Jordan University of Science and Technology

Faculty of Engineering

Civil Engineering Department

CE 453

“Environmental lab”

“Jar Testing of Coagulation-Flocculation Process”

Experiment (7)

Student Name: Anas Mohammad Maghayreh.

Student ID: 20120023117.

Section #:1

Submission Date: 5/8/2015.

Submitted to: Dr. Hani Abu Qdais

Abstract: Jar testing is a pilot-scale test of the treatment chemicals used in a particular

water plant. It simulates the coagulation/flocculation process in a water

treatment plant and helps operators determine if they are using the right

amount of treatment chemicals, and, thus, improves the plant’s performance.

Introduction: Turbidity is the technical term referring to the cloudiness of a solution and it is a

qualitative characteristic which is imparted by solid particles obstructing the

transmittance of light through a water sample. Turbidity often indicates the presence of

dispersed and suspended solids like clay, organic matter, silt, algae and other

microorganisms.

The jar test is a method of measuring the effect of coagulation, flocculation, and

sedimentation on turbidity. Although the procedure is not outlined in Standard Methods,

it is used in most water treatment plants to find the best coagulant dosages under varying

conditions.

Coagulation/flocculation is the process of binding small particles in the water together

into larger, heavier clumps which settle out relatively quickly. The larger particles are

known as floc. Properly formed floc will settle out of water quickly in the sedimentation

basin, removing the majority of the water's turbidity.

In many plants, changing water characteristics require the operator to adjust coagulant

dosages at intervals to achieve optimal coagulation. Different dosages of coagulants are

tested using a jar test, which mimics the conditions found in the treatment plant. The first

step of the jar test involves adding coagulant to the source water and mixing the water

rapidly (as it would be mixed in the flash mix chamber) to completely dissolve the

coagulant in the water. Then the water is mixed more slowly for a longer time period,

mimicking the flocculation basin conditions and allowing the forming floc particles to

cluster together. Finally, the mixer is stopped and the floc is allowed to settle out, as it

would in the sedimentation basin.

The type of source water will have a large impact on how often jar tests are performed.

Plants which treat groundwater may have very little turbidity to remove are unlikely to be

affected by weather-related changes in water conditions. As a result, groundwater plants

may perform jar tests seldom, if at all, although they can have problems with removing the

more difficult small suspended particles typically found in groundwater. Surface water

plants, in contrast, tend to treat water with a high turbidity which is susceptible to sudden

changes in water quality. Operators at these plants will perform jar tests frequently,

especially after rains, to adjust the coagulant dosage and deal with the changing source

water turbidity.

:Objective*

To become familiar with fundamentals of jar testing used for the evaluating of

coagulation and flocculation and determinations of velocity gradient vs. mixture rpm

relationship ,optimal coagulant dosage , and optimal PH in coagulation –flocculation

process.

*Apparatus:

1. Jar testing mixing assembly.

2. Four 1 liter Pyrex beakers.

3. Aluminum sulfate (Alum) Solution.

4. Pipets.

5. Timer.

6. The pH meter.

7. Distilled water turbidity meter calibration.

8. Colorimeter device or any other available turbidity meter.

Picture (1):NephelometricTurbidimeter Picture (2):Jar mixer

*Procedure: 1. test the timer and rpm meter attached to the mixer for smooth functioning

2. Record the temp. , pH , and turbidity of initial water

3. make the sol. (800ml )by adding (2,4,6,8 )ml from Al2(SO4)3

4. fill the baker and put it in its place such that the mixer rotating shafts remain

approximately at the center of the beakers

5. Mixing the sol. at rpm meter is 170 rpm

until 1 min. (flash mixing to distribute the coagulant homogenously in sol.)

6. mixing the sol. at rpm meter is 80rpm until 20 min ( gentle mixing )

7. Close the motor and keep the sol. to precipitation the sol.

8. Measure the pH, temperature and recorded it.

9. Compare the turbidity of each baker after coagulation and flocculation process

with that of initial water.

10. Find the optimum alum. we must added to the sample

:Results and Calculations sample size:

)PAU(turbidity: 460 initial

80 70 60 50 40 30 0 Concentration(mg/L)

78 64 35 18 63 36 460 Turbidity (FTU)

Discussion: Coagulation –flocculation process removes turbidity ,organics, inorganics, color,

bacteria, pathogens, and testes of water .in the process. The coagulation step is usually

proceeded by the flocculation and floc setting processes for the coagulation.

Aluminum sulfate known as dry alum –are widely used coagulants, depending on water

PH and alkalinity, the cat ionic part of the coagulant combines with the hydroxide

complex of AL(OH)3

And Fe(OH)3 are precipitates which entrap each other .suspended solids ,and colloids

from water body and form flocs in the subsequent process of flocculation .the grown

flocs settle down by their own weight.

Turbidity is linked to the look of water and therefore the public’s perception of water

quality.

Table (1): Turbidity and concentration DATA

In drinking water, the higher the turbidity level, the higher the risk that people may

develop gastrointestinal diseases.

In drinking water turbidity should equal zero.

The greater the amount of total suspended solids (TSS) in the water, the murkier it

appears and the higher the measured turbidity

The major source of turbidity in the open water zone of most lakes is typically

phytoplankton.

The lower the NTU number the cleaner the water.

Turbidity is usually measured using an optical instrument in a laboratory called a

Nephelometric Turbidimeter.

Conclusion

Turbidity is proportional to the concentration of solution.

Turbidity is proportional to the absorbency of solution.

Colloidal particles causes turbidity because of their specific gravity is lower than

specific gravity of the solution and because their negative charge.

Releasing turbidity can by be coagulation and fluctuation process.

Colloidal particles cause sun light regression which affect marine life.

Turbidity can be indicate from the amount of light absorbency and transmitted.

Temperature variation affects the coagulation-flocculation process. At higher

temperature, some coagulants were found to be more effective in the removal of water

turbidity.

References:

*Sanitary LAB. Manual (Experimental Water Quality Engineering)

*The LAB Lecture note.

Appendix: