Contoh report jar test

8/18/2019 Contoh report jar test

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1.0 INTRODUCTION

Jar testing is a method of simulating a full-scale water treatment process,

providing system operators a reasonable idea of the way a treatment chemical will

behave and operate with a particular type of raw water. Because it mimics full-scale

operation, system operators can use jar testing to help determine which treatment

chemical will work best with their system’s raw water using the optimal chemical

dosages.

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.

Jar testing entails adjusting the amount of treatment chemicals and the

sequence in which they are added to samples of raw water held in jars or beakers.

The sample is then stirred so that the formation, development, and settlement of floc

can be watched just as it would be in the full-scale treatment plant. (Floc forms

when treatment chemicals react with material in the raw water and clump together.)

The operator then performs a series of tests to compare the effects of different

amounts of flocculation agents at different pH values to determine the right size flocfor a particular plant.

Benefits of jar testing are:-

a.

Better finished water quality

b. Longer filter runs

c. Overall prolonged filter life

d. Lower chemical costs

2.0 OBJECTIVE

To determine the optimal coagulant dose which will produce the highest removal

of a given water turbidity.

3.0 LEARNING OUTCOME

1. To identify the most common coagulant used in the coagulant process.

2.

To determine the most effective and optimum dosage of coagulant for a

particular mixing intensity and duration.


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3. To understand the complex interrelationships that exists between the

chemicals and the constituents of the water being treated, as well as other

factors such as pH, temperature, the intensity and duration of mixing.

4.0

THEORY

Raw water and wastewater are normally turbid containing solid particles of

varying sizes. Particles with sizes greater than 50 µm settle fairly rapidly. The

settling velocities of colloidal particles of sizes less than 50 µm are very slow. Thus,

these particles are encouraged to collide leading to coalescence of particle to form

flocs particles, which are bigger and heavier. These particles will have higher

settling velocities and easily settle out.

Colloidal particles do not agglomerate by itself due to the presence ofrepulsive surface forces. A process is needed to suppress these forces so as to allow

flocs formation. This process is called coagulation process. It is actually the

addiction of chemical coagulant to the raw water or wastewater. Coagulant that

normally used are salts of aluminium namely aluminium sulphate and ferric salts

namely ferrous sulphate and ferric chloride.

The next process that follows the coagulation process is flocculation. It is the

process that promotes particles collision due to gentle agitation resulting in

agglomeration of smaller non-settleable particles into flocs (bigger particles) which

settles easily to produce clarified water. Addition of coagulant aid such as synthetic

polymer will accelerate settling.

Majority of ions in surface water consist of negatively charged particle/colloids

which are stable in nature (stable = existing in ionized form). They repel other

colloidal particles before they collide with one another. The colloids are continually

involved in Brownian movement.


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5.0 EQUIPMENT AND MATERIALS

1.

Jar test apparatus with six rotating paddles blade

2. Six (6) beakers

3. pH meter

4. Turbidity meter

5. Pipette

REAGENT

Aluminum sulfate (alum) with a known concentration or anionic/cationic

coagulant such as ferrous sulfate and ferric chloride


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6.0 PROCEDURE

1.

The wastewater sample is prepared.

2. The temperature, pH and turbidity of water sample is measured.

3.

The prepared wastewater is placed from (1) into six (6) different beakers

(Plexiglas graduated beakers) with one litre each.

4.

1 -5 ml of coagulant (alum/ferrous sulfate) is added by using a measuring

pipette into beaker 1,2,3,4 and 5 while in beaker 6, no alum was added as it

acts as a control sample.


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5. The pH and turbidity of each beaker is measured by using pH and turbidity

meter

6.

Each beaker is started stirring rapidly (60 to 80 rpm) for 3 minutes

7. Then the speed is reduced (30 rpm) for about 20 minutes

8.

The flocculation process is observed and the flock formation is recorded in

final 10 minutes by referring to the chart of particle sizes provided in lab

sheet.

Note: Record the qualitative characteristics of flocks as bad, moderate,

good and very good. Cloudy samples indicate bad coagulation while good

coagulation refers to rapid flock formation resulting in clear water

formation on the upper portion of the beaker.

9. After the stirring period is over, the stirrer is stopped and the flocks are

allowed to settle for about 5 minutes.


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10. 500 mL of settled water is separated out into another beaker

11. The temperature, pH and turbidity of the clarified water is determined.

7.0 RESULT AND DATA ANALYSIS

Results

JAR TEST 1 (Set the coagulant dose)

Initial turbidity: 47 NTU

Initial pH: 6.8

pH adjustment (base): -

pH adjustment (acid): -

Coagulant concentration: 3%

JAR No 1 2 3 4 5 6

pH 4.36 4.30 4.23 4.22 4.19 6.29

Coagulant dose

(mg/L)

1 2 3 4 5 Control

Agitate

(minute)

23 23 23 23 23 23

Fast (rpm) 80 80 80 80 80 80

Slow (rpm) 30 30 30 30 30 30

Settling depth

(mm)

6 5 4 6 5 None

Turbidity

(NTU)

1 3 8 3 2 45

Floc formation

(final 10

minutes)*

Fine(Size C)

Fine(Size C)

Very fine(Size B)

Very fine(Size B)

Very fine(Size B)

None

* F loc formati on can be recorded by referr ing to the measurement scale as provided in lab sheet.


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Data analysis

a. Compare the level of tur bidi ty in each sample .

Turbidity is a measure of the degree to which the water loses its transparency

due to the presence of suspended particulates. The more total suspended solids

in the water, the murkier it seems and the higher the turbidity.

JAR No 1 2 3 4 5 6

pH 4.36 4.30 4.23 4.22 4.19 6.29

Turbidity

(NTU)

1 3 8 3 2 45

From the results as above, it can be seen that sample 6 which acts as a controlhas the highest turbidity of 45 NTU whereas for the other 5 samples which was

added with coagulant of different dosage have varies turbidity. Sample 3 has

the highest among the 5 samples while sample 2 and sample 4 have the same

turbidity. The lowest turbidity goes to sample 1 which only result as 1 NTU.

The turbidity of the samples are affected by the flocs content in the sample.

However, the results might not be as accurate as the wastewater used was

taken from the FKAAS lake which its contamination may be affected due to

rain just shortly before it was obtained. Surface water plant is susceptible to

sudden changes in water quality.


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b. With the aid of a graph, show the relationship between pH and turbidity with

respect to coagul ant dosage.

0

1

2

3

4

5

6

7

8

9

4.15 4.2 4.25 4.3 4.35 4.4

T u r b i d i t y ( N T U )

pH

Graph of Turbidity vs pH

4.18

4.2

4.22

4.24

4.26

4.28

4.3

4.32

4.34

4.36

4.38

0 1 2 3 4 5 6

p H

Coagulant Dosage (mg/L)

Graph of pH vs Coagulant Dosage

0

1

2

3

4

5

6

7

8

9

0 1 2 3 4 5 6

T u r b i d i t y ( N T U )

Coagulant Dosage (mg/L)

Graph of Turbidity vs Coagulant Dosage


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c. From the graph, get the optimum value for pH and coagulant dose of the

coagulant process.

From the graph in question 2, the optimum value for pH and coagulant dose are

4.36 and 1mg/L respectively. However, the results may not be accepted as the

graph supposed to be U-shape rather than bell shape. Hence it is shown that the

results obtained is not accurate. This is due to error such as human and random

error.

d. Explain the impli cations of using different dosage of alumin ium sulphate in

the treatment process.

Finely dispersed suspended and colloidal particles producing turbidity

and color of the water cannot be removed sufficiently by the ordinary

sedimentation process. Adding a coagulant with mixing and stirring

the water causes the formation of settleable particles. These flocs are large

enough to settle rapidly under the influence of gravity, and may be removed

from suspension by filtration.

Alum was found to be effective coagulant in reducing solids, organics

and nutrients in the dairy industry effluent to reuse it in irrigation. In terms of

turbidity the process of increase in turbidity removal can be observed by

increment of coagulant concentration, although the removal efficiency is almost

steady due to alum dosage increment in high concentration of coagulant.

8.0 DISCUSSION

1. By using aluminium sulphate, the mechanism i s :

Al 3 + + 3H 2 O Al(OH) 3 + 3H

Describe the mechanism of r eaction i f the aluminium sulphate is replaced

by ferum chloride (FeCl 3 ).

The properties of iron with respect to forming large complexes, dose, and pH

curves are similar to those of alum. In the presence of alkalinity is:

FeCl3 + 3HCO3 + 3H2O Fe(OH)3.3H2O(s) + 3CO2 + 3Cl-

For the mechanism without alkalinity the reaction will be presence as follow:

FeCl3 + 6H2O Fe(OH)3.3H2O(s) + 3HCI


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2. How the coagulant works?

When coagulant is added into the water, it helps to promote coagulation. The

coagulant encourages colloidal material in the water to join together into small

aggregates or “flocs” (microfloc). Coagulant neutralizes the electrical charges

of particles in the water which causes the particles to clump together. Properly

formed floc will settle out of water quickly in the sedimentation basin,

removing the majority of the water's turbidity. Hence impurities can be easily

removed.

3. Name 3 types of acid and base which are sui table for pH neutrali zation.

a) Acid: sulfuric acid, ferum chloride, hydrochloric acid and tartaric acid.

b) Base: sodium hydroxide, magnesium oxide, hydrogen chloride and

potassium hydroxide.

4. What are the benefi ts of using coagulant aids?

i. Improve coagulation;

ii. Build a stronger, more settleable floc;

iii. Overcome slow floc formation in cold water;

iv.

Reduce the amount of coagulant required;

v. Reduce the amount of sludge produced.

vi.

Add toughness to the flocs so that they will not break up during the

mixing and settling processes.

5. I n what way the dosage of aluminium sulphate in the treatment process can

be reduced?

By using coagulant aids such as lime and bentonite.

6. I nstead of Al 2 (SO 4 ) 3 , name another three coagulants that can be best used

as coagulant aid.

i. Bentonite (clay)

ii. Calcium carbonate (CaCO3)

iii. Sodium silicate (Na2SiO3)


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9.0 RECOMMENDATION

To obtain more accurate and precise results, make sure wastewater source

obtained were not taken right after weather changes such as rain because

surface water plants are susceptible to sudden changes in water quality thus

affect the results.

Make sure gloves are worn to avoid fingerprints on turbidimeter sample

cells which will affect turbidity readings.

Avoid air bubble in pipette when measuring alum dose.

Use distilled water as control before testing turbidity for every samples.

10.0 CONCLUSION

In conclusion, the objective to determine the optimal coagulant dose which

will produce the highest removal of a given water turbidity of the experiment is

achieved. The optimum value of pH and coagulant dose are 4.6 and 1mg/L

respectively.

Theoretically, adding coagulant such as alum does help to reduce the turbidity

of the wastewater until a certain point. However, the results obtained in our

experiment did not show a positive results due to few avoidable errors. For instance,

weather factor as the rain affected the contamination of the wastewater hence the

results were affected as well and not as desired. This is due to surface water plants

tend to treat water with a high turbidity which is susceptible to sudden changes in

water quality.

In a nut shell, 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.

11.0 REFERENCES

Principle of Environment Engineering and Science, McGraw Hill 2004,

Mackenzie L.Davis and Susan J.Masten

Prentice Hall: Introduction to Environmental Engineering: Fourth edition:

McGraw Hill International Editions


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12.0 APPENDIX

Documents

Contoh report jar test