Table of Contents
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.
What are the two most common coagulants?
Traditional chemical coagulation uses aluminum and iron coagulants. The most common aluminum coagulants are aluminum sulfate, aluminum chloride, and sodium aluminate. Iron coagulants include ferric sulfate, ferrous sulfate, ferric chloride, and ferric chloride sulfate [4].
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 benefit can we get through sedimentation process?
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.
What are common flocculants?
The following natural products are used as flocculants: Chitosan. Isinglass. Moringa oleifera seeds (Horseradish Tree) Gelatin. Strychnos potatorum seeds (Nirmali nut tree) Guar gum. Alginates (brown seaweed extracts).
Is gypsum a flocculant?
Gypsum can coagulate or bridge clay particles, which accelerates settling. Flocculants should be used to prevent damage to sensitive water resources such as ponds, lakes and trout streams or whenever turbidity control is required. The best thing to do is a jar or bucket test using slightly varying rates of gypsum.
What is meant by flocculant?
A flocculant is a compound or agent which is added to a vessel to make particles stick together and form larger particles. Flocculants are added to encourage floc formation and enhance settling and compression rates. Flocculation involves the addition of a flocculant that causes the particles to stick together.
Where are coagulants used?
Flocculants & Coagulants. Flocculation and coagulation treatment chemicals are used in effluent water treatment processes for solids removal, water clarification, lime softening, sludge thickening, and solids dewatering.
What makes a good coagulant?
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. The advantage of a low basicity coagulant is even more pronounced in full softening applications, and the non-sulphated PACl is the coagulant of choice.
How turbidity can be removed?
These options mechanically (through filtration) or chemically (through flocculation and settling of suspended material) remove particles and reduce turbidity.
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.
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.
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 is coagulant made of?
Chemically, coagulant chemicals are either metallic salts (such as alum) or polymers. Polymers are man-made organic compounds made up of a long chain of smaller molecules. Polymers can be either cationic (positively charged), anionic (negatively charged), or nonionic (neutrally charged.)
What is form when coagulant is added to water?
Explanation:When coagulant is added to water, then white gelatinous precipitate is formed called floc. Coagulant aid Chemicals (typically synthentic polymers) added to water to enhance the coagulation process.
Is na2so4 a coagulant?
Sodium sulfate is a well-known coagulant for PVA, and it is used in the coagulation bath of PVA before wet spinning of vinylon fibers.
How effective is coagulation?
Several studies have reported the effectiveness of dual coagulants application when dealing with various types of wastewater where it can reduce up to 90% of COD, total suspended solids (TSS), turbidity, and colour.
What are examples of coagulants?
Examples of primary coagulants are metallic salts, such as aluminum sulfate (referred to as alum), ferric sulfate, and ferric chloride. Cationic polymers may also be used as primary coagulants.
What is meant by coagulant?
Coagulants are a substance which cause particles in a liquid to curdle and clot together. Coagulants carry the opposite charge to the particles and therefore cause the charge to ‘destabilise’ when added to the water; resulting in the particles clinging together.
How does a coagulant 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.
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 are natural coagulants?
They are mainly composed of polymers of natural origin extracted from plants, algae or animals. Among these are polysaccharides and water soluble substances that act as coagulation and / or flocculation agents.
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.
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. Let’s examine these steps in more detail.
What is the most common coagulant in water treatment?
Inorganic coagulants are largely aluminium or iron based. Aluminium sulphate is the most commonly used chemical to treat waste water globally, though other examples include aluminium chloride, polyaluminium chloride, aluminium chlorohydrate, ferric and ferrous sulphate, and ferric chloride.
