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Summary:
The objective is to present the step by step of the unt test of jugs where the different tests prior to the sample of water and materials used are evidenced.

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Jar tests are used to determine the most effective coagulant doses for a specific water during coagulation and flocculation control in a treatment plant, especially when the water quality fluctuates rapidly. It can also be used to determine sedimentation rates for the design of sedimentation tanks and to know the potential raw water for direct filtration.

The amount of reagent to be dosed is obtained by the Jarras test, this test allows to determine the dose of coagulants that produce the fastest destabilization of the colloidal particles in the plant and cause a heavier and more compact floc to form which is easily retained in the settler and do not break when going through the filtering process.

The jar test apparatus basically consists of a variable speed multiple agitator that can create turbulence simultaneously in six beakers. This is about reproducing the conditions in which flocculation occurs in a treatment plant.

The turbidity measurement of water after flocculation is usually considered as the most important parameter to characterize the process. The measurement of pH before and after flocculation is of basic importance, therefore a measuring system must always be available.

The main reagent is the aluminum sulfate solution. It is common that when performing a jar test the results obtained do not allow to establish an optimal dosage. This happens when the flocculant agent that is tested is not the most suitable for a certain type of water

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Materials

 Flocculator
 Three beaker 1000 ml
 A 1000ml test tube
 One volumetric flask with 100 ml of 10% aluminum sulphate solution
 Digital pH meter and tube
 Groundwater sample
 Analytical balance

Jars Test Procedure

 Two liters of a sample of groundwater was taken for the development of the practice.
 With one liter of the water sample taken, the pH, turbidity was measured.
 Known volumes of aluminum sulfate are taken as coagulant, to make the test with three 400 ml beakers.
 With 400 ml of sample, different coagulant doses were applied per sample. 5g / L, 10 g / L, 15 g / L. Rapid mixing was performed for one minute and mixing slowly for 15 minutes, until the formation of the floc was observed.
 Clarified water measure pH and turbidity.
 Photographic record was taken.

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Results

 The measurement of the groundwater sample resulted in: pH 5.2 at a temperature of 27 ºC and turbidity 15.3
 Quick mix for one minute

| Dose | pH | Turbiedad
| 5g/L | 4.55 | 18.7
| 10g/L | 4.30 | 14.2
| 15g/L | 4.10 | 23.4

 Slow mixing for fifteen minutes
| Dose | pH | Turbiedad
| 5g/L | 4.33 | 28.8
| 10g/L | 4.11 | 31.8
| 15g/L | 3.9 | 29.6

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Discussion

It is evident that the experiment went wrong, the turbidity results of the jar test came out higher with the coagulant aluminum sulfate than with the groundwater sample, probably due to the fact that larger amounts of dosage were used, that is, grams were used instead of mg in aluminum sulfate, in consequence increase the degree of turbidity.

In the slow and rapid mixture a significant decrease in pH was observed compared to the groundwater sample, this due to the high doses of aluminum sulfate. It was also observed that there was no floc formation in either of the two mixtures.

With this experiment we realize that we must use the indicated amounts of coagulant for drinking water treatment, if an incorrect dose is used it could have negative physicochemical consequences in the water, such as increasing the degree of turbidity, pH decrease, affectation in the water. flavor and color

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Bibliography

Salazar Gámez, L. (2017). Design Module of Water Treatment Plants. Colombia: Retrieved from: http://hdl.handle.net/10596/10050

MINVIVIENDA. (2010). Good engineering practice manuals. Title B. Technical Regulation of the Potable Water and Basic Sanitation Sector - RAS. Recovered: http: //www.minvivienda.gov.co/Documents/ViceministerioAgua/TITULOB%20030714.pdf