Table of Contents
Rapid or Flash mixing is the process by which a coagulant is rapidly and uniformly dispersed through the mass of water. This process usually occurs in a small basin immediately preceding or at the head of the coagulation basin.
What is the purpose of rapid mixing in water treatment?
Rapid mixers are used to violently agitate the water with the chemicals for a short period of time before being released into the flocculation basin.
What is the purpose of rapid mixing in jar test?
Rapid mixing of the water and coagulant is important to ensure thorough and even distribution of the coagu- lant. Flocculation is a slow gentle mixing of the water to encourage the flocs to forn and grow to a size which will easily settle out. This mixing is often done in a chamber or a series of chambers.
What is the purpose of rapid and slow mixing?
It is a common practice to provide an initial rapid (or) flash mix for the dispersal of the coagulant or other chemicals into the water. Slow mixing is then done, during which the growth of the floc takes place.
How do you conduct a jar test?
The jar test procedures involves the following steps: Add the coagulant to each container and stir at approximately 100 rpm for 1 minute. Turn off the mixers and allow the containers to settle for 30 to 45 minutes. Reduce the stirring speed to 25 to 35 rpm and continue mixing for 15 to 20 minutes.
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.
What is mixing in water treatment?
Mixer. Coagulation/Flocculation is the process of creating conditions for particulates to come together to form flocs of solids and then settle in treated water.
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 chemicals are added during the flash mix of water treatment?
A rapid (or flash) mixer is used to uniformly disperse and blend chemicals, such as coagulant aids, chlorine, and sulfur dioxide into the process stream. These chemicals, either in solution or slurry form, are added for the purpose of neutralization, odor & color control, and/or to aid in the removal of solids.
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.
How does sedimentation work in water treatment?
Sedimentation is the process of allowing particles in suspension in water to settle out of the suspension under the effect of gravity. The particles that settle out from the suspension become sediment, and in water treatment is known as sludge.
Why sedimentation is importance in water treatment?
The sedimentation process is used to reduce particle concentration in the water. The advantage of sedimentation is that it minimizes the need for coagulation and flocculation. Typically, chemicals are needed for coagulation and flocculation, but improved sedimentation controls the need for additional chemicals.
Which polyelectrolyte is used in water treatment?
Polyelectrolyte ETP Chemicals. Aquafloc 401: is a liquid cationic coagulant based on polyamines used in water clarification. They may be used independently or supplemented with inorganic coagulants or with coagulants aids based on polyacrylamide.
What is the use of jar test?
Jar test is a pilot-scale laboratory test that simulates coagulation or flocculation with differing chemical doses. The purpose of the jar test is to estimate the minimum coagulant dose required to achieve certain water quality goals.
How do you mix chemical water?
If you’re dealing with an acid or a base, mixing it with water is likely to be an exothermic reaction. Be sure you mix the chemicals with the water slowly and stir constantly to evenly distribute the heat. If the mixture heats up too rapidly, it could boil the water in the solution.
What is the difference between coagulant and flocculant?
Flocculants differ from coagulants in that they are often polymers, whereas coagulants are typically salts. Generally speaking, anionic flocculants are used to catch mineral particles while cationic flocculants can capture organic particles.
What is coagulation of water?
Coagulation is the chemical water treatment process used to remove solids from water, by manipulating electrostatic charges of particles suspended in water. This process introduces small, highly charged molecules into water to destabilize the charges on particles, colloids, or oily materials in suspension.
What is the purpose of the rapid mixing of coagulants in the coagulation tank?
A high-energy, rapid-mix to properly disperse the coagulant and promote particle collisions is needed to achieve good coagulation and formation of the microflocs. Over-mixing does not affect coagulation, but insufficient mixing will leave this step incomplete.
What are the 4 types of sedimentation process?
Type 1 – Dilutes, non-flocculent, free-settling (every particle settles independently.) Type 2 – Dilute, flocculent (particles can flocculate as they settle). Type 3 – Concentrated suspensions, zone settling, hindered settling (sludge thickening). Type 4 – Concentrated suspensions, compression (sludge thickening).
What two chemicals are commonly used as water coagulants?
Aluminum sulfate (alum) is the most common coagulant used for water purification. Other chemicals, such as ferric sulfate or sodium aluminate, may also be used.
How the coagulant works in 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. The microfloc formed after coagulation further undergoes flocculation and is allowed to settle.
What are the steps in water treatment?
Community Water Treatment Coagulation and Flocculation. Coagulation and flocculation are often the first steps in water treatment. Sedimentation. During sedimentation, floc settles to the bottom of the water supply, due to its weight. Filtration. Disinfection.
How is Jar test calculated?
0.1 gram and dissolve in 1000 ml distilled water. Calculate the volume of a 1 % Ferric Chloride solution that would be added to get the dosage required. A jar test indicates that the required amount of phosphorus removal can be achieved using a dosage of 3 ml of a 1% ferric chloride solution in a liter of wastewater.
How coagulants are help in treatment of water?
Coagulation treatment neutralizes the negative electrical charge on particles, which destabilizes the forces keeping colloids apart. Water treatment coagulants are comprised of positively charged molecules that, when added to the water and mixed, accomplish this charge neutralization.
How do clarifiers work?
The clarifier works by permitting the heavier and larger particles to settle to the bottom of the clarifier. The particles then form a bottom layer of sludge requiring regular removal and disposal. Clarified water then proceeds through several more steps before being sent for storage and use.
