Jar Test Apparatus

Jar Test Apparatus

A pilot-scale laboratory test, known as the "jar test", replicates coagulation or flocculation using different chemical doses. The jar test is used to determine the minimum coagulant dose required to meet specific water quality objectives. The four- or six-place gang stirrer used in jar testing can be used to mimic the mixing and settling conditions in a clarifier.

Jar testing helps to determine the correct dose of treatment chemicals: the lowest dose of chemicals used to treat the water will produce adequate sedimentation. 

The Jar Test allows chemical coagulants to be correctly selected and dosed to remove suspended solids and other contaminants from water treated in wastewater treatment plants.

In fact, the results of the laboratory Jar Test, which simulates full-scale operation in water treatment plants, determine the choice and dosage of chemical coagulants.

Lime (calcium hydroxide), alum (aluminium sulphate) and iron salts (ferric or ferrous) are the most commonly used coagulants.

Any water treatment process must include flocculation or coagulation as a necessary step in the sedimentation, filtration and disinfection processes before water is distributed for domestic and industrial use.

The jar method works by dividing your money into many different categories. At the beginning of the month, or whenever you get paid, instead of having a single bank account balance, you divide the money you have received into your jars.

Key Components of a Jar Test Apparatus

A laboratory process that replicates flocculation and coagulation using different chemical doses. The aim of the procedure is to calculate the minimum dose of coagulant required to meet specific water quality objectives. Six jars are used to hold samples of treatment water. Each jar is filled with different concentrations of chemicals, stirred and the settling of solids is observed. The chemical dose used to treat the water is the lowest that provides good settling.

Maintenance and Calibration of a Jar Test Apparatus

Before starting, record the temperature, pH, turbidity and alkalinity of the raw water. To make a stock solution, combine 10.0 grams of alum with 1,000 mL of distilled water. When added to 1,000 mL of the water to be tested, 1.0 mL of this stock solution is equivalent to 10 mg/L (ppm).

Both the 4-place and 6-place models have an illuminated rear panel for glare-free sample viewing, making them suitable for laboratory use. The arrangement of the four stirring points in a circle around a lamp makes it easier to observe the flocculation process.

Modern technology makes the machine maintenance free and ensures optimum ease of use. Infinitely variable stirring speed, digital display of stirring speed, timer function, illuminated rear panel and the possibility of adjusting the height of the stirring blades during operation are the main features of the laboratory beaker testers. Requires 1000 ml and 1500 ml flat bottom beakers.

How does a jar test apparatus work?

Make sure you understand the objectives of the test before you begin. What are the objectives of the water treatment? What is the current treatment method? Does the DAF tank contain water? Is it filtered? All of these questions can greatly simplify the tank test procedure and save you time.

A representative sample of the effluent should then be taken. A representative sample means that you are collecting from the bottom up and that the sample has been thoroughly mixed. You can be confident that you are getting a complete profile of the effluent by using a representative sample.

You won't get material that has settled or has a higher density if you take water from the top of a sample.
Fill four to six 600 mL beakers with water. The beakers should have a capacity of 500 mL.

The samples should be placed on a mixing device, such as an overhead stirrer with multiple paddles. If you don't have a gang stirrer, set a timer and set the stirring time on the device to match how the chemicals will combine during treatment.

Get your Chemicals Ready

This may include your coagulants and flocculants as well as pH adjusters such as sulphuric acid and caustic soda. You may also have an oil emulsifier if the water is greasy.

Check The Ph Of The Sample While Mixing The Water Samples

This will help you decide if pH correction is required. The pH will increase in the presence of caustic soda and decrease in the presence of an acid such as sulphuric acid. It is advisable to check the pH range at which your coagulants and flocculants are most effective. Also review any relevant background material. Depending on the organisation or waste stream from which you are sourcing your water due to differing requirements and regulations, water may occasionally need to be at a specific pH.