Table of Contents
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 is the function of coagulant?
In water treatment, coagulants are used to remove a wide variety of hazardous materials from water, ranging from organic matter and pathogens, to inorganics and toxic materials, like arsenic, chemical phosphorous and fluoride.
How does coagulation work in water treatment?
These chemicals are called coagulants, and have a positive charge. The positive charge of the coagulant neutralizes the negative charge of dissolved and suspended particles in the water. When this reaction occurs, the particles bind together, or coagulate (this process is sometimes also called flocculation).
What are the 5 stages of water treatment?
These include: (1) Collection ; (2) Screening and Straining ; (3) Chemical Addition ; (4) Coagulation and Flocculation ; (5) Sedimentation and Clarification ; (6) Filtration ; (7) Disinfection ; (8) Storage ; (9) and finally Distribution.
What are the water treatment methods?
Coagulation, flocculation and sedimentation are processes used to remove colour, turbidity, algae and other microorganisms from surface waters. Aluminium sulphate and ferric sulphate are two of the most commonly used coagulants , although others are available.
What coagulants are used in water treatment?
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. Coagulation is usually accomplished in two stages: rapid mixing and slow mixing.
Which one is a good coagulant?
Aluminum and iron salts are the most commonly used inorganic coagulants in the wastewater treatment settings. These include based aluminum metals (aluminum chloride, aluminum sulfate, sodium aluminate) and iron based metals (ferrous sulfate, ferric sulfate, ferric chloride) [13, 17, 18].
Which coagulant is best?
A metal based coagulant will consume alkalinity, especially in a well buffered high pH water, which could compromise the softening process. The best coagulant is therefore a pre-hydrolysed species with a high basicity. PACl has been found to be very suitable for lime softening applications.
What are the common coagulants used?
The commonly used metal coagulants fall into two general categories: those based on aluminum and those based on iron. 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.
Why coagulants are used in water treatment process?
Once added to water, the inorganic coagulants form aluminium or iron precipitates. These absorb impurities in the water as they fall, serving to clean the water. This process is known as the ‘sweep-floc’ mechanism. Aluminum Sulfate (Alum) – One of the most commonly used water treatment chemicals in the world.
What is an example of coagulation?
Examples of Coagulation Milk proteins coagulate to thicken the mixture that forms yogurt. Blood platelets coagulate blood to seal a wound. Pectin gels (coagulates) a jam. Gravy coagulates as it cools.
Which coagulant is used for sewage treatment?
Alum is used in water treatment whereas Ferric Chloride is used in sewage treatment.
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.
Which is not example of coagulation?
Rubber plating and chrome tanning.
What is a coagulant and why is it used?
Water treatment coagulants are comprised of positively charged molecules that, when added to the water and mixed, accomplish this charge neutralization. Inorganic, organic, or a combination of both coagulant types are typically used to treat water for suspended solids removal.
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.
How many steps does it take to purify water?
Seven Steps of Water Purification.
What is egg coagulation?
Think about an egg. When it is heated the runny yolk and white (albumen – which is the major source of protein) turn solid. The proteins in the egg start to thicken, a process known as coagulation. Coagulation is irreversible, the proteins cannot be turned back into their liquid form. Another example is heating milk.
What happens during 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 coagulation and flocculation work?
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. Coagulation and flocculation occurs in successive steps, allowing particle collision and growth of floc.
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 causes 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.
What is the most common coagulant?
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.
What are stages of water treatment?
There are three main stages of the wastewater treatment process, aptly known as primary, secondary and tertiary water treatment. In some applications, more advanced treatment is required, known as quaternary water treatment.
