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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.
What is flash mixture?
Flash Mixing in Water Treatment Flash or rapid mixing stage consists in adding chemicals to raw water to foster coagulation, attracting particles which do not settle or are not filtered.
What is the purpose of rapid mixing in water treatment and how is it achieved?
Rapid mixing serves to disperse the coagulants evenly throughout the water and to ensure a complete chemical reaction. Sometimes this is accomplished by adding the chemicals just before the pumps, allowing the pump impellers to do the mixing.
What is the purpose of performing the flocculation procedure?
A Flocculation Test Procedure is used to determine how much Flocculants need be added to solids in suspension (slurry or pulp) to cause the individual particles to collect in the form of flocs. The formation of flocs aids in improved settling rates, better overhead clarity and/or faster filtration rates.
What happens during coagulation?
Blood clots and coagulation Blood vessels shrink so that less blood will leak out. Tiny cells in the blood called platelets stick together around the wound to patch the leak. Blood proteins and platelets come together and form what is known as a fibrin clot. The clot acts like a mesh to stop the bleeding.
How many types of clarifiers are there?
Clarifiers Basic Principle: Bridge support, column support and traction are the three main types of clarifiers, Primary and Secondary clarifiers.
What are the types of coagulants?
The aluminum coagulants include aluminum sulfate, aluminum chloride and sodium aluminate. The iron coagulants include ferric sulfate, ferrous sulfate, ferric chloride and ferric chloride sulfate. Other chemicals used as coagulants include hydrated lime and magnesium carbonate.
What is the use of aeration tank?
Aeration in an activated sludge process is based on pumping air into a tank, which promotes the microbial growth in the wastewater. The microbes feed on the organic material, forming flocks which can easily settle out.
Which bacteria is present in aeration tank?
There are five major groups of microorganisms generally found in the aeration basin of the activated sludge process: Bacteria-Aerobic bacteria remove organic nutrients. Protozoa-Remove & digests dispersed bacteria and suspended particles. Metazoa-Dominate longer age systems including lagoons.
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.
What is rapid mixing?
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 are clarifiers used for?
A clarifier is generally used to remove solid particulates or suspended solids from liquid for clarification and (or) thickening. Concentrated impurities, discharged from the bottom of the tank are known as sludge, while the particles that float to the surface of the liquid are called scum.
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 is the purpose of rapid mixing?
Rapid mixing aims to instantly and efficiently disperse coagulant species into raw water, before flocculation, sedimentation, and filtration processes. Mechanical mixing with a longer retention time cannot guarantee an instantaneous and uniform coagulant dispersion.
What is difference between purifier and clarifier?
The key difference between purifier and clarifier is that the purifier consists of a dam ring to create a line of separation between fuel and water whereas the clarifier consists of a sealing ring to prevent the fuel tank from water and dissolved impurities.
What is sedimentation short answer?
The process of particles settling to the bottom of a body of water is called sedimentation. Layers of sediment in rocks from past sedimentation show the action of currents, reveal fossils, and give evidence of human activity. Sedimentation can be traced back to the Latin sedimentum, “a settling or a sinking down.”
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 are floc particles?
Flocculation, in physical chemistry, separation of solid particles from a liquid to form loose aggregations or soft flakes. These flocculates are easily disrupted, being held together only by a force analogous to the surface tension of a liquid.
What is coagulation process?
Coagulation is a process of combining particles, colloids, and dissolved organic material into larger aggregates (Amirtharajah and O’Melia, 1990). These aggregates are then removed from the water usually by clarification and filtration processes in most conventional WTWs.
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.
How do coagulants work?
Coagulants work by creating a chemical reaction, eliminating negative charges that cause particles to repel each other. The action of these bubbles forces clots or flocs of particles to the water surface where they can be skimmed off. Dissolved air flotation is an alternative to sedimentation.
What are the advantages of aeration?
Advantages of aeration can be reduced odor, nitrification of ammonia to nitrate (thus potentially reducing ammonia emissions and also having a nitrogen form that is readily crop-available but also more prone to leaching), and reduction of greenhouse gases (especially methane) compared to anaerobic treatment.
What is the basic principle of flocculation?
Flocculation refers to the process used to bring the coagulated particles together so that they can combine to form larger, settleable, and filterable masses of particles called floc. Zeta potential is defined and its role in coagulation described.
What happens during aeration tank?
Aeration brings water and air in close contact by exposing drops or thin sheets of water to the air or by introducing small bubbles of air and letting them rise through the water. Dissolved gases are then removed from the solution and allowed to escape into the surrounding air.
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.
