LABORATORY 5: JAR TEST
1.0
INTRODUCTION
The jar test is a method of measuring the effect of coagulation, flocculation, and sedimen sedimentati tation on on turbidit turbidity. y.
Althou Although gh the procedure procedure is not outlined outlined in Standard 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, larger, heavier clumps which which settle out relatively quickly. quickly. The larger larger particles are know known n as floc floc..
Prop Proper erly ly form formed ed floc floc will will sett settle le out out of wate waterr quic quickl kly y in the the
sedimentation basin, removing the majority of the water's turbidity.
In this laboratory, we will perform the jar test on a lake water samples taken from the Lake in Cheras Public Park. By adding varying amounts amounts of alum and measuring initial and final pH values, conductivity, temperature, and turbidity, we were able to determine the optimum dosage of alum solution added to water sample by looking at trends in the data what the most effective approach to the lake water treatment.
2.0
OBJECTIVE
I.
To visualiz visualizee the the coagul coagulatio ation-fl n-floccu occulati lation on process process in the laborat laboratory ory
II.
To det determ ermine ine the the opti optimu mum m dosag dosagee of alu alum m solu solutio tion n adde added d to wate water r sample.
3.0
i.
APPARATUS
Six be beakers (5 (500ml)
ii. ii.
Stock solution ion (10 (10g/l) /l)
iii.
Measuring cylinder
iv. iv.
Jar Jar Test Testin ing g Mac Mach hine ine (Flo (Flocc ccul ulat ator or))
v. vi.
Turbidity Meter Watch
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4.0
PROCEDURE
1. Firstly, water sample is filled into measuring cylinder and being analyze for turbidity and initial pH by manually stir it up for 10 times then measuring is taking by using the turbidity meter. These steps are repeated for 3 times to collect the average reading from the result analyze and the data is recorded in the Initial Turbidity Table.
2. Secondly, filled each of the six 500 mL beakers with water sample and labeled each of beakers with 1 till 6.
3. Thirdly, the alum dosage required for each jar and the volume of alum solution to be added are calculate to preparing the stock solutions. Stock solutions are prepared by dissolving 20.0 grams of alum into 500 mL distilled water so each 1.0 mL of the stock solution will equal 10 mg\L (ppm) when added to 1,000 mL of water to be tested. The stock solution of 0, 1,2,3,4 and 5mL was measured and filled into the bottle.
4. The 6 Beakers contain the prepared sample is placed in the Jar Testing Machine. The paddles are release and adjusted to be in middle of the beakers then beginning the two stirrers using rapid mixing (coagulation) that is at 100 rpm for 1 minute.
5. After the rapid mixing, immediately add 0, 1, 2, 3, 4, and 5 mL of stock solution in each beaker respectively then reduce the stirrer speed to 40 rpm and flocculate for 10 minutes.
6. After the flocculation period, remove the paddles and allow solids to settle for 30 minutes. The floc settling characteristics is being observed. (A hazy sample indicates poor coagulation. Properly coagulated water contains floc particles that are well-formed and dense, with clear liquid between the particles)
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7. The final turbidity being measured by taking a sample from the center of each one sample, about 2 inches down, and being done carefully for not disturb the flocs that have settled.
8. Graph of Turbidity versus Alum dosage is plotted using the data recorded.
5.0
SAFETY AND HEALTH PRECAUTION
i.
Wear KLIUC jacket, long pan and shoe before enter laboratory
ii.
Check the equipment before using it and handle it with caution
iii.
Use glove when handing with sample
iv.
Record all the test
6.0
RESULTS CALCULATION AND DISCUSSION
Data obtained from the Jar test in the following tabular form.
Alum Stock Solution Concentration 10,000 mg/L
JAR
Alum Stock Solution Added (mL)
Alum Dosage (mg/L)
Initial Turbidity (NTU)
Residual Turbidity (NTU)
Residual pH
1
10
20
87.3
12.8
6.80
2
15
30
87.3
3.90
6.84
3
20
40
87.3
1.39
6.85
4
25
50
87.3
0.630
6.81
5
30
60
87.3
0.402
6.76
3
6
35
70
87.3
) U T N ( y t i d i b r u T
0.311
6.68
Optimum Dose
Alum Dose (mg/L)
Graph of Turbidity versus Alum concentration as shown above and determine the optimum alum dose
7.0
CONCLUSION AND RECOMMENDATION
As base on our data and observation, the sample indicates poor coagulation. Properly coagulated water contains floc particles that are well-formed and dense, with the liquid between the particles clear. The turbidity tests of the water in each beaker by using a turbidometer giving us the result that our sample is least turbid and it is correspondent with the optimal coagulant dosage that being used.
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This is because alum will make the water more acidic, and it is for this reason that buffer is added at the same time, and in the same amount as the alum. After analyzing the data, we have decided that the optimum dosage of alum for this system is approximately 30.0 mL of alum. We reached this conclusion based on the fact that the turbidity is at a minimum at this point, at 3.90 NTU. Our recommend for this type of water sample is based on how often jar tests are performed here. These lakes 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, they can have problems with removing the more difficult small suspended particles typically found in groundwater. So system operators at this lake should perform jar tests frequently, especially after rains, to adjust the coagulant dosage and deal with the changing source water turbidity.
8.0 APPENDIX AND REFERENCE
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References: 1. http://www.ci.slc.ut.us/utilities/parleys/ 2. http://www.phippsbird.com/products.html#pb-700 3. http://www.maca.gov.nt.ca/operations/water/docs/class%20I.pdf 4. http://water.me.vccs.edu/courses/env211/lab5_print.htm
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