Jar Testing

Jar Testing

The jar test is intended to simulate the coagulation and flocculation process in your plant. Consequently, designing a jar test procedure to match conditions in your plant takes a little thought and practice. However, when you have developed the proper routine and then properly applied the results, you will be producing the best water possible at the lowest cost.

Introduction

Jar tests are used to best advantage in the study of clarification. The unit processes most generally simulated in jar tests are the following:

  • Raw water clarifiers—suspended solids and color removal
  • Lime softening equipment—suspended solids removal, silica removal
  • Primary waste treatment clarifiers—suspended solids, color, BOD, and phosphorous removal
  • Secondary waste treatment clarifiers—suspended solids, color, BOD, and phosphorous removal
  • Dissolved air flotation units—suspended solids removal
  • Sludge dewatering—concentration of solids

Jar Test Equipment

When jar testing, it is convenient to have the following reagents and equipment:

  • Gang Stirrer or jar tester capable of simultaneously stirring several beakers of water
  • Four 500 or 1,000 mL beakers
  • Graduated 1, 3, 5 and 10 mL syringes for the viscous liquid polymers
  • A 100 mL graduated cylinder and dilution bottles
  • A balance to weigh out 0.5 or 1.0 gm samples of powdered polymer
  • Polymer samples
  • Jar test data sheets to record results
  • pH paper and a stopwatch
Syringes in a beaker used in polymer jar testing

The gang stirrer is the most important tool in testing polymers. This piece of equipment allows multiple, simultaneous evaluations of different polymers and dosages.

Preparing Stock Polymer Solution Samples

Dilution strength depends primarily on the polymer type and application in which it is being used. For example, in clarification applications, emulsion polymers achieve effective results at fairly low dosages, but in thickening and dewatering applications, relatively high dosages are required. For dosing and testing purposes, however, liquid polymers are generally diluted to a 1% stock solution prior to making subsequent dilutions.

Liquid Polymers

While there are many different types of functional groups represented, all liquid polymers are completely miscible in water. This feature means that one basic solution preparation can be used for all liquid product types.

1% Stock Solution

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Procedure to make a 1% solution:

  1. Add 99 mL of tap water to a 4-ounce bottle.
  2. Using a syringe, add 1 mL of product.
  3. Or you can use 198 mLs of water to 2 mLs of polymer.
  4. Shake vigorously for at least 30 seconds.
  5. Let the solution “age” for at least 30 minutes before using.

Dry Polymers

On occasion, solutions must be made from dry polymers. The one drawback to preparing solutions from dry polymers is that they hydrate rapidly, often resulting in “fish-eye” formation. Dry polymer test solutions may be prepared by two different methods. Typical solution strengths of 0.1% are employed in clarification studies, whereas solution strengths up to 1.0% are typically used in sludge dewatering studies.

The following procedure uses high shear conditions to allow the polymer to hydrate without clumping.

0.1% Stock Solution

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Procedure to make a 0.1% solution:

  1. Place a 1,000 mL beaker on a magnetic stirrer.
  2. Pour 500 mL of water into the beaker.
  3. Adjust stirrer speed until a vortex forms in the water.
  4. Sprinkle 0.50 grams of dry polymer into the edge of the vortex and allow the solution to mix until solubilization is complete.
  5. Let the solution age for at least 30 minutes before using.

Example

Emulsion Polymers

The solution preparation (inversion) requirements of emulsion polymers are different than those of other polymers. Only when these requirements are met will the full activity of the product become available.

1% Stock Solution

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-OR-

0.1% Stock Solution

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Procedure to make a 1% (or a 0.1%) solution:

  1. Vigorously shake sample polymer until it is homogeneous.
  2. Measure 99 mL of tap water into a 4-ounce bottle.
  3. Using a syringe to measure 1.0 mL of product to the water. This makes a 1% solution.
  4. Shake vigorously for at least 1 minute.
  5. Let stand for at least 30 minutes to ensure full activity. If you want to make a more dilute solution, proceed to the next step.
  6. After 30 minutes, add 90 mL of water to a second 4-ounce bottle.
  7. Use a syringe to add 10 mL of the 1% solution to the second 4-ounce bottle. This makes a 0.1% solution in the second bottle.
  8. Shake vigorously for at least 1 minute.
  9. Let stand for 30 minutes to ensure full activity.
  10. Use the 0.1 % solution unless higher dosages are needed.

Special Precautions:

  • Use clean, dry syringes because emulsion polymers can “invert” in a wet syringe.
  • Be sure that after adding the polymer to the water it is not allowed to sit on the bottom of the bottle for any extended period of time before mixing, as it will tend to cling to the bottle and not go into solution.
  • The use of high-speed mixers to invert emulsion polymers is not recommended since they may shear the polymer molecule.