Contents
What is the purpose of rapid mixing in jar test?
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.
Why we use mixers in coagulation?
Rapid mixing is generated to disperse the coagulant throughout the liquid. As a result of the coagulant action, charge neutralization occurs and the suspended particles bind together to form larger particles or flocs. Once formed, the large flocs are easily removed by filtration, straining, floatation or sedimentation.
Why is coagulation flocculation necessary?
To separate the dissolved and suspended particles from the water coagulation and flocculation processes are used. Most solids suspended in water possess a negative charge; they consequently repel each other. This repulsion prevents the particles from agglomerating, causing them to remain in suspension.
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.
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 principle of coagulation?
Coagulation and flocculation are related terms describing the process of preparing colloidal materials for removing by sedimentation. Coagulation is the process used to reduce the energy forces present around particles that tend to keep them from joining together to form a larger mass.
How long does it take for coagulation in a rapid mix?
A high-energy, rapid-mix to properly disperse coagulant and promote particle collisions is needed to achieve good coagulation. Over-mixing does not affect coagulation, but insufficient mixing will leave this step incomplete. Contact time in the rapid-mix chamber is typically 1 to 3 minutes.
Which is the best coagulant to use for mixing?
Even though they may be more expensive, a smaller amount may be needed, thereby saving money. Organic polymers also typically produce less sludge. Typical coagulants and aids are discussed in further detail below: Chemicals commonly used for primary coagulants include aluminum or iron salts and organic polymers.
Why is coagulation important in the water treatment process?
Coagulation is an essential component in water treatment operations. Evaluation and optimization of the coagulation/rapid mixing step of the water treatment process includes a variety of aspects. Optimal coagulant dosages are critical to proper floc formation and filter performance.
When does coagulation occur and when does flash mixing occur?
However, optimum coagulation occurs when negatively charged forms of alum predominate, which occurs when the pH is between 6 and 8. 2 flash mixing is critical to the success of the process. When the primary mechanism is entrapment, effective flash mixing is less critical than flocculation.