What Is The Purpose Of A Jar Test

A laboratory procedure that simulates coagulation/flocculation with differing chemical doses. The purpose of the procedure is to estimate the minimum coagulant dose required to achieve certain water quality goals.

What are the two objectives of jar tests?

The objectives of the jar test experiment are to estimate the optimum concentration of aluminum sulfate for the removal of suspended matter and to investigate the change in alkalinity as a result of aluminum sulfate addition.

How is Jar testing done in lab?

The purpose of the laboratory jar test is to select and quantify a treatment program for removal of suspended solids or oil from raw water or a dilute process or waste stream. Jar tests are conducted on a four- or six-place gang stirrer, which can be utilized to simulate mixing and settling conditions in a clarifier.

How is the process of coagulation done?

The coagulation process involves adding iron or aluminum salts, such as aluminum sulphate, ferric sulphate, ferric chloride or polymers, to the water. The positive charge of the coagulant neutralizes the negative charge of dissolved and suspended particles in the water.

Which gas is released when alum is added to water?

Explanation: Carbon dioxide gas is released when alum is added to water, which is corrosive to metals.

What is the main purpose of coagulation flocculation?

Coagulation and flocculation are used to separate the suspended solids portion from the water. Suspended particles vary in source, charge, particle size, shape, and density.

Why does pH affect coagulation?

Since pH values affect the surface charges and forms of the coagulants and impurities to be removed, controlling the level of pH would significantly improve the coagulation process. Therefore, not only coagulant dosage, but also pH value should be optimized to maximize the removal of impurities present in raw water.

What is the best coagulant?

Generally, alum is the first coagulant of choice because of its lower cost and its widespread availability. For coloured, low turbidity, low pH/alkalinity surface waters pre-treatment with lime, soda ash or caustic soda will normally be required to ensure that the optimum coagulation (dosed-water) pH is achieved.

How do I make a 10% alum solution?

If an alum solution of 1.0% by weight is not on hand, please follow the guidelines below to prepare a solution. Dry Products: Weigh 10 grams of chemical and dissolve in DI water to make a 1,000 mL solution. This is a 10 g/L solution or 1.0% by weight.

What is the purpose of coagulation?

Coagulation is a process used to neutralise charges and form a gelatinous mass to trap (or bridge) particles thus forming a mass large enough to settle or be trapped in the filter.

Is FeCl3 a coagulant?

Ferric chloride (FeCl3) is the most common iron salt used to achieve coagulation. Its reactions in the coagulation process are similar to those of alum, but its relative solubility and pH range differ significantly from those of alum. Both alum and ferric chloride can be used to generate inorganic polymeric coagulants.

How does pH affect coagulation and turbidity?

At varying sample pH values, the coagulation process may suffer from less than optimum ions being formed in solution. The size of the coagulated particles is also affected by pH, which, in turn, determines the density of the flocculated slime and its tendency and rate of settling out.

Why did the pH change in jar test?

If water contains no alkalinity, the pH changes dramatically because sulfuric acid is produced instead of CO2 as express in equation (2). Sulfuric acid is a strong acid that dissociate 100 % to proton, or H+.

How much alum do I put in my water?

Make an alum solution by adding 7.5 grams of alum to one liter of tap water.

What is the coagulation in jar test?

The dose of the coagulant to be used can be determined via the jar test. The jar test involves exposing same volume samples of the water to be treated to different doses of the coagulant and then simultaneously mixing the samples at a constant rapid mixing time.

How is Jar test calculated?

1. Jar Testing of Chemical Dosages. Prepared By.
2. Jar Testing. Equipment Needed:
3. 1 Graduated Cylinder, 1000 ml. Scale for weighing chemicals.
4. For alum, lime, other dry materials: Use a 1 % solution.
5. Use a 1 % solution.
6. 45 % X 1.49 X V₁ = 1 % X 1000 ml.
7. Have 45 % Ferric Chloride Solution.
8. 1 % X 1000 ml.

What are the side effects of alum?

Side effects of Alum The excessive amount of alum intake may cause breathing difficulty, facial puffiness, pricking sensation & small ulcers on the skin, chest/throat tightness, and burns rarely seen in some cases.

What is the coagulant?

Coagulants are a substance which cause particles in a liquid to curdle and clot together. Coagulation treatment chemicals are used in effluent water treatment processes for solids removal, water clarification, lime softening, sludge thickening, and solids dewatering.

Is Lime a coagulant?

Lime (Ca(OH)2 or CaO): Lime, or calcium hydroxide, is predominantly used to adjust pH, but as a softener, it can also be used as a coagulant aid. The lime bonds with the other particles and increases the size/weight of the flocs which then increases the speed with which they settle out of the water.

What is the difference between flocculant and coagulant?

Depending on the charge and chemical composition of your wastewater, flocculants can either be used on their own or in combination with coagulants. Flocculants differ from coagulants in that they are often polymers, whereas coagulants are typically salts.

What is the importance of slow mixing in jar test?

Here colloids are destabilized and the nucleus for the floc is formed. Slow mixing brings the contacts between the finely divided destabilized matters formed during rapid mixing. Velocity gradient „G‟ and detention time „t‟ are the decisive parameters for dispersion and mixing of coagulant as well as floc formation.

Is alum a coagulant or flocculant?

To accomplish this, the water is treated with aluminum sulfate, commonly called alum, which serves as a flocculant. Raw water often holds tiny suspended particles that are very difficult for a filter to catch. Alum causes them to clump together so that they can settle out of the water or be easily trapped by a filter.

What happens if you add too much coagulant?

If too much or not enough coagulant is added, the removal of suspended matter will be less efficient. If too much coagulant is added, the cost of treating the water will also increase.