A Gritty Face-Off:A Gritty Face Off:Mechanical Vortex Versus Stacked

Tray Grit RemovalTray Grit RemovalJeff Sober

May 27, 2011

Filename.pptNTMWD

Today, we will discuss:

1 North Texas Municipal Water District’s 1. North Texas Municipal Water District s Panther Creek Regional WWTF

2. Why we decided to put two technologies y e dec ded to put t o tec o og esside-by-side

3. How we did it for as cheap as possiblep p4. The grit testing methods used5. The results!5. The results!

Filename.ppt

In 2007, Panther Creek Regional WWTF was built for 5 mgd average flowg g

Filename.ppt

In 2009, Panther Creek underwent an expansion from 5 to 10 mgdg

Filename.ppt

The headworks has both forced and free vortex grit basinsand free vortex grit basins

Filename.ppt

Forced vortex basins have a low capital costcapital cost

95%65%

100 200 300 400Micron Size

• Low headloss

Micron Size

Filename.ppt

The Headcell in theory provides higher efficiency grit removalhigher efficiency grit removal

95%

100 200 300 400Micron Si e

• Large surface area in a small

Micron Size

• Large surface area in a small footprint

• Short settling distanceN i t i b i• No moving parts in-basin

• Same level of O&M effort

Filename.ppt

How can we provide this at the lowest possible cost? Don’t design Headcell for peak flow Don t design Headcell for peak flow Provide system in existing footprint Optimize flow between systems Optimize flow between systems

Filename.ppt

The headworks is rated for 10 mgd average, 30 mgd peak

Filename.ppt

Flows of 0 to 15 mgd are sent to the Headcell

Filename.ppt

Peak flows of 15 to 30 mgd are routed to the vortex

Filename.ppt

GRIT TESTINGGRIT TESTING

Filename.ppt

To compare the units, we utilized two testing protocols

l1. Total grit accumulation testing performed by performed by NTMWD

2. Third Party vertical flow profile testingp g

Filename.ppt

For the first test, we isolated each unit for one week at a time

Filename.ppt

This four week test required weighing grit every two hours

Filename.ppt

This test focused on total grit removed from the classifiers

Filename.ppt

This test focused on total grit removed from the classifiers

Filename.ppt

There was a significant difference in the total pounds

2,000

1,600

1,800

1,000

1,200

1,400

un

ds

Week 2Vortex Week 4

Vortex

600

800

,000

Po

u

Week 1Headcell Week 3

200

400

Week 3Headcell

Filename.ppt

0

We also measured TS and VS

7,000Total Pounds Removed

5 000

6,000 Total Solids Removed

Grit Removed (Inorganics)

4,000

5,000

Per

Week

2,000

3,000

s R

em

oved

P

1,000Po

un

ds

Filename.ppt

0

Week 1 (Headcell) Week 2 (Vortex) Week 3 (Headcell) Week 4 (Vortex)

Results were not as expected250

y

200

ed

Per

Day

150

ds

Rem

ove

Grit Removed (Inorganics)

100

ag

e P

ou

nd

50

Avera

Filename.ppt

0

Headcell Average Vortex Average

TEST PROTOCOL NO. 2 –TEST PROTOCOL NO. 2 THIRD PARTY TESTING

Filename.ppt

Grit Solutions ran vertical profile tests before and after the grit basinsg

Filename.ppt

This test measures the amount of grit that makes it past the grit basinsg

Filename.ppt

A non-native grit was also used

Filename.ppt

The results show that the grit basin was working as designed6,000

88% Removal

5,000

6,000

97% Removal

Removal

3,000

4,000

unds

2,000

Tota

l Pou

0

1,000

Filename.ppt

Headcell Influent

Headcell Effluent

Vortex Influent

Vortex Effluent

Why did this test not agree with our previous results?

Filename.ppt

The system was adjusted

1 Blow down sequence frequency increased1. Blow down sequence frequency increased2. Wash water rates increased

Filename.ppt

Another week of testing had improved results

2,000

1,600

1,800

1,200

1,400

s

Week 2Vortex

Week 4Vortex

800

1,000

Po

un

d

Week 1

SeparateTest

Headcell

400

600Headcell

Week 3Headcell

Headcell

Filename.ppt

0

200

Another week of testing had improved results

1,200

1,000 Pounds Removed

Solids Removed

800

emoved

 

Solids Removed

Grit Removed (Inorganics)

400

600

Poun

ds Re

200

Filename.ppt

0

Headcell Average Vortex Average Headcell Test 2 Average

Let this be a lesson, your eyes can fool you!

Don’t assume a system is optimized, even if it is proprietary black box information

Filename.ppt

it is proprietary black box information

In summary, the new grit system does remove less organicsg

80%

Vortex Average Headcell Average

74%

80%

45%

30%

Filename.ppt

Percent Solids Percent Inorganics

Acknowledgements

1. Steve Kramer, Plant Manager2 Elizabeth Turner NTMWD Lab2. Elizabeth Turner, NTMWD Lab3. Drew Satterwhite, NTMWD Engineer

Filename.ppt