a continuous belt or

interlocking panels

Technology Band Screen

BAND SCREEN Advantages

1. Ideal for vertical applications

2. Can clean channels with smaller openings

(channel depth)

3. Able to remove non-bulky debris—excellent as

secondary screen for 1mm or 2mm

Technology Band Screen

DRUM SCREEN INTERNAL Advantages

1. Exceptionally fine screening available

2. No carryover

3. Available in-channel and above grade configurations

4. Common technology for membrane protection

Technology Drum Screen - internal

Technology

Drum Screen

- external

Technology -

Climber or Reciprocating RakeClimber arm that operates along a track with a chain to drive the cycle arm

CLIMER RAKE

Advantages

1. No trapped sprockets/tracks or wear in the

channel

2. Cleaning/raking mechanism does not remain in

the channel

3. Cleans coarse screens

Technology Helical Screw

DEFINED:

Cylindrical

screening basket in

the channel, solids

conveyed via helical

screw or augers

with brushes

HELICAL SCREW

Advantages1. Have some washing and light compaction all in

one unit – low capital cost

2. Ideal for low flow situations (up to 5 mgd) and

small channels

3. Completely contained process

Technology

Multi Rake

Flex Rake

Bottom Sprocket

Cantenary Screen

CHAIN/SPROCKET - Advantages

1. Trapped travel of flights/chain operates in back

current

2. Trapped travel—operates in side currents

3. Torque overload protection/reverse shuts unit

down if unable to clear debris

4. Easy-to-understand technology

Different Types of Technology

Step Screen

Band Screen

Drum Screen

Climber or Reciprocating Rake

Helical Screw or Basket

Multi Rake

AWWA

Hydraulics

for

Operators

Continuity Equation

Q = AVFlow (Q) = Cross Sectional Area (A) x Velocity (V)

Continuity Equation

Q = (W x D) * V

Aver Max

Bar Opening (regression) (regression)

(in.) (f^3/MG) (f^3/MG)

0.125 15.4 32.3

0.25 12.3 24.9

0.375 9.8 19.1

0.5 7.8 14.5

0.625 6.2 11.0

0.75 4.9 8.3

1 3.1 4.9

1.25 2.1 3.1

1.5 1.4 2.3

1.75 1.0 1.8

2 0.8 1.5

2.25 0.6 1.2

2.5 0.4 0.9

2.75 0.3 0.8

3 0.3 0.7

3.25 0.3 0.6

3.5 0.2 0.4

As Slot Opening Decreases,

Debris Removal Increases

Headloss Testing

Headloss vs. Approach Velocity

• Measured

• Calculated

Test Channel

Storage

Tank

Slope Adjustment

Pump

Headloss Testing

Open Channel Flow Equations

Bernoulli – 1740’s

Darcy-Weisbach - 1845

Manning - 1870

Hazen-Williams – 1920’s

Kirschmer – 1920’s

Commonly Used Equations in Open

Channel Flow

Bernoulli

Kirschmer HL = β (w/b)1.33 hv sin θ

HL = (V2-ν2)

C(2g)

ANY FINAL QUESTIONS?

Steve Aiken

Duperon Corporation

(O) 989-401-7710

(F) 989-754-2175

(M) 989 556-5265

1200 Leon Scott Court

Saginaw, MI 48601

saiken@duperon.com