Coagulants

A coagulant is a highly charged cationic material. It can be either inorganic or organic. They include:

• Inorganic-Ferric Salts
• Aluminum Salts
• Organic-Polydadmac (diallyl-dimethyl ammonium chloride)
• Epi Dma (epichlorhydrin)

In general Coagulants have a molecular weight under 100,000.
Coagulants are normally supplied as an Aqueous Solution

Stabilization of Colloids

Chemical Theory
Stability results from ionized groups on the surface of the colloid. The charges associated with these ionized groups cause particle repulsion.

Double Layer Theory
Stability results from electrical charges that develop at the particle / water interface. The origin of these charges is due to the absorption of hydroxyl ions from the water into the particle surface, creating a negatively charged colloid.

Colloidal Destabilization
The intensity of the charges on the particle is reduced. The chemicals added to reduce these repulsive forces are called coagulants.

Factors which affect Coagulation:

1. Mixing Energy
2. Temperature
3. Particle Size
4. pH
5. Presence of oxidants (chlorine, permanganate, ozone)
6. Flow (Hydraulic capacity of system)
7. Retention Time

Feeding of Coagulants

1. All coagulants should be fed neat to a point where turbulent conditions exist.
2. No day tanks dilutions (or aging) should be made because activity rapidly decreases after 3-4 hours.

Organic Coagulant Advantages

1. No sludge contribution
2. Wider effective pH range
3. Eliminate post pH adjustment
4. Does not hydrolyze with water

Making-Up Liquid Polymer Solutions

Based on volume of polymer to a volume of water

1. Batch Make-Up
   Gallons of solution wanted X decimal equivalent of desired solution = Gal of neat polymer to add
2. Fill tank with just over bottom propeller
3. Close fill line. Pour in polymer slowly. (stream should be approximately the size of a finger)
4. Finish filling with water
5. Stir cationic polymer solutions for 20 to 30 minutes - then turn off mixer
6. Stir anionic polymer solutions for 20 to 40 minutes - then turn off mixer
7. Stir as needed to keep homogenous

Rule of Thumb

• With emulsion /liquid polymer DO NOT make less than a .25 % (.0025) solution.
• See Chart for percentage to decimal equivalents

Liquid Polymer Addition

1. Flow from plant in GPM
2. Multiply by 8.34 Lbs./Gal (for Wastewater)
3. Divide by 1,000,000
4. Multiply by the ppm dosage found from jar test
5. Equals pounds of neat polymer per minute=
6. Divide by weight of neat polymer per gallon
7. Equals gals/min of neat polymer
8. Divide by desired percentage make-up solution of polymer
9. Equals Gal/Min of polymer solution needed
10. Multiply by 3,785 ml/Gal
11. Equals ml/min of polymer solution to add

Important Notice:

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