1/9/2015

1

Turbidity Control Passive Treatment using Polyacrylamide

(PAM)

Melanie McCaleb, CPESC

NTU, Inc Melanie@ntuinc.com

919-412-7537 www.ntuinc.com

Jacob Wiseman, EIT NCSU

Jacob_wiseman@ncsu.edu 919-513-3841 www.ncsu.edu

What is Turbidity?

• Turbidity is the measure of relative water clarity

• Caused by clays/silts

• Measured in NTU’s – Nephelometric Turbidity Units

Photo from James G. Carver,

Department of Geography and Geology,

University of South Alabama

1/9/2015

2

Basin Design for 99% Capture

• Surface Outlet

• Porous Baffles - Coir.

• Stable Slopes & Inlet

• 25 year sizing

Maximizing Your BMPs Efficiencies

• May increase sediment

capture from 60% to 90+%.

• This will increase

maintenance needs.

• Turbidity will still be an issue

• Values far exceeding

regulation standards

1/9/2015

3

What To Do?

• Filter: often impractical because effective filters require maintenance (e.g.

backflushing).

• Infiltrate: ideal solution (no runoff!) but often soil properties or high

groundwater prevent it.

• Chemically Assisted Settling: effective, may not require much change,

inexpensive.

Polyacrylamide (PAM) • Water soluble synthetic polymer

• Forms: dry powder, effervescent tablets, solution, emulsion, logs/blocks

1/9/2015

4

Flocculation • Flocculants bind suspended sediment by attaching to several soil particles

forming a larger aggregate or floc.

Flocculation

• The larger (and now heavier) flocs then settle out of suspension.

1/9/2015

5

Polymer Testing

• Jar test with sediment or muddy water

• Usually want to test a variety of products or chemistries.

• Looking for rapid flocculation

and settling.

Approach

• Check dams with dry granular polymer

• Other granular polymer uses

• Polymer logs or socks (in pipes and other structures)

Passive dosing is any system that relies on gravity flow in a conveyance to achieve flocculation.

1/9/2015

6

Fiber Check

Dams with

granular PAM

Sprinkle 100 grams of PAM (½ cup) over the

lower center portion of the wattle and on the

blanket above and below.

55 lb bag

(~250 uses)

1/9/2015

7

Check Dam pooling

Drop Inlets –

Another Good

Option

for flocculants

1/9/2015

8

Flocculant Treatment in Pipes

Polyacrylamide Effervescent Tablets

1/9/2015

9

Runoff Has to Pass Through System

Capture Treated Water and Collect Flocs

1/9/2015

10

Passive Treatment of Pumped Water • Water is passed over solid flocculants in the pipe

Passive Dosing with PAM in Pipes Cuts for PAM block

insertion

Discharge point

stabilized

1/9/2015

11

Current Methods for Treating Pumped Construction Site

Water • Pumped into a sediment bag made of geotextile fabric

Sediment Bags and PAM?

1/9/2015

12

Rain-Driven Liquid Doser • Created in New Zealand

• Doses runoff with solution of coagulant or flocculant based

using rainfall

Cationic, Anionic, Turbidity:

Reproduction Effects

0%

20%

40%

60%

80%

100%

120%

0.1 1 10 100 1000

Concentration (mg/L) or Turbidity (NTU)

Neo

na

tes

Pro

du

ce

d (

% o

f c

on

tro

l)

705

9907

Turbidity

Cationic

Anionic

Turbidity

1/9/2015

13

Suspended Sediment Effectson Aquatic Organisms (from Newcombe & McDonald, 1991)

0

2

4

6

8

10

12

14

0 10 20 30 40 50 60 70 80

Exposure Time (hours)

Se

ve

rity

In

de

x

10 mg/L

100 mg/L

1,000 mg/L

10,000 mg/L

>40% Mortality

<20% Mortality

Stress & histological changes

Poor Condition

Reduced Feeding

Alarm, avoidance

Suspended Sediment

Concentration

Questions?

Melanie McCaleb, CPESC

NTU, Inc

Melanie@ntuinc.com

919-412-7537

www.ntuinc.com