Effectiveness of Coanda Screens for Removal of Sediment, Nutrients,

and Metals from Urban Runoff

Presented to

bySteve EsmondRobbin Webber

June 26, 2012

Henri Coanda1886-1972

Romanian inventor

Aerodynamics pioneer

Builder of world's first jet powered aircraft

Inventor of the Coanda Effect:"A moving stream of fluid in contact with a curved surface will tend to follow the curvature of the surface rather than continue traveling in a straight line."

US Patent No. 2,052,869“Device for Deflecting a Stream of Elastic Fluid Projected into an Elastic Fluid”by Henri Coanda, Sept. 1, 1936

How the Coanda Effect WorksTilted Wedgewire Screen Technology

Wahl, Tony, US Bureau of Water Reclamation, Denver, CO, “Hydraulic Performance of Coanda-Effect Screens,” Journal of Environmental Engineering Division, ASCE, Vol. 127, No. 6, June 2001,

How the Coanda Effect WorksTilted Wedgewire Screen Technology

* “Design Guidance for Coanda-Effect Screens,” Report No. R-03-03, U.S. Department of the Interior, Bureau of Reclamation Technical Service Center, Water Resources Services, Denver, Colorado, July 2003.

Advantages of Coanda Screens

“These screens have large flow capacities and are hydraulically

self-cleaning without moving parts, so they require minimal

maintenance.” *

Advantages of Coanda Screens

1. Built with no moving parts

2. Self-cleaning and maintenance-free except for periodic trash pickup

3. Corrosion-resistant 100 percent stainless steel construction

4. Designed to remove 100 percent of trash and sediment at peak flow

Curb Inlet BMP Design

Curb Inlet Installation

Curb Inlet Study Performed by USC Focus on Debris and Sediment

Plastics, paper, cans Leaves, sticks, wood chips

Mulch, grass, bark, nurdles Sediment, seeds

Pollutant Removal USC StudyPollutant Percent

Removal

Turbidity NTU 79

Dissolved Solids 10

Chemical Oxygen Demand 25

Biochemical Oxygen Demand 25

Total Organic Carbon 25

Total Phosphates --

Total Nitrates 80

Total Iron 72

Zinc 81

Debris & Nutrient Removal Rates Two-Year Case Study in Texas

Enlarged view of a residential neighborhood

draining into a major Dallas water supply lake

which suffers from eutrophication

Residential Curb Inlet

BMP In Service

Debris After Removal

Debris Collected, Lbs/Ac/Day

0.00

0.20

0.40

0.60

0.80

1.00

1.20

1.40

Jul-09 Aug-09 Sep-09 Oct-09 Nov-09 Dec-09 Jan-10 Feb-10 Mar-10

Date

Debr

is C

olle

cted

, lbs

per

acr

e p

Percent Debris Composition by Wt

0%10%20%30%40%50%60%70%80%90%

100%

Jul-09 Aug-09 Sep-09 Oct-09 Nov-09 Dec-09 Jan-10 Feb-10 Mar-10

Date

Debr

is C

ompo

sitio

n by

Wei

Nutrients & Metals Removed in Sediment

Sediment vs Debris

Sediment 40%

Debris 60%

Total-NSediment 26%

Debris 74%

Total-PSediment 23%

Debris 77%

Arsenic

Sediment 32%

Debris 68%

CadmiumSediment 50%

Debris 50%

Copper

Sediment25%

Debris 75%

LeadSediment 29%

Debris 71%

NickelSediment 28%

Debris 72%

ZincSediment 25%

Debris 75%

Fecal ColiformSediment 26%

Debris 74%

Capture Coefficients kg/km2 per yearDebris Sediment Total

Debris 15,300 -0- 15,300

Sediment -0- 10,200 10,200

Total-N 87 31 118

Total-P 19.0 6.4 25.4Arsenic 0.086 0.041 0.127

Cadmium 0.010 0.006 0.016Copper 0.248 0.081 0.329Lead 0.067 0.027 0.094

Nickel 0.179 0.067 0.246Zinc 1.15 0.040 1.55

Loadings vs. CaptureKg per km2 per year % Capture

Loading Capture

Debris 15,300 100%

Sediment 10,200 100%

Total-N(Lee) 415 118 28%

Total-P(Lee) 255 25.4 10%Arsenic(s) 0.127

Cadmium(s) 0.016Copper(s) 2.8 0.329 12%Lead(s) 12.6 0.094 1%

Nickel(s) 0.246Zinc(s) 32.0 1.55 5%

Sediment Buildup in Lake

1968 – Lake Completed, began to fill.2005 – Cumulative Sediment = 37,960 AF

Lake Drainage Area = 1,074 sq.mi.

Therefore, the historical Sediment Accumulation Rate = 8,700 kg/km2 per year.

Sediment Capture Coefficient measured in this study was 10,200 kg/km2 per year.

Comparative BMP Performance

Pollutant of Concern

Treatment Control BMP Categories

Biofilters Detention Basins

Infiltration Basins

Wet Ponds or

WetlandsFiltration

Hydrodynamic

Separator Systems

Coanda Screens

Trash & Debris L M/H U U M/H M/H HSediment Turbidity M/H M/H M/H M/H M/H M/H H

Nutrients L M M M M L MOrganic Compounds L L U L/M M L L/M

Bacteria U U M/H M/H M/H L L/M

Oil & grease M/H M/H U U M/H L/M LPesticides U U U U U L L

Legend: L=Low, M=Medium, H=High, U=Unknown. Sources: Guidance Specifying Management Measures for Sources of Nonpoint Pollution in Coastal Waters (1993), National Stormwater Best Management Practices Database )2001), Guide for BMP Selection in Urban Developed Areas (2001), and peer-reviewed field performance data.

Conclusion #1

Capture Efficiency:

• 100 percent for both coarse and fine debris,

• 30 percent for nitrogen,

• 10 percent for phosphorus,

• Variable but measureable percentage for metals.

Comment on Conclusion #1

“On average, 45% of the phosphorus load and up to 50% of the metal (cadmium, copper, zinc) load is present in stormwater in dissolved form.”

Andrew J. Erickson, PE, “Advanced Stormwater Treatment: Dissolved Pollutants,” University of Minnesota, St. Anthony Falls Laboratory, Stormwater Magazine, February 2, 2012, http://www.foresteruniversity.net/advanced-stormwater-treatment-pollutants.html

Conclusion #2

Fecal Coliform Capture:

1012 CFU per sq.km. per year.

Conclusion #3

If 5.0 mm particle size is employed as a regulatory standard for trash, then approximately half of the solids, and almost one third of the nutrients and metals, and half of the bacteria, will pass into the environment, carried by particles ranging from 0.5 mm to 5.0 mm.

Summary Implementation Costs

Installation Cost ~ $1,500 per acre

O&M Cost:

• $150 per ton

• $20 per acre per year

• 250 lbs of debris per acre per year

Cost To Remove 1 Lb of Sediment & Debris

Capital Cost = $1,500 per acre =

$101 per acre per year amortized for 20 years @ 3%.

CC = 101 / 250 = $0.404 per lb.

O&M Cost = $150 per ton = $0.075 per lb.

Total Cost = 0.404 + 0.075 = $0.479 per lb.

Cost Comparison Structural BMP Cost to Remove 1 Lb of

TSSDredging 1 $ 0.01Street Sweeping 2 $ 0.11Coanda $ 0.48Detention Basin 2 $ 0.63Sand Filters 2 $ 4.28Infiltration Basin 2 $ 4.56Catch Basin Insert 2 $ 4.65Hydrodynamic Separator 2 $ 5.32

1 Paul Pounds, Ft. Worth Water Dept. 5/7/12 Lake Worth Dredging Project2 Karen Nichols and Hilary Ahrens, “What’s the Cost to Remove One Pound of Sediment From Stormwater?” StormCon 2011

Life Cycle

• LA County - more than 10 years

• USBR – more than 20 years

• Coanda – 30 to 40 years

For Further Information

Contact:Steve Esmond, PE

(714) 389-2113sesmond@coanda.com

Robbin Webber(972) 463-3913

rwebber@rowlett.com